LOWER EXTREMITY MUSCLE FATIGUE INFLUENCES NONLINEAR VARIABILITY IN TRUNK ACCELERATIONS

Area of Science:

• Biomechanics
• Human Movement Science
• Gait Analysis

Background:

• Lower extremity fatigue is linked to reduced postural stability, altered walking, and increased fall risk.
• While linear measures of gait variability under fatigue are understood, nonlinear dynamics remain less explored.
• Investigating nonlinear gait variability is crucial for a comprehensive understanding of fatigue's effects.

Purpose of the Study:

• To investigate the influence of localized lower extremity muscle fatigue on nonlinear gait variability in healthy adults.
• To analyze changes in complexity and fractal dynamics of trunk kinematics during walking post-fatigue.

Main Methods:

• Ten healthy participants (5 male, 5 female) underwent treadmill walking before and after induced lower extremity fatigue.
• An Inertial Measurement Unit (IMU) sensor recorded trunk movement, generating stride interval time series (SIT) and signal magnitude difference (SMD) time series.
• Nonlinear analysis techniques, including approximate entropy, multiscale entropy, and Detrended Fluctuation Analysis (DFA), were applied to SIT and SMD signals.

Main Results:

• Fatigue significantly increased the complexity of SMD signals (p=0.04).
• Fatigue significantly decreased the fractal properties (anti-persistence) of SMD signals (p=0.013).
• No significant changes were reported for SIT signals.

Conclusions:

• Localized lower extremity muscle fatigue alters trunk kinematic variability, specifically increasing complexity and inducing anti-persistence.
• These findings highlight the impact of fatigue on the nonlinear temporal structure of human gait.
• Further research is needed to correlate kinematic variability changes with fall risk in fatigued adults.