Phosphagen and lactate contents of m. quadriceps femoris of man after exercise.

Muscle biopsies were taken from the m. quadriceps femoris of man immediately after termination of dynamic and isometric exercise. These were analyzed for adenosine triphosphate (ATP), adenosine 5'-diphosphate (ADP), adenosine 5'-phosphate (AMP), phosphorylcreatine (PC), creatine, pyruvate and lactate. Regardless of type, intensity, and duration of the preceding exercise, a general pattern of the relation between high-energy phosphates and lactate content could be observed. PG showed a nonlinear relationship to the muscle lactate content. The ratio of ATP to ADP appeared to decrease linearly when lactate content increased. The relationships are believed to be the consequence of a steady-state condition where muscle pH is one of the major determining factors.