Geometric positioning of the foot and transfer of plantar loads can be adversely affected when muscular control in gastrocnemius-soleus (G-S) complex is abnormal. This study aims to develop a 3-D musculoskeletal finite element (FE) model of the foot to quantify the precise role of the G-S complex in biomechanical behavior of the foot. Movements of the ankle and metatarsophlageal joints, as well as forefoot plantar pressure peaks and pressure distribution under the metatarsal heads (MTHs) were all found to be extremely sensitive to reduction in the muscle load in the G-S complex. The findings may provide clinicians with knowledge to understand the underlying mechanism for relieving pain, injury or other structural deformities under metatarsal areas in patients who suffer from GS muscle contracture.