Dynamical systems-based metrics reveal fatigue-related biomechanical changes during running in endurance-trained male and female runners
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Updated: Nov 1, 2026
Comparative Analysis of Lower Limb Kinematics between the Initial and Terminal Phase of 5km Treadmill Running
Published on: July 17, 2020
Yiyang Chen1, Jill Emmerzaal2, Gleydciane A Fernandes3
1Department of Kinesiology and Physical Education, McGill University, Montreal, Canada; College of Health and Human Sciences, The University of Memphis, Memphis, United States.
Background:
Linear and nonlinear metrics derived from a small number of accelerometers provide global insight into fatigue-related changes and injury risk.
Research Question:
This study aimed to determine the effects of fatigue on movement dynamics estimated from lower-back accelerometry between endurance-trained male and female runners.
Methods:
Thirty-two endurance-trained runners (16 females) performed a fatiguing running task until volitional exhaustion (20 on the Borg CR20 scale), while wearing one inertial measurement unit (IMU) placed on their pelvis/lower back. Step and stride regularity (unbiased autocorrelation), root mean square (RMS)-based measures of variability (absolute RMS and RMS ratio), complexity (Sample Entropy), jerk-based measure of smoothness (Log Dimensionless Jerk; LDLJ), and stability (short- and long-term Lyapunov Exponent) were calculated from the raw accelerations.
Results:
Significant main effects of fatigue were observed across both sexes for gait regularity, with an 8% reduction in anteroposterior step regularity and an 11% reduction in stride regularity. Fatigue also altered variability characteristics, resulting in a 12% increase in mediolateral absolute RMS, a 13% increase in anteroposterior absolute RMS, a 2% decrease in vertical RMS ratio, a 6% increase in mediolateral RMS ratio, and an 8% increase in anteroposterior RMS ratio. Fatigue increased movement complexity, as evidenced by a 14% increase in vertical Sample Entropy and an 11% increase in anteroposterior Sample Entropy. In addition to these overall fatigue effects, RMS-based measure of variability showed sex-specific responses. Interaction effects showed that males exhibited a 4% increase in the vertical absolute RMS of lower-back acceleration with fatigue, whereas females did not.
Significance:
Both male and female endurance-trained runners may adopt a less regular and less predictable whole-body movement pattern with fatigue, while RMS-based variability showed sex-specific responses, with increased fatigue-related changes in males. These findings highlight the importance of considering both general and sex-specific adaptations when monitoring fatigue.
