The effects of muscle fatigue and proprioceptive deficits on the passive joint senses of ankle inversion and eversion

Objective: To investigate whether muscle fatigue of ankle invertors and evertors reduces the ability to detect inversion and eversion angles in subjects with an ankle proprioceptive deficit. Design: A cross-sectional before-after study with repeated measures design. Setting: Research laboratory. Subjects: Thirty young adults with defective passive joint sense of ankle inversion were recruited into this study and compared with 30 similar controls without ankle proprioceptive deficits. Interventions: Muscle fatigue of ankle invertors and evertors was defined as occuring when the maximal isokinetic torque declined to below 50% of the peak torque. Main measures: The absolute differences between the angles detected and assigned, with target angles at inversion 10 degrees, inversion 20 degrees, and eversion 10 degrees trialled in random orders. Results: Proprioceptive deficits and muscle fatigue of ankle inversion and eversion had a significant interaction with the ability to detect small amplitude target angles. Detecting 10 degrees of ankle eversion and inversion showed significantly greater errors than for 20 degrees of ankle inversion. Following muscle fatigue or in subjects with proprioceptive deficits there were greater errors in detecting small amplitudes of ankle positions (10 degrees of ankle inversion and eversion). Conclusions: The potential deleterious effects of fatigue and proprioceptive deficits on the ability to detect the small range of lateral movements of ankle joint was addressed in this investigation.. Fatigue worsens chronic proprioceptive ankle deficits and hence may enhance the risk of injury.