The motor activity involves the activation of an extremely complex function that begins even before the action becomes perceptible. The very large number of degrees of freedom possessed by the hand seems to provide almost endless possibilities of movements. To grasp an object, it is necessary to take into account all its physical characteristics (topography, orientation, size and shape). When transmitting strength though his hand during the act of prehension, the subject must take into account the estimated weight of the object, the texture of its surface as well as the degree of stability he is aiming at. Thus, the number of parameters to deal with in order to perform the grasp seems very large. However, Napier (1956) tried to simplify the study of the prehension movement by defining two types of grip: the precision grip and the power grip. Their analysis provided a new parameter, named the opposition axis (Napier, 1955; Iberall et al. 1986), in reference to the spatial line connecting the index to the thumb and through which the forces applied to the object are transmitted during the grasp. In order to further study the prehension through the observation of the opposition axis behavior, we have performed the kinematics analysis of the hand during a prehension movement of cylindrical objects using a precision grip. A computerized motion analyzer was used to record the position of the markers placed on the hand during the grasp. A special attention was give to the position of the opposition axis at the end of the movement. Three experiments were performed involving real and simulated grasps of cylindrical objects. The results show that the opposition axis behaves as a controlled variable of both real and simulated prehension movements. This result is analyzed from a modular point of view according to the pragmatic theory of the prehension movement.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMUQ.2961 |
| Date | 12 1900 |
| Creators | Frak, Victor |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Detected Language | English |
| Type | Thèse acceptée, NonPeerReviewed |
| Format | application/pdf |
| Relation | http://www.researchgate.net/publication/43979405_Codage_visuel_des_mouvements_de_prhension._Visual_coding_of_prehension_movements, http://www.archipel.uqam.ca/2961/ |
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