Kinematic analysis documents the specific features of a motion, specifically linear and angular displacement, velocity, and acceleration of goal-directed movements. Young controls portray bell-shaped
Figure 1 Fitts' Law: Movement times (ms) for young and older adult subjects as index of difficulty increases. SOURCE: Ketcham, C. J.; Seidler, R. D.; Van Gemmert, A. W. A.; and Stelmach, G. E. (in Press) "Age Related Kinematic Differences as Influenced by Task Difficulty, Target-Size, and Movement Amplitude." Journal of Gerontology: Psychological Sciences.
velocity profiles in accurate point-to-point movements (see Figure 2B). Specifically, the ratio between the acceleration and deceleration phases of a movement is approximately 1.0. The acceleration phase coincides with the portion of a movement before peak velocity, and the deceleration phase, consequently, is the portion of a movement after peak velocity (see Figure 2B; 2E). Older adults demonstrate shorter acceleration phases and prolonged deceleration phases, thus portraying asymmetric or skewed velocity profiles. This suggests that it is the terminal, or deceleration, portion of movement that primarily contributes to slower movement outputs. Furthermore, older adults consistently produce lower peak velocity and acceleration amplitudes compared to young adults, which also contributes to slower movements.