Creatine kinase and glutamic oxalacetic transaminase activity in serum: Kinetics of change with exercise and effect of physical conditioning

Serum creatine kinase (CK) and glutamic oxalacetic transaminase (GOT) activity following a standardized 6 minute period of moderately severe exercise has been studied in 7 normal women and 7 normal men before and in 11 of the individuals after a 3 to 5 week period of physical conditioning. Before physical conditioning the exercise resulted in a marked increase in serum CK activity with a peak rise at 8 to 16 hours. There was also a slight, but statistically significant, increase in serum GOT with a peak at 16 to 24 hours. Following a period of physical conditioning, the same exercise resulted in little or no change in either the serum CK or GOT level. This appears to represent another manifestation of muscle adaptation to increased work. A lack of circadian variation in serum CK activity was also demonstrated.