Aging effects on object transport during gait

The ability to manipulate objects deteriorates with increasing age. In the coordination of fingertip forces underlying object manipulation, older adults use excessive grip (normal) forces but maintain anticipatory force control during simple manipulations. Daily activities are often more complex and involve grasp manipulations while simultaneously performing other activities. When walking while carrying an object, young adults couple grip forces to gait-induced inertial force changes (anticipatory control). It is unclear if anticipatory control is preserved in older adults during demanding tasks. The purpose of this study was therefore to investigate aging effects on grasp control when walking and transporting an object. We included gait perturbations to vary task difficulty and step regularity associated with walking. Twelve healthy older (65-84 years) and young (20-30 years) adults transported a hand-held object during unperturbed walking, obstacle crossing and step-length changes. While older subjects employed higher grip-inertial force ratios, they showed a strong force coupling comparable to that of the young during unperturbed walking and step-length changes. During obstacle crossing the forces in the older group were less tightly coupled (grip force delays). Gait patterns were similar between groups. Our findings indicate that older adults maintain anticipatory control during regular and irregular walking. Grasp control changes in older adults only during obstacle crossing suggest that overall task demands (balance requirements, attention demands) may contribute to declines of manual dexterity in functional tasks. This highlights the need to investigate grasp control within complex tasks when aiming to understand impairments of older adults encountered in daily life.

► We examined anticipatory grasp control in older adults during a functional, daily task: object transport while walking. ► Older adults maintained anticipatory control of grasping forces during regular walking and during step length changes. ► Grasp control changes in older adults occurred during obstacle crossing, suggesting that overall task demands (balance requirements, attention demands) may contribute to declines of manual dexterity during functional tasks.