Key result
The stable maintenance heat rate was maximal at a muscle length 7-16% shorter than the length for maximal tension, indicating tension is not the sole determinant of energy liberation.
In frog striated muscle, the maintenance heat rate varies considerably with muscle length near the length of maximum tension, implying tension is not the sole determinant of energy liberation.
Should not change clinical management of cardiac muscle length; leaves open applicability of frog muscle findings to human myocardium.
Tension and heat rate were measured as a function of muscle length in the range 0.75--1.25 lO in 10-sec isometric tetani in frog striated muscle at 0 degrees C in seven experiments. lO was defined as the length at which maximal tension was developed. 2. The length at which the stable maintenance heat rate (hB) was maximal was 7--16% lO shorter than the length at which tension was maximal (Pmax). 3. The range of hB at the length at which tension was maximal was 0.82-0.97 times the maximum value of hB. 4. For equal values of tension of 0.9 Pmax on each side of lO, hB was almost 40% greater at the shorter muscle length. 5. The results show that h(B) varies considerably with muscle length near lO, where tension varies little, and imply that tension is not the sole determinant of energy liberation in this little region.
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Aubert et al. (1980) studied this question. Muscle length variation (0.75-1.25 lO) was evaluated on Tension and heat rate as a function of muscle length. The stable maintenance heat rate was maximal at a muscle length 7-16% shorter than the length for maximal tension, indicating tension is not the sole determinant of energy liberation.
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