Important Joints
The three joints described here are the key joints of concern for the sprinter.
HipsHip flexion and extension is instigated by the muscles of the glutes and lower core. The hip flexor muscles, which link the hip and core to the leg muscles, will be mainly responsible for flexion of the hip.
KneesThe knee joint flexes in extension and flexion. The pennate fibres in the hamstrings and gastrocnemius muscles will redirect a great deal of energy, as well as using stored elastic energy, when the knee is driven into the extension action. Add this to the ground reaction force (GRF) and you have a great tool to make best use of the power generated from the glute muscles around the hip joint, whether going in a straight line, around a bend or over hurdles.
AnklesThe ankle joint has the least amount of muscle surrounding it, or rather above it in the calves, but it has an array of nerves and tendons that help create the right responsive balance, called proprioception.
The body experiences a point of triple extension when the hip, knee and ankle joints are aligned. At that point the body can make the best use of productive forces between the body and the ground