Effects of progressive asymmetrical load carrying on locomotion control in older adults with a history of falls.

Abstract

Older adults with a history of falls (fallers) demonstrate worse gait performance, balance problems, and impaired perception of verticality than their counterpart non-fallers. During locomotion, three strategies for dynamic balance control are employed: anticipatory, predictive, and reactive. Carrying an asymmetric load (e.g., bags, purses, etc.), which is carried on only one side of the body, can lead to postural destabilization if predictive control fails to accurately estimate the magnitude of the perturbation generated by the load. This includes muscular torques and other postural adaptations necessary to counterbalance the perturbation and maintain postural stability. However, little is known about the functioning of predictive control in fallers. Therefore, it raises the question of whether fallers exhibit proper functioning of predictive control during gait and whether this control adequately scales the necessary adaptations according to the carried load. Fifteen older adults (65-85 years) with a history of falls in the past six months will participate in this study. They will walk on a flat surface (distance of 9 meters) under six experimental conditions: walking without carrying a dumbbell and walking while carrying a dumbbell with their dominant hand (2%, 4%, 6%, 8%, and 10% of their body mass). Thirty-nine body markers (Plug-in Gait Full Body Model) will be attached to specific anatomical landmarks on the participants' skin, and two additional markers will be placed on the dumbbell. The markers will be tracked using a motion capture system consisting of nine cameras. The analysis will include the mediolateral margin of stability calculated based on the extrapolated center of mass, trunk roll angles, shoulder flexion-extension angles, and electromyographic activity of trunk and lower limb muscles. One-way repeated measures analyses of variance will be performed, considering the six conditions (no load, load: dumbbell at 2%, 4%, 6%, 8%, and 10% of body mass). Planned comparisons will be used to investigate the effect of load progression and load carriage. The significance level will be p<0.05.