The effect of chronic physical overload on skeletal muscle metabolism and adrenocortical activity
Kôrge, P.; Viru, A.; Roosson, S.
Acta Physiologica Academiae Scientiarum Hungaricae 45(1-2): 41-51
1974
ISSN/ISBN: 0001-6756 PMID: 4283484 Document Number: 73838
The effect of chronic physical overload of various durations on white and red skeletal muscle water and electrolyte metabolism, Na+ + K+-ATPase activity and plasma corticosterone content was investigated. The most regular change was the Na uptake and K loss by both red and white fibers. Tissue water content and its distribution between extracellular and intracellular compartments were essentially unaltered. The disturbances in the tissue electrolyte content were accompanied by the decrease in red muscle Na+ + K+-ATPase activity and fall of blood plasma corticosterone content. When overtrained animals were exercised until exhaustion, a slight increase in the skeletal muscle K and decrease in Na content were observed. In red muscles the ionic shifts correlated with the increase of Na+ + K+-ATPase activity. The additional exertion also increased the adrenocortical activity. The changes in red skeletal muscle electrolyte metabolism were reversible. The results suggest that the mechanism of active transport of ions in red skeletal muscle has a great adaptive capacity and cannot completely be disturbed by a short period of overtraining. The possible role of the adrenal cortex in the regulation of that mechanism is discussed.