Adherence and Postural Control: A Biomechanical Analysis of Transient Push Efforts
- 3.3k Downloads
This chapter focuses on the question of the interface between the body and its physical environment, namely adherence and friction. First, a short survey of literature is presented and some basic statements on adherence reviewed. They help define the adherence constraints associated with different motor tasks. Then, a new paradigm is presented, the transient push paradigm, which offers manifold facilities. In particular, it makes it possible: i) to exert transient external force in the absence of external movement; ii) to divide the body into a focal and a postural chain; and iii) to manipulate the surface contacts between the body and its supports, without perturbing body balance.
The chapter is documented with recent results on transient isometric pushes performed under two conditions of surface contact. A biomechanical model is presented. Based on an experimental recording of the main terms of the model, it is concluded that transient muscular effort induces dynamics of the postural chain. These observations support the view that there is a postural counter-perturbation, which is associated with motor acts. Changing ischio-femoral contact has been proven to modify postural chain mobility, which appears to be a key factor of performance.
The influence of adherence was considered from the adherence ratio, that is, μ = RT/RN (with μ being the adherence ratio, RT and RN, the instantaneous tangential and normal reactions at the contact surface). It was found to evolve, during the course of the effort, up to a certain value, which is close to the coefficient of friction to within a security margin, at the seat contact surface, at least. Lastly, the adherence effects on motor programming are highlighted, and the possibility of considering the centre of pressure as the postural control variable is discussed. It is proposed that the instantaneous adherence ratio, with reference to the coefficient of friction, might be one of the rules for controlling muscle activation to accomplish voluntary efforts, when there is the risk of loosing balance.
KeywordsPostural dynamics ramp push efforts adherence motor control
Unable to display preview. Download preview PDF.
- André-Thomas (1940) Equilibre et équilibration. Paris: Masson et Cie., 1–568.Google Scholar
- Bernstein N (1967) The Co-ordination and regulation of Movements. Oxford, UK: Pergamon, 1–196.Google Scholar
- Bouisset S and Le Bozec S (2002) Posturo-kinetic capacity and postural function in voluntary movements. In Latash, ML (Ed): Progress in Motor Control, volume II: Structure-Function Relations in Voluntary Movements. Human Kinetics. Chapter 3: 25–52.Google Scholar
- Bouisset S, Zattara M (1983) Anticipatory postural movements related to a voluntary movement. In Space Physiology, Cepadues Pubs, 137–141.Google Scholar
- Carlsöö S (1962) A method for studying walking on different surfaces. Ergonomics, 5: 271–274.Google Scholar
- De Koning JJ, Van Ingen Schenau GJ (2000) Performance-Determining factors in speed skating. In Biomechanics in sports, IX (Zatsiorsky VM, ed.). 232–246Google Scholar
- Gaudez C, Le Bozec S, Richardson J (2003) Environmental constraints on force production during maximal ramp efforts. Archiv Physiol Biochem 111: 41.Google Scholar
- Gelfand IM, Gurfinkel VS, Tsetlin ML, Shik ML (1966) Problems in analysis of movements. In Gelfand IM, Gurfinkel VS, Fomin SV and Tsetlin ML (Eds). Models of the structural functional organisation of certain biological systems (American translation, 1971) 330–345. MIT Press, Cambridge, Mass.Google Scholar
- Grieve DW(1979) Environmental constraints on the static exertion of force: PSD analysis in task design. Ergonomics 22: 1165–1175.Google Scholar
- Horak FB, MacPherson JM (1995) Postural orientation and equilibrium. Handbook of Physiology. Oxford University Press, New York, 255–292.Google Scholar
- Latash ML (1993) Control of Human Movement. Human Kinetics, Champaign, Il 1–380.Google Scholar
- Le Bozec S, Goutal L, Bouisset S (1996). Are dynamic adjustments associated with isometric ramp efforts? In Gantchev G.N., Gurfinkel V.S., Stuart D., Wiesendanger M., Mori S. (Eds). Motor Control Symposium VIII, Bulgarian Academy of Sciences, 140–143.Google Scholar
- Le Bozec S. Goutal L. Bouisset S (1997) Dynamic postural adjustments associated with the development of isometric forces in sitting subjects. CR Acad Sci Paris 320: 715–720.Google Scholar
- Lino F, Duchêne JL, Bouisset S (1992) Effect of seat contact area on the velocity of a pointing task. In Bellotti P. Capozzo A (eds) Biomechanics, Universita La Sapienza, Rome, 232.Google Scholar
- Lino F (1995) Analyse biomécanique des effets de modifications des conditions d’appui sur l’organisation d’une tâche de pointage exécutée en posture assise. Thèse de Doctorat d’Université, Orsay, 1–211.Google Scholar
- Macpherson JM (1991) How flexible are synergies? In Humphrey DR. Freund HJ (eds) Motor Control Concepts and Issues, 33–47.Google Scholar
- Nigg B (1986) Biomechanics of running shoes. Human kinetics Pub., Champaign, Il. 1–180.Google Scholar
- Vandervael F (1956) Analyse des mouvements du corps humain. Paris: Maloine. 1–155.Google Scholar
- Whitney RJ (1957) The strength of the lifting action in man. Ergonomics 1: 101–128.Google Scholar
- Wing AM (1996) Anticipatory control of grip force in rapid arm movement. In Wing AM, Haggard P, Flanagan JR (Ed). Academic Press, London. 301–324.Google Scholar
- Wing AM, Haggard P, Flanagan JR (1996) Hand and brain. The neurophysiology and psychology of hand movements. Academic Press, London. 1–513.Google Scholar