EXPLOITATION OF ELASTICITY IN COPYING GEOMETRICAL PATTERNS - THE ROLEOF AGE, MOVEMENT AMPLITUDE, AND LIMB-SEGMENT INVOLVEMENT

An experiment is reported in which 12 adults and 12 10-year-old childr en copied three-segment geometrical patterns under various size and li mb-segment involvement instructions. Next to an assessment of movement pauses, analyses of pen-tip displacements focussed on: (1) the accura cy of size reproduction, (2) movement time, and (3) ratio of peak-over -mean velocity. A low value of the latter measure was considered to re flect the adoption of a cyclical movement regime facilitating the expl oitation 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 w ere accompanied by prolonged movement times. Peak-over-mean velocity r atios were smallest in adults, in large patterns, and when the arm ins tead 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 elastic ity of muscles and tendons. These attempts are accompanied in the pres ent task, however, by an increased risk of having to pause between sub sequent segments of a movement sequence, possibly for energy-dissipati on reasons. (C) 1998 Elsevier Science B.V. All rights reserved.