The peroneus longus, the gastrocnemius and the soleus muscles are involved in plantar flexion. The muscles work together to allow a body to stand up on its toes. The peroneus longus muscle is also referred to as the fibularis longus because it is the longest muscle attached to the fibula.
Plantar flexion refers to the flexion or extension of the foot at the ankle. It is the movement that decreases the angle between the back of the leg and the sole of the foot. An example of plantar flexion is a ballerina extending her foot in line with her leg.