Effects of dietary protein on enzyme activity following exercise-induced muscle injury

The objective of this investigation was to determine the effects of varying levels of dietary protein on the postexercise increase in serum and muscle enzyme activity normally observed following exercise-induced muscle injury. Serum creatine kinase (CK), serum aspartate aminotransferase (AST), and muscle glucose-6-phosphate dehydrogenase (G-6-PD) activities were measured in rats fed for 10 days on high (50%), normal (12%), or low (4%) protein diets following a single bout of eccentric exercise (treadmill running at 16 m/min, -16 degrees incline, 90 min). The exercise intervention resulted in significant increases in serum CK and AST activities in all diet groups. Serum CK demonstrated peak activity immediately postexercise with increases reaching 910 +or- 94, 594 +or- 53, and 283 +or- 52 IU/litre for animals on high, normal, and low protein diets, respectively. Similarly, peak postexercise AST activity for high, normal, and low protein diets reached 193 +or- 10, 147 +or- 3, and 162 +or- 9 IU/litre, respectively. The exercise intervention resulted in increases in muscle G-6-PD activity for all diet groups; however, LP rats demonstrated significantly lower values than NP or HP rats. These data show that dietary protein intake can significantly effect both serum and muscle enzyme activity following acute exercise-induced muscle injury..