European Journal of Applied Physiology and Occupational Physiology

, Volume 60, Issue 5, pp 346–352

Twitch contractile adaptations are not dependent on the intensity of isometric exercise in the human triceps surae


  • Stephen E. Alway
    • School of Health, Physical Education and RecreationThe Ohio State University
  • Digby G. Sale
    • Departments of Medicine and Physical EducationMcMaster University
  • J. Duncan MacDougall
    • Departments of Medicine and Physical EducationMcMaster University

DOI: 10.1007/BF00713497

Cite this article as:
Alway, S.E., Sale, D.G. & MacDougall, J.D. Europ. J. Appl. Physiol. (1990) 60: 346. doi:10.1007/BF00713497


Ultrastructural and twitch contractile characteristics of the human triceps surae were determined in six healthy but very sedentary subjects before and after 16 weeks of isometric training at 30% maximal voluntary contraction (MVC). Following training, twitch contraction time was approximately 16% shorter, although no differences were observed in one-half relaxation time or peak twitch torque. Percent fibre type was not changed by training. The mean area of type I and type II fibres in the soleus increased by approximately 30% but only type II fibres showed an increase in area in the lateral gastrocnemius (30%). Despite such changes in fibre area the volume density of the sarcoplasmic reticulum-transverse tubular network averaged 3.2 ± 0.6% and 5.9 ± 0.9% in type I and type II fibres respectively, before and after training in the two heads of the gastrocnemius. The results indicate that contractile adaptations to isometric training at 30% MVC were limited to twitch contraction time and were not directly related to changes in percent fibre distribution or the volume of sarcoplasmic reticulum and transverse tubules in either type I or type II fibres. The data further demonstrate that substantial fibre hypertrophy is achieved by training with low-intensity contractions.

Key words

Skeletal muscleIsometric trainingContactile propertiesSarcoplasmic reticulum

Copyright information

© Springer-Verlag 1990