Immediate effects of muscular fatigue on postural stability and motoneuron pool excitability in healthy adults

BACKGROUND: The dynamic effect that fatigue plays on acute neuromuscular excitability has been studied at length without arriving at either an accepted explanation or adequate understanding. Researchers agree that the mode by which fatigue is achieved may contribute to the body's response and recovery. Eccentric exercise, as a method by which fatigue is achieved, is commonly incorporated due to its qualities of producing a high muscle strain and low energy expenditure simultaneously. The influence of eccentric-induced fatigue, as it pertains to postural stability and motoneuron pool excitability, is not well understood. PURPOSE: The aim of this study is to investigate the impact of fatigue on motoneuron pool excitability and postural stability in healthy adults. HYPOthesis: Motoneruon pool excitability will be facilitated despite a simultaneous inhibition in postural stability. METHODS: Twelve volunteers (24.4 ± 6.7 yrs; female n=6; male n=6) participated in a single 10-minute bout of eccentric exercise-induced fatigue. H-reflex measurements, used to measure motor pool excitability, and a Limits of Stability (LOS) test, used to quantify postural stability, were administered prior to and immediately following exercise participation. T-tests were utilized to compare eccentric fatigue's effect on the specific neural functions previously delineated. RESULTS: Statistical significance (tn=+2.408, p=0.035) was found on one measure of postural stability, in which there was a facilitation. CONCLUSION: Implications for such findings indicate that eccentric-induced fatigue may more actively be prescribed as part of an appropriate rehabilitation and physical therapy protocol without exposing clients to a risk for increased neuromuscular compromise. Such findings are intended to serve as preparation for extending the investigation to an elderly cohort who may benefit more directly from the integration of eccentric exercise within therapeutic protocols.