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Journal of Applied Physiology, Vol 77, Issue 4 1769-1775, Copyright © 1994 by American Physiological Society
ARTICLES |
C. Coirault, B. Riou, N. Pery-Man, I. Suard and Y. Lecarpentier
Institut National de la Sante et de la Recherche Medicale Unite 275-Laboratoire d'Optique Appliquee-Ecole Nationale Superieure des Techniques Avancees-Ecole Polytechnique, Palaiseau, France.
Mechanics of human quadriceps muscle strips (vastus lateralis; n = 10) were investigated over the whole load continuum. Mechanical experiments were performed at 29 degrees C and in both twitch and tetanus modes. For a given level of isotonic total load (P) and over a large part of the contraction phase, instantaneous velocity (V) was shown to be a unique function of instantaneous length (L), regardless of time and initial length. By considering this time- and initial length-independent mechanical property between instantaneous L and instantaneous V over the whole P continuum, a three-dimensional P-V-L relationship was constructed. Any variations in stimulation conditions modified the time-independent P-V-L diagram. Such modifications in the P-V-L relationship were characteristics of changes in contractile performance. Moreover, characteristics of the P-V relationship were investigated in both twitch and tetanus modes. The curvature of the P-V hyperbola was significantly higher in tetanus at 30 Hz than in twitch mode (P < 0.001). In conclusion, our study indicates that, in human quadriceps muscles, contractility can be defined as the time- and initial length-invariant part of a three-dimensional P-V-L relationship. Moreover, our data are consistent with an increase in economy of force generation in tetanus contractions compared with that in twitches.
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C. Coirault, D. Chemla, J.-C. Pourny, F. Lambert, and Y. Lecarpentier Instantaneous force-velocity-length relationship in diaphragmatic sarcomere J Appl Physiol, February 1, 1997; 82(2): 404 - 412. [Abstract] [Full Text] [PDF] |
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