AJP - Regulatory, Integrative and Comparative Physiology, Vol 263, Issue 3 586-R590, Copyright © 1992 by American Physiological Society

ARTICLES

Muscle, joint, and tendon contributions to the torque profile of frog hip joint

R. L. Lieber and S. D. Shoemaker
Department of Orthopedics, University of California, San Diego.

The relative contributions of muscle force, moment arm, and tendon compliance were determined as a function of joint angle in the frog semitendinosus-hip joint system. Muscle, joint, and tendon properties were individually measured and then combined to predict the torque generated at the hip joint as a function of joint angle (i.e., the hip torque profile). Predicted torques were then compared to experimentally measured torques using a stepwise regression model to quantify the relative importance of muscle, joint, and tendon contributions to the hip torque profile. Variation in moment arm accounted for 74% of the variability observed in the hip torque profile, while addition of the muscle's intrinsic sarcomere length-tension property accounted for an additional 19% of the torque profile variability. Tendon compliance, which permitted a small amount of sarcomere shortening, accounted for only about 4% of the torque profile variability. We conclude that in this muscle-joint system, the relative fiber length-to-moment arm ratio is the major determinant of the shape of the isometric joint profile. The fiber length-to-moment arm ratio in other mammalian systems is also discussed.

This article has been cited by other articles:

				R. D. Kooistra, C. J. de Ruiter, and A. de Haan Muscle activation and blood flow do not explain the muscle length-dependent variation in quadriceps isometric endurance J Appl Physiol, March 1, 2005; 98(3): 810 - 816. [Abstract] [Full Text] [PDF]

				N. D. Reeves, M. V. Narici, and C. N. Maganaris Effect of resistance training on skeletal muscle-specific force in elderly humans J Appl Physiol, March 1, 2004; 96(3): 885 - 892. [Abstract] [Full Text] [PDF]

				W. J. Kargo, F. Nelson, and L. C. Rome Jumping in frogs: assessing the design of the skeletal system by anatomically realistic modeling and forward dynamic simulation J. Exp. Biol., June 15, 2002; 205(12): 1683 - 1702. [Abstract] [Full Text] [PDF]