Kinetics of Anaerobic Recovery in Muscle Contraction.

Abstract

In an earlier paper 1 the authors called attention to the fact that the lactic acid liberated per contraction in striated muscle made to contract isometrically is dependent upon the interval between contractions, and presented a curve relating lactic acid produced per contraction to the contraction frequency. The location of at least 2 of the points on the earlier curve, at frequencies of 12 per second and 4 per second, was only approximate, since the number of experiments at those frequencies was small. We have since conducted a larger number of experiments, approximately 50 each at frequencies of 12 per sec., 6 per sec., 4 per sec., 2 per sec., 1 per sec., and 1 per 2 seconds all at 22°C. We believe the number to be sufficient to indicate with reasonable accuracy the course of the time interval-lactic acid curve. The standard deviation is in each case about 0.02 mg. per 100 gm. of muscle. Stimulation was through the nerve by means of maximal break shocks from a Harvard inductorium, through a mechanical circuit breaker and make-shock eliminator.

In the earlier paper it was shown that at infinite intervals between contractions, (when the interval becomes greater than 2 seconds at 22°) the lactic acid produced per stimulation becomes constant. Evidence was presented to show that at intervals shorter in duration, removal is not complete. If we may assume the concentration of lactic acid reached when intervals are infinite to be a concentration maximum, and that in each successive contraction the concentration of lactic acid is built up to that maximum, then the amount of new lactic acid which appears in each contraction is an index to the amount removed in the preceding interval.