Fig. 4. Measured AP recovery (symbols) compared with the volume-averaged model of AP recovery (solid line) in small (A) and large (B) fibers. The measured AP data have been normalized to a resting concentration of 34.3 mmol l^–1 to coincide with that of the model. In the model, the myosin ATPase was activated long enough to cause a decrease in AP that was comparable to the measured data. The dotted line indicates the resting concentration.