The effect of local and general fatigue on knee proprioception.

PURPOSE The purpose of this study was to compare the effects of local and general fatigue loads on knee proprioception. TYPE OF STUDY Experimental controlled study. METHODS Proprioception of the knee joint was evaluated by measuring absolute angular error (AAE) at matching defined index angles before and after 2 different types of fatigue protocols (local load and general load) in 27 healthy male volunteers. Local load was provided with maximum isokinetic knee flexion-extension on the isokinetic dynamometer, and general load was 5 minutes running on a treadmill. RESULTS After local load, a significant decrease in peak torque of knee flexors and extensors was found, but no significant change in AAE was seen. In contrast, after general load, a significant increase of AAE was noted without significant muscle weakness. CONCLUSIONS The different results in previous studies evaluating the effect of fatigue on knee proprioception may have been affected by the difference of fatigue protocols, whether local or general load. Although local load was intended to produce local fatigue of the knee, which may cause dysfunction of muscle mechanoreceptors, general load may have produced general fatigue and affected other mechanisms in the proprioceptional pathway. The results of the present study suggest that decreased reproduction ability after general load is not due to the loss of peripheral afferent signals, but to other factors, especially deficiency of central processing of proprioceptive signals. CLINICAL RELEVANCE To prevent knee injury caused by fatigue-induced proprioceptional decline, muscle endurance training alone is not enough, and neuromuscular training, including central motor programming, is essential.