The Effect of Small Asymmetric Shoulder Loads on Postural Control in Older People

Abstract

Background: Asymmetrical load carrying can impair balance and increase fall risk, especially in older adults. This study compared postural control in 33 older (mean age 72.2 ± 11.0 years) and 27 younger (mean age 33.5 ± 15.8 years) adults. Methods: Participants performed three 20 s quiet standing trials on a force plate: no load, 3 kg left shoulder load, and 3 kg right shoulder load. Center-of-pressure (COP) variability, range, mean velocity, and sample entropy were computed. This was a quasi-experimental study with a mixed-design ANOVA (Group as between-subjects factor; Load and Plane as within-subjects factors). Results: Younger adults showed better overall stability than older adults across conditions. Older adults had larger COP range than younger adults with no load and with the right-sided load. Notably, no significant difference in COP range was found between groups with the left-sided load. Key statistical findings included the significant Load × Group interaction (F(2, 116) = 3.9, p = 0.024, ηp2 = 0.06) for COP range. Conclusions: A small asymmetrical load on the left side may be associated with postural control in older adults, possibly through familiar sensory cues. Conversely, a right-sided load appears to negatively impact their balance. These findings highlight the differential effects of load side on postural control in older individuals.