Abstract
The lever arm (L) and power arm (P) lengths in the two dimensional saggital plane of the human gastrocnemius and soleus muscles were estimated from the measurements of 10 male cadavers. The L/P values, defined as the ratio of these two lengths, were then calculated to determine functional characteristics of the architecture of these two muscles. Analysis of the L/P values suggested the following characteristics of the triceps surae muscle: 1. The gastrocnemius, which was morphologically considered a two joint muscle, had greater effectiveness on the speed of contraction for ankle joint plantar flexion than for knee joint flexion. 2. The soleus, which was morphologically considered a one joint muscle, was more effective on the production of muscular force than the gastrocnemius. Thus, the soleus is specialized for muscular force generation and the gastrocnemius is specialized for the speed of the joint excursion. 3. The distal expansion of the origin of the soleus did not reflect on its functional characteristics. These results agree with the accumulated data of the histological and biochemical features of this muscle, and could be correlated with the human bipedal habit.
