Relationship between plasma potassium and ventilation during successive periods of exercise in men

Summary During and after two successive incremental cycle ergometer tests (tests A and B), plasma potassium concentration ([K⁺]_p), plasma pH (pH_p), plasma partial pressure of carbon dioxide, blood lactate concentration ([Lac^–]_b) and ventilation (V_E) were measured. While there was a good correlation between the increase in [K⁺]_p and V_E or pH_p, respectively, in test A, in test B a close correlation was found only between the increase in V_E and [K⁺]_p (r>0.9 for nearly all single cases; r was 0.84 and 0.89 for all (pooled) cases in tests A and B, respectively; the correlation coefficients between changes in pH_p and V_E in tests A and B were r=0.74 and r=0.28, respectively, and r=0.89 and r=0.10 between the changes in [Lac^–]_b and V_E in tests A and B). The close relationship for individuals between V_E and [K⁺]_p in tests A and B supported the hypothesis that the extracellular increase in [K⁺] may contribute to the ventilatory drive during exercise. The comparison of the results of tests A and B further indicated that the relationship between pH_p and V_E was dependent on the experimental design, and that pH_p and V_E changes are unlikely to be cause and effect.The study was carried out in the Centre of Physiology, Department of Sports- and Exercise Physiology, Medical School, W-3000 Hannover, Federal Republic of Germany