Biomedical subjects

E Yiou

Publications and source records attributed to E Yiou.

3 recordsLinked to original sources

PubMed2001

In a complex sequential movement, what component of the motor program is improved with intensive practice, sequence timing or ensemble motor learning?

We investigated whether the higher maximum speed of complex athletic movements attained by experts compared with novices might solely be ascribed to the acquisition of a more efficient timing of the initiation of the simple movements that comprise complex sporting gestures. Six novices in fencing and five experts in fencing performed three experimental series: 7 trials of touche, 7 trials of lunge (control series) and 50 trials of lunge + touche (test series), where the touche and lunge were initiated with different chronological sequences imposed by the experimenter. The lunge and the touche can be assimilated to a fast forward step and to a pointing task, respectively. We compared the maximum speed of touche between the two groups, recorded by an accelerometer fixed to the hand guard of the foil, and the speed of the centre of mass obtained from a force plate. The speed of the centre of mass was not statistically different between the two groups in the control and in the test series. The maximum speed of touche was not statistically different between the two groups in the control series. In contrast, in the test series, the maximum speed of touche was higher in the fencers' than in novices' groups, while the timing of initiation of the lunge and the touche was similar. The results of the test series show that the higher maximum speed of touche of fencers compared with novices cannot solely be ascribed to the acquisition of a more efficient initiation timing in motor programming. In a complex fencing gesture, the higher maximum speed of touche following intensive practice is discussed with regard to the inhibition of negative effects linked to the "refractory period" associated with the initiation of two closely spaced motor programs.

Adult↗

PubMed2000

In fencing, does intensive practice equally improve the speed performance of the touche when it is performed alone and in combination with the lunge?

Global movements are generally composed of several simple movements. In this study we tested the hypothesis that the effects of practice on the performance of a simple movement cannot be highlighted when it is performed alone but only when it is part of a global movement. For this purpose we examined the performance of the touche movement in fencing, in terms of maximal speed of the foil, when it is performed alone and in combination with the lunge. The touche can be assimilated to a pointing task towards a target while the lunge can be assimilated to a forward stepping movement. Four international class fencers and five novices were tested. The results show that 1) the performance in the isolated touche condition was comparable between the two test populations, 2) the performance was higher in the expert population compared to the novice population in the sequential touche + lunge condition, and 3) the velocity of the centre of mass at the time of the peak velocity of the touche was higher in the expert population than in the novice population in the sequential touche + lunge condition. In line with Bernstein's concepts on the effects of practice on motor control it is suggested that the experts exploit to advantage the forces developed during the lunge whereas the novices do not.

Adult↗

PubMed1999

Do centrally programmed anticipatory postural adjustments in fast stepping affect performance of an associated "touche" movement?

Ensuring maximum speed in executing a sequence of two voluntary movements requires the second movement to be triggered only after some delay. This is due to the existence of a "relative refractory period." If the second movement is initiated during the refractory period, its speed decreases (movement time increases). In the present study we tested the existence of a refractory period during the execution of a sequence of movements involving both the upper and the lower limbs. More precisely, we examined whether the maximal speed of the touche fencing movement is affected by the anticipatory postural adjustments (APA) preceding a voluntary lunge. The touche and the lunge are similar to a pointing task and a stepping forward movement, respectively. touche consists of hitting a target with a foil at maximal velocity. The results show that (a) when the touche was initiated prior to the onset of the APA of the lunge, the maximal foil velocity remains similar to that of an isolated touche, and (b) when the touche is initiated during the development of the APA of the lunge, the maximal foil velocity is lower than in the isolated touche. Furthermore, the maximal foil velocity decreases with the temporal progression of the APA and reaches its minimal value when initiated at the time of voluntary lunge execution ('foot off'). The discussion suggests that the centrally programmed APA that are elicited in the stepping forward movement induces a refractory period which affects performance of the pointing task.

Adult↗