Influence of aging and visual feedback on the stability of hand grip control in elderly adults

Aging causes a gradual decrease in maximal grip strength and leads many elderly people to have to rely on visual feedback to compensate for poorer muscle strength in performing daily activities and preventing accidents. Previous studies have investigated age and visual feedback-related changes in grip strength. However, little is known about methods of determining the quality and stability of hand grip strength control in the elderly, which is important for understanding their ability to generate grip force when handling objects with and without visual feedback in daily living. Therefore, the purpose of this study was to investigate the influence of aging and visual feedback on the stability of hand grip control in both hands in elderly adults. Forty-four healthy elderly persons (age 80.5 ± 4.53 years) and 36 young adults (age 32.69 ± 16.48 years) were recruited to execute grip force stability tasks using both hands at a 2 kg target force level. To perform the grip force stability task, the participants were asked to hold the dynamometer tightly in an attempt to achieve the target force level under visual and non-visual feedback conditions. Strength performances (grip force and coefficient of variation values) and stability of strength control (deviation error, variation error and force stability index values) for hand grip force stability tasks were calculated and analyzed. Compared with the visual feedback condition, the stability of grip force control in the hands of the young and elderly groups were significantly reduced in the non-visual feedback condition by 23.5%-57.1% (p < .05). The elderly group also showed significantly worse hand grip strength performances and stability of hand strength control than the young adult group (p < .05). Aging and non-visual feedback reduced the hand grip force output and stability of grip strength control of the hands. This may reveal the difficulty with manipulating hand-held objects in the absence of visual feedback while performing activities of daily living among the elderly.