Figure 2. Protocol for mechanical and X-ray data collection.

A and B, force response (upper trace) to three release–restretch (A) and stretch–release (B) cycles (lower trace) superimposed on the steady force developed at the plateau of an isometric tetanus. Middle trace: X-ray exposure time windows. In the inset, one cycle on a faster time base. Time zero marks the start of stimulation. C, relationship between the force attained at the end of the first step in each cycle and the step amplitude (mean ± SEM from five muscles).