Predicting muscle force generation during fast-starts for the common carp Cyprinus carpio

Muscle contractile properties have been characterised for white myotomal muscle from the common carp Cyprinus carpio at 10, 15, and 20 degrees C. The time course of muscle force development was measured when one, two, or three stimuli were delivered at the onset of constant velocity shortening. As the shortening velocity increased several parameters decreased including the maximum force, the time course for the contraction and the relative duration of the deactivation compared to the activation. The maximum force and the relative rates of activation to deactivation for the contraction were relatively independent of temperature, whereas the duration of the contraction decreased with increasing temperature. A predictive model was developed which was based on fitting a modified Weibull distribution to these observations. The model was used to interpolate the expected contractile forces during cyclic length-changes. Measured and predicted values for force and power during such cyclic work-loop experiments showed an excellent agreement over the range of shortening regimes typically found during swimming behaviours. However, the predicted force was overestimated during the deactivation phase of the contractions when the shortening velocities exceeded those found during swimming.