Muscle guide · Thighs
Also called hamstring muscles, back of the thigh muscles
The hamstrings are the muscles at the back of the thigh. Three of them run from the sit bone, past the back of the knee, to the top of the shin: the biceps femoris, semitendinosus and semimembranosus. The biceps femoris has a second, short head that starts on the thigh bone.
They bend the knee and straighten the hip, and in running they work hardest at the end of each swing, braking the lower leg before the foot lands.
| Part | Starts at | Attaches to | What it does |
|---|---|---|---|
| Biceps femoris, long head | The sit bone (ischial tuberosity) | Outside of the knee, on the head of the fibula | Bends the knee, turns the shin outward, straightens the hip |
| Biceps femoris, short head | Back of the thigh bone | Outside of the knee, on the head of the fibula | Bends the knee and turns the shin outward; does not cross the hip |
| Semitendinosus | The sit bone | Inside of the shin below the knee (pes anserinus) | Bends the knee, straightens the hip, turns the shin inward |
| Semimembranosus | The sit bone | Inner back of the top of the shin | Bends the knee, straightens the hip, turns the shin inward |
In a 12-week trial, seated leg curls (hip bent) grew the hamstrings more than lying leg curls: about 14% against 9%.
3D demoNordic curlAdvanced · An anchor point
3D demoSeated Leg CurlBeginner · Strength machine
3D demoMachine leg curlBeginner · Strength machine
3D demoBarbell Romanian deadliftIntermediate · A barbell
3D demoSingle-leg Romanian deadliftAdvanced · A dumbbell
3D demoSlider hamstring curlIntermediate · No equipment
3D demoGlute-ham raiseAdvanced · Other / check instructions
3D demoBarbell good morningIntermediate · A barbellGood for range of motion. Stretching on its own has not been shown to prevent hamstring injuries or re-injury.
Among the most common injuries in sport: a sharp pain at the back of the thigh, sometimes with a pop. The biceps femoris is injured most often, and about one in three athletes re-injures within a year of returning.
Sprinting injuries usually hit the upper biceps femoris; overstretching injuries (dancing, high kicks) tend to hit the upper semimembranosus tendon and take longer to heal.
Each grade rates the evidence for the correction.
Across 25 randomised trials in sport, stretching programmes did not lower injury rates, while strength training cut them to about a third. Stretch for range of motion and comfort, not as injury insurance.
For hamstrings specifically, flexibility training alone has not been shown to reduce re-injury; progressive eccentric strengthening is recommended instead.
A 2019 meta-analysis reported up to 51% fewer injuries in programmes that included it. A 2021 reappraisal limited to true randomised trials judged the effect inconclusive. It is a hard, useful eccentric exercise; the size of its protective effect is uncertain.
A 12-minute routine to loosen tight hamstrings with strap stretches, PNF, folds and hinges.
12 minBeginner7 movesNo equipmentA gym leg day: back squats, leg press, leg curls, Bulgarian split squats, leg extensions and calf raises.
55 minIntermediate9 movesA wall, A barbellA gym lower body workout for legs and glutes: trap bar deadlifts, hip thrusts, reverse lunges, leg curls, hip abduction, calf raises and core.
50 minIntermediate13 movesOther / check instructions, A barbellThe biceps femoris (long and short heads), semitendinosus and semimembranosus, at the back of the thigh.
Seated leg curls grew the hamstrings more than lying curls in a 12-week trial. Romanian deadlifts and good mornings work their hip-straightening role, and the Nordic curl is a hard eccentric option.
Not on its own. Stretching programmes have not lowered injury rates in trials; strength training, especially eccentric work, has a better record.
The biceps femoris, followed by the semimembranosus and semitendinosus.
Anatomy and movement education, not a diagnosis or treatment plan. If you have pain that follows an injury, is severe or getting worse, or comes with numbness, weakness or swelling, get it assessed. Health disclaimer.
