Walking Stability and Kinematic Variability Following Motor Fatigue Induced by Incline Treadmill Walking

Detecting motor fatigue during rigorous activities is essential for preventing injuries, falls, and over-exertion. While research has focused on developing fatigue indices using motion capture or wearable sensors, the method of inducing fatigue can impact movement patterns differently. This study compared the effects of whole-body motor fatigue induced by incline treadmill walking with localized fatigue induced by leg presses and isolated ankle movements, as investigated in our prior study. Twenty healthy young participants walked at 1.25 m/s for 5 min before (PRE) and after (POST) motor fatigue. We computed POST-to-PRE ratios for walking stability and variability measures, including dynamic margins of stability (MOS), step spatiotemporal measures, kinematic variability, and local dynamic stability based on short-term local divergence exponents (LDEs) of trunk movement. Localized fatigue increased mean step width (p = 0.002), mean mediolateral MOS (p = 0.015), knee joint angle variability (p < 0.001), and the mean peak mediolateral center of mass velocity (p < 0.001) more than whole-body fatigue. Whole-body fatigue reduced short-term LDE values of anterior-posterior trunk motion (p = 0.021), indicating greater improvement in local dynamic stability. The findings indicate that localized fatigue has a greater impact on gait variability and stability than whole-body fatigue. The methods of inducing motor fatigue led to different changes in gait.