Temperature influence on phases of the tension response to sudden reduction of muscle length.

Phasic tension transients following a quick release in muscle length were studied to obtain information about the mechanism of force generation at different temperatures. The isometric tetanic tension increased (Q10 = 1.5) in the temperature range of 1.4 degrees C to 11.4 degrees C. The instantaneous stiffness (tension drop during the applied quick release in relation to the percentage of change of length) is slightly reduced by increasing temperature (Q10 = 0.9). The rate constant of the early tension recovery (phase 2) increased with increasing temperature (Q10 = 1.8). The results indicate that the increase of tetanic tension with increasing temperature is due to an increasing amount of force, generated by each cross bridge and a higher speed of rotation of the myosin head. The number of force generating cross bridges defined by the instantaneous elasticity is nearly independent of temperature range studied.