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

Purpose: The objective of this investigation was to determine the effects o f varying levels of dietary protein on the postexercise increase in serum a nd muscle enzyme activity normally observed following exercise-induced musc le injury. Methods: Serum creatine kinase (CK), serum aspartate aminotransf erase (AST), and muscle glucose-6-phosphate dehydrogenase (G-6-PD) activiti es 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 degrees incline, 90 min). Results: The exercis e intervention resulted in significant increases in serum CK and AST activi ties in all diet groups. Serum CK demonstrated peak activity immediately po stexercise with increases reaching 910 +/- 94, 594 +/- 53, and 283 +/- 52 I U.L-1 for animals on high, normal, and low protein diets, respectively. Sim ilarly. peak postexercise AST activity for high, normal, and low protein di ets reached 193 +/- 10, 147 +/- 3, and 162 +/- 9 IU.L-1, respectively. The exercise intervention resulted in increases in muscle Gd-PD activity for al l diet groups; however, LP rats demonstrated significantly lower values tha n NP or HP rats. Conclusions: These data show that dietary protein intake c an significantly effect both serum and muscle enzyme activity following acu te exercise-induced muscle injury.