Hyperkalemia During Progressive Dynamic Exercise

Abstract

Serum potassium levels, catecholamines, and plasma renin activity are elevated during maximal dynamic exercise. Catecholamines and plasma renin activity have been shown to rise nonlinearly during exercise and to parallel changes in venous blood lactate. Since the hyperkalemia of exercise is modulated by catecholamines, we studied the changes in serum potassium in relation to attaining the exercise intensity associated with a rise in blood lactate (the lactate threshold). Eight healthy male subjects 25 to SO years of age underwent progressive cycle ergometry (PE) at increments of 25 W/4 min. During PE, absolute levels of peripheral venous potassium increased significantly only after the lactate threshold was exceeded (T < .01). In a control study (TC), subjects exercised to their lactate threshold and remained at that work rate for a time equal to that of PE. During TC, there were no significant increases in potassium until the final four minutes of exercise (T < .05). Plasma aldosterone levels rose comparably during PE and TC. These results demonstrate that significant potassium elevation during dynamic exercise begins at the lactate threshold. This threshold response of potassium may have clinical implications for exercise prescription in patients with impaired potassium homeostasis.