Influence of exercise-induced hamstrings fatigue on proprioceptive reweighting strategies and postural performance in bipedal stance in recreational athletes.

Objective: An optimal proprioceptive reweighting strategy is necessary to maintain posture. A suboptimal strategy was associated with injury determinants and whether the strategy can be modified is unknown. Muscle fatigue can be used to investigate proprioceptive reweighting. The aims of this study were to evaluate the effects of local fatigue on proprioceptive reweighting strategies and postural stability as well as relationships between fatigue and these postural parameters.

Design: Fourteen recreational athletes were included. Relative proprioceptive weighting (RPW) was characterized according to the perturbation of the center of pressure (CoP) displacement generated by muscle vibration on a firm and foam surface. RPW evolution <95 % indicated that individuals were able to reweight proprioception from the ankle to lumbar signals according to the surface while evolution >105 % indicated that athletes maintained an ankle-steered strategy. Student's t-tests were used to compare RPW evolution, CoP velocity, and root mean square (RMS) before and after exercise-induced hamstring fatigue. Spearman's rank correlation coefficient was used to test the relationship between fatigue variables, RPW evolution, and stability variables.

Results: Hamstring fatigue induced an ankle-steered strategy characterized by an increase in RPW evolution when the surface was changed (P = 0.002) and an increase in CoP velocity (P = 0.045) and CoP RMS (P = 0.005) on firm surface. None of the correlation coefficients testing the relationship between the parameters proved to be significant.

Conclusion: Local fatigue leads to suboptimal proprioceptive reweighting strategies and impaired stability on firm surface. Results suggests that proprioceptive reweighting strategies are modifiable. Whether this predisposes participants to injury remains to be defined.