Abstract
Lactic acid was determined in the urine of two subjects before and after a measured exercise. Two groups of four experiments each were made with each subject. In one group the subject breathed air, and in the other oxygen-enriched air containing about 40 per cent of oxygen. In order to eliminate the possible effects of training, the air and oxygen experiments were alternated. The exercise consisted in carrying a 30 pound load for five minutes on a treadmill with 7-inch steps, operated at the rate of 80 to 85 steps per minute, the work performed being about 6000 kgm. in five minutes. The resting rate of excretion of lactic acid bodies in the urine was determined before each exercise period, and the excess excretion above this level during approximately a half-hour period after the exercise. Determinations were made in duplicate by the method of Clausen, using permanganate oxidation as recommended by Long.
Both subjects showed a lower excess excretion of lactic acid when breathing oxygen-enriched air than when breathing air. Average figures for the four experiments in each group are as follows:
We believe the diminution in lactic acid excretion when breathing oxygen-enriched air to be due to lessened lactic acid accumulation in the muscles.
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