Role of the Lumbopelvic-Hip Complex in Bipedal Acceleration

Abstract

A majority of sporting competition involves short bursts of acceleration; yet most running literature focuses on constant velocity locomotion. The acceleration phase is a critical component to performance in athletes and is marked by increasing velocity, step lengths and arm and leg movements. However the purpose of the arm and leg motion is mostly speculative. Therefore the purpose of this project was to investigate the influence of arm and leg constraint on bipedal acceleration. Specifically, the goals of this study were: 1) To determine the role of the lumbopelvic-hip complex during the initial acceleration phase of a sprint, 2) To investigate the effects of constraint conditions of the upper arm (CUA), full arm (CFA) and hip constraint (CH) on the spatial-temporal kinematics during acceleration, 3) To investigate the effects of conditions CUA, CFA and CH on the joint kinematics during acceleration, 4) To investigate the effects of conditions CUA, CFA and CH on the gait kinetics during acceleration and 5) To investigate the effects of conditions CUA, CFA and CH on the latissimus dorsi (LD) and gluteus maximus (GM) muscle activity during bipedal acceleration. The results demonstrate that the CUA condition decreased step length (SLL), velocity (VEL), and anterior pelvic girdle rotation at initial contact (APPGRIC). In contrast, an increase in stance time (STL) was noted with the CUA compared to an unconstrained (N) condition. The CFA condition produced decreases in SLL, VEL, and lateral pelvic girdle rotation at initial contact (LPGRIC) while increasing STL. Furthermore, the CH condition decreased peak braking ground reaction force (BGRFPEAK) and impulse (BGRI), SLL, VEL, knee angle at toe off (KATO), APPGRIC and an increase in STL and ipsilateral LD activity at toe off (ILLDTO). Results suggest primarily that arm constraints diminished acceleration. Additionally, the increase in arm motion in the presence of hip constraint suggests that the arms do more than conserve angular momentum within the LPHC. A cross effect was noted between the LD and GM while the LD was not significantly less active in arm constraints suggest that the LD has an additional role to the pelvis.