An example of the force-length relation (A) observed in the experiments for staircase at 22°C. Individual points represent twitch contractions either prior to (Pt, solid line) or after (Pt*, dashed line) 10 s of 10 Hz stimulation at selected sarcomere lengths. Similar to the situation at 35°C, potentiation was greater at short sarcomere lengths than at long sarcomere lengths. In B, the results from 5 muscles are shown. In this case (as in Figure 2B), the force is expressed as Pt*/Pt. Regression analysis gave r2= 0.48 and Pt*/Pt = -0.39·SL + 2.34 (where SL is sarcomere length).