The musculoskeletal model for simulations of countermovement jumping (right side shown) consisted of rigid segments representing the trunk and two legs, with each leg consisting of a thigh, shank, patella, and three-part foot for a total of 13 degrees of freedom (flexion/extension at the hip, knee, ankle, mid foot and toes of each leg along with vertical and horizontal translation and rotation of the trunk). The model was driven by 25 musculotendon actuators per leg grouped into 13 muscle groups based on anatomical function: IL (illiacus, psoas), GMAX (gluteus maximus, adductor magnus), GMED (anterior and posterior regions of the gluteus medius), VAS (3-component vastus), RF (rectus femoris), HAM (medial hamstrings, biceps femoris long head), BFsh (biceps femoris short head), GAS (medial and lateral gastrocnemius), SOL (soleus, tibialis posterior), TA (tibialis anterior, peroneus tertius), PR (peroneus longus, peroneus brevis), FLXDG (flexor digitorum longus, flexor hallucis longus) and EXTDG (extensor digitorum longus, extensor hallucis longus). PR, FLXDG, and EXTDG are not shown. Each muscle within a group received the same excitation pattern.