Contractile adaptations in the human triceps surae after isometric exercise

Stephen Alway, J. D. MacDougall, D. G. Sale

Research output: Contribution to journalArticle

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Abstract

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 ~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 ~30%, but only type II fibers showed an increase 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.

Original languageEnglish (US)
Pages (from-to)2725-2732
Number of pages8
JournalJournal of applied physiology
Volume66
Issue number6
StatePublished - Jan 1 1989

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Sarcoplasmic Reticulum
Exercise
Torque
Muscles

All Science Journal Classification (ASJC) codes

  • Physiology
  • Physiology (medical)

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Contractile adaptations in the human triceps surae after isometric exercise. / Alway, Stephen; MacDougall, J. D.; Sale, D. G.

In: Journal of applied physiology, Vol. 66, No. 6, 01.01.1989, p. 2725-2732.

Research output: Contribution to journalArticle

Alway, Stephen ; MacDougall, J. D. ; Sale, D. G. / Contractile adaptations in the human triceps surae after isometric exercise. In: Journal of applied physiology. 1989 ; Vol. 66, No. 6. pp. 2725-2732.
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