Biomechanical Modeling of Hip Abduction Exercise Using Optimized Inverse Dynamics

Abstract

Background: Hip abduction is considered an effective exercise to strengthen the gluteus medius muscle due to its performance simplicity and proper muscle involvement. Objectives: The present parametric study aimed at the assessment of the hip abductor muscle activity in two different modes of exercise, two muscular strength conditions (normal and weak) and three weight loads (0, 2.5, and 5 kg). Methods: A comprehensive musculoskeletal model (AnyBody, version 5.3.1) was used to calculate the activities of the gluteus medius muscle based on the optimized inverse dynamics approach. The model performed side-lying and upright standing hip abduction exercise in an iso-kinetic mode. Results: The side-lying exercise required 40% activation of the muscle in the no-weight normal case while the standing exercise needed lower than 20% in the same condition. The addition of extra weights to the abducting leg caused a considerable increase in the muscle recruitment and the muscle weakness induced greater endeavor of the gluteus medius. Conclusions: The rehabilitation of the weak hip abductor muscles may start with standing no-weight cases and continue by adding extra weights. The side-lying exercise may extremely involve the muscle, specifically in weaker individuals.