Adrenaline and muscular exercise

Abstract

The mobilization of liver glycogen under the influence of adrenaline has generally been regarded as a factor which may be of importance during muscular exercise, since it may facilitate the transference of glucose to the active muscles. It is, however, by no means clear whether or not this will result in an enhanced use of carbohydrate as a source of energy in the muscles. Dill, Edwards and de Meio (1935) found that a subcutaneous injection of 0·5-1·0 mg. adrenaline during muscular work increases the respiratory quotient and the concentration of glucose and lactic acid in the blood, and concluded that the rise of quotient is mainly due to an increase in the proportion of carbohydrate oxidized. We ourselves (Courtice, Douglas and Priestley 1939), after following in detail the behaviour of the respiratory quotient after the administration of adrenaline and insulin to the resting subject, felt doubtful whether this conclusion was justified, and we have now made a further series of observations on the influence of the subcutaneous injection of adrenaline during muscular exercise. We have followed the same general procedure as in our previous experi­ments, using the same methods for the determination of the respiratory exchange, the concentration of glucose and lactic acid in the blood, and the CO 2 combining power of the blood. The subject was always in the post-absorptive state. After making preliminary determinations of the respiratory exchange and taking blood samples whilst at complete rest reclining in a deck chair, continuous work was done at a steady rate on a Krogh electric brake bicycle ergometer for a period of 2½-3 hr., conditions being kept comfortable by the draught from an electric fan. We restricted our observations to either light or moderate work so that there should be no risk of the added complication of the accumulation of a material excess of lactic acid in the blood as a result of the mere muscular activity, as well as to avoid fatigue since neither of the two subjects, Courtice and Douglas, were in athletic training. We felt, too, that any change in the respiratory quotient caused by adrenaline might become relatively insignificant, and therefore more difficult to interpret, if the total respiratory exchange were greatly exaggerated. Light work was equivalent to 210 kg. m./min., involving an oxygen consumption during the first half hour of about 680 c. c./min. in Courtice and 750 c. c. in Douglas, or rather more than thrice the resting metabolism, and moderate work was equivalent to 700 kg. m./min., involving an oxygen consumption during the first half hour of about 1540 c. c./min. in Courtice, or seven times the resting metabolism. Adrenaline chloride (Parke, Davis and Co., 1 : 1000 solution) was injected subcutaneously into the upper arm after the work had been in progress for half an hour.