Effect of motor imagery on the neurological activation of the immobilized soleus muscle

Injuries to the lower leg occur often in the physically active population and immobilization of a short time is used as part of the treatment protocol. However, immobilization has been found to alter the neurological system of the lower extremity. This study seeks to investigate whether the use of motor imagery can attenuate any detrimental effects of immobilization. Participants were healthy with a moderate physical activity level as well as moderate imagery ability. Fifteen individuals were divided into two groups: an imagery (4 males, 3 females) and control group (6 males, 2 females). All participants were immobilized in a walking boot for 5 days and the H-reflex was measured. The imagery group underwent imagery training three times a day whereas the control group received no intervention. A 2 x 3 RM-ANOVA was used to investigate the effect of motor imagery on motoneuron pool excitability during immobilization. The H-reflex was the dependent variable and time (baseline, day 3 and day 5) and group (imagery, control) the independent variables with significance set at 0.05. No significant interaction was found, suggesting no change in motoneuron pool excitability with the use of imagery compared to the control group. Therefore, the use of imagery had no influence on the neurological activity of the lower leg as measured by the H-Reflex in this study. The absence of a time effect indicated that immobilization did not have the expected effect on the H-reflex. Participant responses were highly variable and several measurement issues may have affected the results. A majority of the imagery were able to stabilize their H-reflex with imagery over 5 days. The results of this study enhance understanding of the neurological mechanisms and changes occurring during immobilization and the role motor imagery plays. Furthermore, this study serves as a base to build upon for future research.

NEUROLOGICAL ACTIVATION OF THE IMMOBILIZED SOLEUS MUSCLE by Stefanie A thesis submitted to the faculty of The University of Utah requirements degree Department of Exercise and Sport Science The University of Utah December 2009 THE EFFECT OF MOTOR IMAGERY ON THE NEUROLOGICAL Stefanic Bengel in partial fulfillment of the req uirements for the dC!,'Tce of Master of Science Uni versity Copyright © Stefanie Bengel 2009 All Rights Reserved T H E U N I V E R S I T Y OF U T A H G R A D U A T E S C H O OL SUPERVISORY COMMITTEE APPROVAL of a Stefanie thesis following satisfactory. Chair: Bradley TV Hayes L I.) -S-Cl 2£ Melinda A. Houston H E UN VERSITY UTA H GRADUATE SC HOOL ora thesis submitted by Stefanic Bengel This thes is has been read by each member of the fo llowing supervisory committee and by majority vote has been found to be sati sfactory. 12-3 - 0'1 /) - 3-oQ T H E U N V E R S I T Y U T A H G R A D U A T E S C H O OL FINAL READING APPROVAL To the Graduate Council of the University of Utah: I have read the thesis of Stefanie Bengel [n fma\ fo rm format, bibliographic are acceptable; (2) its illustrative materials including figures, tables, and charts are in place; satisfactory submission to The Graduate School. Hayes' AT Chair: Supervisory Committee Approved for the Major Department Approved for the Graduate Council Charles A.1 Wwhig ht Dean of The Graduate School THE UN I VERSITY OF UTAH GRADUATE SCHOO L Uni versi ty 1 thes is c--::-_-,----,,-_S:::.'::c.::fa:,:,::ic::..;:B;:c:' ;;'g:;:c::I_---;-c-_;-- in its fina l form and have found that ( 1) its fomlal, citations, and bibl iograph ic style arc consistent and materia ls fi gures, arc and (3) the final manuscript is sati sfactory to the supervisory committee and is ready for submiss ion Date Bradley T. Hayes Chai r: Commin c I arry 8. 'Shultz Chai r/Dcan J A.'Wight ABSTRACT Injuries to the lower leg occur often in the physically active population and immobilization of a short time is used as part of the treatment protocol. However, immobilization has been found to alter the neurological system of the lower extremity. This study seeks to investigate whether the use of motor imagery can attenuate any detrimental effects of immobilization. Participants were healthy with a moderate physical activity level as well as moderate imagery ability. Fifteen individuals were divided into two groups: an imagery (4 males, 3 females) and control group (6 males, 2 females). All participants were immobilized in a walking boot for 5 days and the H-reflex was measured. The imagery group underwent imagery training three times a day whereas the control group received no intervention. A 2 x 3 RM-ANOVA was used to investigate the effect of motor imagery on motoneuron pool excitability during immobilization. The H-reflex was the dependent variable and time (baseline, day 3 and day 5) and group (imagery, control) the independent variables with significance set at 0.05. No significant interaction was found, suggesting no change in motoneuron pool excitability with the use of imagery compared to the control group. Therefore, the use of imagery had no influence on the neurological activity of the lower leg as measured by the H-Reflex in this study. The absence of a time effect indicated that immobilization did not able stabilize have the expected effect on the H-reflex. Participant responses were highly variable and several measurement issues may have affected the results. A majority of the imagery were ab le to stabi lize their H-reflex with imagery over 5 days. The results of this study enhance understanding of the neurological mechanisms and changes occurring during immobilization and the role motor imagery plays. Furthermore, this study serves as a base to build upon for future research. v TABLE OF CONTENTS 1. 1 Significance of Study 6 Research Question 7 Hypotheses 8 Limitations 8 Delimitations 9 Assumptions 9 Definition of Terms 9 Neurological Role in Muscle Strength 20 Imagery 24 The H-reflex as a Measure of Neurological Changes 32 Summary of Literature Review 38 Participants 40 Measures 40 Instrumentation 42 Procedures 43 Research Design and Statistical Analyis 47 4. 48 Demographic Information 48 Imagery Ability and Physical Activity Requirements 48 Results 49 5. DISCUSSION 51 ABSTRACT ..........••......... ••......... ••........ •• •.........••........ .••........ •. ............. iv Chapter I. INTRODUCTION ...... . ...................... .... . . . .. . . . .. ... .. . .. .............. . ....... .... 1 Signi ficance ....... .. ................... . . ........... . ....... . . ........... Research Question ............. . . ........... .• ........ . . •......... . ................ 7 Hypotheses .............................. . . •. ....... . •......... .......... . •• ... . .. ... 8 Limitations .... .. ............. .....• _ ................................................ 8 Delimitations ............................... _." .... . .. ... . ........ . . .... ................ 9 Assumptions ........................ ... ......... ............ . ........ .. ............. 9 Definition ofTenns .......... .......... ... ........ .. ......... .. ........ .... ........ 9 2. LITERATURE REVIEW ................... ....................... . . . ................. ....... 11 The Ankle ................................................ ........... . .......... ... .. 11 ....... ..... .... . ... . ........ ..... ....... .............................................. .. .................... .. ........ Theories of Imagery .....................................................•. ........ 26 renex ..........•............... ..................... .... ......................... .38 3. METHODS .............................................. . . .. ..... . ... .......................... ..40 ................. . .......................... . . ........ ................... 40 .................................. ......... ............ ........... . . ......... 40 lnstrumentation ................................................ •........ .. .......... 42 ........................ . .. .............. .... ...... . .... . ..... ....... .... .. 43 ........ . ..... .... .. ...... ... . .......... 47 4. RESULTS . . ............... . ....................................... .. . ......... . •............... .48 Demograph ic lnfomlation ... . ....... ............................................ .48 Activi ty ....... .. .... ....... .... 48 .............................. .................... ............ •..... ....... . .. .49 5. DiSCUSSiON .................. .................................... ..................... ........ .5 1 Immobilization H/M Ratio Effects Imagery Future Summary 58 Appendices INTERNATIONAL REVISED SCRIPT IMAGERY LOG vii Effects of Immobilization on the HIM Ratio . ... .. ....... . ................. .. 51 Effects of imagery .............................................................. .. 53 Limitations and Future Directions .................................. . ......... .. 55 Implications and ......................... .. ........................... Appendices A. INTERNATIONAL PHYSICAL ACTIVITY QUESTIONNAIRE ............... 61 B. MOVEMENT IMAGERY QUESTIONNAIRE-REVISED ..................... ... 66 C. IMAGERY SCRiPT ....... ...... ............... .. .... .. ............ . ... ......... ....... .... 69 D. IMAGERY AND IMMOBILIZATION DAILY LOG ........ ..................... 73 E. TABLES OF RAW DATA ............................................... ............ .... 76 REFERENCES ............................ ... ........ . .............. .. ............................ 79 VII NCAA fractures III In CHAPTER 1 INTRODUCTION The National Collegiate Athletics Association (NCAA) reported an average of 1700 ankle injuries per year occurring in colleges across the nation. With 15% of all injuries reported, ankle ligament injuries were the most common injuries in the NCAA population (Hootman, Dick, & Agel, 2007). These ligamentous injuries include inversion ankle sprains, eversion sprains, and syndesmotic (high ankle) sprains. Besides ligament injuries, ankle injuries include fractures of the fibula as well as ankle dislocations. The standard treatment for ankle injuries includes a period of immobilization, followed by active rehabilitation exercises (Prentice, 2006). The purpose of immobilization is to facilitate recovery and healing. This is achieved through protection of the joint and prevention of movement. Movement of the injured area can result in a delayed healing of soft tissues as well as nonunion of fractures (Kadakia et al., 2008). The duration of immobilization can last from 1 to 10 days for grade I and II ankle sprains and 3 to 6 weeks for grade TIT sprains. Tn case of fractures, immobilization can range from 4 to 8 weeks and dislocations need up to 8 weeks of immobilization (Birrer & O'Connor, 2004; Doughtie, 1999; Prentice, 2006). Prolonged immobilization of a joint results in decreased neurological activity, decreased voluntary muscle activation, loss of muscle strength, and reduction of muscle 2 & al., al., al., immobilization has been found to accelerate the recovery process, reduce muscle atrophy and joint & Vioreanu et al., 2007). Knowing that functional training enhances recovery, health care & & cross sectional area (Birrer O'Connor, 2004; Prentice, 2006; Stevens et a1., 2005; Thorn et a1., 2001; Vandenborne et a1., 1998). These studies included immobilization that ranged from 10 days to 8 weeks whereas research has not investigated whether the same effects occur after a short-term immobilization of 1 to 5 days, a time that reflects a clinically applicable timeframe for immobilization. Studies have compared functional training as an early treatment method during immobilization and found that early movement enhances recovery. Functional training, which includes early movement of the joint in comparison to complete immobilization stiffness, and provide an overall faster return to activity (Jones Amendola, 2007; a1., providers can use a shorter immobilization time in their treatment plans. An alternative option that could be applied during the time of immobilization is imagery. Imagery is widely used in sport psychology for performance enhancement and psychological skills training. Imagery is defined as a mental recreation of a task, which, in order to be most effective, should involve all five senses (Morris, Spittle, & Watt, 2005). In the rehabilitative setting, different types of imagery include soothing, healing, and motor imagery. Overall, imagery during rehabilitation is used less than during training and competition (Driediger, Hall, Callow, 2006; Sordoni, Hall, Forwell, 2000). Motor imagery is a type of imagery in which injured athletes imagine a sport specific movement or a rehabilitative skill. Motor imagery has a positive influence on the nervous system and uses similar pathways as motor execution. In one study, individuals 3 & & & tomography (PET), studies with brain damaged patients, functional MRIs, and transcranial magnetic stimulation. Results agreed that the same cortical pathways were used in imagery and movement. In fact, a case study showed that motor execution and imagery of thumb to finger opposition in a stroke patient used the same brain structures and progressed similarly throughout the recovery process (Nair et al., 2004). & performed & group underwent 10 sessions of guided imagery whereas the placebo group received who imagined a motor task exhibited an increase in heart rate and respiration (Oishi, Kasai, Maeshima, 2000). In other studies (Jeannerod Frak, 1999; Nair, Fuchs, Burkart, Steinberg, Kelso, 2005) the brain structures used during motor imagery were investigated and compared to actual movement. These studies included positron emission MRls, thumh aI., Motor imagery uses the same brain structures as motor execution; therefore, imagery can potentially be used to influence strength development of the muscle. According to Enoka (1988), initial strength gains have neurological origins that include but are not limited to increase in reflex potentiation, greater efficiency in neural recruitment patterns, enhanced motoneuron excitability, as well as increased central nervous system activation (Enoka, 1988; Mc Ardle, Katch, Katch, 2007). Yue and Cole (1992) investigated imagery and strength gain in which healthy individuals perfonned either imagery of maximal contraction of the fifth digit, actual isometric contractions, or neither for 4 weeks. Results of this study indicated that imagined contractions of and isometric contractions had a similar strength increase whereas participants who did neither had a significant decrease in strength (Yue Cole, 1992). Cupal and Brewer (2001) studied athletes who underwent ACL surgery. The treatment encouragement, attention, and support and the control group received no intervention. 4 group (0.63 +/- 0.13). play a & & forearm. Individuals who had their wrist immobilized, performed either mental rehearsals of wrist flexion and extension, or no intervention for 10 days. Results showed that performing mental rehearsal resulted in a lower strength loss of wrist extension (F (1, 15) = 17.25; /?<0.001) and flexion (F (1,15) =14.90; p< .02) as compared to the control group which did show a significant amount of strength loss in wrist flexion and extension H-reflex & Turker, al., easily elicited by stimulating the percutaneous nerve that innervates the muscle studied. Knee strength measured with a dynamometer (in foot pounds) was significantly greater in the imagery group (0.83+/- 0.11) compared to the control (0.66 +/- 0.14) and placebo As reported previously, immobilization decreases muscle strength and motoneuron excitability. Because motor imagery uses similar pathways to motor execution and can playa role in strength development, imagery could be used to prevent a decrease in motoneuron excitability during immobilization. There are mixed results on the effects of motor imagery during disuse and immobilization (Clark, Manini, Bolanowski, Ploutz-Snyder, 2006; Newsom, Knight, Balnave, 2003). Newsom and colleagues (2003), found a decrease in strength loss due to imagery in the immobilized p<1, IS) with immobilization. Measurements to study neurological changes due to imagery have included MRI's, PET scans, EMG measurements, and the Hoffmann reflex (H-reflex). The H­reflex is a widely used valid method to measure the monosynaptic connection between sensory and motoneurons (Misiaszek, 2003; Tucker, Tuncer, Tiirker, 2005). If a strict protocol is observed, the H-reflex can be used to study neuromuscular excitability, recruitment patterns, and changes (Misiaszek, 2003; Tucker et aI., 2005). The H-reflex is 5 the la Gandevia, 1997). When the H-reflex was studied in conjunction with different levels of imagery, results revealed that H-reflexes increased with imagery and with the level of colleagues (2008) supported these findings in their study on the effect of motor imagery on spinal excitability. H-wave amplitudes during motor imagery were increased in 2 5% on the H-reflex during a short time period has not been examined within the literature. of returning Because strength After stimulation, fhe ratio of the H-wave (representing the stimulation of sensory Ia afferent fibers) and M-wave (the directly activated maximal motor response) are compared pre and post treatment. The H-reflex is able to detect small changes in motoneurons excitability due to resistance training or during imagery (Aagaard et al., 2003; Cowley, Clark, & Ploutz-Snyder, 2008; Gandevia, 1997; Misiaszek, 2003). Motor imagery has been shown to have an immediate effect on motoneuron excitability. When motor imagery was conducted during testing, the H-reflex increased (Cowley et al., 2008; complexity of the movement imagined (Gandevia, 1997; Misiaszek, 2003). Cowley and comparison to the H-wave amplitudes at rest and after motor imagery. Imagery of a contraction at 100% also resulted in a greater H-wave amplitude than at 25% of their imagined effort. However, the influence of motor imagery's use as a rehabilitation tool Although a necessary and common treatment option for ankle injuries, immobilization of the joint, leads to several neurological changes. These neurological changes include but are not limited to muscular atrophy, reduction in cross-sectional area and strength loss, which slows down the process ofretuming to activity. Motor imagery uses the same pathways as motor execution. In addition, imagery has been found to enhance strength in the upper body and knee, as well as prevent strength decrease due to immobilization of the wrist. Becausc the nervous system is the initial source of strenbl1:h 6 in one study which investigated the upper extremity. To date, no study has been done to investigate the effect of short-term immobilization on the neurological system and whether imagery can be useful in preventing neurological changes over a short period in the lower extremity. Because immobilization of the lower extremity occurs frequently with injury, using motor imagery as a tool to prevent the negative changes that occur with immobilization would be useful, thus decreasing recovery time and enhancing return to activity. The purpose of this study was to examine whether motor imagery can help to decrease the neurological changes in immobilized muscles of the lower leg. This study also aimed to see whether motor imagery can provide such changes within a short and clinically applicable timeframe. gain during training, and motor imagery uses the same pathways, imagery may be able to maintain neurological function of the immobilized muscle. Perhaps the use of motor imagery can prevent the neurological changes associated with immobilization, which has been confirmed systcm bc uscful timeframe. Significance of Study Immobilization is necessary in rehabilitation however, negative effects such as joint stiffness, muscle atrophy, and decreased motoneuron excitability, occur as a result of its use. This study used a short-term immobilization period, thus examining whether these changes can be seen in a clinically applicable timeframe of less than 5 days after 72 and 96 hours of immobilization. This study also investigated whether motor imagery could be used to prevent any neurological adaptations that would result in a faster recovery and return to activity. Because early movement of the ankle has been shown to be effective in recovery of ankle 7 al., H-injuries, perhaps motor imagery could be used as a rehabilitative adjunct to speed up the process in the nonweight bearing phase by maintaining the neurological activity of the muscle. This study adds to the existing literature by examining if the impact of immobilization and imagery in the lower extremity is similar as in the upper extremity (Newsom et aI., 2003). In addition, this study investigates whether motor imagery conducted as a regular training tool has similar enhancing effects on the neurological activation seen in the upper extremity as measured by the H-reflex. Imagery is used frequently by athletes during performance and training, but less frequent during rehabilitation. This study provides data to health care providers to understand the impact imagery use can have on the recovery and healing process. This knowledge will be helpful to promote and encourage motor imagery use during rehabilitation and can potentially add another beneficial tool for health care professionals. Research Question The following research questions were addressed in this study: 1. Does 3 and 5 day immobilization of the ankle decrease motoneuron pool excitability of the soleus muscle in healthy college students? 2. Does motor imagery training influence neurological adaptations that occur in the muscle during short term immobilization? 3. What is the effect of motor imagery on motoneuron excitability after 3 days compared to 5 days of immobilization? 8 immobilization Hypotheses The following hypotheses were posed in this study: 1. Immobilization of the ankle will result in decreased motoneuron pool excitability in healthy college students after 3 and 5 days of immobilization with a greater decrease after 5 days. 2. The decrease in motoneuron pool excitability after 3 and 5 days of immobilization will be smaller in individuals performing motor imagery. 3. Motoneuron pool excitability changes with the use of motor imagery will be less at 5 days of immobilization compare to baseline and 3 days. Limitations The following limitations applied to this study: 1. This study evaluated healthy individuals instead of injured individuals, which limited the application of the results to an injured population because no tissue disruption has occurred and no healing is necessary. 2. This study was limited to participants from the University of Utah, which limited the ability to generalize the results to a broader population. 3. This study was limited in the ability to control whether the participants performed imagery correctly and whether participants fully complied with the immobilization protocol by not moving their foot during the intervention period. 4. This study involved physically active college students, therefore results might not be able to be generalized to the general population. 9 plantarflexion. given. fibers neurons & Delimitations The following delimitations applied to this study: 1. This study recruited participants from a narrow age range (18-30) and similar physical activity backgrounds in order to provide a homogeneous population. 2. The soleus muscle was studied in comparison to the gastrocnemius in order to eliminate influence from movements besides plantarflexion. Assumptions The following assumptions were the basis of conduct for this study: 1. Participants were expected to adhere to all the immobilization instructions gIven. 2. Participants were expected to perform the intervention correctly and as instructed. 3. Participants were expected to complete any questionnaires honestly and to their best ability. Definition of Terms H-reflex: A measurement tool to examine the monosynaptic connections between sensory fibers and motor ncurons by eliciting a stretch reflex through electrical stimulation (Misiaszek, 2003). Imagery: Mental recreation of an event or movement, using multiple senses in the absence of external stimuli (Weinberg Gould, 2007). 10 Immobilization: order to protect injured structures and promote healing (Kadakia et al., 2008). spindles activation & Motoneuron excitability: The extent to which motoneurons can be activated & & Participating more days a week or vigorous activity for 20 minutes on three or more days per week Immobili zation: Preventing movement of a joint with braces, splints, or tape in ct aI., Injury: An act that damages or hurts structures of the body (Prentice, 2006). Motoneuron: Neurons that originate from the spinal cord, innervate the muscle spi ndles and cause movement of the muscle after acti vation (Kandel, Schwartz, Jessell, 2000). ex tent motoneUTons (Kandel, Schwarts, Jessell, 2002). Motor imagery: Mental stimulation of voluntary motor actions by imagining an actual movement using all senses (Oishi Mashima, 2004). Physical activity: Parti cipating in moderate activity for 30 minutes on five or activi ty (Davis, 2007). excitability. H-reflex immobilization point Strength, Reflex Neurological Changes, and Summary of Literature Review. The Ankle Anatomy The ankle is comprised of the distal parts of the tibia and fibula in the lower leg. These two bones articulate with the superior portion of the talus making up what is termed the talocrural joint. The tibia articulates with the superior surface of the talus whereas the fibula attaches to the lateral side. The talus is positioned on the superior surface of the calcaneus, which serves as the insertion point for the plantarflexor muscles and is called the subtalar joint. The deltoid ligament, comprised of four ligaments, CHAPTER 2 LITERATURE REVIEW The purpose of the study was to investigate the effect of motor imagery on the neurological system during immobilization of the ankle. The H-reflex is a measure for muscle fiber recruitment and motoneuron pool exci tability. Thus changes in the H-rcflex during immobili zat ion with the use of imagery can poi nt to the influence of imagery on the nervous system. This literature review is organized as follows: The Ankle, Neurological Role in Muscle Stren!,>1h, Imagery, The H- Refl ex as a Measure of di stal tal us talofibular ligaments and the calcaneofibular ligament. Situated more proximal on the tibia and fibula are the anterior and posterior tibiofibular ligaments. Additionally, there is a connective tissue that runs between the tibia and fibula termed the syndesmosis (Starkey & Ryan, 2002). Function The talocrural joint of the ankle allows for movement in the sagittal plane, termed plantar flexion and dorsiflexion, which describes the extension and flexion of the foot. The subtalar joint allows for inversion and eversion of the foot which, is the inward and outward motion and often is the mechanism that leads to an injury. The muscles primarily involved in plantarflexion are the gastrocnemius and soleus. Other muscles contributing to this motion include the tibialis posterior, plantaris, peroneus longus and brevis, flexor digitorum longus, and flexor hallucis longus. However, we will focus on the primary plantarflexors of the talocrural joint in the ankle. The gastrocnemius consists of a medial and lateral head which merge to insert on the calcaneus via the achilles tendon. The lateral head originates from the lateral condyle of the femur, whereas the medial head originates at the medial condyle. The attachment to the femur makes the gastrocnemius a two-joint muscle. Therefore, the gastrocnemius is not only involved in the motion of the ankle but also assists in knee flexion. The soleus on the other hand, originates at the fibular head and the middle 1/3 of the tibia and inserts at the calcaneus together with the gastrocnemius (Hislop & Montogmery, 2002; Starkey & Ryan, 2002). The soleus shows continuous activity during symmetrical standing as well as higher levels of background muscle activity. During 12 the. flexor flexion. 13 strong contraction or fast development of tension, the soleus shows most activity in dorsiflexion, which is a lengthening contraction. The gastrocnemius, on the other hand, shows most activation during the plantarflexion phase. During the stance phase of walking, the soleus is activated earlier than the gastrocnemius (Tucker et al., 2005). Both muscles are innervated by the tibial nerve that originates from the sciatic nerve at the S1 and S2 level of the lower spine and which can be accessed superficially in the popliteal fossa (Hislop & Montgomery, 2002; Tucker et al., 2005). In order to isolate the soleus, the knee has to be slightly flexed, which will result in a 70 % decrease of gastrocnemius activity (Hislop & Montgomery, 2002; Starkey & Ryan, 2002). Immobilization of Ankle Injuries There are different injuries of the ankle including sprains, dislocations, and fractures of the lower leg and foot. The literature reveals that in order for faster and stronger healing to occur in the initial phases of the inflammation process, the injured ligaments should be held in a stable position (Prentice, 2006). Doughtie (1999) investigated the treatment of syndesmotic ankle sprains and reported that 70% of NFL Athletic Trainers use immobilization as a way of injury management. Especially after fractures and surgery, proper immobilization of the joint is important in order to maintain a stable position of the foot and ankle and to allow for soft tissue recovery (Kadakia et al., 2008; Raikin, Parks, Noll, & Schon, 2001). Kadakia et al. (2008) explained that immobilization was necessary to prevent nonunion between the fractured sites, which could occur due to macro and micro movement of the joint. thc aI., S 1 aI., aI., aI. 14 The amount, time, and degree of immobilization depend on the type and severity of the injury. According to the recent literature and primary textbooks used for orthopedic injury by Birrer and O'Connor (2004) and Prentice (2006) inversion ankle sprains, which injure the anterior talofibular, posterior talofibular, and calcaneofibular ligaments are the most common injury in the body and require non-weight-bearing activities for one to two days for a grade one sprain, 2 to 10 days for a grade two, and 3 to 6 weeks for a grade three sprain. After the non weight bearing phase, protective immobilization with increased weight bearing is recommended for a timeframe between 2 and 6 weeks. The same times are required for eversion sprains of the medial ankle ligaments. Another common injury is the high ankle sprain or syndesmotic sprain which occurs at the syndesmosis between the fibula and tibia. Immobilization times are longer than for inversion or eversion ankle sprains. Immobilization time can be 3 to 6 weeks, for a grade two injury or after surgical procedure of a grade three injury (Birrer & O'Connor, 2004). case of fractures of either the tibia or fibula, immobilization of 4 to 8 weeks is required in a walking cast (Birrer & O' Connor, 2004) and ankle dislocations need an immobilization of 6 to 8 weeks (Prentice, 2006). Therefore, according to the literature, many if not all injuries sustained at the ankle joint require various periods of immobilization. Types of Ankle Immobilization There are different ways to provide immobilization and support to the ankle after injury. One immobilization technique is with a cast that is manufactured around the joint amount: O'Connor, In 0' by the physician. Common materials used for casts are plaster and fiberglass. Another method of immobilization of the ankle is using walking boots and braces. Among the commonly used braces are rigid and semirigid braces (Raikin et al., 2001; Van Durme & Gravlee, 2007). Semirigid braces provide less stability and include lace up braces or stirrup braces. Stirrup braces are braces that align with the sides of the leg and prevent inversion and eversion of the ankle. In comparison with other braces, stirrup braces are the most efficient in preventing these motions (Raikin et al., 2001). Rigid braces do not allow for any motion and use a hard shell, which immobilizes the whole foot and lower leg. The differences among rigid braces lie in the inner lining of the boot. Pneumatic walkers and also foam walkers have medial and lateral pneumatic air chambers that provide stability that adapts to the shape of the joint. In addition to air filled champers on the sides, the pneumatic boot also has chambers anteriorly and posteriorly, thus providing a complete enclosure of the ankle and preventing motion in all directions (Kadakia et al., 2008; Raikin et al., 2001). The traditional method has been to put the injured ankle into a cast, however, recently walking boots have been used to provide immobilization, the advantage of the walking boot being that they can be easily removed for functional training or adapted to changes in muscle size and edema reduction (Kadakia et al., 2008; Kadil, Segal, Orendrurff, Shofer, & Sangeorzan, 2004). The question that has been posed in the literature is whether casts or boots provide better immobilization. Kadil et al. (2004) investigated the EMG activity of the gastrocnemius, soleus, and the peroneal muscles while participants were walking barefoot, wearing a cast, or wearing a boot. Results revealed that the immobilization boot had significantly less muscle activity in all muscles 15 aI., ct aI., aI., aI., aI., 16 than barefoot walking. The cast provided a significant reduction in the soleus and the peroneals but not the gastrocnemius. This leads to the suggestion that boots provide better prevention of gastrocnemius movement than casts. There was no statistical significance between the boot and cast in the soleus and the peroneals. The authors concluded that walking boots can be as effective as casts as an immobilization device. Kadakia et al. (2008) compared sagittal plane stability between fiberglass casts and four types of boots (Aircast FP Foam Walker, Aircast XP Pneumatic Walker, Aircast SP walker and Donjoy Max Trax Walker). Specifically, they examined how many degrees of dorsiflexion and plantarflexion these devices allowed. By using radiographic imaging and comparing the results to a baseline of motion without immobilization. Results revealed that the cast provided the least mean amount of range of motion (8.4 degrees) than any of the boots. The authors noted that this can change as soon as the muscle atrophies and edema is reduced, which leaves more space between the cast and the joint. Among the boots, the Aircast SP walker allowed significantly greater range of motion (39 degrees) than any of the other boots. No significant difference was noted between the remaining boots, all of them ranged between 16 and 19 degrees of range of motion. The authors concluded that although the cast provided strongest prevention of movement, taking the change of muscle size and reduction of edema into consideration, a boot such as the FP Foam Walker or Pneumatic Walker could effectively immobilize the ankle. Other researchers (Raikin et al., 2001) have shown that the pneumatic boot also showed the best resistance against plantarflexion and dorsiflexion when compared with other bracing devices besides casting. An advantage of using a boot is the ability to take it off for wound cleaning and functional training and to adjust the tightness of the walkIng. aI. aI., thc immobilization (Kadakia et al., 2008; Raikin et al., 2001). Summarizing the literature, one can suggest that although casts provide immobilization, boots are also beneficial in providing prevention of movement if adjusted and worn properly. Immobilization Versus Early Mobilization Although immobilization is part of the treatment plan of ankle injuries, there are some undesired effects of immobilization. Prolonged use of immobilization can lead to joint stiffness, chronic pain, and weakness of the joint (Gravlee & Van Durme, 2007; Thorn et al., 2001; Vandenborne et al., 1998). Thorn, et al. (2001) investigated the effects of 10- day immobilization on the quadriceps. Eight individuals received lower limb cast immobilization for 10 days and muscle biopsies were analyzed for sarcoplasmic reticulum (SR) Ca regulation as well as the quadriceps cross sectional area and one repetition maximum leg extension strength. Results revealed a decrease in SR Ca uptake rate. Muscle strength and cross sectional area of the muscle fibers decreased 11.8 % and 4.6 %, respectively. Additionally, immobilization has been found to decrease voluntary muscle activation, cross section and peak torque of plantarflexion muscles (Stevens et al., 2005). In this study, nine subjects who received surgical treatment of malleolar fractures were immobilized for 7 weeks and received rehabilitation for up to 10 weeks. Measurements of voluntary muscle activation, maximal cross-sectional area, and peak torque were obtained after immobilization and throughout the rehabilitation stages. All 3 factors were significantly decreased after the 7-week immobilization period. Muscle activation was aI., aI., 17 etfects aI., aI., ai. ci 2 ct aI., also found to be the significant contributor of strength gain during rehabilitation during the first 5 weeks of rehabilitation (Stevens et al., 2005). A case report by Vandenborne et al. (1998), investigated the metabolic, morphologic, neurologic and functional adaptations in the plantarflexors of one participant during eight weeks of immobilization and throughout the rehabilitation stages. These variables were tested, using a variety of measurements including magnetic resonance imaging (MRI), spectroscopy, isokinetic and isometric muscle testing, and functional tests. MRI images showed a significant atrophy of the triceps surae group. The highest rate of atrophy occurred in the lateral gastrocnemius within the first 2 weeks of immobilization. During isometric and isokinetic testing, the involved and uninvolved leg were compared in the rehabilitation phase but overall showed more resistance to fatigue than the uninvolved leg. The involved leg showed a 50% deficit in plantarflexion strength during the first week after immobilization. Other results included an increase of functional performance throughout rehabilitation with most improvement in walking occurring within the first 5 weeks of rehabilitation (Vandenborne et al.,1998). Summarizing the previously discussed studies one can conclude that immobilization leads to muscle atrophy, decreased physiological and neurologial activity, and ultimately strength loss. Another common finding of these studies is that these changes occur within the early stages of immobilization but it is unknown whether changes can be seen within the first few days of immobilization. In a review of literature, Jones and Amendola (2007) investigated differences in outcomes (return to activity, subjective instability and reinjury) between immobilization and functional treatments of lateral ankle sprains. Functional training refers to early ofrehabi1itation a1., 18 a1. p1antarflexors 1atcra1 p1antarflexion a1., neuro10gia1 ofliterature, rcfers 19 movement of the foot such as range of motion exercises. The results of this review revealed that 4 out of 5 studies showed a shorter return to activity for participants undergoing functional treatment. 2 out of 5 studies showed more complaints of subjective instability with functional treatment and five of six studies reported less re-injuries occurring in the functional treatment groups. Although these studies varied in the type and time of treatment interventions, this review demonstrates that functional training accelerates the recovery process and provides prevention of reinjury. Vioreanu and colleagues (2007) also studied the difference between immobilization and functional treatment. In this study, participants who underwent surgery after an ankle fracture were put in 2 groups. Both groups were immobilized; one group was immobilized in a non-weight-bearing below the knee cast and the other group received early mobilization in a removable custom made fiberglass cast, which was also non-weight-b earing. The early mobilization group was doing exercises 3 times a day for 10 minutes. These exercises consisted of different range of motion exercises. In the mobilization group, there was significantly less calf atrophy. Additionally, range of motion and function were significantly improved. The mobilization group also revealed a shorter time to return to activity. These results support the use of early mobilization. The literature agrees that although immobilization of the joint is essential in the initial stages of healing, early mobilization decreases the negative effects that prolonged immobilization brings. These negative effects can include but are not limited to stiffness, muscle atrophy, circulatory constrictions, and slower return to activity (Birrer & O'Connor, 2004; Hunter, 1994; Jones & Amendola, 2007; Prentice, 2006; Thorn et al., 2001; Vioreanu et al., 2007). According to Hunter (1994), limited stress on the protected bearing. arc stiffness, ankle can promote healing and helps in proper realignment of collagen as well as reduce the unwanted effects of immobilization. Summary Injuries to the ankle joint are common and treatment includes immobilization in order to provide protection and promote healing. Immobilization times range from several days until up to 6 weeks depending on the type and severity of injury. There are a variety of devices that can be used with rehabilitation. These immobilization devices include casts, rigid and functional braces, and splints all of which prevent movement of the foot. Despite the necessity of immobilizing researchers agree that early mobilization of the injured joint reduces unwanted effects of immobilization such as muscle atrophy, joint stiffness, circulatory restrictions, and slower return to activity. Neurological Role in Muscle Strength a- motoneurons can be activated. One way is through the spinal cord, for example in a spinal reflex. The motor neuron reacts involuntarily to a sensory signal sent through the spinal cord from a sensory neuron such as proprioceptors. Another way to elicit a neurological reaction is through the brain in which the brain sends a message to the 20 'Physiology of Muscle One must understand the interaction between the neurological and motor system and its contribution to strength gain. Each muscle fiber is innervated by an u- motor neuron, which stems from a nerve originating in the spinal cord. Muscle contraction is the result of neurological impulses on the motor fibers. There are two ways by which motoncurons system to move and thus activates the motoneuron to produce a voluntary motion (Mc Ardle et al., 2007). Nervous System and Strength Gain In his review, Enoka (1988) discussed the role of the nervous system in strength gain and stated that strength gain is initially due to neurological adaptations. As an example, the author described electromyostimulation sessions in which participants underwent electromyostimulation and achieved strength gain. The time of treatment was less than five weeks, which is considered too short to gain morphological changes such as gain in muscle size. Also when compared, participants who trained using electromyostimulation, needed a lower intensity (33% of maximal strength) to achieve the same strength gain as those who did isometric training (who needed 78% of their maximal strength). These findings support that stimulation of the nerves increased strength, which points to the importance of the neurological system in strength gain and motoneuron recruitment. Another fact that underlines the impact of the nervous system on strength gain is the phenomenon of cross training. Enoka (1988) discussed that several studies revealed that training one limb resulted in strength gain of the contralateral limb. No changes in the muscle fibers or enzymes of the contralateral limb could be detected; therefore, the author suggested that the reason for this strength gain lies in neurological adaptations between the limbs. With training, there is a significant increase in strength which is disproportional to the increase of muscle size (Enoka, 1988; McArdle et al., 2007). This increase in strength aI., 21 aI., 22 was 90% due to neural factors during the first 2 weeks of resistance training. Neural factors influence strength for 40-50% for the next 2 weeks. After 2 weeks muscular changes are increasingly the factors that influence strength gain (McArdle et al., 2007). Neural adaptations have been found to be the reason for the increase in muscular strength. These adaptations include a greater efficiency in neural recruitment patterns, increased motoneuron excitability, increased central nervous system activation, and a lowering of neural inhibitory reflexes (McArdle et al., 2007). According to Enoka (1988), evidence for the existence of neural adaptations during strength training is found with electromyography (EMG) measurements. Integrated EMG's (IEMG) measures the composite sum of all muscle fiber action potentials within the volume of the recording electrode. Motor unit recruitment and firing frequency can be obtained with IEMG measurements (Aagaard, 2003; Enoka, 1988). Sale (1982) reported that although most studies showed an increase in IEMG after the first 3 weeks of training one study, which examined a training regime of 24 weeks, produced IEMG changes only after 12 weeks whereas changes in hypertrophy were present earlier. A study by Narici et al., (1996) investigated hypertrophy, cross sectional area, torque, and neural activation (IEMG) of the quadriceps muscle during a 6-month training. The authors found that each variable besides the IEMG increased, leading to the conclusion that physical training induces changes in the muscular architecture instead of the nervous system. However, measurements were taken at baseline and after 2, 4, and 6 months. This implies that neurological changes that are prevalent during the initial phases of strength training were not examined and could have been missed in the recording. aI., aI., firing aI., 23 a study by Aagaard (2003), neurological adaptations due to resistance training were investigated using the H-reflex and V- wave as a measure. Although the H-reflex reflects the activation of the sensory afferent fibers, the V-wave represents the efferent neural drive from the motoneurons. Both measures increased after a 14-week resistance training program. The H-reflex amplitude increased 20% while the V-wave increased to 50% comparing values before and after training. Results obtained while at rest did not produce any changes. These results suggest that neurological changes occur with resistance training. Another neurological factor that plays a role in strength gain is reflex potentiation. Reflex potentiation is the degree to which certain reflex EMG responses are activated by maximal voluntary contractions. In order to obtain these results, supramaximal nerve stimulations are compared at rest and during voluntary contractions (Sale, 1982). Sale (1982) described studies that revealed that the degree of motor unit activation through voluntary contraction correlated with the degree of reflex potentiation. Specifically, patients with upper motor neural lesions had decreased reflex potentiation whereas weight lifters and sprinters showed an increase. H-reflex studies, which are used to measure neurological activation of the spinal nerves, demonstrated that there is increased neurological activity during contraction compared to rest. Reflex potentiation, H-reflex, and the V-wave were recorded to be higher with contractions (Aaagard, 2003; Enoka, 1988). In V -efferent H -V -24 Summary Sale (1982) stated that "adaptations in the CNS plays an important role at the start and in the very early portion of the training career" (p. 133). The author continued in stating that following neurological adaptations, muscular changes are the main factors in strength gain (Sale, 1982). This review supports the idea that initial strength gain is mostly influenced by enhancements of the nervous system that leads one to believe that training the nervous system could help to enhance muscular strength or potentially limit the amount of atrophy present. Imagery Definition Mental imagery practice has been described as the mental recreation of an event or movement, using multiple senses in the absence of external stimuli (Morris et al., 2005; Weinberg & Gould, 2007). The main uses of imagery in sport psychology are performance enhancement and motivation. For injury purposes the areas for the use of imagery are: healing, soothing, pain management, and injury prevention (Driediger et al., 2005). Imagery Use by Athletes Athletes have been using imagery for a long time and most of its use and research has been conducted in the area of performance enhancement (Evans, Hare, & Mullen, 2006). In the context of injury rehabilitation, motivational imagery is used for goal setting, pain relief, and to foster a positive attitude whereas cognitive imagery is useful to eNS ofthe ai., ai., learn proper rehabilitation techniques but also to remain in the sport by imagining sports movements (Driediger et al., 2005; Martin et al., 1999). Sordoni et al., (2000) examined the use of imagery during rehabilitation in injured athletes. Seventy-one athletes, competing in different sports and levels completed a self-report survey about the extent of injury, the Athletic Injury Imagery questionnaire (AIIQ), and a survey about the athlete's previous use of imagery in their sport. The AIIQ represented questions regarding the nature of imagery (cognitive or motivational) injured athletes were using during rehabilitation. In this study, athletes reported to be using motivational imagery more than cognitive imagery. Overall they reported less overall imagery use during rehabilitation in comparison with use during regular training. Those who used imagery in rehabilitation before were more likely to use it again. The authors concluded that although imagery during rehabilitation served the same purposes as during training and competition, athletes generally failed to use imagery skills in the rehabilitative setting. More recently, Driediger, Hall, and Callow (2006) interviewed 10 injured athletes, undergoing physiotherapy regarding their use of imagery during injury rehabilitation. Results were similar to those reported above, that injured athletes used motivational imagery the most. This method of imagery would include imagining being back in the sport, getting ready for rehabilitation sessions, maintain focus, and increasing self-efficacy of being able to complete the session as well as being able to return to the sport. Cognitive imagery was also reported as being used, mostly in rehabilitation skill acquisition and rehearsal of movements. Lastly, healing imagery and pain management was employed by injured athletes in which they imagined the healing process or to distract themselves from the pain by imagining a place where the athlete is not in pain. 25 Oriediger aI., aI., aI., AlIQ), thc Oriediger, bcing 26 The types of imagery used were visual, auditory, kinesthetic, imagery of past events, and of the athlete's health. Kinesthetic imagery, which involves feeling, was reported to be used the most. This study extended and supported the Sordoni et al., (2000) study by investigating the types of imagery used. The authors of this study also mentioned that overall use of imagery in injury rehabilitation is less than during other contexts although the imagery skill is available in athletes. Both studies point out that it is the role of the health care provider to encourage and facilitate the use of imagery during rehabilitation because the athlete might not be aware that the same skills can be used in rehabilitation as they are in training and competition (Dreidiger et al.; Sordoni et al.). Theories of Imagery Many theories are available to explain how imagery affects motivation, performance, and learning. In order to provide a possible explanation of the link between imagery and muscle activity, this review will focus on two major theories that contain a physiological component. One theory is the bioinformational theory of imagery, which was originally proposed by Lang (1977). According to this theory, imagery involves the activation of information that is stored in long-term memory. This information can be stored in two categories: stimulus characteristics and behavioral responses. Stimulus information includes characteristics of the imagined situation (e.g., touch, smell, sound) and behavioral responses include physiological and behavior changes (e.g., heart rate, EMG). According to this theory the imagery script has to describe situations in which physiological changes occur, the imagined action has to directly include physiological changes, the imagers have to have adequate imagery ability and experience with the bioinfonnational 27 imagined activity (Hecker & Kaczor, 1988; Weinberg & Gould, 2007). Hecker and Kaczor (1988) conducted a study to investigate the role of personal experience in the activation of the response. Participants were asked to imagine four scenes which varied in extent of significance to athletic experience; they ranged from neutral, over action, athletic anxiety to fear. The participant's heart rate was recorded and they filled out information about their imagery vividness for each scene. The results revealed that imagery of familiar events, in this case action and athletic anxiety, induced the greatest increase in heart rate and were described as most vivid. These results support that personal experience with the imagined activity plays a significant role in the physiological changes that occur thus supporting the bioinformational model that imagery is based on stimulation of events and responses stored in long-term memory. Another widely discussed theory of imagery is the psychoneuromuscular theory. Originally stated as the "ideo-motor principle" by Carpenter, this theory suggests that images in the brain produce minute activations of the nerves in the muscles, those innervations being the same as used in actual movement (Hale, 1982). Hale (1982) investigated this theory and found that participants who used internal imagery (imagining the movement) of a biceps curl produced a higher EMG activation in the biceps muscle than those who used external imagery (visualizing what it looks like to a dumbbell). This study supports findings of Jacobsen's study in 1931 in which action potentials of the biceps brachii and the ocular muscles were compared with internal and external imagery and similar results were found including a higher response in the ocular muscles during external imagery (Hale, 1982; Jowdy & Harris, 1990). lift J acobscn' s 28 Motor Imagery and Effect on Autonomic and Nervous System In this study motor imagery, which is the imagining of performing a specific movement, was used. Motor imagery has been defined as "a mental stimulation of voluntary motor actions" (Oishi & Maeshima, 2004, p. 255), which has been used as a training and rehabilitation method. This type of imagery requires imagining the actual movement and involves all senses-thus belonging to the kinesthetic type of imagery (Oishi & Maeshima, 2004). Motor imagery has been studied as a rehabilitation tool for recovery after stroke. A major finding of this study was that imagery uses similar pathways as motor execution (Jeannerod & Frak, 1999; Johnson-Frey, 2004; Nair et al., 2005, Oishi, Kasai, & Maeshima, 2000). Oishi et al., (2000) studied the effects of motor imagery on the autonomic response including heart rate, skin resistance, and respirations. An imagined motor task (speed skating) was performed and compared to a mental arithmetic task. Although both mental tasks showed an effect on the autonomic system, the increase in heart rate of the motor imagining was significantly greater during the imagining task than during the arithmetic task. More experienced speed skaters showed larger changes in these autonomic responses and their imagery was described as more vivid, more internal and it had a better correlation of their actual speed (Oishi & Maeshima, 2004). These results lead to the conclusion that imagery follows similar pathways as it does during motor execution. Jeannerod and Frak (1999) reported on the similarity between imagined and executed action and found that across the literature, motor imagery has been found to & aI., aI., follow similar pathways on the brain as does motor execution. Experiments using positron emission tomography (PET) demonstrated that during mental imagery the same brain structures are used as in movement. The authors reported that patients who suffered from cortical degeneration were still able to produce motor imagery tasks but the simulated movement was slowed down to the same extent as was the actual performed movement supporting the finding that imagery stimulates brain regions used in movement. A question that is being investigated is to what degree imagery stimulates the motor pathways, especially the primary motor cortex. According to Jeannerod and Frak (1999), Functional MRI's (FMRI) consistently showed activation of the motor pathways during imagery and muscular movement. Using transcranial magnetic stimulation (TMS), which measures the excitability of the cortico-spinal structures of the motor cortex, motor evoked potentials were increased in those muscles that were involved in the imagined motor task. Those changes in excitability could only be seen during motor imagery, compared to visual imagery. These results point to the influence motor imagery has in the motor cortex (Jeannerod & Frak, 1999). Summarizing these studies one can say that imagery has not only an effect on the autonomic system but also uses the same pathways and brain structures as used during motor execution. This leads to the suggestion that imagery can influence the nervous system and motor activation as much as can actual movement of the muscle. 29 usmg suffered corti co-30 Imagery and Strength Previously discussed literature has revealed that imagery activates physiological responses such as heart rate, EMG, and action potentials. The question that is posed next is whether those activations influence the body enough to lead to strength gains. In a study done by Yue and Cole (1992), 30 individuals performed either imagery of maximal contraction of the fifth digit, actual isometric contractions, or neither for 4 weeks. Results of this study indicated that imagined contractions and isometric contractions showed similar strength increases whereas participants who did neither had a significant decrease in strength. Cupal and Brewer (2001), measured knee strength, re-injury anxiety, and pain in 30 competitive and recreational athletes who underwent anterior cruciate ligament (ACL) surgery and completed physical therapy along with an intervention. The participants of the treatment group were given relaxation and imagery instructions. The imagery included re-experience of the surgery, facilitation of range of motion, reduction of edema, foreign tissue acceptance, strength gain, reducing anxiety, achieving peak performance, and increasing confidence in the replaced ligament. The results of the treatment group were compared with the placebo (physical therapy and quiet sitting with visualization of a peaceful place) and control group (no treatment or attention support along with physical therapy). The treatment sessions were conducted by a clinician for 30-40 minutes every 2 weeks and participants of these groups were asked to listen to an audiotape daily, which included the treatment intervention. Overall the participants received 10 instructional sessions over an approximately 24-week time span. The variables of knee strength, re­injury anxiety, and pain were assessed before and after intervention. Results revealed that Vue ~1fOUp trcatment 31 re-injury anxiety and pain in the treatment group was significantly reduced in comparison to the other groups. Knee strength, measured with a Cybex 6000 isometric dynamometer showed that the participants in the imagery group produced significantly greater knee strength than those in the placebo and control groups. This study reinforces that imagery can have an effect on muscle strength gain. Only limited research has been done on the effect of imagery on reducing effects of immobilization. Clark and colleagues (2005) did not find a significant difference in the use of imagery versus a control group on the H-reflex following a 4-week lower body limb suspension. Imagery in this study was only conducted 4 times a week which may be not enough to achieve an effect on motoneurons excitability. Imagery has been found to reduce strength loss that occurs due to immobilization of the upper limb. Newsom, Knight, and Balnave (2003) immobilized the forearms of 18 individuals. The experimental group underwent 5-minute imagery sessions in which they imagined squeezing a rubber ball whereas the control group received no intervention. Although the control group experienced a significant loss in wrist flexion, extension and grip strength, the experimental group revealed no significant change which leads to the suggestion that imagery can be used to prevent strength loss associated with immobilization. Imagery can have an effect on the strength development of muscles. To summarize the results of these studies suggests that imagery can influence strength gain during training and rehabilitation reduces strength loss during immobilization. 32 Summary Imagery is a widely used tool in sport psychology to enhance performance, learn techniques, and increase motivation. In rehabilitation, imagery is used to increase confidence, to remain connected to the sport, and to rehearse rehabilitative techniques. Overall athletes use imagery more in performance than the rehabilitative setting. During motor imagery, the performance of an actual movement is imagined. The effectiveness of motor imagery can be explained using the bioinformational theory or the psychoneuromuscular theory. Both imply that imagery affects and is affected by the cortical and nervous structures of the body, thus implying that imagery can have an influence on these structures. Motor imagery has been found to increase autonomic responses such as heart rate. Studies of the brain also revealed the activation of similar brain structures during imagery and the actual performance of the movement. Imagery has been found to show similar strength increases as isometric contractions. In addition, imagery has had an effect of reducing strength loss during immobilization of the upper extremity. No study has been found that investigated imagery and strength loss in the immobilized lower extremity. These results are leading to the suggestion that motor imagery can have an impact on the motor system and that imagery can be used to reduce the amount of strength loss due to immobilization. The H-reflex as a Measure of Neurological Changes The Hoffmann Reflex (H-reflex) is commonly used to measure the monosynaptic connections between sensory fibers and motor neurons. This is done by eliciting a stretch reflex through direct stimulation of sensory muscle fibers also called la afferent fibers Ia 33 (Kandel, Schwartz, & Jessel, 2000; Misiaszek, 2003; Tucker et al., 2005). Stretch reflexes are initiated with the lengthening of a muscle, which stimulates la afferent fibers. These sensory fibers connect in the spinal cord with two types of motor neurons: alpha motor neurons, which innervate the same muscle, and motor neurons that innervate other muscles that assist in the movement. Activation of these motor neurons leads to contraction of the lengthened muscle. At the same time, la afferents connect to inhibitory interneurons that connect to the motor neuron of the antagonist muscle thus leading to an inhibition and relaxation of this muscle. The H-reflex directly stimulates the la fibers and records the reflex response of the alpha motor neurons (Kandel, Schwartz, & Jesssel, 2000; Misiaszek, 2003; Tucker et al., 2005). H-reflex measurements include the assessment of the motor response by EMG by relating the directly activated motor response (M-wave) to the motor response activated through stimulation of the sensory neurons (H-wave). The M-wave activates the motor axons directly and measures direct motor nerve stimulation and maximal motor response. The H-wave measures the stimulation of the muscle through sensory afferent la fibers which, after stimulation, send the signal through the spinal cord before a motor response is elicited (Tucker et al., 2005). Afferent la fibers have a larger diameter and a lower threshold for activation thus, are stimulated earlier than the motor fibers. Therefore, resulting muscle activity of the H-wave is visible at stimuli that have less intensity. With an increase in the stimulus the M-wave occurs before the H-wave because of the direct stimulation of the motor neurons. Also, the M-wave continues to grow whereas the H-wave declines with increases in stimulus intensity (Kandel et al., 2000; Tucker et al., 2005). During testing, the nerve is &: Ia ofthe Ia Ia ofthe Ia Ia H­wave M­wave 34 stimulated at a constant rate, increasing the intensity in small increments. H-wave and M-wave amplitudes, peak values are recorded and the ratio between the maximal H-wave and M-wave are calculated. The M-wave provides information about the amount of total muscle activation of motoneurons available to be elicited and should be assessed with every trial (Tucker et al., 2005). Several factors have to be considered before using the H-reflex as a tool in research. Misiaszek (2003) lays out the assumptions that can influence the use of the H-reflex. The first assumption is that the H-reflex solely arises from the afferent la fibers of the muscle that connects to the motoneuron. Instead, there are connections outside the monosynaptic connection between the la afferent fiber and the motoneurons that contribute to the reflex response especially in the later phases of the H-reflex. Evidence of oligosynaptic pathways from la afferents to the muscle has been established in humans and animals. Moreover, Misiaszek (2003) mentioned that along with stimulation of the la afferents and motor neurons, other neurons can be stimulated as well such as smaller lb diameter afferents, which connect to Golgi tendon organs, cutaneous afferents, or muscle spindle afferents all of which could potentially contribute or disrupt the H-reflex recordings. Tucker et al. (2005) pointed out that when a mixed nerve, such as the tibial nerve, is stimulated with a high enough intensity, two types of action potentials are evoked in both la afferent and motor axons. Potentials from the motor nerve that travel orthodromically produce the M-wave and those from the la afferent nerve produce the H-wave. At the same time, antidromic action potentials are elicited which propagate in the opposite direction, toward the motoneurons in the motor nerve and the test muscle in la M­wave infonnation ofmotoneurons aI., H­reflex. Ia Ia Ia Ia Ib aI. Ia Ia H­wave. Ia 35 afferents. In the la afferents this does not affect measurements but in the motor nerve the antidromic motor action potential travels opposite the incoming orthodromic potential from the la afferent nerve, leading to a collision between the la afferent orthodromic volley and the motor nerve antidromic volley. This collision results in significant reduction of the H-reflex magnitude (Kandel et al., 2000; Tucker et al., 2005). According to Misiaszek (2003), one of the most troubling assumptions is that the H-reflex measures the excitability of the motor neuron pool. The author stated that the amplitude of the H-reflex depends on the amount of neurotransmitters that are released from the la afferent terminals and this release is affected by presynaptic inhibition and postsynaptic depression. Presynaptic inhibition occurs with activation of distant afferents such as changing the posture, contracting the muscle as well as passive motion of the contralateral leg, during testing. Other sources of presynaptic inhibition can arise from descending supraspinal structure such as the brainstem. Misiaszek (2003) reported a study that stimulated the brainstem of paralyzed cats and thus evoked a monosynaptic reflex. In humans H- reflexes were smaller following sudden whole body tilts. Individuals who were mentally rehearsing or observing a movement were shown to have decreased H-reflex amplitudes (Misiaszek, 2003; Oishi & Maeshima, 2000). These changes were not able to be explained by changes in background EMG but were contributed to presynaptic inhibition (Misiaszek, 2003). Misiaszek (2003) concluded that movement of the body as well as activation of the brain that includes movement during testing plays a role in presynaptic inhibition and may contribute to variations in H-reflex amplitudes. Knowing that mere thoughts of measurcments Ia afferents 36 movements influence H-reflex results is a reason why we assumed that imagery can influence sensory neuron activity. According to Misiaszek (2003), post-activation depression results from a decreased release of neurotransmitters from synaptic terminals that have been activated before. Any pre-activation of la afferents can therefore lead to a decrease in neurotransmitter ejection resulting in depletion of neurotransmitter storage. With H-reflex testing this pattern has been observed with subsequent H-reflexes being smaller than preceding amplitudes and lasts about 8 seconds. This happens especially during movements that change the length of the muscle. By this the stretch receptors are stimulated, which in turn activates the la afferent fibers whose activation then leads to post-activation depression and a diminished H-reflex. Although not completely eliminating the effects of post-activation depression, a method to reduce activation of the stretch reflex is to brace the joints that the muscle crosses. Besides these factors, other influences of the H-reflex are background EMG activity of the muscle, and variations of intrinsic properties of the muscle such as changes of the muscle properties due to training and position of the muscle and joint tested (Misiaszek, 2003; Tucker et al., 2005). After taking these limitations into consideration when designing a research study, the H-reflex becomes a useful tool to study the role neurology plays in movement. Misiaszek (2003) reported that the H-reflex can be used to study and describe neural connections and changes in motoneuron excitability. Knowing the role that presynaptic inhibition plays in the H-reflex, studying the H-reflex can be used to assess the amount and function of presynaptic inhibition. The H-reflex can also be used to monitor motoneuron excitability. If the H-reflex remains constant between 2 conditions, the decrcased Ia tum aI., 37 excitability of the motoneuron pool is constant as well. The most important use of the H-reflex in regards to this study is its use for investigation of adaptations of spinal structures. These adaptations can occur due to training, injury, or disease or due to therapeutic interventions. H-reflex has been reported to increase during motor imagery emphasizing the notion that imagery can be used to decrease the effects of immobilization on motoneuron excitability (Cowley et al., 2008; Gandevia, 1997). An example of such use is the study conducted by Gandevia (1997) in which 6 participants were asked to either relax, or mentally practice a range of simple to complex activities of their wrists while muscle spindle activity, EMG, and H-reflexes were recorded. The imagined movements included weak flexion and extension of the wrist, flexion and extension at increasing speed and strength, and the third mental activity was to imagine performing complicated movements such as handwriting, backward handwriting, or threading a needle. H-reflexes of the wrist flexors or extensors were elicited, stimulating the median or radial nerve and H-reflex amplitude was analyzed for the mental rehearsal activity. The resting condition was compared to the imagery condition. Results of this study revealed that the amplitude of H-reflexes increased with imagined motor activities. With increase of complexity of the imagined task, the H-reflex amplitude increased. Background EMG increased as well during imagined contractions. H-reflexes in 7 out of 10 participants could be elicited and analyzed. When increases in H-reflex amplitude were compared with increase of background EMG a tendency could be seen in which background EMG and H-reflexes increase at a similar rate during mental imagery. Compared with weak contractions of the muscle, the increase of H-reflex amplitude was small but still significant. The presence of rriotoneuron H­reflex ofH-H -38 increased H-reflexes with mental imagery implies that mental rehearsal of a movement can activate the afferent pathways of the spinal reflex and thus influence muscle activation. Summary The H-reflex is a monosynaptic reflex that is elicited through electrical stimulation of a percutaneous nerve. The H-reflex is an easy to use measurement that is commonly used in research studies. After stimulation of the nerve, the ratio of the maximal H-wave and the maximal M-wave, representing the motor excitability, is taken and compared from pre to posttreatment. Although commonly used, the H-reflex measurements have to be interpreted with caution bearing in mind that other factors such as presynaptic inhibition and post activation depression play a role in changes of the H-reflex. Nevertheless, if followed by a restricted and well-observed protocol, the H-reflex can be used to study adaptations to the spinal structure due to training or therapeutic interventions such as imagery. Summary of Literature Review The reviewed literature reveals that immobilization of the injured ankle is necessary but effects the joint negatively including strength loss, muscle atrophy, and joint stiffness (Birrer & Cooper, 2004; Hunter, 2004; Jones & Amendola, 2007; Prentice, 2006; Vioreanu et al., 2007). The review also showed that strength is initially gained through neurological adaptations (Enoka, 1988). Motor imagery has a stimulating effect on the autonomic and nervous system. Imagery has been found to increase strength gain (Cupal rcflex playa Imagery. stiffness aI., 39 & Brewer, 2001; Yue & Cole, 1992). Another study revealed that imagery decreased strength loss in the immobilized arm (Newson et al., 2003). No study has been found to investigate whether these effects can be seen in the immobilized lower extremity as well. Lower leg injuries require immobilization. There have been studies using the H-reflex as a measure for neurological changes due to imagery (Clark et al., 2006; Gandevia, 1997; Oishi, 2000). If used properly, the H-reflex has been established as a valid measurement of muscle activation and was used in this study. In summary, these findings suggest that because the nervous system plays an important role in strength gain, imagery could stimulate the nervous system during immobilization, thus reducing the weakening effects that result with immobilization. In order to add to the existing literature, this study investigated how imagery influences the H-reflex and whether or not motor imagery could influence the negative effects of immobilization. 2001 ; Vue 1992}. ann aI., in vestigate immobilization . a!., Ifused reflcx study_ cffects imagcry CHAPTER 3 METHODS Participants Twenty-two healthy adults between the ages of 18 and 30 were recruited for this study. Participants were physically active individuals with no self-reported cognitive impairment, neurological impairment, or lower extremity injury or surgery within the previous 12 months. Further criteria for participation included the ability to remain immobilized for 5 days and not participate in physical activity. Measures Physical Activity Being physically active was defined as participating in moderate activity for 30 minutes on 5 or more days a week or vigorous activity for 20 minutes on 3 or more days per week (Davis, 2007; IPAQ, 2005). Physical activity was measured using the International Physical Activity Questionnaire ( IPAQ; see Appendix A). The version used was the "Short last seven days version," which has been found to be suitable for nationwide measurements on physical activity ( IPAQ, 2005). During the questionnaire, the participants were asked about the amount of time they have spent in vigorous, Twenty-two healthy adults between the ages of 18 and 30 were recruited for this study. Participan ts were physically active individuals with no self-reported cognitive impainllcnt, neurological impainnent, or lower extremity injury or surgery within the previous 12 months. Further criteria for participation included the ability to remain immobilized for 5 days and not participate in physical activity. part icipat ing act ivity morc Acti vity 41 "During the last seven days, how much time did you spend..." and is followed by different levels of activity such as vigorous, moderate, walking, and sitting. The participant then reports the amount of days, hours, and minutes and individual scores were calculated to a final score and assigned a category of low, moderate, or vigorous physical activity. Those individuals assigned to the moderate or vigorous category were considered for participation in the study. The IPAQ has been reviewed in 12 countries and validity and reliability have been supported (Craig et al., 2003; Hagstromer, Oja, & Sjostrom, 2006; IPAQ, 2005). Imagery Ability The Movement Imagery Questionnaire-Revised (MIQ-R; see Appendix B) is an eight-item instrument that measures an individual's ability to perform visual and kinesthetic imagery and has been established as an appropriate tool to measure motor learning (Morris et al., 2005). In this measure, participants are given eight scenarios in which they have to perform a movement and then imagine doing (kinesthetic imagery) or seeing (visual imagery) themselves doing the same action. Odd numbered items represent kinesthetic imagery ability and even items represent visual ability. Participants then have to rate on a seven point Likert-type scale assessing how easy or difficult the task was with one being very hard to see or feel and seven being very easy to see or feel (Hall & Martin 1999). In agreement with previous research (Smith, Wright, Allsopp, & Westhead, 2007) participants who scored higher than 16, which indicates moderate imagery ability, were be used for the study. The MIQ-R possesses good psychometric qualities and internal consistency (Gregg, Nederhoff, & Hall, 2005; Morris et al., 2005) and has been used in a spend ... " oflow, IP AQ ai., IP AQ, ai., orleel feel ai., 42 variety of studies to evaluate imagery ability for intervention studies (Gregg et al., 2007; Smith et al., 2007). Instrumentation The Hoffmann reflex (H-reflex) examines the monosynaptic connections between la sensory fibers and alpha motoneurons. The amplitude of the maximal H-wave, which measures the sensory fiber activation, to the maximal M-wave amplitude which represents the maximal motor response possible due to direct motoneurons activation, was compared before, during, and after the intervention period. In order to prevent misinterpretation of the data due to measurement error, strict protocols were followed. Surface electromyography (MP 100, BIOPAC Systems Inc., Santa Barbara, California, USA) was used to measure the H-reflex and M-wave. After shaving, abrading and cleaning the skin with isopropyl alcohol; pre-gelled, self-adhesive disposable vinyl Ag-AgCl recording electrodes were placed over the soleus muscle as well as the ipsilateral lateral malleolus. An electrical stimulator (S88, Grass Instruments Inc., W. Warwick, RI, USA) was used to elicit a spinal reflex response. For stimulation of the soleus, an unshielded surface electrode (12 mm) was applied on the skin over the tibial nerve behind the knee. To identify correct electrode placement, the stimulating electrode was moved over the nerve until a muscle response was elicited. This point determined the optimal stimulating location. After the optimal stimulation location was identified, electrodes were secured with tape and outlined with permanent marker in order to ensure that the electrodes were placed at the same location during subsequent data collection. In order to limit the risk of electric shock, a constant current unit (CCU1, Grass Instruments. aI., aI., bcforc, MPI 00, AgCI CCU 1, 43 Inc. W. Warwick, RI, USA) and a stimulus isolation unit (SIU5, Grass Instruments, Inc.) were used. Individuals were tested in the prone position, with the ankle positioned and maintained at 90° dorsiflexion. A body pillow was used to standardize body, head, and hand position for each participant. The exact body position and electrode placement used for baseline testing was used during subsequent testing. Furthermore, participants were reminded to refrain from moving the leg and other parts of the body during testing. The H-reflex was measured by percutaneous electrical stimulation of the tibial nerve (vialms pulses). Following low stimulus intensity, consistent increments of the intensity were given until the maximum H-reflex and M-wave amplitudes were obtained. The ratio of the maximal amplitude of the H-reflex (Hmax) and maximal amplitude of the M wave (Mmax) were used to develop the dependent measure (Hmax/Mmax). Procedures Participant Selection and Preparation After IRB approval, participants were recruited through announcements in classes of the Exercise and Sport Science (ESS) Department. Participants were invited to attend an informational meeting in which the process of the study was explained and which was followed by signing of the informed consent form. The participants were assured that participation was voluntary and that the opportunity to drop out of the study existed at all times. After the introduction, the eligibility screening was conducted with completion of the IPAQ to evaluate the participants' level of physical activity. Individuals with moderate or vigorous levels of physical activity were considered for participation. The 900 IP AQ MIQ-R was administered to determine imagery ability with 16 points or higher being the score needed to participate in the study. In addition, each participant completed an additional questionnaire regarding demographic data and information regarding injury history and use of imagery. The orientation meeting including conduction of eligibility tests took approximately 30 minutes for each participant. Participants were then randomly assigned to the experimental-imagery or control group using a Latin Square. A handout with instructions about the immobilization protocol including restrictions about physical activity and group descriptions was given to each participant at that time. Individuals in the imagery group also received instructions on the imagery intervention, an audio recording and a written copy of the imagery script. Immobilization Participants of both groups had their left ankle immobilized using an immobilization walking boot (MaxTrax Walker, DonJoy Orthopedics, LLC, Vista, CA, USA) that prevented movement of the foot, in particular plantarflexion. A walking boot was used because of the ability to provide superior immobilization and resistance of plantarflexion (Kadakia et al., 2008; Raikin et al. 2001). The participants were immobilized for 5 days, a time frame that was chosen to simulate clinically relevant immobilization time for ankle injuries (Birrer & O'Connor, 2004; Prentice, 2006). Additionally, participants were instructed to remain immobilized the entire time of the study, including during the intervention and sleeping, with the exception of taking a shower. In this case, participants were told to keep their foot still during showering and reapply the boot when finished. 44 adminIstered The intervention in this study was to use motor imagery. The motor imagery script (see Appendix C) was recorded as an electronic file and sent to those participants in the imagery group. Participants were instructed to download the file and use the recording during the intervention time. They were also instructed not to listen to the script at other times. The intervention sessions were conducted three times each day and each imagery session lasted 5 minutes. These time requirements were adapted from a similar study conducted by Newsom and colleagues (2003). After one supervised imagery training session on the first day, the participants did the imagery on their own three times a day. They recorded each session in a log (see Appendix D) that was collected on the days of measurement of the study. In this log, participants recorded the day and number of the session, how long it lasted, comments on the quality of imagery and on external circumstances that might have interfered with the intervention such as movement of the foot during the session. The imagery session started with a breathing relaxation exercises and then, the individuals were lead through a motor imagery program in which they imagined pushing against a theraband 10 times with their left leg. This exercise was chosen because of the simplicity and because the task is used in rehabilitation of ankle injuries. Participants were familiar with the motion and this exercise also specifically strengthens the calf muscles. Imagining a resistance helped to maintain the intensity of the session. Research on imagery revealed that using as many senses as possible during imagery increases the efficacy as well as conducting imagery in the setting or with the equipment (Smith et al., 45 Intervention colleeted aI., 2007). Therefore, each participant was instructed to do the imagery in a position in which they would do the exercise and the exercise was described in detail including the feel and smell sensation of the theraband. During the imagery sessions the participants remained immobilized and they were instructed and reminded to imagine the movement but not actively perform the movement. The participants were instructed to "imagine pushing your foot against the resistance of the theraband. Feel the resistance and push against it. Hold it there, imagine the force of your foot against the theraband but keep your muscles relaxed." The control group was immobilized but given no intervention treatment. They were instructed not to engage in any imagery activity. Individuals in this group also were required to record in a daily log about the immobilization experience. Table 1 describes the timeline for data collection. Measurements of the H-reflex H-reflex measurements were conducted three times per individual. The baseline H-reflex was measured before the intervention. The second measurement took place 72 hours after immobilization on day 3, in order to see early effects of imagery in the immobilized muscle. The last measurements were taken after conclusion of the study 96 hours after immobilization on day 5. H-reflex measurements were obtained at the same time during the 3 days of testing. Participants remained immobilized until the final H-reflex measurements were obtained. During the testing times, intervention logs were collected as well. All testing was conducted by the same investigator in the HPER Athletic Training Room at the University of Utah, Salt Lake City, UT. 46 perfonn ofthe H -H­reflex 47 Research Design and Statistical Analysis This study was a pretest-posttest control group design. The dependent variable was the H-reflex and the independent variables were the different groups with 2 levels (imagery and control) and time with 3 levels (baseline, after day 3, and after day 5). Type I error was set at .05 whereas power was assumed to be 0.8. This study aimed for a moderate effect size of > 0.5. Hmax /Mmax ratios were analyzed and compared between and within groups with this mixed factorial repeated measures design. RMANOVA performed. table of F-values to determine statistical significance, which was set at a < 0.05. The SPSS 14.0 package (SPSS 14.0, SPSS Inc. Chicago, Illinois, USA) was used. variab les of> IMmax wefe 6'TOUPS A 2 x 3 factorial RMANOV A factorial was perfonned. The results were compared with a ofF-dctennine Ct Illinoi s, CHAPTER 4 RESULTS Demographic Information Demographic data illustrating age and year in school can be found in Table 2. The imagery group consisted of seven participants (4 males, 3 females) and the control group included eight participants (6 males, 2 females). The age range was 19-29 years with a mean of 22 years old. Initially, 22 individuals were recruited, 3 of which dropped out at the beginning of the study, 2 individuals dropped out midways, 1 individual did not meet the criteria needed for H-reflex testing, and another individual did not meet the physical activity requirement. All data discussed in this paper represent the 15 participants who completed the entire study. Imagery Ability and Physical Activity Requirements order to participate in this study, participants were required to have a minimum level of imagery ability with a score of 16. Previous exposure to imagery was recorded for participant characteristic information. Fourteen participants had "none" to "somewhat" experience in imagery; only one individual used imagery more than twice a week. Despite the lack of imagery use in the majority of participants, all participants scored moderately high to high on the MIQ-R. As can be seen in Table 2, random of22 In 49 Table 2 Descriptive Data for Demographic Data of the Population Imagery Group Control Group N Min. Max. M SD TV Min. Max. M SD Age 1 20.00 29.00 22.71 3.30 8 19.00 26.00 21.25 2.38 IE 7 0.00 7.00 2.43 2.15 8 0.00 2.00 .25 .71 VIA 7 16.00 28.00 23.29 4.15 8 17.00 27.00 21.38 4.07 KIA 7 19.00 28.00 23.43 2.76 8 6.00 24.00 17.75 5.52 PA 7 1.00 2.00 1.57 .54 8 1.00 2.00 1.38 .52 Note: IE: Imagery Experience; VIA: Visual Imagery Ability; KIA: Kinesthetic Imagery Ability; PA: Physical Activity assignment of participants had a significant difference in kinesthetic imagery ability with the imagery group exhibiting higher scores in the kinesthetic imagery ability ( F ( l , 13) = 6.038, p < .05, n 2= .317) compared to the control group. An additional requirement for participation was physical activity level. Individuals who participated in moderate to vigorous physical activity were included in the study. All individuals reported to be participating in moderate or vigorous physical activity. Results To answer the research questions, means and standard deviations were calculated for H/M ratios at baseline, day 3, and day 5 for the imagery and control group. The means indicated that H/M ratios decreased with time of immobilization in both groups (Table 3). The results for the RMANOVA did not show statistical significance for any main or interaction effects. The first hypothesis of this study stated that immobilization of the Data/or a/the Population GrouQ GrouQ N 7 1.00 !,IfOUp 1, 11 2= to HIM HIM RMANOV A Table 3 Means and Standard Deviations for H/M ratios after Pre, Mid and Post Testing for Each Group Imagery Group Control Group M M H/M pre .5041 .2149 .5821 .2255 H/M mid .4774 .1448 .5800 .2185 H/M post .4570 .1790 .5155 .1464 study did not find a significant difference between baseline, day 3 and 5 (F (2, 24) = 1.412; p > .05), thus this hypothesis was not supported. The second hypothesis suggested a difference in H/M ratio between the imagery and control group. No significant difference was found (F (2, 24) = 0. 748; p > .05), therefore this hypothesis was not supported. The third hypothesis stated that the decrease in H/M ratio would be greater after 5 days of immobilization compared to three days. Because no significant time effects were found with immobilization, no post hoc tests were performed, thus no difference in length of immobilization could be determined. 50 Tab1c3 alld !-11M SD SD HIM .504 1 .2 149 .582 1 HIM .2 185 HIM pOSl . 1790 . 1464 ankle would result in a decreased motoneuron pool excitability within 3 and 5 days. This signi ficant = P .05), thus this hypothesis was not supported. hypothes is HIM 2,24) = O. th is thi rd HIM perfonned, th us detennined. CHAPTER 5 DISCUSSION The purpose of this study was to examine whether motor imagery can be used to attenuate neurological changes that may occur during immobilization. A repeated measures pretest- posttest design was used and is discussed in this chapter. In the first section, the effects immobilization has on motoneuron recruitment during the course of five days is discussed. In the second section I address the influence of motor imagery on these effects. Finally, in the third and fourth sections, the limitations and future directions are presented and I conclude the chapter with possible implications that can be drawn from this study along with a short summary. Effects of Immobilization on the H/M Ratio The first hypothesis in this study stated that there would be a decrease in H/M ratio of the soleus muscle. Raw data revealed a decline; however, statistical significance was not met. Thus our hypothesis was not supported. The literature shows equivocal results about the effects of immobilization on the H/M ratio. For example, the H/M ratio has been reported to increase after one week of wrist immobilization in a recent study. In this study, H-reflex testing was conducted at rest and during voluntary contraction at baseline, immediately after immobilization, and one week after cast removal (Lundbye- HIM HIM HIM HIM 52 Jensen & Nielsen, 2008). Our data refute these findings. However, in the Lundbye-Jensen and Nielsen study, multiple tests such as maximal voluntary contraction were conducted at the same time which could influence the results of H/M ratio. The increase of H/M ratio was explained by a reduced presynaptic inhibition that could occur during immobilization, thus enhancing the spinal excitability of sensory motoneurons (Lundbye- Jensen & Nielsen, 2008). Presynaptic inhibition is the suppression of neurotransmitter release by the neuron terminals due to activation of remote muscle afferents. This activation includes contraction of the contralateral limb and of the limb tested, or changes in posture and remote contractions. Activation of cortical structures, such as mental rehearsal of movement or stimulation of the brainstem, also have been found to induce presynaptic inhibition (Misiaszek, 2003). According to Lundbye-Jensen and Nielsen (2008), presynaptic inhibition is limited during immobilization, which would lead to an increased H-reflex. In contrast to our study, Lundbye-Jensen and Nielsen studied the wrist, which can be the reason for the difference in results. Complete immobilization is more possible with upper body immobilization; thus presynaptic inhibition can play a stronger role. Clark and colleagues (2006) did not find significant changes in H/M ratios with 3 weeks upper body immobilization between the times of testing or between the immobilized and the non immobilized group, thus supporting our data. Participants were tested after 1, 2, and 3 weeks of immobilization. The immobilization group experienced an initial increase after one week and a return to baseline values after 3 weeks of immobilization (baseline: 38.2 +/- 4.9 %; 1 week: 47.3 +/- 7.7 %; 3 weeks: 38.2 +/- 4.5 %) (2006). In our study, the H/M ratio of the immobilized limb exhibited a decrease. HIM HIM Lundbye­Jensen playa HIM +1- +1- +1- HIM 53 Similar to Clark and colleagues' study the change was nonsignificant but contrary to the Clark et al. study, H/M ratio decreased within 5 days of immobilization. The discrepancy of the results between these studies could be explained by the fact that this study evaluated the lower leg instead of the upper body which could have influenced the amount of disuse and presynaptic inhibition taking place. According to Lundbye - Jensen and Nielsen (2008) and Misiaszek (2003), presynaptic inhibition is limited during immobilization due to disuse which would lead to an increased H-reflex. Because the participants in this study were using a walking boot, complete disuse of the limb was not possible, thus the amount of presynaptic inhibition may have been maintained or possibly been increased. Because no significant effects were found, no post hoc tests were performed to determine a difference between 3 and 5 days of immobilization to test hypothesis 3. Overall, the results of this study reveal that there is no significant effect on the H/M ratio during the course of immobilization; however, data show a non significant tendency of H/M ratio to decrease over time. Effects of Imagery Imagery was hypothesized to have an attenuating effect on the neurological adaptations occurring in the lower leg. Results of this study failed to reveal a statistically significant difference between the imagery and control group, thus not supporting hypothesis 2. However, when comparing the data of each group, it has been shown that the decrease of H/M ratio of the imagery group is smaller and less drastic than in the control group. Although any conclusions need to be drawn with caution, this observation S3 a1. HIM Lundbye­Jensen HIM HIM Imagcry HIM 54 leads to the possibility that imagery might have had an influence in reducing the effects of immobilization on the H/M ratio. This could be due to the fact that the imagery group underwent mental training, thus maintaining the neurological function of the leg. Neurological activity is a key factor to strength gain and maintenance (Aaagard, 2003; Sale, 1982) and motor imagery uses the same neurological pathways as motor execution (Jeannerod & Frak, 1999). Therefore, a possibility exists that motor imagery could have maintained some of the neurological activity during the time of immobilization. Motor imagery has been found to decrease strength loss in the immobilized forearm (Newsom et al., 2003), and increase strength in non immobilized participants (Cupal & Brewer, 2001, Yue & Cole, 1992). A difference between Newsom's study and this study is that Newsom immobilized the upper body and that the outcome variable was voluntary muscle contraction instead of H/M ratio. The H-reflex can be used to detect small changes in motoneuron excitability but the time of immobilization in this study possibly was not long enough for those changes to occur. Previous studies have measured the H-reflex while subjects were undergoing motor imagery and have found that the H/M ratios increased (Cowley et al., 2008; Gandevia, 1997). However, these studies have not investigated whether there is an effect when imagery is done for an extended period of time outside the laboratory. In Clark and colleague's study (2008), the mental imagery group had no different results in the H-reflex during a 4 week unweighting period than did a control group. Because this is a longer time frame than this study, a plausible conclusion might be that motor imagery is not strong enough to have a long lasting effect on motoneuron pool excitability. A possibifity effects HIM aI., Yuc HIM HIM aI., mcntal H­reflex 55 limitation of the Clark et al. study may have been that imagery was performed only 4 times per week, which could be less than needed to reach effects. Hale and colleagues (2003) investigated whether motor imagery at stronger intensities results in higher H-reflex amplitudes. They did not find that the intensity of the imagined contraction played a role in H-reflex amplitude, but they concluded that changes in H-reflex amplitude were due to mental practice. Thus the question remains whether consistent and regular practicing of motor imagery can result in an increase of motoneuron recruitment. In addition, there is uncertainty whether the intensities used in each imagery session were the same for each participant at all times. Another question that remains unclear is whether an increase in the number of regular imagery sessions or a longer time of immobilization would result in more significant differences in this present study as well as in the existing literature. Limitations and Future Directions Although the H-reflex is a reliable and often used measure of motoneuron pool excitability, there are limitations and possible sources of error when using this method. For example, the results of the H-reflex measurements are highly sensitive to changes in head and body positioning, eye movement, and remote as well as close muscle contractions (Misiaszek, 2003; Palmieri, Ingersoll, & Hoffmann, 2004). Actions to limit this weakness were taken by using the same positioning each testing time, by marking the sites of the electrode placement, and by reminding the participants to remain in the same position throughout testing and to remain still. In addition, the averages of the three highest amplitudes were taken to determine the maximal H and M wave amplitude. Ciark Hand 56 However, there is no certainty that the participants were following these directions at all times; thus any motion and change in posture could have influenced the results of this study. Another limitation that can be linked to the H-reflex measurement is that H/M ratios were used. H/M ratios are used based on the assumption that the M-wave is stable throughout testing (Palmieri et al., 2004). In our data, M-waves were fluctuating within and between individuals (see Appendix E). These fluctuations may indicate some weakness in the measurement procedures. However, no statistically significant differences in M-wave amplitudes were found. When immobilized in a walking boot, complete cessation of motoneurons activity is almost impossible because mere standing activates muscle fibers as well as contralateral movement. Complete non-weight-bearing would possibly have resulted in more significant findings. However, one of the aims of this study was to produce results that are clinically applicable and wearing an immobilization boot is a commonly used protocol. An additional limitation of this study was that we used healthy participants instead of a pathological population. Injury can induce plastic neurological changes to the individual (Misiaszek, 2003), which could influence how the individual responds to immobilization and imagery. Also, the small sample size explains reduction of power and lack of findings in this study. In terms of the imagery intervention, limitations were posed by the fact that it is difficult to control the imagery quality of the participants and whether they are following the suggested protocol. In addition, having the participants do the imagery intervention HIM HIM thc under supervision or providing a different, more intensive training in imagery before conduction of the study might have resulted in different results. To date, this study is the first to investigate whether motor imagery over time influences the motoneuron recruitment in the soleus muscle during short-term immobilization, thus serving as groundwork for future research. Further research is needed in order to determine the exact mechanisms that underlie the changes that occur with immobilization. Research has shown that immobilization influences the central nervous system but results concerning the H-reflex are ambiguous. Although our study showed a slight decrease in H/M ratio, other studies range from no change (Clark et al., 2008) to an increase (Lundbye-Jensen & Nielsen, 2008) in H-reflexes. Further studies will also be needed to assess whether a specific length and number of sessions of imagery training are needed to see stronger effects. Also, a larger sample size would also be helpful to gain more significant and powerful findings. In addition, using injured individuals will provide more clinically applicable results by taking the healing process into consideration. This study investigated only the H-reflex; using other dependent variables such as maximal voluntary contractions or brain scans would be important in determining the effects of motor imagery. Studies using these outcome variables have shown significant changes with imagery use (Nair et al., 2005; Newsom et al., 2003; Jeannerod & Frak, 1999). If imagery is showing significant changes in one variable and another under the same circumstances conclusions about the effects of imagery would be easier to reach. Lastly, other intervention methods should be compared to investigate which method would be the most beneficial in addition to imagery. Other interventions could ofthe HIM aI., 57 aI., aI., 58 include but are not limited to contralateral training and early functional training. Contralateral training has been shown to attenuate strength loss of the immobilized limb (Farthing, Krentz, & Magnus, 2009; Munn, Herbert, & Gandevia, 2004) and so did imagery (Newsom et al., 2003). Because the non immobilized limb was used throughout this study, the influence of the contralateral leg on presynaptic inhibition in the immobilized limb could be the reasoning for the results. Future research would be needed to compare these intervention methods with motor imagery and to find whether one method is more efficient than the other or whether a combination of interventions would be most beneficial. Implications and Summary Injuries to the lower leg occur frequently and often require immobilization. Even minor injuries require some short-term immobilization. For any individual working with injured people, the main goal is to return them to activity as soon and safely as possible. The findings of this study have important implications for rehabilitation professionals such as athletic trainers and physical therapists and anyone working with an injured physically active population (Gravlee & Van Durme, 2007; Stevens et al., 2005). Immobilization of 3 and 5 days did not result in a significant change in H/M ratio, which suggests that this time frame may not be as harmful to the immobilized limb. This time frame is common for grade I sprains. Different results might have been shown if a longer time frame would have been used. Knowing the influence immobilization has on the body is essential in understanding how important early intervention and rehabilitation are in order to reduce some of these adverse effects. no(aI., aI., HIM hannful T 59 The decrease in H/M ratio in the imagery group was less than the decrease in the control group over the time of five days. Four of 7 participants in the experimental group showed that imagery stabilized the H/M ratio. Because no statistical significance was found, these results need to be interpreted with caution, but they point towards the potential attenuating effects motor imagery can have on motoneuron recruitment. A smaller decrease of H/M ratio indicates that motor imagery served as a training tool keeping the motoneurons active during the time of immobilization. Knowing that motor imagery could help to retain neurological function will help practitioners to encourage the use of this intervention method. This study can provide awareness to rehabilitation workers that imagery can be a useful tool, thus increasing the use of imagery in the rehabilitation setting (Dreidiger et al., 2006; Sordoni et al., 2000). A third implication is that this study serves as groundwork for future research. Further investigation is needed to fully understand the mechanisms of immobilization and the role motor imagery can play in reducing the adverse effects of immobilization. This study provides a first insight into these questions and can be used as a base to build upon. As a summary, immobilization is necessary but requires complete cessation of movement for a certain period of time. Often people think they cannot do anything during that time and that they are unable to prevent the adverse effects of immobilization. For a health care practitioner, the aim is to find ways to keep the injured person motivated and active during the time of immobilization as well as to find ways to reduce the negative effects of immobilization. Motor imagery uses the same pathways as motor execution and has been found to decrease strength loss. Although more research is needed, knowing that motor imagery can help to maintain neurological activation of motoneurons gives hope decreas'e HIM days, HIM HIM that there is a way to "exercise" the immobilized limb safely during the time of disuse. With further research, this intervention option can be investigated and developed into a possible rehabilitation method that can be used during the time of immobilization. rehabi li tation 60 APPENDIX A INTERNATIONAL PHYSICAL ACTIVITY QUESTIONNAIRE 62 We are interested in finding out about the kinds of physical activities that people do as part of their everyday lives. The questions will ask you about the time you spent being physically active in the last 7 days. Please answer each question even if you do not consider yourself to be an active person. Please think about the activities you do at work, as part of your house and yard work, to get from place to place, and in your spare time for recreation, exercise or sport. Think about all the vigorous activities that you did in the last 7 days. Vigorous physical activities refer to activities that take hard physical effort and make you breathe much harder than normal. Think only about those physical activities that you did for at least 10 minutes at a time 1. During the last 7 days, on how many days did you do vigorous physical activities like heavy lifting, digging, aerobics, or fast bicycling? days per week No vigorous physical activities Skip to question 3 2. How much time did you usually spend doing vigorous physical activities on one of those days? hours per day 62 bei ng phys ically days. acti vities ne nnal. 1. 7 bicycl ing? pcr wcek D act ivities ....... usuall y doi ng ph ysical _ _ 63 minutes per day • Don't know/Not sure Think about all the moderate activities that you did in the last 7 days. Moderate activities refer to activities that take moderate physical effort and make you breathe somewhat harder than normal. Think only about those physical activities that you did for at least 10 minutes at a time. 3. During the last 7 days, on how many days did you do moderate physical activities like carrying light loads, bicycling at a regular pace, or doubles tennis? Do not include walking. days per week • No moderate physical activities Skip to question 5 4. How much time did you usually spend doing moderate physical activities on one of those days? hours per day minutes per day pcr D knowlNot Slire nonna!. tim e. act ivities pcr D No moderate physical activities ~ Skip to qlte~·tioll 5 usuall y pcr pcr • Don't know/Not sure Think about the time you spent walking in the last 7 days. This includes at work and at home, walking to travel from place to place, and any other walking that you might do solely for recreation, sport, exercise, or leisure. 5. During the last 7 days, on how many days did you walk for at least 10 minutes at a time? days per week • No walking ^ Skip to question 7 6. How much time did you usually spend walking on one of those days? hours per day minutes per day • Don't know/Not sure 64 o knowlNot incl udes p lace, lei sure. PCI- o No walking ~ Skip to questio" 7 YOLI o knowlNot 65 The last question is about the time you spent sitting on weekdays during the last 7 days. Include time spent at work, at home, while doing course work and during leisure time. This may include time spent sitting at a desk, visiting friends, reading, or sitting or lying down to watch television. 7. During the last 7 days, how much time did you spend sitting on a week day? hours per day minutes per day Don't know/Not sure This is the end of the questionnaire. Thank you for participating. sitt ing televi sion. __ D knowlNot APPENDIX B MOVEMENT IMAGERY QUESTIONNAIRE-REVISED APPE DIX 67 MIQ-R (Hall & Martin, 1999) Instructions This questionnaire concerns two ways of mentally performing movements which are used by some people more than by others, and are more applicable to some types of movements than others. The first is attempting to form a visual image or picture of a movement in your mind. The second is attempting to feel what performing a movement is like without actually doing the movement. You are requested to do both of these mental tasks for a variety of movements in this questionnaire, and then rate how easy/difficult you found the tasks to be. The ratings that you give are not designed to assess the goodness or badness of the way you perform these mental tasks. They are attempts to discover the capacity individuals show for performing these tasks for different movements. There are no right or wrong ratings that are better than others. Each of the following statements describes a particular action or movement. Read each statement carefully and then actually perform the movement as described. Only perform the movement a single time. Return to the starting position for the movement just as if you were going to perform the action a second time. Then depending on which of the following you are asked to do, either (1) form as clear and vivid a visual image as possible of the movement just performed, or (2) attempt to feel yourself making the movement just performed without actually doing it. After you have completed the mental task required, rate the ease/difficulty with which you were able to do the task. Take your rating from the following scale. Be as accurate as possible and take as long as you feel necessary to arrive at the proper rating different 68 for each movement. You may choose the same rating for any number of movements "seen" or "felt" and it is not necessary to utilize the entire length of the scale. RATING SCALES Visual Imagery Scale 7 6 5 4 3 2 1 Very easy Easy to Somewhat Neutral Somewhat Hard to Very hard to see see easy to (not easy hard to see see see not hard) see Kinesthetic Imagery Scale 7 6 5 4 3 2 1 Very easy Easy to Somewhat Neutral Somewhat Hard to Very hard to feel feel easy to (not easy hard to feel to feel feel not hard) feel Scoring instructions: Odds numbered items represent Kinesthetic imagery, evens Visual imagery. Both are scored out of a total of 7 x 4 = 28. Higher the score = the better the ability movemenf. rati ng util ize RA TING SCALES to sec I magcry 5 Kinesthet ic sco red = = APPENDIX C IMAGERY SCRIPT APPENDIXC 70 Get yourself in a comfortable position. Let yourself relax. Feel relaxation spread through your body. Focus on your breathing. Breathe easily and slowly. As you breathe in feel your stomach rise and as you breathe out feel your body relax. Breathe in-let your stomach rise; breathe out- relax. Take one more deep breath in and out. Breathe easily and slowly. Relax your neck (pause) and your jaw. Feel your head sink into a completely relaxed and comfortable position- Relax your forearms, your upper arms, and your shoulders. Now focus on your fingers. Think warmth into your fingers. Let them totally relax. Focus on the muscles in your lower back. Think relaxation into those muscles. Think into your upper legs. Let them relax. Now think relaxation into you lower legs. Let your calf muscles relax. Feel your legs sink into a completely relaxed state. Feel the relaxation loosen up your muscles. Become aware of your feet. Let them relax. Feel your whole body sink into a deep state of relaxation. (Pause) Scan your body for possible areas of tightness and relax those areas. Feel your entire body encircled with soothing warmth. Enjoy this wonderful state of complete relaxation. (Pause) Turn your attention to your left foot. Feel the boot around your foot. Feel the tightness of the boot around your foot. Don't move your foot but imagine warmth into your foot. As you breathe, breathe warmth into your lower leg. Light, comforting, warm. Now, imagine moving your foot. It is outside the boot. It feels free and light. Imagine moving your foot in all directions. Feel how the movement feels light and easy. Up and down-left and right. Feel the movement in your ankle. Up and down. Left and right. in--Iet out-- wannth Tum wann. down--Ieft 71 Now imagine holding a theraband in your hands and wrapping it around the sole of your foot. Feel the band touching your foot, feel the stretch. Smell the rubber of the theraband. See the color of the theraband, and how it wraps around your foot. Imagine holding the theraband firmly in your hands, feel your hands wrapping around the ends of the band. Now imagine pushing your foot down against the resistance of the rubber band. It is a high resistance so imagine pushing with all the strength you have in your foot. Don't move your foot but imagine how it feels. Imagine bringing your foot up again. Recovering from the push. Now imagine pushing down again, feel the resistance of the theraband, push as hard as you can and bring it back up. You will repeat this eight more times. Push down as hard as you can, and bring it backup. Push down and feel yourself pushing against the resistance, and up, Push down-feel the push without moving your foot, and bring it back up. Push down, strong and hard and bring it back up. Push down, you do not move the foot but you can feel the movement. Keep pushing down, and bring it backup. Down, you can feel your muscles becoming stronger with each push, And back up. ... Push down, feel the movement you're not moving your foot still but imagine pushing with all your strength and bring your foot back up And one last time feel yourself pushing against the resistance of the theraband, as hard and strong as possible, feel your muscle working hard and bring it back up. Feel how your foot feels after this exercise: warm and strong. Enjoy this feeling of a good workout and imagine bringing your foot back to a still position. up .... 72 Now come back to your breathing, breathe easily in and out and relax. In and out and relax. You feel strong, and comfortable. And whenever you are ready, slowly open your eyes. to- casily comfortable. APPENDIX D IMAGERY AND IMMOBILIZATION DAILY LOG DAILY IMAGERY LOG Date/ session Time (from-to) Imagery experience Any distractors Comments 74 from- to) 75 DAILY IMMOBILIZATION JOURNAL Difficulties encountered with immobilization: Emotions and thoughts about immobilization: Date: Difficulties encountered with immobilization: Emotions and thoughts about Date: Difficulties encountered immobilization: Emotions and thoughts about Date: Diffic~u~h'i-e'-,~e'-n'o-'o-uC ntered with immobil ization: Dale: immobilization: Diffi c'-u~h'i-o'-,~e'-n'o-'o-Cunte red with immobil izaliol1: immobilization: __________________________________ _ APPENDIX E TABLES OF RAW DATA 77 Table 4 Means and Standard Deviations for H and M Max Values and H/M Ratios of Each Participant Pre, Mid and Post Testing for the Control Group H Max M Max H/M Ratio M SD M SD 2: Pre 2.603 0.251 7.953 0.035 0.109 Mid 1.023 0.612 4.683 0.009 0.218 Post 1.225 0.677 5.362 0.225 0.233 3: Pre 4.583 0.081 7.179 0.059 0.638 Mid 4.585 0.046 7.308 0.034 0.632 Post 3.841 0.120 6.349 0.310 0.605 7: Pre 2.912 0.043 4.759 0.074 0.612 Mid 1.700 0.189 4.761 0.045 0.357 Post 1.617 0.351 4.019 0.467 0.409 8: Pre 3.181 0.044 3.964 0.006 0.802 Mid 3.145 0.022 4.381 0.008 0.718 Post 4.147 0.011 6.147 0.006 0.674 11: Pre 3.622 0.046 6.923 0.013 0.523 Mid 3.984 0.172 6.864 0.008 0.583 Post 3.800 0.316 7.344 0.018 0.517 13: Pre 3.218 0.067 5.397 0.011 0.059 Mid 3.521 0.146 3.761 0.112 0.936 Post 2.834 0.163 4.527 0.034 0.626 15: Pre 5.344 0.157 7.348 0.025 0.727 Mid 5.220 0.095 8.092 0.139 0.645 Post 4.762 0.384 7.799 0.029 0.611 16: Pre 1.203 0.088 2.182 0.004 0.551 Mid 1.203 0.088 2.182 0.004 0.551 Post 1.221 0.079 2.720 0.025 0.449 MeollS alld Deviations/or alld alld I-11M o.fEach Partieipalll Pre. Testillg/or COlllro! Croup Participant MMax HIM 0.08 1 0. 120 2.9 12 0. 189 4. 147 I I: 0.1 72 0.3 16 13 : 0.01 1 3.52 1 0.1 46 0.6 11 2. 182 Table 5 Means and Standard Deviations for H and M Max Values and H/M Ratios of Each Participant Pre, Mid and Post Testing for the Imagery Group H Max M Max H/M Ratio M SD M SD 4: Pre 2.120 0.104 11.273 0.034 0.195 Mid 2.143 0.261 7.435 0.026 0.288 Post 0.635 0.024 4.931 0.048 0.130 5: Pre 3.812 0.019 5.483 0.016 0.697 Mid 2.701 0.222 5.716 0.038 0.472 Post 3.345 0.317 6.034 0.071 0.554 6: Pre 2.185 0.075 4.243 0.049 0.515 Mid 2.166 0.063 4.482 0.034 0.483 2.678 0.227. 5.480 0.066 0.489 9: Pre 3.947 0.101 8.157 0.051 0.484 Mid 3.062 0.347 6.272 0.020 0.488 Post 2.268 0.138 4.903 0.018 0.463 10: Pre 2.182 0.016 6.169 0.039 0.354 Mid 2.472 0.089 5.445 0.059 0.454 Post 2.815 0.077 6.027 0.022 0.468 12: Pre 3.055 0.095 6.849 0.022 0.438 Mid 2.821 0.040 7.178 0.010 0.393 Post 3.459 0.099 9.162 0.062 0.377 20: Pre 5.685 0.060 6.719 0.036 0.846 Mid 3.524 0.060 4.617 0.046 0.764 Post 3.325 0.081 4.630 0.006 0.718 alld Slandard fI filM Participont Pre. alld Testing/or ImagelY Group HIM 0. 195 2. 143 0.Q48 3.8 12 0.Q38 0.D75 0.5 15 Post 0. 101 0.05 1 0. 138 0.0 18 6.1 69 0.0 10 4.6 17 78 REFERENCES Aaggaard, P. 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