Elderly subjects are impaired in spatial coordination in fine motor control

Elderly and young control subjects performed back-and-forth handwriting movements in various orientations, therefore varying the coordination demands. Elderly subjects showed higher normalized jerk and straightness scores than the young subjects. However, jerk scores were independent of the coordination demands in either group. In contrast, the straightness scores were highly dependent on stroke orientation for the elderly, but they remained constant across orientations for the young controls. Moreover, group differences in stroke size and stroke duration were not significant, and orientation effects were unrelated. It is suggested that the orientation-dependent straightness scores in the elderly may result from unequal timing or improper scaling of muscle forces. These data suggest that aging deteriorates the spatial coordination of finger and wrist movements, but not accelerative force control.