Reaching forward: effects of a preceding task and aging.

Abstract

Forward reaching is an integral part of many essential daily activities. It is often performed while standing quietly or after standing up from a seated position. This study sought to determine how a preceding balance task and aging would affect the task performance and movement strategy. Twenty-two healthy young and 20 older adults participated in this study and performed forward reaching under two task conditions. In forward reach (FR), reaching was performed during quiet standing. In up-and-reach (UR), subjects stood up from a seated position and then reached forward. A motion analysis system was used to calculate the location of the center of mass (COM) and joint angles at the initial and final positions, and the finger, COM, and joint angular displacements during the reaching task. For both groups, UR was initiated in a more flexed posture and had a significantly shorter reach distance and greater ankle dorsiflexion angle, compared to FR. The location of the COM, however, did not differ between the two task conditions. Older adults were found to significantly slow down their downward and forward COM motions in UR but not young adults. These findings showed that a preceding balance task increased the task demand and required modifications in the movement strategy. For older adults, the impact of increased task demand was greater, and adopting a cautious strategy could help to complete the task safely.