The effect of age and activity level on simple and choice fractionated response time.

Simple and choice knee extension response time was measured on four groups of subjects: Old Active, Old Inactive, Young Active, and Young Inactive. Each response measure consisted of total reaction time plus movement time. Total reaction time was further fractionated into premotor time, which represents the central processing component, and motor time, which represents the peripheral muscular component. All simple and choice fractionated response components demonstrated an age-related lengthening with motor time showing the least amount of lengthening. Although activity level enhanced the speed of all components in aged subjects, movement time was affected to the greatest extent and motor time was affected the least. It is particularly noteworthy that (1) motor time is so little influenced by age and level of activity and (2) the deterioration in speed of movement with age is almost completely negated in Old Active subjects. The results suggest that a life style of regular physical activity has a beneficial effect on several aspects of performance, especially in regard to speed of movement.