Although plantar flexor torque increases the sprint velocity by enhancing the ground reaction force, it is yet unkown whether the proportions of the triceps surae muscle and ankle joint, both of which are related to the production of plantar flexor torque, affect sprint performance. Therefore, in the present study, we examined the relationship of the triceps surae muscle with ankle joint proportions and performance in sprinters. Thirty-two well-trained sprinters participated in this study. The proportions of the triceps surae muscle and ankle joint were measured by using magnetic resonance imaging. In the proportions of the triceps surae muscle, the muscle volume of the gastrocnemius medialis (GM), not the gastrocnemius lateralis and soleus, was significantly correlated with the sprinter's personal best time in a 100-m race (R=-0.391, P=0.032). Moreover, location of the muscle-tendon junction of the GM was also significantly correlated with the 100-m performance (R=0.445, P=0.014). In contrast, the ankle moment arm length, a proportion of ankle joint, was not significantly correlated with the 100-m performance; however, only a trend was noted (R=-0.317, P=0.088). The present findings suggest that a larger muscle volume and a lower location of the muscle-tendon junction of the GM in the triceps surae muscle may help achieve a successful sprint performance, potentially by producing a larger plantar flexor torque.
