Combined Effects of Fatigue and Decision Making on Landing Mechanics

Abstract

The continued sports related ACL injury epidemic evident within the US is suggested to stem from a limited understanding of the underlying injury mechanism. While recent research has focused on the potential contributions of both fatigue and decision making to this mechanism, their combined impact remains unclear. Considering fatigue implicates through both central and peripheral pathways however, poor reactions, decisions and hence movement responses appear feasible when fatigued. PURPOSE: The current study examined the combined effects of fatigue and decision making on lower limb 3D joint mechanics during landing tasks. METHODS: Twenty four female (21.4 ± 2.1 yrs) NCAA athletes had 3D lower limb kinematics quantified during anticipated (AT) and unanticipated (UT) single leg (left and right) landing tasks, both before and during exposure to a fatigue protocol. Jump direction was governed by a series of light stimuli, activated prior to and during the pre-land phase of AT and UT tasks respectively. For the fatigue trials, subjects performed five squats immediately followed by a randomly ordered landing task, with this cycle repeated until squats were no longer possible. Subject-based peak stance phase (0% - 50%) 3D joint angles were then calculated across pre-fatigue trials, and for trials denoting 100% and 50% of maximal fatigue. These data were then submitted to a 3-way mixed design ANOVA, testing for the main effects of fatigue time, decision and leg, and subsequent interactions between these factors. RESULTS: UT induced significant (p<0.01) increases in peak hip internal rotation and knee abduction and internal rotation, and decreases in hip and knee flexion compared to AT. Significant (p<0.01) decreases in hip and knee sagittal plane, and increases in all hip and knee out of plane rotations were also observed in the presence of fatigue. Fatigue induced increases in peak knee abduction and internal rotation were also more pronounced in UT compared to AT tasks (p<0.01). CONCLUSIONS: The combined effects of fatigue and decision making present as a potentially high-risk manifestation within dynamic landings. The interaction between these factors further suggests that ACL injury may stem from fatigue induced changes in both central and peripheral processing. This work was Supported by NFL Charities