Metabolic changes in man during long-distance swimming.

Sixteen young adults were investigated before, immediately after and 24 h after swimming 5,200 +/- 618 m in 90 min. Mean pulse rate at the end of exercise was 151.3 min-1; skin and rectal temperature both slightly increased. Except for a marked leukocytosis, no changes were observed in other blood parameters (hematocrit, hemoglobin, erythrocytes). Serum enzyme activities showed (except for triosephosphate dehydrogenase) marked increases which in the case of creatine kinase and of malate dehydrogenase did not return to preexercise level on the next day. No hypoglycemia occurred in any of the subjects. Blood lactate increased to 4.2 mmol/l at the 15th min of exercise and at the end was still slightly above the resting value. Free fatty acids, free glycerol, 3-hydroxybutyrate, serum urea and uric acid rose markedly after swimming, whereas alpha-amino nitrogen, triglycerides, and serum magnesium significantly decreased. The electrical excitability of the two investigated muscles (M. vastus med. quadr. and M. deltoides) showed opposite changes, which was ascribed to their different involvement during swimming.