Abstract
Humans frequently assume asymmetrical postures while walking or standing in a crowded space with an object in one hand (a cellphone or a cup of coffee) and experience a body perturbation. Understanding the role of such a body asymmetry in the presence of the body perturbation is important for the optimization of the postural control. 10 young healthy individuals stood on the force platform and held an object in the right (target) hand. They were exposed to external perturbations applied to their shoulders while standing with either normal or narrow base of support (BOS). Bilateral eletromyographic activity (EMG) of dorsal and ventral trunk and lower extremities muscles and center of pressure (COP) displacements were recorded during the phases typical for the anticipatory and compensatory postural adjustments. Integrals of EMG and indexes of co-contraction (C) and reciprocal (R) activation of muscles were calculated and analyzed. Reciprocal activation of muscles on the target side and co-activation of muscles on the contralateral side was observed when standing asymmetrically and being symmetrically perturbed. Decreased magnitudes of co-contraction and reciprocal muscle activation in APA phase were seen while standing with the narrow BOS. Peak COP displacement was increased when participants stood with the narrow BOS. The findings highlight the importance of investigating the role of body asymmetry in control of vertical posture and provide a foundation for future studies focusing on improvement of postural control in individuals with body asymmetry due to unilateral impairment.