Figure 5.

The dynamic FL relation produced by the four groups investigated in this study. (a) Force was normalized by the isometric forces produced before the first length change in each experiment (approx. 5 s after the initial activation). Solid line shows the theoretical FL relation (Gordon et al. 1966) using the filament lengths from the rabbit psoas muscle (Sosa et al. 1994). The results of four experiments with myofibrils activated with Ca²⁺ to produce purely isometric contractions are also shown. The shapes of the dynamic FL relations are significantly different, except by the two stretch conditions that were similar to each other. (b) Force normalized by the maximal force produced during the protocol. The shapes of the FL relation are significantly different, except by the two stretch conditions that were similar to each other. All results are mean ± s.e.m. Filled circle, ADP-SHO; open circle, ADP-STR; filled inverted triangle, Ca²⁺-SHO; open triangle, Ca²⁺-STR; open square, isometric.