Gastrocnemius

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Other Names Calf Heads Medial Head Lateral Head Movement Ankle Plantar Flexion [1, 2 ] Knee Flexion [1, 2 ] Attachments Origin Femur Medial Condyle (Posterior) [1 ] Lateral Condyle (Posterior) [2 ] Insertion Calcaneous Achilles Tendon [1, 2 ] Related Muscles Soleus Comments The biarticulate gastrocnemius muscle [1, 2 ] enters passive insufficiency through the completion of ankle dorsal flexion when the knees are more extended or through the completion of knee extension when the ankles are more dorsal flexed. The biarticulate gastrocnemius muscle [1, 2 ] enters active insufficiency through the completion of knee flexion when the ankles are more plantar flexed (hamstrings becomes more active) or through the completion of ankle plantar flexion when the knees are more flexed (soleus becomes more active). In the seated calf raise (knees flexed to 90º), the gastrocs are virtually inactive while the load is borne almost entirely by the soleus. In moderate force, the soleus is preferentially activated in the concentric phase, whereas the gastrocnemius is preferentially activated in the eccentric phase. The gastrocnemius becomes even more activated at higher lengthening velocities (Nardone & Schiepatti, 1988). During hopping, the gastrocnemius, with its greater proportion of fast twitch motor units, is preferentially activated over the soleus (Moritani et al., 1990). During stationary cycling, the gastrocnemius is also preferentially activated at higher pedaling speeds (Duchateau et al., 1986). Although the involvement of the lateral and medial heads would not seem to be altered by medial or lateral rotation of the hip, magnetic resonance imaging (MRI) research by Dr. Per Tesch (Sweden) suggests "toes in" activate both heads and "toes out" activate the medial head to a higher degree. See dorsiflexion inflexibility.