Breakdown and Resynthesis of Phosphorylcreatine and Adenosine Triphosphate in Connection with Muscular Work in Man

Hultman, E., Bergström, J. & McLennan Anderson, N. Breakdown and Resynthesis of Phosphorylcreatine and Adenosine Triphosphate in Connection with Muscular Work in Man. Scand. J. clin. Lab. Invest. 19 56–66, 1967. Needle biopsies were performed in the m. quadriceps femoris of normal subjects, at rest and in connection with work on a bicycle ergometer.The concentrations of PC and ATP were determined in the biopsy material. The normal values in resting muscle were as follows: ATP 2.43 mmole per 100 g dry muscle (S.D. 0.21), PC 6.78 mmole per 100 g dry muscle (S.D. 0.70).The PC concentration was found to decrease rapidly during the first 2 minutes of continuous work, then remaining at a relatively constant level. The resynthesis of PC after work is complete within a few minutes.It has been demonstrated that a reverse relationship exists between the work load and the PC concentration in the muscle during work. At very high work loads the PC concentration decreases rapidly down to zero and the contractive capacity of the muscles ceases.When the glycogen store is considerably decreased, the PC level at work is lower than when work with the same load is carried out with the glycogen store intact.The ATP concentration also decreases during the first minutes of work, but during continuous work with low or moderately high loads the concentration of ATP tends to return to the basal level. At heavy work with pronounced decreases of PC, the ATP concentration also stays decreased. When the PC level is near zero the ATP decrease is approximately 40 per cent of the basal value.