Myoelectric changes in the triceps surae muscles under sustained contractions

Evidence for synergism
  • A. V. Sirin
  • A. E. Patla
Article

Summary

Synergistic behaviour of triceps surae muscles (medial gastrocnemius-MG, lateral gastrocnemius-LG, soleus-SOL) during sustained submaximal plantarflexions was investigated in this study. Six male subjects were asked to sustain an isometric plantar flexor effort to exhaustion at two different knee angles. Exhaustion was defined as the point when they could no longer maintain the required tension. The loads sustained at 0 and 120 degrees of knee flexion represented 50% and 36% of their maximum voluntary contraction (MVC) respectively. MVC was measured at 0 degree knee flexion. During the contractions, electromyograms (EMG) from the surface of the triceps surae muscles were recorded. Changes in the synergistic behaviour of the triceps surae were assessed via partial correlations of the average EMG (AEMG) between three muscle combinations; MG/LG, MG/SOL, LG/SOL, and correlation between SOL/MG+LG and MG/SOL+LG. The latter combinations were based on either common fibre type or innervation properties. Two types of synergisms were identified: trade-off and coactivation. Trade-off and coactivation synergies were defined by significant (p<0.05) positive and negative correlations respectively. Coactivation synergism was found to occur predominantly under conditions of high load or reduced length of the triceps surae, and increased with the duration of the contraction. Trade-off synergism was evident when the muscles were at their optimum length and the loads sustained were submaximum. Complete shutdown of one muscle activity was ruled out. It is postulated that, in the absence of voluntary strategies on the part of the subjects, changes in the syznergistic behaviour of the triceps surae muscles, manifested through trade-off and coactivation, is dependent on the load placed on the muscle and the muscle effectiveness as characterized by the force/length curve.

Key words

Synergism Myoelectric signal Sustained contraction Tradeoff Coactivation Triceps surae 

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References

  1. Basmajian JV, DeLuca CJ (1985) Muscles alive. Williams and Wilkins. BaltimoreGoogle Scholar
  2. Bower JS, Sandercock TG, Rothman E, Albbrecht PM, Dantzkes DR (1984) Time domain analysis of diaphragmatic electromyogram during fatigue in men. J Appl Physiol 57:913–916Google Scholar
  3. Clark GT, Carter MC (1985) Electromyographic study of human jaw-closing muscle endurance, fatigue and recovery at various isometric force levels. Arch Oral Biol 30:563–569Google Scholar
  4. Gellhorn E (1947) Patterns of muscular activity in man. Arch Physiol Med 28:568–574Google Scholar
  5. Hellsing G, Lindstrom L (1983) Rotation of synergistic activity during isometric jaw closing muscle contraction in man. Acta Physiol Scand 118:203–207Google Scholar
  6. Hof AL, VanDenBerg J (1977) Linearity between the weighted sum of the EMGs of the human triceps surae and the total torque. J Biomech 10:529–539Google Scholar
  7. Lippold OCJ (1955) Fatigue in finger muscles. J Physiol 128:33Google Scholar
  8. Lippold OCJ, Redfearn JWT, Vuco J (1960) The electromyography of fatigue. Ergonomics 2:121–131Google Scholar
  9. Lopes JM, Mulle NL, Bryan MH, Bryan AC (1981) Synergistic behaviour of inspiratory muscles after diaphragmatic fatigue in the newborn. J Appl Physiol 51:547–551Google Scholar
  10. Sirin A, Patla AE, Frank JS, Green H, Hughson R (1984) EMG characteristics of synergistic muscles during submaximal contractions to fatigue. Proc 3rd biannual conference of the Canadian Society for Biomechanics, Human Locomotion III, Winnipeg, 47–48Google Scholar
  11. Sirin A (1985) Synergistic behaviour of the triceps surae during sustained submaximal contractions. M. Sc. Thesis, University of Waterloo, WaterlooGoogle Scholar
  12. Viitasalo JHT (1982) Function of the knee extensor muscles during fatigue. In: Matsui H, Kobayashi K (Eds), Biomechanics VIII. University Park Press, Baltimore, pp 271–277Google Scholar
  13. Weathersby HT (1966) The forearm stabilizers of the thumb: An electromyographic study. Anat Rec 154:439Google Scholar

Copyright information

© Springer-Verlag 1987

Authors and Affiliations

  • A. V. Sirin
    • 1
  • A. E. Patla
    • 1
  1. 1.Neural Control Laboratory, Department of KinesiologyUniversity of WaterlooWaterlooCanada

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