SPATIOTEMPORAL INVARIANTS IN HURDLE RACING PATTERNS

Hurdle racing was chosen as an experimental model of complex and sequential motor skills, to investigate the way the motor system controls all the parameters and handles the numerous degrees of freedom involved in this acquired activity. Subjects' cyclical adaptation to the presence of hurdles gives rise to particular spatial and temporal running patterns, the stability of which was tested in athletes trained in this event. In the first part of the 100-metee hurdle course, comprising three hurdles, the standard situation was modified in four different spatial or temporal ways: the subjects were asked to run the course with the inter-hurdle intervals one metre shorter than usual, at maximum (C2) or minimum (C3) speed, to imitate the standard hurdle race but without any actual hurdles (C4), or to step across flat marks on the ground at maximum speed (C5). The duration and the amplitude of the strides in the hurdles area were analysed under these conditions and compared with the standard condition (C1) in order to measure the resistance of the spatio-temporal running pattern to these changes in the task conditions. The results showed that the running pattern was remarkably stable across all subjects, inter-hurdle intervals and conditions. Any changes in the stride proportions were very limited, except under condition C5 (where the basic shape of the standard pattern was nevertheless preserved). Changes were detected in both the temporal and spatial patterns under condition C2, and in the spatial pattern only under conditions C3 and C4. This suggests that, here, as in some sequential hand activities (writing, typing), time (relative timing and rhythm) is the most invariant component and forms, to some extent, a stable framework within which other adjustments can be made. © 1990.