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To determine how maximal shortening velocity relates to isomyosin composition and fibre types in the soleus muscles of mice, rats, and guinea-pigs.

September 1, 1989The Journal of PhysiologyOpen Access

Maximal shortening velocities, isomyosins and fibre types in soleus muscle of mice, rats and guinea‐pigs.

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To determine how maximal shortening velocity relates to isomyosin composition and fibre types in the soleus muscles of mice, rats, and guinea-pigs.
Characterized fibre types (type I composition) and isomyosin profiles (SM1, SM2, IM) across mouse, rat, and guinea-pig soleus muscles.
Measured maximal unloaded shortening velocity (V0) and computed muscle maximal velocity (Vmax) using the Hill force-velocity relationship.
Maximal unloaded shortening velocity (V0) was highest in mouse soleus (6.11 Lf s-1), intermediate in rat soleus (4.16 Lf s-1), and lowest in guinea-pig soleus (1.67 Lf s-1).
V0 equalled Vmax in guinea-pig soleus (100% type I fibres and SM2), whereas V0 was approximately twofold greater than Vmax in mouse and rat soleus muscles containing mixed isomyosins.
V0 scaled positively with fibre isomyosin composition in the hierarchical sequence of SM2 < SM1 + IM < IM.

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Species differences in rodent soleus V0 reflect fiber-type composition; leaves open translation to human cardiac or skeletal muscle function.

Asmussen et al. (1989) studied this question.

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Species differences in rodent soleus V0 reflect fiber-type composition; leaves open translation to human cardiac or skeletal muscle function.