02/23/2014
Functional Mechanics of the Peroneus Longus. Ankle rehab, prehab and activating the spring system of the foot.
Standard kinesiology says that the peroneus longus plantar flexes and everts the foot. This is functionally not what is does, however. It's primary function is to slow down the force of gravity as the foot comes crashing into the ground, absorb that force, and hold the foot on the ground as the knee and hip extend.
Functionally, it eccentrically loads as the forefoot enters the ground and decelerates dorsiflexion of the first ray (joint of the first metatarsal and middle cuneiform) and holds it on the ground for push-off of the big toe. Also, it decelerates dorsiflexion of the ankle, midtarsal joint inversion, and subtler joint eversion.
Picture 1 shows the muscle origin and insertion
Picture 2 shows the neutral foot. Notice how the heel bone (calcaneus) is not sitting directly under the leg but off to the outside.
Picture 3 shows how, in foot strike, this orientation allows the foot to pronate, load the posterior calf muscle, and absorb gravity to unload into propulsion.
Picture 4 shows a foam rolling technique to release this important muscle of the foot spring system. This muscle can be particularly sore right below the outside bump below the knee (the head of the fibula).
Self treating this muscle is a great way to prevent injuries and maximize ankle performance prior to working out.