Effects of isokinetic ankle fatigue on the maintenance of balance and postural limits

Objective: To quantify changes in balance parameters and ranges of postural control at the ankle after isokinetic fatigue. Design: Before-after trials, with a 5 X 6 repeated-measures design. Setting: General community. Participants: Twenty-four men (age, 24.9 +/- 3.92y, height, 177.79 +/- 6.36cm; weight, 80.78 +/- 13.22kg) without ankle trauma within 2 years. Interventions: Fatigue of the plantarflexors and dorsiflexors was induced by isokinetic contractions. Balance was assessed by using a unilateral test (15-s quiet stance, 10-s lean test) on a force platform immediately before and at 0 (TO), 10 (T10), 20 (T20), and 30 (T30) minutes postfatigue. Main Outcome Measure: Mediolateral (ML) and fore-aft (FA) sway as well as ML and FA displacement were analyzed by analysis of variance with repeated measures for time (alpha = .05). Results: In quiet stance, ML sway was greater at TO, whereas total sway increased at all time points postfatigue (P < .05). For the lean test, FA sway increased at TO and T 10, and total sway increased at all time points (P < .05). Both ML and FA displacement significantly differed at TO (P < .05). All sway parameters returned to baseline within 20 minutes. Conclusions: Isokinetic fatigue of ankle plantarflexors and dorsiflexors significantly influences sway parameters and ranges of postural control in healthy young men. These perturbations are transient, and recovery occurs within 20 minutes.