muscle fatigue

The effect of fatigue on knee mechanics in older adults: Does physical activity matter?

INTRODUCTION. Increased age is associated with changes in gait mechanics and decreased muscle function. As the knee extensors (KE) are prime movers in gait, altered KE function (strength, power, fatigability) could alter knee mechanics. This study aimed to determine whether a bout of exercise induces KE fatigue and changes in knee mechanics in two older groups with different physical activity levels: sedentary adults and runners. METHODS. Adults aged 55-70 who were either runners (≥15 miles/wk) or sedentary (≤3x30 min exercise bouts/wk) completed gait and strength testing before and after a 30 minute treadmill walk (30MTW). Joint kinematics were calculated using the point cluster technique. Externally-referenced moments were calculated using inverse dynamics. KE power and isometric strength were assessed via isokinetic dynamometry. Changes in KE power and knee mechanics were calculated; within-group changes were examined using paired t-tests (p<0.1). RESULTS. Sedentary adults displayed a drop in KE power at 6/8 contraction velocities vs. 2/8 in runners (poster Figure 2). Both groups showed an increase in knee flexion angle at heel strike and runners displayed decreased knee flexion moments post-30MTW (poster Figure 3). CONCLUSIONS. Vigorous physical activity may allow older adults to maintain fatigue resistance. Sensitivity of knee mechanics to KE fatigue remains unclear as few changes were seen even in a fatigued group. Global, rather than discrete, measures of joint function may provide more sensitive measures of the response of gait mechanics to muscle fatigue and may allow for a more complete picture of the impact of muscle function on gait.
Listed In: Biomechanics, Gait