Aging and rapid aiming arm movement control.

The authors explored the motor control of target-oriented arm movements across 3 age groups: 20 20- to 30-year-olds, 2 groups (n = 38) of older adults (54 to 64, and 65 to 80). Each individual completed 2 arm movement tasks that had the same movement difficulty but different movement directions. A mixed design was used to examine the differences among age groups and movement directions in reaction time (RT), variability in RT, movement time (MT), timing variability, and inter-segment-interval (ISI). Comparing to the young participants, the senior adults initiated movement tasks slower (RT) and with more RT variability, and executed the arm movements slower and less consistently. The two older groups had greater timing variability in their movements, showed more delays (longer ISI) when reversing arm movement direction, and had lower correlations among segments of the movements than the younger group. The quality of the elderly's control of rapid aiming arm movements showed a regression, which suggests a lack of movement planning, resulting in greater use of visual feedback during movement execution.