Figure 1.

Influence of [Ca²⁺] on power generation. (A) Representative work loop traces from one fiber show the tension response to a 0.75% ML change. The inset shows that the same fiber was symmetrically oscillated through a sinusoidal waveform at 125 Hz. The oscillatory pattern of the ML change started at the base of the sinusoidal waveform. Thus, the tension level starts at the F₀ level for that pCa and increases. Wide black traces show fiber shortening, and thin gray traces show fiber lengthening. Arrows also indicate shortening and lengthening. (B) Maximum power was determined at seven [Ca²⁺] by optimizing strain amplitude with 0.25% increments, and frequency with 25 Hz increments for each [Ca²⁺] using the work loop technique. The data are fit with a Hill curve, as described in the legend of Fig. 3. N = 7 fibers; values are mean ± SE.