Pennation angles of ankle dorsiflexor and plantarflexors depending on muscle contraction intensity

In this study, we investigated the pennation angles of ankle muscles as they relate to muscle contraction intensity (MCI). Eight male subjects with no history of musculoskeletal injuries participated. In each patient, the ankle joint was fixed at 15° dorsiflexion and 0°, 15° and 30° plantarflexion. Ultrasound images (SonoAce Pico, Samsung Medison, Korea) were taken to measure the pennation angle of tibialis anterior (TA), gastrocnemius medial (GCM), gastrocnemius lateral (GCL), and soleus (SOL). The torque dynamometer (Biodex system 3, Biodex Medical System, USA) was used to measure the ankle contraction intensity corresponding to 0, 30, 70 and 100% of maximum voluntary contraction (MVC) respectively. Pennation angles in ankle muscles on sub-maximal muscle contraction were determined. In the present study, the significant differences was found at between 0% of MVC and sub-maximal MVCs, between 0° and 15° of dorsiflexion, and between 15° of plantarflexion and 15° of dorsiflexion. This study may be beneficial in implementing a more realistic muscle model of muscle force.