The Effects of Trunk Fatigue on Proximal Joint Kinematics and Coupling During Running

Abstract

Fatigue is a risk factor for injury and may alter neuromuscular coordination. The trunk accounts for a large percentage of overall body mass and relies on local musculature to control the body’s center of mass (COM). As the trunk fatigues, it has a reduced ability to control the COM and may alter joint mechanics and coordination leading to injury. PURPOSE: To determine how trunk fatigue changes trunk and pelvis excursion and coupling during running. METHODS: Instrumented gait analysis was performed on 32 subjects (16 M, age 21 ± 3 yrs, H: 1.7 ± 0.1 m, M: 65.3 ± 12.5 kg, Tegner: 6.4 ± 1.3). Subjects ran at a self-selected speed (3.1 ± 0.5 m/s) until reporting a 14 on the Borg scale. Next, the subjects performed a trunk fatiguing circuit. Once fatigued, the subjects ran at their previous speed for a 2nd gait analysis. Visual3D and MATLAB were used to calculate joint excursion and angle-angle plots for the trunk and pelvis motions during the stance phase of running. A line of best fit was applied to all angle-angle plots to assess joint coupling. Paired t-tests were used to test differences between the fresh and fatigued conditions. RESULTS: There was a significant reduction in pelvic excursion when fatigued in all three planes (Table 1). There were no significant differences in trunk or hip excursion or joint coupling between the fresh and fatigued states. CONCLUSIONS: Reduced pelvic excursion may be an adaptation to reduce the work the trunk muscles perform. However, no changes in joint coupling were found suggesting that coordination patterns within limbs are maintained. Potentially, trunk fatigue may affect conditions such as anterior knee pain which have been linked to altered pelvic mechanics. Research reported was supported through grant number TL1TR00015.