SODIUM, POTASSIUM, AND LACTIC ACID AFTER MUSCULAR EXERCISE IN THE RAT

Abstract
Untrained young rats were exercised on a treadmill for a standard time at different speeds. A linear correlation between the intensity of the exercise and the degree of plasma [K] rise was observed. On the other hand, exercise at standard speed for varying durations was found to cause an increase in plasma [K] only during the early stages of the exercise. A fall in plasma [Na] was a constant accompaniment of exercise but no definite correlation to either intensity or duration was found. Lactic acid rose only with relatively severe exercise or with excitement. Blood sugar did not vary. Old rats responded to even mild exercise with a marked [K] shift accompanied by a well-defined rise in lactic acid.