Exploitation of elasticity in copying geometrical patterns: the role of age, movement amplitude, and limb-segment...

An experiment is reported in which 12 adults and 12 10-year-old children copied three-segment geometrical patterns under various size and limb-segment involvement instructions. Next to an assessment of movement pauses, analyses of pen-tip displacements focused on: (1) the accuracy of size reproduction, (2) movement time, and (3) ratio of peak-over-mean velocity. A low value of the latter measure was considered to reflect the adoption of a cyclical movement regime facilitating the exploitation of elastic properties of muscles and tendons during execution. Subjects generally produced size overshoots which, particularly for the children, were most pronounced for small patterns. These effects were accompanied by prolonged movement times. Peak-over-mean velocity ratios were smallest in adults, in large patterns, and when the arm instead of the hand was required as effector. Although adults paused more frequently than children, pause durations were similar in both groups. It is suggested that fast movements with low peak-over-mean velocity ratios reflect successful attempts by subjects to exploit the elasticity of muscles and tendons. These attempts are accompanied in the present task, however, by an increased risk of having to pause between subsequent segments of a movement sequence, possibly for energy-dissipation reasons.