| Description |
Low-load resistance exercise with blood-flow restriction (REBFR) is an effective way to increase muscle mass and strength, making it potentially useful in rehabilitation settings. However, blood-flow restriction (BFR) causes pain and discomfort, detracting from its use in rehabilitation. The purpose of this study was to determine if two different intermittent BFR strategies would result in similar increases in muscle hypertrophy and strength, but with less pain and perceived effort than continuous BFR. Healthy untrained males were randomly assigned into two groups, intermittent and time-matched. Subjects' legs in the intermittent group (n = 10) were randomly assigned to receive either continuous BFR (IntBFRcon) as the active control, or intermittent BFR (IntBFRint). Subjects' legs in the time-matched group (n = 10) were randomly assigned to receive continuous BFR (TmBFRcon) as the active control, or time-matched intermittent BFR (TmBFRtm). Each of the 20 unilateral training sessions consisted of four sets of unilateral knee extensions using 20% 1RM for that leg. Training took place 5 days per week (Monday-Friday), alternating continuous and intermittent protocols. Muscle thickness of the quadriceps was assessed using panoramic ultrasound. One-repetition maximum (1RM) was tested on a knee extension machine. Pain was assessed with a visual analog scale (VAS). Perceived exertion was assessed using a session rating of perceived exertion (SRPE) scale. Three-factor ANOVAs with repeated measures were used for muscle thickness, 1RM strength, pain, and SRPE. For each ANOVA model with a significant effect, Tukey's honestly significant different (HSD) tests were performed post hoc to localize the effect(s). Total repetitions were not significantly different between groups. There was also no significant difference in load-volume between groups. There were no significant effects for time, group, or time by group interaction for mean muscle thickness. There was a main effect of time for 1RM scores pre- and posttraining (p < .005). There was a main effect of time (p < .005) and group (p < .05) for mean pain and SRPE scores pre- and posttraining. After training, the IntBFRint mean pain and SRPE scores were significantly lower than the TmBFRcon scores (p < .05). This study found that duration of BFR had no significant effect on muscle thickness despite significant increases in 1RM strength. Study results also suggest that an intermittent protocol may reduce the pain and perceived effort experienced with REBFR. |
