Effect of Fatigue on Hamstring Reflex Responses and Posterior-Anterior Tibial Translation in Men and Women

Abstract

Anterior cruciate ligament (ACL) rupture ranks amongthe most common injuries in sports. The incidence of ACL injuries is considerablyhigher in females than in males and the underlying mechanisms are still underdebate. Furthermore, it has been suggested that muscle fatigue can be a riskfactor for ACL injuries. We investigated gender differences in hamstring reflex responsesand posterior-anterior tibial translation (TT) before andafter fatiguing exercise. We assessed the isolated movement of the tibia relativeto the femur in the sagittal plane as a consequence of mechanically inducedTT in standing subjects. The muscle activity of the hamstrings was evaluated.Furthermore, isometric maximum voluntary torque (iMVT) and rateof torque development (RTD) of the hamstrings (H) andquadriceps (Q) were measured and the MVT H/Q as well as theRTD H/Q ratios were calculated. After fatigue, reflex onset latencies were enhanced in women.A reduction of reflex responses associated with an increased TT was observedin females. Men showed no differences in these parameters. Correlation analysisrevealed no significant associations between parameters for TT and MVT H/Qas well as RTD H/Q. The results of the present study revealed that the fatigue protocolused in this study altered the latency and magnitude of reflex responses ofthe hamstrings as well as TT in women. These changes were not found in men.Based on our results, it is conceivable that the fatigue-induced decreasein neuromuscular function with a corresponding increase in TT probably contributesto the higher incidence of ACL injuries in women. © 2013 Behrens et al.