Serum creatine phosphokinase and lactate dehydrogenase activities in the rat after variable durations of downhill running

Serum lactage dehydrogenase and creatine phosphokinase level were studied in sixty male Sprague-Dawley rats weighing 400 to 680 grams. Five groups of ten rats each ran forty-five minutes (16 m/min) with variable percentages of the total bout consisting of downhill running (16° incline): Group I- 0%, Group II- 22%, Group III- 50%, Group IV- 78%, Group V- 100% downhill. Group VI consisted of ten sedentary controls. Serial blood samples were obtained immediately after exercise, 12, 24, 36, 48, and 60 hours found to exist between a non-trained rat’s weight and its ability to finish the exercise bout and live beyond 48 hours.Each exercise group, except Group V, showed s significant decrease in the CPK activity at 24 and/or 36 hours post-exercise. Group V showed a significant elevation (P