The relative muscle volume of triceps surae differs among sprinters, runners and untrained subjects

The relative muscle volume is the critical parameter to estimate the contribution of individual muscle on joint torque. Because muscle hypertrophy is prominent in the fast than slow twitch muscle, it is hypothesized that the relative muscle volume of triceps surae may vary among subjects according to the training status. We examined this hypothesis by comparing the relative muscle volume among sprinters, runners, and untrained subjects. Magnetic resonance imaging was used to calculate the total and relative muscle volumes of medial gastrocnemius (MG), lateral gastrocnemius (LG) and soleus (SOL). The total muscle volume was significantly larger in the sprinters than the runners and untrained. The relative muscle volume of MG was larger and that of SOL was smaller in the sprinter than in the runners and untrained. These results indicate that the relative muscle volume can vary among subjects, possibly due to the fiber type-dependent muscle hypertrophy.