The lactic acid in the blood of dogs in exercise

Abstract

In the course of our study of fatigue, it became desirable to make determinations of the concentration of lactic acid in the blood. Ryffel's method was used with the modification that the formaldehyde standard was tested against a known lactic acid solution in each experiment. The blood was obtained from the jugular vein of dogs which were exercised on a motor-driven treadmill. The results of typical experiments are given in Tables I and II.

It will be seen from Table I that severe exercise of short duration brought about a marked increase in the concentration of the lactic acid in the blood. The results given in Table II, however, show that when the exercise was of moderate intensity and long continued, the concentration of lactic acid in the blood was decreased. We believe that the increase of the lactic acid in the blood in the initial stages of severe exercise may be associated with the hyperpnea occurring at that time, and that its subsequent decrease, due perhaps to an increased efficiency of the oxidative processes, may be related to “second wind.” In view of the fact that no increase has been found in the lactic acid in exercise however long continued, its significance as a primary factor in physiological fatigue, not carried to exhaustion, would seem open to question.