AJP - Cell Physiology, Vol 273, Issue 3 C1049-C1056, Copyright © 1997 by American Physiological Society

ARTICLES

Determinants of work produced by skeletal muscle: potential limitations of activation and relaxation

V. J. Caiozzo and K. M. Baldwin
Department of Orthopaedics, College of Medicine, University of California, Irvine 92717, USA.

The objective of this study was to estimate the limitations imposed by the kinetics of activation and relaxation on the ability of slow skeletal muscle to produce mechanical work. These estimates were made by the following methods: 1) using the work loop technique and measuring the actual mechanical work (WA) produced by rat soleus muscles (n = 6) at four different frequencies (0.5, 1, 2, and 4 Hz) and seven different amplitudes of length change (1, 2, 3, 4, 5, 6, and 7 mm); 2) determining the force-velocity relationships of the soleus muscles and using this data to quantify the theoretical mechanical work (WT) that could be produced under the work loop conditions described above; and 3) subtracting WA from WT. The difference between WT and WA was interpreted to represent limitations imposed by activation and relaxation. Under certain conditions (high frequency, small strain), factors controlling the kinetics of activation and relaxation reduced the mechanical work of the soleus muscle by approximately 60%. Hence, activation and relaxation collectively represent important factors limiting the production of mechanical work by slow skeletal muscle.

This article has been cited by other articles:

				F. Seebacher and R. S. James Plasticity of muscle function in a thermoregulating ectotherm (Crocodylus porosus): biomechanics and metabolism Am J Physiol Regulatory Integrative Comp Physiol, March 1, 2008; 294(3): R1024 - R1032. [Abstract] [Full Text] [PDF]

				S. Van Wassenbergh, A. Herrel, R. S. James, and P. Aerts Scaling of contractile properties of catfish feeding muscles J. Exp. Biol., April 1, 2007; 210(7): 1183 - 1193. [Abstract] [Full Text] [PDF]

				D. A. Syme, K. Evashuk, B. Grintuch, E. L. Rezende, and T. Garland Jr. Contractile abilities of normal and "mini" triceps surae muscles from mice (Mus domesticus) selectively bred for high voluntary wheel running J Appl Physiol, October 1, 2005; 99(4): 1308 - 1316. [Abstract] [Full Text] [PDF]

				D. A. Syme and D. M. Tonks Fatigue and recovery of dynamic and steady-state performance in frog skeletal muscle Am J Physiol Regulatory Integrative Comp Physiol, May 1, 2004; 286(5): R916 - R926. [Abstract] [Full Text] [PDF]

				A. N. Ahn and R. J. Full A motor and a brake: two leg extensor muscles acting at the same joint manage energy differently in a running insect J. Exp. Biol., February 1, 2002; 205(3): 379 - 389. [Abstract] [Full Text] [PDF]

				V. Brezina, I. V. Orekhova, and K. R. Weiss The Neuromuscular Transform: The Dynamic, Nonlinear Link Between Motor Neuron Firing Patterns and Muscle Contraction in Rhythmic Behaviors J Neurophysiol, January 1, 2000; 83(1): 207 - 231. [Abstract] [Full Text] [PDF]

				V. Brezina and K. R. Weiss The Neuromuscular Transform Constrains the Production of Functional Rhythmic Behaviors J Neurophysiol, January 1, 2000; 83(1): 232 - 259. [Abstract] [Full Text] [PDF]