Lactate dehydrogenase activity in muscle after prolonged severe exercise in man.

Abstract

Muscle samples were obtained by needle biopsy from the lateral portion of the quadriceps muscle before and after prolonged severe exercise, which in 4 subjects consisted of a 2-2.5 hr. competition in cross-country running and in 2 subjects of 4-4.5 hr. bicycle or treadmill exercise ([image]O2 = 70% of [image]O2max)- LDH [lactate dehydrogenase] activity in the muscle increased 21 (16-31) % (P< 0.001) with the prolonged exercise. Three of the subjects starved for 24 hr. after the prolonged exercise and in 2 of them the muscle LDH activity was still elevated. The very low blood lactate concentration during exercise found after a previous prolonged exercise period can obviously not be explained by low LDH activity. Whether the elevated LDH activity is explained by an increased amount of enzymes or a change in the Michaelis constant cannot be determined.