Control of rapid aimed hand movements in younger and older adults: Behavioural and electromyographic data

In this study we examined age differences in a movement paradigm that typically (i.e. with young adults) shows a "one-target advantage." This phenomenon refers to the finding that movements are executed faster when the hand is allowed to stop on the target than when it has to proceed and hit a second target. In Experiment 1, two groups of 14 participants (mean ages 20.4 and 80.4 years) each performed aiming movements in three conditions: (a) a single target (1-tap), (b) one target and immediately to another target without a change in direction (2-tap:extension), and (c) one target and immediately back to the start location (2-tap: reversal). In contrast to the younger adults, the older adults did not show the one-target advantage-instead, they showed a new phenomenon, namely a reversal disadvantage: longer movement times for the reversal movement than for the continuation movement in the two-tap sequences. This result was replicated in Experiment 2 that used electromyographic (EMG) technology to determine muscle activation patterns. The EMG data suggested that the one-target advantage was related to both preplanned strategies as well as movement implementation processes during execution. We discuss the theoretical implications of these findings for theories of motor control and aging.