Mechano‐Elastic Properties of Human Muscles at Different Temperatures

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Abstract
The effect of changes in the muscle temperature on their ability to store elastic energy was studied by having 5 trained subjects perform maximal vertical jumps on a force platform, with and without counter movement, at muscle temperatures between about 32.degree. C and 37.degree. C. The heights of vertical jumps were considerably reduced at lowered temperature, but the gain in height after a counter movement in the form of a jump down from a height of 0.4 m over the force platform, was significantly higher in the cold condition. To test whether this was due to an increased stiffness of the muscles, experiments with imposed sinusoidal length variations at 14 Hz were performed. .DELTA.force .times. .DELTA.length-1 (stiffness) increased with isometric tension independent of muscle temperature. Experiments in which the rate of tension development and relaxation in voluntary maximal contractions were measured at different muscle temperatures showed that maximal isometric tension changed by less than 1%/degree but the rate of tension development and relaxation by 3-5% and 5%/degree, respectively, in the temperature range studied (30.degree.-40.degree.). These data may be explained by the hypothesis that the series elastic components of the active muscle are located in the cross-bridges between myosin and actin filaments. The storage of elastic energy would be enhanced if the rate of breaking of these bridges were decreased at lower temperatures.

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