EFFECTS OF FATIGUE ON KNEE PROPRIOCEPTION

Objective: To investigate the effects of muscular fatigue on knee join t proprioception. Design: Prospective study. Setting: Exercise physiol ogy laboratory. Participants: Sixteen (eight men and eight women) heal thy volunteers ages 19-27 years, with no history of neuromuscular diso rders, vestibular disorders, or lower limb injuries (e.g., ligament/me niscus tear). Intervention: Three separate fatigue protocols [ramp tes t (RT), continuous test (CT), and interval test (IT)] were performed. All tests consisted of lower limb cycling on a computer-driven cycle e rgometer (Lode). The RT was used to calculate the maximal aerobic powe r (VO(2)max) and determine the work rates for the CT and IT. Work rate for the RT increased 20/25 W/min to maximal exhaustion. The CT consis ted of cycling at 80% VO(2)max until maximal exhaustion. The IT consis ted of cycling alternately at 120% VO(2)max and at 40% VO(2)max for 30 s each to the point of maximal exhaustion. Main outcome measure: In t he standing position, subjects were instructed to perform a two-legged squat to specific knee flexion angles. The absolute angular error (AA E) was measured for each test angle using an electrogoniometer (Penny & Giles, Blackwood, Gwent, U.K.) placed laterally across the dominant knee joint. AAE was defined as the absolute difference between test an gle and subject perceived angle of knee flexion. Results: A statistica lly significant increase in AAE after the RT (1.0 +/- 0.66 degrees, p < 0.01), CT (0.70 +/- 0.66 degrees, p < 0.03), and IT (1.24 +/- 0.79 d egrees, p < 0.01) protocols was observed in the male subjects. Female subjects reported a statistically significant increase in AAE after th e CT (0.73 +/- 0.73 degrees, p < 0.03) and IT (1.1 +/- 0.89 degrees, p < 0.01) protocols and a nonsignificant increase in AAE (0.19 +/- 0.70 degrees p > 0.5) after the RT protocol. Conclusion: These findings su ggest that exercising to fatigue may produce a change in subjects' rep roduction ability of knee joint angles. This may represent a decline i n proprioceptive function after heavy exercise bouts. Whether this sug gested proprioceptive decline is at the clinical significance level (e .g., significantly altering joint stability and motion) cannot be dete rmined from the present findings.