Journal of Applied Physiology, Vol 81, Issue 2 665-672, Copyright © 1996 by American Physiological Society

ARTICLES

Adaptive responses of hypertrophying skeletal muscle to endurance training

J. Stone, T. Brannon, F. Haddad, A. Qin and K. M. Baldwin
Department of Physiology and Biophysics, University of California, Irvine 92717, USA.

We determined the effects of 6 wk of endurance running on citrate synthase (CS) activity and myosin heavy chain (MHC) expression in bilateral surgical-overloaded rodent fast-twitch plantaris and slow-twitch soleus muscles. The overload induced significant hypertrophy in both muscle types, and this response was enhanced by endurance training. The overload-induced compensatory hypertrophy was accompanied by a proportional increase in muscle CS content. Although endurance training produced significant increases in CS concentration in either muscle type of the normal-trained groups (P < 0.05), it was not effective in causing similar changes in the overloaded trained muscles. Also, overload of either the sedentary or trained groups produced an increase in slower MHC isoforms (i.e., type I in the soleus and types I and IIa in the plantaris) and a concomitant decrease in the faster MHC isoforms (type IIa in the soleus and IIb in the plantaris; P < 0.05), whereas endurance training alone produced the opposite effect, especially in the plantaris. Collectively, these data suggest that 1) increments in muscle oxidative enzyme content due to endurance training are compromised when a hypertrophying process is occurring concomitantly; and 2) the relative loading state imposed on the muscle during repetitive locomotor activity is critical in regulating the pattern of MHC plasticity.

This article has been cited by other articles:

				K. A. Zwetsloot, M. J. Laye, and F. W. Booth Novel epigenetic regulation of skeletal muscle myosin heavy chain genes. Focus on "Differential epigenetic modifications of histones at the myosin heavy chain genes in fast and slow skeletal muscle fibers and in response to muscle unloading" Am J Physiol Cell Physiol, July 1, 2009; 297(1): C1 - C3. [Full Text] [PDF]

				J. A. Hypolite, S. Chang, E. LaBelle, G. J. Babu, M. Periasamy, A. J. Wein, and S. Chacko Deletion of SM-B, the high ATPase isoform of myosin, upregulates the PKC-mediated signal transduction pathway in murine urinary bladder smooth muscle Am J Physiol Renal Physiol, March 1, 2009; 296(3): F658 - F665. [Abstract] [Full Text] [PDF]

				P. M. Fuller, K. M. Baldwin, and C. A. Fuller Parallel and divergent adaptations of rat soleus and plantaris to chronic exercise and hypergravity Am J Physiol Regulatory Integrative Comp Physiol, February 1, 2006; 290(2): R442 - R448. [Abstract] [Full Text] [PDF]

				J.-s. Kim, K. W. Hinchcliff, M. Yamaguchi, L. A. Beard, C. D. Markert, and S. T. Devor Exercise training increases oxidative capacity and attenuates exercise-induced ultrastructural damage in skeletal muscle of aged horses J Appl Physiol, January 1, 2005; 98(1): 334 - 342. [Abstract] [Full Text] [PDF]

				K. M. Baldwin and F. Haddad Plasticity in Skeletal, Cardiac, and Smooth Muscle: Invited Review: Effects of different activity and inactivity paradigms on myosin heavy chain gene expression in striated muscle J Appl Physiol, January 1, 2001; 90(1): 345 - 357. [Abstract] [Full Text] [PDF]