Fig. 3. The force–velocity relationships of maximally stimulated muscle (177c, 179) while shortening isotonically at different force levels. Both graphs represent the same data set, but are plotted with different abscissas. Each symbol represents a different animal (N=4 for each muscle). The filled symbols and solid line represent muscle 177c, whereas the open symbols and dashed line represent muscle 179. Force–velocity relationships were established for each individual (see text). The Hill coefficients were then averaged to obtain the overall force–velocity relationships for each muscle, represented by the lines. (A) Absolute force–velocity relationship. In absolute terms, the muscles shorten maximally at the same velocity during running (arrows; approximately 15 mm s^–1). (B) Relative force–velocity relationship. Muscle 177c was more than twice as long as muscle 179. Therefore, in relative terms, maximum shortening velocity, V_max, for muscle 177c was 5.7±0.4 L s^–1 (N=4), where L is muscle length. The maximum in situ contraction velocity was approximately one-third V_max or 1.7±0.2 L s^–1 (N=7; solid arrow) for 177c. V_max for muscle 179 was 4.9±0.4 L s^–1 (N=4), while the maximum in situ relative contraction velocity of 179 was 3.7±0.1 L s^–1 (N=6), which is near its V_max (dashed arrow). The Hill constants, which represent the curvature of the force–velocity relationship are a=0.5±0.3 and b=2.7±1.3 (N=4) for muscle 177c and a=0.6±0.2 and b=2.5±0.9 (N=4) for muscle 179. Values are means ± S.D.

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