THE OXYGEN-CONSUMPTION OF ISOLATED MUSCLES FOR ISOTONIC AND ISOMETRIC TWITCHES

Abstract

By means of a differential-volumeter, the increased O consumption of a frog sartorius muscle after stimulation of the nerve by single induction shocks has been observed, for isometric twitches and for isotonic twitches of different loads. Two types of experiments were performed; in the 1st, the excess O consumption was determined for a series of 20-60 stimulations occurring in 1 or 2 min., while in the 2nd type the equilibrium consumption was measured for continuous stimulation with a frequency of 2-6 per min. Isotonic twitches with large loads, where little shortening occurs, have a higher O consumption than isometric twitches, while isotonic twitches with small loads and consequently large shortenings need less O than the isometric twitches. The value of 0380 for the O consumption per gm. tension and unit of muscle length is in good agreement with the corresponding values of heat measurements. The maximal efficiency observed was 13.8%. From the experiments the conclusion is drawn that the energy liberated in a twitch depends on 2 factors, the length of the fibres during contraction and the work done (Fenn effect).