Leg Curl: Muscles Worked and How to Do It
TL;DR
The leg curl works your hamstrings as the prime mover, bending your knee against resistance from the machine's pad. Because it isolates knee flexion without involving your hips, it's one of the most direct ways to build hamstring size and strength without loading your lower back.
- Primary muscle:
- Hamstrings
Muscles worked
Your hamstrings are the sole prime mover in a leg curl, contracting to bend your knee and pull the pad toward you. Unlike a Romanian deadlift, which trains the hamstrings through hip extension, the leg curl isolates the other job your hamstrings do: flexing the knee.
Because the movement happens only at the knee, with your hips staying still, the leg curl lets you fatigue your hamstrings directly without your lower back or glutes taking over any of the load, which makes it a useful accessory to hip-hinge movements.
Log Leg Curl in PR Streak
PR Streak's library has 873 exercises, each with photos and step-by-step instructions like this one. Log this move and see what you lifted last time right next to every set, with every PR caught automatically and a chart for every exercise.
How to do it
- Adjust the machine lever to fit your height and lie face down on the leg curl machine with the pad of the lever on the back of your legs (just a few inches under the calves). Tip: Preferably use a leg curl machine that is angled as opposed to flat since an angled position is more favorable for hamstrings recruitment.
- Keeping the torso flat on the bench, ensure your legs are fully stretched and grab the side handles of the machine. Position your toes straight (or you can also use any of the other two stances described on the foot positioning section). This will be your starting position.
- As you exhale, curl your legs up as far as possible without lifting the upper legs from the pad. Once you hit the fully contracted position, hold it for a second.
- As you inhale, bring the legs back to the initial position. Repeat for the recommended amount of repetitions.
Form tips
- Keep your hips pressed into the pad or bench throughout the set.
- Curl the pad all the way toward your glutes without letting your hips lift.
- Lower the weight slowly instead of letting it snap back down.
- Point your toes toward your shins to keep tension on your hamstrings rather than your calves.
- Avoid arching your lower back to help finish the rep.
Exercise details
| Equipment | Machine |
|---|---|
| Level | Beginner |
| Mechanic | Isolation |
Used by lifters following PPL, 5x5, upper/lower, and more.
Frequently Asked Questions
Should I do leg curls or Romanian deadlifts for hamstrings?
They train different jobs your hamstrings do. A Romanian deadlift works the hamstrings through hip extension, while the leg curl isolates knee flexion. Using both covers the full range of what your hamstrings do, rather than relying on one movement pattern.
How many reps of leg curls should I do?
For muscle size, work in the 6-12 rep range at 67-85% of your one-rep max, curling under control rather than using momentum. Higher reps of 12 or more at lighter weight also work well as a finisher after heavier hip-hinge movements.
More hamstrings exercises
Exercise instructions and photos come from the free-exercise-db library, public domain, the same library used inside the PR Streak app.
