Lactic Acid Accumulation During Work. A Suggested Standardization of Work Classification

¹ From the Department of Physiology-Biophysics, School of Aviation Medicine, USAF, Randolph Air Force Base, Texas

The correlation of blood lactate production in man with respiratory and circulatory adaptations resulting from physical exercise during an established work capacity test was studied. From physiologic criteria observed, an attempt was made to prepare a general classification of work intensity. Three distinctly different increments of lactic acid accumulation in the blood during gradually increased work indicates the following classification: I, light work: pulse rate not exceeding 120 beats per minute, no lactic acid increase significantly above the resting level; II, heavy work: pulse rate between 120 and 160 beats per minute, a lactic acid increase from approximately 20 to 40 mg %; III, severe work: pulse rate above 160 beats per minute, a lactic acid increase to 100 mg % or more.