Figure 4. Typical experimental records arising from the work‐loop protocol at 5 Hz.

A, twitch stress of a trabecula undergoing progressively decreasing afterloaded work‐loop contractions (b–g), bounded by return to isometric contractions at L _o (a). The first twitch illustrates the rested‐state contraction immediately following the commencement of electrical stimulation. B, the corresponding rates of heat output, where the dotted line is drawn to signify the heat‐rate baseline. C, steady‐state twitch stress profiles at various afterloads. D, the corresponding steady‐state muscle length trajectory during each twitch in C. E, parametric plots of the stress and length profiles shown in C and D, resulting in stress–length work‐loops. In all panels, data were obtained from an RV trabecula (length, 3.4 mm; cross‐sectional area, 0.087 mm²).