Acute Effects of Asymmetric Loading on Hip Loading and Oblique Muscle Activation During Walking Gait

Asymmetric load carriage is a common daily task and may alter gait mechanics, potentially increasing the risk of musculoskeletal strain and injury. This study examined the acute effects of asymmetric loading on hip joint mechanics and external oblique muscle activity during walking in healthy young adults. Six participants (4 female, 2 male; mean age 21.6 ± 1.1 years) completed three walking trials each of unloaded, symmetrically loaded, and asymmetrically loaded (right side) conditions, with loads equal to 10% of body weight. Kinematic, kinetic, and electromyographic data were collected using a motion capture system, force plate, and surface EMG sensors placed on external obliques. Hip joint angles, moments, and forces were analyzed across one gait cycle. Results showed no significant differences in hip flexion-extension or abduction-adduction angles across conditions, and most kinetic measures were also unchanged. However, hip abduction-adduction joint moment differed between sides in the asymmetric condition (p = 0.0111), and right hip longitudinal forces were significantly greater in loaded compared to unloaded trials. EMG data indicated that the left external oblique was more active in the asymmetric condition than in the bilateral or unloaded conditions, suggesting increased contralateral trunk muscle engagement. These findings indicate that while mild asymmetric loading does not substantially alter hip joint angles or sagittal-plane moments, it provokes localized adaptations in frontal-plane moments and trunk muscle activation, reflecting compensatory strategies to maintain stability during gait and highlighting potential implications for occupational and rehabilitation contexts.