Fig. 1. Mean power output of eel fast muscle versus cycle frequency under optimal stimulus conditions and a strain of ±5%. Values are means ± S.E.M. (N=6). Optimal stimulus at a given frequency is shown as onset/duty cycle in degrees. Stimulus onset was measured relative to a 360° sinusoidal strain cycle. At 0°/360°, the preparation was at l₀ and lengthening, where l₀ is the preparation length that yielded maximum isometric stress. Data from 0.45BL are shown as filled circles with a solid line, data from 0.75BL are shown as open circles with a dashed line. BL, total body length.