FormTwin › Exercises › Leg Curl

What muscles does the Leg Curl work?

The leg curl isolates the hamstrings through knee flexion — the one job the big hip-hinge lifts don't fully cover.

Primary muscles worked

Secondary muscles worked

See these muscles on your own body

FormTwin gives you a living 3D twin of your anatomy. Tap any muscle to see how to train it, and watch the muscles you work light up as you log your sessions.

Get FormTwin — free on the App Store

How to do the Leg Curl

  1. Set the pad just above your heels (lying or seated).
  2. Keep your hips down and pinned to the pad.
  3. Curl your heels toward your glutes.
  4. Squeeze, then lower slowly under control.

Common mistakes

Variations

Seated leg curlLying leg curlNordic curl

Frequently asked questions

What muscles does the leg curl work?

The leg curl isolates the hamstrings through knee flexion, with a little calf involvement. It complements hip hinges like the RDL, which train the hamstrings' other function at the hip.

Seated vs lying leg curl — is there a difference?

Yes. The seated leg curl stretches the hamstrings more (hips flexed), which several studies link to greater growth; the lying version works them in a shortened position. Doing both covers all bases.

Do I need leg curls if I deadlift?

Deadlifts and RDLs train the hamstrings at the hip, but not knee flexion. Adding leg curls develops the hamstrings more completely and can help protect the knee.

Related exercises

DeadliftBack SquatBench PressPull-UpPush-Up

This guide is general fitness information, not medical advice. Muscle involvement varies with form, grip and individual anatomy. Consult a professional before starting a new program.