Recovery heat in muscular contraction without lactic acid formation

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Abstract
Muscles poisoned with mono-iodo-acetic acid (Lundsgaard) contract without producing lactic acid. After contraction in O a delayed heat production occurs, similar to that which in normal muscles is associated with recovery. After the first 1 or 2 contractions of a poisoned muscle the "recovery" heat may be of normal amount in relation to the initial heat. After 30 or 40 twitches it is less than the normal, but still a considerable fraction of it. The heat production rate in O of a muscle poisoned with iodo-acetic acid and exhausted may remain, for long periods, far higher than that of a normal resting muscle. If the O be removed for a period the heat rate falls, and a "heat-deficit" occurs which is partly, but only partly, balanced by a "heat-excess" when 0 is readmitted. In a twitch or a short tetanus, as found by others, the ratio of tension developed to heat produced is entirely unaffected by poisoning with iodo-acetic acid. Functional recovery in O after stimulation, can be demonstrated under certain conditions, in muscles poisoned with iodo-acetic acid. The persistence of "recovery" heat when functional recovery has been eliminated suggests that one effect of iodo-acetic acid is to interfere with the mechanism by which the energy released in oxidation can be employed in driving the endothermic reactions necessary for functional recovery. It does not interfere with oxidation as such, at least in the concentrations used.

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