Hamstrings

Three muscles down the back of the thigh that both bend the knee and extend the hip — and, most importantly, decelerate the leg at speed. They are the most commonly strained muscle in sprinting sports.

This muscle in 3D

Drag to rotate · scroll to zoom — see the shape, origin and insertion of the hamstrings. 3D model via Sketchfab (CC-BY).

Anatomy

Muscles: Biceps femoris, semitendinosus, semimembranosus

Origin: Ischial tuberosity (sitting bone); short head of biceps femoris from the femur.

Insertion: Around the knee — biceps femoris to the fibula (outside), semitendinosus & semimembranosus to the tibia (inside).

Actions:

Knee flexion
Hip extension (with the glutes)
Deceleration of the swinging leg (eccentric, key in sprinting)
Rotation of the flexed knee

How the muscle works

As two-joint muscles they extend the hip and flex the knee at once. In sprinting their biggest demand is eccentric — braking the fast-forward-swinging shin just before foot contact — which is exactly when strains happen.

Fibre-type bias: Fairly fast-twitch, built for powerful and high-speed eccentric work.

Functional role: Sprinting, jumping, bending and lifting; knee stability alongside the ACL.

Common problems

Hamstring strain (sprinting)
Proximal hamstring tendinopathy (sitting-bone pain)
Weak eccentric strength → re-injury

Training & stretching

Romanian deadlifts, Nordic hamstring curls, hip hinges, glute-ham raises.

Supine leg-raise (with strap), standing forward fold, hip hinge with flat back.