POTASSIUM AND VENTILATION DURING EXERCISE ABOVE AND BELOW THE VENTILATORY THRESHOLD

Increases in arterial plasma potassium during exercise may provide an important drive to ventilation. We examined the changes in arterialize d venous plasma potassium concentration ([K+]av) and ventilation that occur during sustained exercise at workloads above and below the venti latory threshold (VT) in young healthy humans. After the onset of exer cise at a workload below-VT, [K+]av rose by 0.3 (+/-0.1) mmol l(-1) (m ean +/- SEM). Following 30 min of exercise at this intensity [K+]av ha d fallen (P < 0.05: ANOVA) by an amount approximately equal to one thi rd of the initial increase. While [K+]av fell, ventilation remained st able. Al 5 min after the onset of sustained exercise above the VT [K+] av had risen by 0.7 (+/- 0.1) mmol l(-1) and thereafter remained const ant. Ventilation slowly increased throughout the above-VT protocol. Th ese results show significant differences in the time course of the cha nges in [K+]av and ventilation. They do not support the hypothesis tha t changes in [K+]a during moderate exercise cause linearly related cha nges in ventilation. (C) 1997 Elsevier Science B.V.