Fig. 2. Example of a work loop (A) generated during 8 Hz sinusoidal length changes (strain of 10%) for the musculus protractor hyoidei (m-pr-h) of an 80.1 mm cranial length C. gariepinus, with (B) the corresponding instantaneous relative speed, (C) force per muscle cross-sectional area and (D) muscle-mass-specific power output. In A, raw data points are shown as well as the work loop curve after Butterworth filtering. The force produced by only the actively contracting components of the muscle was calculated by subtracting the force measured without stimulation (passive work loop) from the force with stimulation (active work loop).