Muscular exercise, lactic acid, and the supply and utilisation of oxygen.—Parts ӏ-ӏӏӏ

Abstract In a recent paper under the general title of this series A. V. Hill and Lupton (1) gave a preliminary account of experiments made on man, in an attempt to press to its logical conclusion the physico-chemical view of muscular contraction arrived at by the investigation of the isolated muscle. The present series of papers contains a more adequate account of these experiments, which are still in progress. (a) The “ Initial ” Process. In the isolated muscle the complete cycle of contraction and relaxation, as distinguished from recovery, appears to be accompanied by no chemical change of any importance, other than the conversion of glycogen into lactic acid, and the subsequent neutralisation of the latter (2) (4). These “ initial ” phases of muscular activity are entirely non-oxidative in character (3), and the following “ balance sheet ” (Table I) shows that, if any other chemical changes do actually occur, they are negligible from the energy standpoint.