Relationship between Mediolateral Margin of Stability and Load Weight During Walking with a Unilateral Load

Carrying a unilateral load shifts the body ’s center of mass (CoM) laterally, making foot placement adjustments critical for maintaining frontal-plane stability. The margin of stability (MoS), which quantifies the distance between the extrapo- lated CoM and base of support, provides a dynamic measure for assessing such stability control strategies. Although previous studies have examined segmental effects of asymmetric load carriage, they are limited in capturing whole-body dynamic stability. In this study, the impact of unilateral load carrying on dynamic sta- bility was analyzed using MoS. Furthermore, the re- spective contributions of foot placement adjustments and trunk movement were explored. The findings revealed that, under moderate load conditions, MoS was primarily maintained through adjustments in foot placement. Conversely, under high load conditions, significant inter-individual variability was observed, with strategies ranging from foot placement adjust- ments to repositioning the CoM via trunk move- ment.Additionally, variations in trunk tilt direction were associated with distinct strategies aimed at re- ducing shoulder joint load. These findings provide new insights into the movement mechanisms underlying stability maintenance during unilateral luggage car- rying and may lead to the development of assistive devices tailored to individual physical characteristics.