Effects of endurance exercise on serum enzyme activities in the dog, pig and man.

Daily levels of GOT, GPT, AK and LDH did not change consistently with exercise in any species. The level of CPK each day before exercise presented a consistent rise during the week of exercise in the dog and man but not in the pig. By the third day of resting, all enzyme activities were at control levels. The probable tissue of origin for AK and LDH at rest as well as after exercise was the heart, liver, skeletal muscle and kidney in all three species. Serum CPK was the most sensitive index of acute exercise stress in the trained dogs and men. We have shown that the pig, which exhibits responses to exercise resembling those of man, can be exercise trained. The pig may, therefore, be the more appropriate model for endurance exercise studies.