Interrelationship between pH, plasma potassium concentration and ventilation during intense continuous exercise in man.

During resting conditions plasma hydrogen ion concentration ([H+]P) is known to influence ventilation (VE), whereas the control of plasma potassium concentration ([K+]P) at rest and of both [K+]P and VE during exercise are controversial issues. To obtain more information about these variables during muscular work, eight trained men performed two successive intense continuous cycle-ergometer tests, the first (test I) during metabolic acidosis, the second (test II) with an alkalotic pH. No correlation was found between [H+]P and [K+]P or VE in the direction of change of these variables in test I. Furthermore, no correlation between [H+]P and [K+]P in test I and II was seen. Instead [K+]P and VE changed in relation to the exercise intensity. We suggest that the results confirm [K+]P as an indicator of muscular stress. In addition, the similar behaviour of relative values of [K+]P and VE changes in test I (r = 0.9, m = 1.0, where m is the slope of the regression curve) supports the hypothesis that extracellular potassium controls VE and thereby [H+]P also.