HIGH-ENERGY PHOSPHATE-COMPOUNDS DURING EXERCISE IN HUMAN SLOW-TWITCH AND FAST-TWITCH MUSCLE-FIBERS

  • 1 January 1982
    • journal article
    • research article
    • Vol. 42  (6) , 499-506
Abstract
Concentrations of ATP and creatine phosphate, the high-energy phosphates, were investigated in slow-twitch (ST) and fast-twich (FT) muscle fibers in sprinters and in long-distance runners at rest, during light sprinting exercise and during an extremely exhaustive running exercise. At rest, the long-distance runners had significant (P < 0.005) more creatine phosphate in ST than in FT muscle fibers. Both the light and the exhaustive exercise induced breakdown of creatine phosphate to very low levels (10-15 mmol/kg; dry wt) in FT muscle fibers. In response to the exhaustive exercise, creatine phosphate in the ST fibers of the sprinters fell to a significantly (P < 0.05) lower value than of the long-distance runners in the ST fibers. During the recovery period, the synthesis of creatine phosphate seemed to be more rapid in FT and ST muscle fibers in light exercise (P < 0.02) and in sprinters in exhaustive exercise (P < 0.05). During short-term exercise FT muscle fibers consume more of their creatine phosphate stores than ST muscle fibers; in vigorous exercise athletes trained for sprinting are able to recruit not only the FT but also the ST muscle fibers; and in such trained sprinters creatine phosphate is possibly resynthesized more rapidly in FT than in ST muscle fibers.