Oxygen Deficit and Muscle Metabolites in Intermittent Exercise

Abstract

Muscle ATP, CP, ADP, glycogen, G‐6‐P. lactate, and blood lactate concentration were studied in three subjects during intermittent exercise. One min of extremely heavy bicycle work was followed by five min of rest, which was repeated five times. Oxygen uptake was determined continuously and oxygen deficit could be calculated for each activity burst. Oxygen uptake was also measured during the first 60 min of recovery following the last exercise period. The accumulated oxygen deficit increased with each work period. The ratio between oxygen deficit and oxygen debt was 0.55.The breakdown of ATP and CP stores showed progressive phosphagen depletion with each burst of activity while the muscle lactate concentration reached its highest level, ca 23 mmoles × kg^‐1 wet muscle, as early as after the first work period. Blood lactate increased gradually during the first 15–20 min of interval periods and then reached a level of 20 mmoles × l^‐l. Muscle glycogen concentration was reduced with each work period but did not become completely depleted in any of the subjects. The subjects were as exhausted after the first work period as after the last one. Of the studied metabolic variables muscle lactate concentration was then the one best related to the point of exhaustion.