Bimanual Isometric Force Control in Young and Older Adults

Abstract

Abstract Background: Several activities of daily living require bimanual force coordination during interactions with objects. However, while the decline of sensory perception and motor functions with age have been largely studied, the impact of aging on the bilateral control of isometric forces is less investigated. This study aims at providing a comprehensive description of the bimanual force control strategies adopted by unimpaired young and older adults in an isometric force tracking task. Methods: Participants were required to apply with the two hands simultaneously the same amount of isometric force by pushing on two decoupled plates, which appeared as two lateral faces of a box on a table. The total force had to match a force profile composed of time-variant and constant phases, reaching three target force levels: low, medium, and high. Visual feedback was provided only for the total force, but not for the force exerted by each hand. Thirty-one volunteers participated in the study: 15 of age 25±1 std years and 16 of age 77±7std years. Differences between the two groups were tested with repeated measure ANOVA with the group as a between-subjects factor. Results: The older group had higher matching errors and more variable force profiles compared to the younger group. Most of the older participants also undershot the highest force level. Both groups had more difficulty matching a time-variant than a constant force profile, and this difficulty was higher for the older group. As for differences between the force applied by the two hands, the older group had lower lateral symmetry, although the hand applying more force varied across participants and target forces. For the lower target level, the amount of total force applied by the left hand correlated with its variability expressed by the coefficient of variation. Conclusions: This study provides the first proof of concept that the proposed paradigm, based on a low-cost sensorized device, can be used to characterize and quantify age-related differences in bimanual isometric force control. The device and the paradigm can be used for assessment in clinical settings and then explored as a possible rehabilitative tool.