Asymmetries in the hip joint moments during uni- and bilateral lifting and carrying tasks in healthy adults - A biomechanical study.

Abstract

Frequent occupational load handling can result in coxarthrosis. However, it remains unclear whether unilateral lifting and carrying leads to asymmetric hip joint loading, potentially contributing to unilateral coxarthrosis. Therefore, this study aimed to investigate potential asymmetries in hip joint moments during occupational tasks. Twenty healthy subjects performed uni- and bilateral lifting and carrying tasks of different objects weighing 20 kg while three-dimensional motion and ground reaction forces were captured. Time series data of internal hip joint moments of the sagittal, frontal, and transverse plane, and their resultant moment were calculated to assess side differences using statistical parametric mapping. A symmetry index was calculated from the resultant moments averaged over time to describe asymmetries. During one-handed carrying, resultant moments were up to 2.9 times higher on the contralateral than the ipsilateral joint, primarily due to increased abduction and external rotation moments. Conversely, during one-handed lifting, resultant moments were up to 1.8 times higher on the ipsilateral than the contralateral side, with increased moments across all planes. No significant side differences existed during two-handed carrying and lifting, and carrying on one shoulder. Symmetry indices for one-handed carrying and lifting were 48.73 % and 44.74 %, respectively. Due to the asymmetric hip joint loading during one-handed lifting and carrying, frequent execution of these tasks with heavy weights should be avoided and weights should be handled two-handed. As the more loaded side differs between one-handed lifting and carrying, the long-term effects of frequently performing both tasks remain unclear and require further investigation.