Cortes, N., Morrison, S., & Onate, J. (2013). Fatigue increases variability of joint angles and forces during a side-step cutting task. Medicine & Science in Sports & Exercise, 45(5), Supplement abstract number 463.

This study assessed the impact of fatigue on joint kinetics and kinematics during a side-step cutting task in female soccer players (N = 11). Kinematic and kinetic data were collected while Ss performed a cutting task before and after a fatiguing intervention. Fatigue was induced using a Slow-Linear Oxidative Fatigue Protocol. This involved a 30-minute run with six intervals of four minutes at 70% of VO2peak speed followed by one minute at 90% of VO2peak speed. Kinematic and kinetic data were captured from two force plates using a VICON system. The impact of fatigue on specific kinematic/kinetic variables was assessed through changes in signal regularity (using Approximate Entropy), mean amplitude, and overall variability.

Significant differences were found for the mean amplitude of the medio-lateral and vertical forces. Differences were also seen for hip abduction and knee abduction angles. A significant fatigue effect was found for the Approximate Entropy of the vertical and medio-lateral forces. Post hoc analyses showed that the forces were more irregular indicating increased variability over the duration of the task. Fatigue also resulted in significant increases in Approximate Entropy values for knee abduction angle and moment.

Implication. Fatigue resulted in an overall decline in signal amplitude while the pattern of movement variability/ complexity increased. The pattern of change due to fatigue may elevate the likelihood of injury.

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