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The purpose of this investigation was to quantitate post-competition lactate (LA) concentrations of swimmers during a competitive collegiate meet. Blood LA was measured by an enzymatic method on 23 subjects 5 min after each race event. The largest mean LA concentration of 25.7 mM/L was observed in swimmers after competing in the 200-yd individual medley. Swimmers in the 200-yd butterfly, back, breast and freestyle races had similar mean blood LA concentrations (ranging from 16.4 to 20.6 mM/L). Swimmers in the two longest events, the 500-yd and 1,000-yd free style races, had mean LA concentrations of 15.6 and 10.0 mM/L, respectively. To account for the effects of motivation, LA concentrations were measured following maximal effort noncompetitive 100 and 200-yd swims. LA concentrations were slightly greater in conjunction with faster performances for the competitive as compared to the noncompetitive 100 and 200-yd swims.

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In the pentobarbital-anaesthetized dog the effect of electrical stimulation of hindlimb skeletal muscles on thoracic and right duct lymph flow and enzyme content was examined. Increase in plasma creatine kinase (CK), L-aspartate-aminotransferase (AST) and lactic dehydrogenase (LDH) during 30-min muscle stimulation were not significantly altered by draining lymph. Both right duct and thoracic duct lymph flow trebled during stimulation. At the same time, the activity of the three enzymes examined decreased in right duct lymph and increased in thoracic duct lymph. Of the latter, only the increase in lymph CK was of a sufficient magnitude to have resulted in a detectable increase in plasma CK. CK was the smallest of the three enzymes studied and apparently preferentially entered the lymph, suggesting that the larger AST and LDH molecules were not likely to have entered the blood plasma directly from skeletal muscle. Rather their entry from some other tissue, possibly the formed elements of the blood, is indicated.

The effect of continuous removal of thoracic duct lymph on plasma activities of creatine phosphokinase (PCK), glutamic-oxaloacetic transaminase (PAST); and lactic dehydrogenase (PLDH), was examined in pentobarbital-anaesthetised dogs over a 5.5- hour period. PCK and PAST declined relative to levels in control dogs while PLDH was unaltered. Lymph/plasma (L/P) ratios for AST and CPK were greater, and for LDH less, than the L/P ratio for total protein. It was concluded that PCK, and to some extent PAST, are normally maintained by introduction of enzyme, escaping from the intracellular compartment, into the circulating blood via the lymphatic system. PLDH and PAST appear to be maintained principally by introduction of enzyme directly from the intracellular to the plasma compartment.