Problems of muscular fatigue--relationship to stimulation conduction velocity and K (+) concentration
Kössler, F.; Caffier, G.; Lange, F.
Zeitschrift für die Gesamte Hygiene und ihre Grenzgebiete 36(7): 354-356
1990
ISSN/ISBN: 0049-8610 PMID: 2396448 Document Number: 358472
Muscle fatigue is accompanied by a series of biochemical correlations as substrate depletion, lactate accumulation, shifts of pH, increase of phosphate (Pi), arise of free radicals or disturbances of ionic balances. In last time high interest has been directed to the increase of extracellular potassium during extensive muscle activity. It was suggested that high K+ concentration in the interstitium may alter propagation of action potential along the T-tubules or induces membrane depolarization with physiological consequences. In order to elucidate the role of potassium accumulation, experiments were performed on isolated rat muscles. An elevation from 5 to 10 mmol K+ of the bath solution causes a significant decrease of the conduction velocity of the action potential. This effect is more pronounced on fatigue-sensitive fast twitch EDL muscles than on fatigue-resistant slow twitch SOL muscles. Moreover, after tetanic stimulations of these muscles in normal solution, the conduction velocity dropped by the same amount as in high K+ solution but, again, differently in both muscle types. Therefore it is supposed that K+ accumulation during intensive muscle activity contributes to fatigue.