Role of Excitation-Contraction Coupling in Muscle Fatigue
- 47 Downloads
The force produced by muscles declines during prolonged activity and this decline arises largely from processes within the muscle. At a cellular level the reduced force could be caused by: (a) reduced intracellular calcium release during activity; (b) reduced sensitivity of the myofilaments to calcium; or (c) reduced maximal force development. Experiments involving intracellular calcium measurements in isolated single fibres show that all 3 of the above contribute to the decline of force during fatigue. Metabolic changes associated with fatigue are probably involved in each of the 3 factors. Thus the accumulation of phosphate and protons which occur during fatigue cause a reduction in calcium sensitivity and a decline in maximal force. The cause of the reduced intracellular calcium during contractions in fatigue is less clear. During prolonged tetani the conduction of the action potential in the T-tubules appears to fail leading to reduced intracellular calcium in the central part of the muscle fibre. However, during repeated tetani there is a uniform decline of intracellular calcium across the fibre and this remains one of the least understood processes which contribute to fatigue.
KeywordsCaffeine Sarcoplasmic Reticulum Muscle Fatigue Contractile Protein Tetanic Stimulation
Unable to display preview. Download preview PDF.
- Allen DG, Lee JA, Westerblad H. Intracellular calcium and tension in isolated single muscle fibres from Xenopus. Journal of Physiology (London) 415: 433–458, 1989Google Scholar
- Donaldson SK, Hermansen L. Differential, direct effects of H+ on Ca2+-activated force of skinned fibers from the soleus, cardiac and adductor magnus muscles of rabbits. Pflügers Archiv 413: 422–428, 1978Google Scholar
- Eberstein A, Sandow A. Fatigue mechanisms in muscle fibres. In Gutman E & Hnik P (Eds) The effect of use and disuse on neuromuscular functions, pp. 515–526, Amsterdam, Elsevier, 1963Google Scholar
- Fabiato A, Fabiato F. Effects of pH on the myofilaments and the sarcoplasmic reticulum of skinned cells from cardiac and skeletal muscles. Journal of Physiology (London) 276: 233–255, 1978Google Scholar
- Godt RE, Nosek TM. Changes of intracellular milieu with fatigue or hypoxia depress contraction of skinned rabbit skeletal and cardiac muscle. Journal of Physiology (London) 412: 155–180, 1989Google Scholar
- Lamb GD, Stephenson DG. Effect of Mg2+ on the control of Ca2+ release in skeletal muscle fibres of the toad. Journal of Physiology (London) 434: 507–528, 1991Google Scholar
- Lee JA, Westerblad H, Allen DG. Changes in tetanic and resting [Ca2+]i during fatigue and recovery of single muscle fibres from Xenopus laevis. Journal of Physiology (London) 433: 307–326, 1991Google Scholar
- Merton PA. Voluntary strength and fatigue. Journal of Physiology (London) 123: 553–564, 1954Google Scholar
- Nakajima S, Nakajima Y, Peachey LD. Speed of repolarization and morphology of glycerol-treated from muscle fibres. Journal of Physiology (London) 234: 465–480, 1973Google Scholar
- Westerblad H, Allen DG. Changes in intracellular pH due to repetitive stimulation of single mouse skeletal muscle fibres. Journal of Physiology, in press, 1992Google Scholar