Background: Exercise leads to an increase in plasma potassium, the animal experiments showed that potassium infusion stimulated ventilation and abolished by peripheral chemodenervation and also showed that combined effects of potassium and hypoxia were greater than the sum of the individual effects. This study proposed to investigate plasma potassium and its correlation with exercise, and to investigate the effects of hypoxia and hyperoxia on potassium and ventilation during steady state exercise.
Methods: Ten male subjects exercised on a cycle ergometer. Each performed (1) incremental exercise test; (2) steady state exercise test with a work rate of about 75% of anaerobic threshold under hyperoxic (FiO2 100%), normoxic (FiO2 21%) and hypoxic (FiO2 12%) conditions, respectively.
Results: Arterial plasma potassium concentration rose from a pre-exercise level of 3.97 +/- 0.40 mEq/L to the post-exercise level of 5.11 +/- 0.49 mEq/L. The increase in plasma potassium during exercise correlated well with the increase in lactate (r = 0.72, p < 0.05) and the decrease in pH (r = 0.69, p < 0.05). During the steady state exercise test, switching the subject from room air to hypoxic (12% O2) conditions led to a significant rise in both plasma potassium (p < 0.05) and ventilation (p < 0.05) with good correlation between the potassium increase and the increase in ventilation (r = 0.85, p < 0.05). Switching the subject from room air to hyperoxic (100% O2) condition resulted in a significant decrease in ventilation (p < 0.05) without significant change in plasma potassium (p > 0.01).
Conclusions: It was concluded that (1) exercise can lead to an increase in arterial potassium, hydrogen ion, lactate in men; (2) hypoxia can stimulate the peripheral chemoreceptor and increase plasma potassium level. Potassium may, therefore, be an important factor by which the magnitude of the peripheral chemoreflex response is augmented during exercise.