Differential effects of fatigue on movement variability

Area of Science:

• Biomechanics
• Exercise Physiology
• Motor Control

Background:

• Movement performance typically declines with fatigue.
• Understanding fatigue's impact on complex movements like cutting is crucial for injury prevention and performance optimization.

Purpose of the Study:

• To investigate the effects of exercise-induced fatigue on lower limb kinetics and kinematics during a side-step cutting task.
• To determine changes in movement performance metrics, including signal variability, following fatigue.

Main Methods:

• Participants performed a side-step cutting task before and after an exercise-induced fatigue protocol.
• Lower limb ground reaction forces (GRF) and knee joint kinematics and moments were measured.
• Analysis included mean amplitude, standard deviation (SD), and Sample Entropy (SampEn) to assess signal variability.

Main Results:

• Post-fatigue, a decrease in mean amplitude and SD of GRF and knee moments indicated reduced force production and variability.
• However, SampEn values increased for GRF, knee kinematics, and moments, suggesting greater signal irregularity and less predictable movement patterns.
• Fatigue differentially affected movement variability metrics.

Conclusions:

• Exercise-induced fatigue impairs force production and alters movement control strategies during side-step cutting.
• Fatigue's impact extends beyond reduced force capacity, affecting the smoothness and predictability of lower limb movements.
• These findings highlight the complex relationship between fatigue and movement variability, with implications for performance and injury risk.