Journal of Applied Physiology, Vol 66, Issue 6 2725-2732, Copyright © 1989 by American Physiological Society

ARTICLES

Contractile adaptations in the human triceps surae after isometric exercise

S. E. Alway, J. D. MacDougall and D. G. Sale
Department of Medicine, McMaster University, Hamilton, Ontario, Canada.

Ultrastructural and twitch contractile characteristics of the human triceps surae were determined in seven healthy but very sedentary subjects before and after 16 wk of unilateral isometric training at 100% maximal voluntary contraction. After training, twitch contraction time decreased by approximately 20%. One-half relaxation time, peak twitch torque, and percent fiber type in any of the muscles of the triceps surae complex were not changed by training. Type I and type II fiber areas increased in the soleus by approximately 30%, but only type II fibers showed an increased in area in the lateral gastrocnemius (40%). Despite such changes in fiber area, the volume density of the sarcoplasmic reticulum-transverse tubular (SR) network averaged 3.2 +/- 0.6 and 5.9 +/- 0.9% in type I and type II fibers, respectively, before and after training in the two heads of the gastrocnemius. Type I SR fraction increased to 3.5 +/- 1.2% after training in the soleus; however, correlations were not significant between the change in the volume density of SR and the change in twitch contraction time (R = 0.46, P = 0.45) or the change in one-half relaxation time (R = -0.68, P = 0.08). The results demonstrate that isometric training at 100% maximal voluntary contraction induced changes in twitch contraction time that were not directly related to changes in the volume density of SR in fibers of the triceps surae.

This article has been cited by other articles:

				A. R Pucci, L Griffin, and E Cafarelli Maximal motor unit firing rates during isometric resistance training in men Exp Physiol, January 1, 2006; 91(1): 171 - 178. [Abstract] [Full Text] [PDF]

				K. Sasaki and N. Ishii Shortening velocity of human triceps surae muscle measured with the slack test in vivo J. Physiol., September 15, 2005; 567(3): 1047 - 1056. [Abstract] [Full Text] [PDF]

				M. P. Harber, P. M. Gallagher, A. R. Creer, K. M. Minchev, and S. W. Trappe Single muscle fiber contractile properties during a competitive season in male runners Am J Physiol Regulatory Integrative Comp Physiol, November 1, 2004; 287(5): R1124 - R1131. [Abstract] [Full Text] [PDF]

				J. F. Signorile, M. P. Carmel, S. J. Czaja, S. S. Asfour, R. O. Morgan, T. M. Khalil, F. Ma, and B. A. Roos Differential Increases in Average Isokinetic Power by Specific Muscle Groups of Older Women Due to Variations in Training and Testing J. Gerontol. A Biol. Sci. Med. Sci., October 1, 2002; 57(10): M683 - 690. [Abstract] [Full Text] [PDF]

				J. J. Widrick, J. E. Stelzer, T. C. Shoepe, and D. P. Garner Functional properties of human muscle fibers after short-term resistance exercise training Am J Physiol Regulatory Integrative Comp Physiol, August 1, 2002; 283(2): R408 - R416. [Abstract] [Full Text] [PDF]

				G. Scaglioni, A. Ferri, A. E. Minetti, A. Martin, J. Van Hoecke, P. Capodaglio, A. Sartorio, and M. V. Narici Plantar flexor activation capacity and H reflex in older adults: adaptations to strength training J Appl Physiol, June 1, 2002; 92(6): 2292 - 2302. [Abstract] [Full Text] [PDF]

				S. D. R. Harridge, R. Bottinelli, M. Canepari, M. Pellegrino, C. Reggiani, M. Esbjornsson, P. D. Balsom, and B. Saltin Sprint training, in vitro and in vivo muscle function, and myosin heavy chain expression J Appl Physiol, February 1, 1998; 84(2): 442 - 449. [Abstract] [Full Text] [PDF]