Fig. 4.

Records from a Dahl-LS trabecula subjected to the work-loop contraction protocol. A: twitch profiles from a series of work-loop contractions at 7 different afterloads. The protocol commences at “A” (an isometric twitch) and decreases in afterload until “I”, before returning to a final isometric contraction. B: the associated muscle length changes for each of the work-loop contractions. C: parametric plot of stress vs. length from A and B. The area within each of the stress-length loops represents the work output of the muscle. D: rate of heat production during the work-loop protocol. Between each pair of work-loop contractions, the muscle performed an isometric contraction.