The effect of experimentally induced gluteal muscle weakness on joint kinematics, reaction forces, and dynamic balance performance during stair climbing.

Background: The purpose of the present study was to investigate the effects of an experimentally induced weakness of the gluteal muscles on joint kinematics, reactions forces, and dynamic balance performance using the center of mass during stair climbing.

Methods: Ten healthy adult volunteers received sequential blocks of superior gluteal nerve to tensor fascia lata, superior, and inferior gluteal nerve on their dominant right leg. A full-body movement analysis during stair climbing was performed. A two-way repeated measured analysis of variances were applied to compare the average rotational kinematics, joint reaction forces and center of mass.

Findings: Following superior gluteal nerve block, 50 % of healthy participants couldn't complete the task. In participants who completed the task, their joint kinematics were significantly different compared to the control condition, demonstrating more hip flexion (average maximum difference at 50 %: 15 ± 14°, p < 0.05) and more internal rotation (average maximum difference at 20 %: 8 ± 5°, p < 0.05) than in the control condition. Significantly lower joint reaction forces were observed following superior und inferior gluteus nerve blocks at the hip compared to the control condition (up 110 % of body weight average maximum difference, p < 0.05). Participants demonstrated also an increased displacement of their center of mass in the mediolateral direction during both stair-ascent and descent under the superior and inferior gluteal nerve block.

Interpretation: A weakness in the hip abductors severely affected stair climbing performance. Those who managed to complete the task demonstrated abnormal kinematics, reduced joint reaction forces, and poorer dynamic balance.