[Age-related changes in some spatial-temporal parameters of ballistic movement in man]

Age-related changes in spatio-temporal parameters of ballistic arm abduction movements were investigated in two groups of healthy volunteers: a group of younger subjects (aged 20-45 years) and a group of older subjects (aged 60-82 years). Arm abduction was performed in a step-tracking task. Older subjects exhibited longer reaction times, greater durations of the initial movement together with lower mean velocities. Accuracy, however, did not significantly differ from that of younger subjects. No differences were found both in the number and in the accuracy of "ballistic" movements, i.e. those completed within one mean reaction time or less. In motor tasks including slight expected perturbations during the movement, the motor performance of all tested subjects was not impaired. Furthermore, older subjects displayed a decrease in the duration of the initial movement and an increase of its mean velocity, without changes in accuracy; the increase of mean velocity became significant under visual closed-loop conditions. The results suggest that only some features of bradykinesia are age-related. Older subjects appear to retain a normal strategy for ballistic movement: the neural mechanisms controlling the generation of sufficient accelerative forces and of the appropriate timing for ballistic movements seem to be poorly activated rather than disrupted, since they may recover under specific circumstances.