Article

During leg flexion from erect posture, postural stability along the medio-lateral
direction is organized in advance during "anticipatory postural adjustments"
(APAs). This study aimed to investigate the influence of temporal pressure on
this anticipatory postural control of medio-lateral stability. Eight young
healthy participants performed series of leg flexions (1) as soon as possible in
response to an acoustic signal (reaction-time condition; condition with temporal
pressure) and (2) in a self-initiated condition (no temporal pressure). Results
showed that APAs duration was shorter in the reaction-time condition as compared
to the self-initiated condition; this shortening was compensated by an increase
in the medio-lateral center-of-pressure displacement so that the dynamic
stability reached at foot-off, as measured by the "extrapolated center-of-mass",
remained unchanged. It is concluded that when a complex task is performed under
temporal pressure, the central nervous system is able to modulate the
spatio-temporal features of APAs in a way to both hasten the initiation of the
voluntary movement and maintain optimal conditions of dynamic stability. In other
words, it seems that the central nervous system does not "trade off optimal
stability for speed of movement initiation under reaction-time condition", as it
had been proposed in the literature.
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Langue : ANGLAIS