Fig. 6. Stimulus phase as a function of cycle frequency. Phase is the time of stimulus onset during the sinusoidal length cycle, in degrees, where 0° is muscle lengthening through resting length and 90° is maximum muscle length just prior to shortening. Data from anterior (ANT) and posterior (POST) locations are shown. Curves show the optimal stimulus phases required to maximize net work output from isolated muscle. Heavy bars show the stimulus phases used by swimming fish (Shadwick et al., 1999). Asterisks indicate optimal phases that are significantly different (P<0.05) from those used in vivo. The limited range of phases from swimming fish reflects the limited range over which fish actually swim using only red muscle. Values are means ± S.E.M., N=3–6.
