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

Purpose: 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. Methods: 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 d on high (50%), normal (12%), or low (4%) protein diets following a single bout of eccentric exercise (treadmill running at 16 m · min^-1, -16°incline, 90 min). Results: 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 ± 94, 594 ± 53, and 283 ± 52 IU · L^-1 for animals on high, normal, and low protein diets, respectively. Similarly, peak postexercise AST activity for high, normal, and low protein diets reached 193 ± 10, 147 ± 3, and 162 ± 9 IU · L^-1, 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. Conclusions: These data show that dietary protein intake can significantly effect both serum and muscle enzyme activity following acute exercise-induced muscle injury.