Power and efficiency: how to get the most out of striated muscle

White muscle fibres from dogfish were stimulated during sinusoidal cycles of shortening and lengthening that mimic the in vivo pattern of movement. The results show that the timing of the stimulation relative to movement and also the frequency of the movement affect mechanical power output and efficiency. Maximum mechanical power is produced at a higher frequency of movement than maximum efficiency. The value of maximum power for a cycle of movement is less than half that produced during ramp shortening of fully active fibres. Higher efficiency is achieved during cyclic movement than during ramps, probably because work can be done with lower "overhead" costs for activation and because little ATP is used during lengthening.