Coordinated movement is critical not only to sports technique and performance but to daily living and as such represents a fundamental area of research. Coordination requires being able to produce the right actions at the right time and has to incorporate perception, cognition, and forceful neuro-muscular interaction with the environment. Coordinated movements of the hands and fingers are some of the most complex activities undertaken where continuous learning and adaptation take place, but the temporal variability of the most basic movement components is still unknown. This thesis investigates the extent of temporal variability in the execution of four different simple hand and finger coordination tasks, with the purpose to find the various intrinsic temporal variability which limit the ability to coordinate the hands in space and time. Study one showed that in a synchronized bi-lateral two finger tapping test (<<1 cm movement to target) the best participant had a temporaltiming variability of 4.8 ms whereas the largest time variability could be as high as 24.8 ms. No obvious improvement was found after transfer practice, whereas the average time variability for asynchronized tapping decreased from 62.1 ms to 30.3 ms after instructed practice indicating a likely change in task grouping. Study two showed that in a unilateral thumb-index finger pinch and release test, the largest mean timing variability was 12 ms for pinching irrespective of performing the task in a slow alert manner or at a faster speed. However, the mean temporal variability for release was only 6.3 ms when the task was performed in a more alert manner and indicates that release is more accurately controlled temporally than grip. Study three suggested that in a unilateral sagittal plane throwing action of the lower arm and hand, that elbow and wrist coordination for dynamic index finger tip location was better with a radial-ulnar deviation, darts-type, throwing action than a wrist flexor-extensor type action, basketball free throw type action (the mean variability was 37.5 ms and 27.2 ms, respectively). Study four compared the variability in bi-lateral finger tapping between voluntary tapping and involuntary finger contraction tapping. Electrically stimulated neural contractions had significantly lower force onset variability than voluntary or direct magnetic stimulation of muscles (6 ms, 9.5 ms, and 10.3 ms for electrically stimulated, voluntary and Transcranial Magnetic Stimulation stimulated contraction). This work provides a comprehensive analysis of the temporal variability in various fundamental digital movement tasks that can aid with the understanding of basic human coordination in sporting, daily living and clinical areas.

Le droit traite principalement l’abstention sous l’angle de la faute d’abstention, mais éprouve des difficultés à appréhender l’abstention du titulaire d’une prérogative qui nécessite une nouvelle approche. Refus temporaire, et non exprimé, de jouir immédiatement des effets de sa prérogative pour les retenir jusqu’au moment le plus opportun, l’abstention crée une situation équivoque. N’ayant ni la clarté d’un exercice actif, ni celle d’une renonciation, elle génère en effet imprévisibilité et insécurité juridique. Cette dernière est d’ailleurs exacerbée par les interprétations erronées dont l’abstention fait l’objet et par l’aggravation dans le temps des conséquences qui touchent celui qui la subit. Ainsi, à défaut de statut légalement défini de l’abstention, il est impératif de se saisir de la problématique d’imprévisibilité de l’abstention du titulaire d’une prérogative pour tenter de l’atténuer, tout en mettant en relief sa légitimité. L’encadrement du comportement de celui qui s’abstient dans le temps est la solution qui s’impose. Ainsi, à compter de la fin d’un délai raisonnable, laps de temps préservant sa liberté au sein du délai imparti, il doit respecter le standard de l’agent raisonnable. À défaut, sa responsabilité pourrait être engagée sans que cela n’exclue la responsabilisation de celui qui subit l’abstention. / French law is usually understanding the abstention as the abstention fault. However, the abstention of the holder of a prerogative can not be analyzed this way and requires a new juridical approach. Abstention creates an equivocal situation by being a refusal, silent and temporary, to immediately enjoy the effects of a prerogative in order to retain them until the most appropriate moment. By being unclear unlike an active exercise or a real renunciation, it generates indeed unpredictability and a lack of legal safety. This insecurity is, moreover, exacerbated by erroneous interpretations of abstention and by the aggravation of the consequences affecting the one who suffers from it with the passing time. As a result, due to the absence of a legal status of abstention, it is imperative to take up the unpredictability problem of the abstention of the holder of a prerogative in order to attempt to mitigate it, while highlighting its legitimacy. The appearing necessary solution finds its way in the regulation of the behavior of the one abstaining in time. Consequently, from the end of a reasonable period, preserving his liberty within the time limit, he has to respect the standard of a reasonable agent. Failing that, his liability could be incurred. This would not exclude the accountability of the person who suffers from abstention.