Lying leg curl
The lying (prone) leg curl builds the hamstrings: in a 12-week MRI trial it grew them by about 9%. In that same trial the seated leg curl grew them more (about 14%), so the lying version is a good second choice rather than the best one, and it works best next to a hip-hinge exercise.
What the science says
- Builds the hamstrings Moderate evidence
In Maeo et al.'s 2021 trial, 20 healthy adults trained one leg on a prone leg curl (5 sets of 10 at 70% of 1RM, twice a week for 12 weeks); MRI showed the whole hamstrings grew by about 9%, with growth in every hamstring muscle.
- Grows less than the seated leg curl Moderate evidence
In the same trial, the other leg trained on a seated leg curl and grew more: +14% versus +9% for the whole hamstrings, with the gap in the muscles that also cross the hip. The short head of the biceps femoris, which crosses only the knee, grew about the same (+10% vs +9%). The authors attribute the difference to training the hamstrings at longer lengths when the hip is flexed.
- Knee-flexion work does not grow every part equally Moderate evidence
Bourne et al. (2017) found that a knee-flexion exercise (the Nordic curl) grew mainly the semitendinosus, while a hip-extension exercise grew the biceps femoris long head more. Maeo et al. (2024) saw the same pattern: knee-flexion-only training favoured the muscles that do not extend the hip. Pairing curls with a hip hinge covers both.
How to do it
Muscles trained: hamstrings, gastrocnemius
- Lie face down with the knees just off the bench edge and the pad just above the heels.
- Keep the hips pressed into the bench; don't let them rise as you curl.
- Curl until the pad nearly touches the glutes, without swinging or kicking.
- Lower under control over about 2–3 seconds to a nearly straight knee.
How to apply it
Treat it as a hamstring isolation exercise: moderate reps, close to failure, with a slow lowering phase, plus a hip-hinge exercise in the same week.
Who should be careful
For healthy adults the main nuisances are hamstring or calf cramps and arching the lower back to finish reps; lighten the load if either happens. Anyone with a current or recent hamstring strain or knee problem should have a physician or physical therapist set their training.
Frequently asked questions
Is the lying or the seated leg curl better for hamstring growth?
The seated one, in the only head-to-head trial: Maeo et al. (2021) found +14% hamstring volume with seated curls versus +9% with lying curls over 12 weeks.
Is the lying leg curl still worth doing?
Yes. It grew the hamstrings by about 9% in 12 weeks, so it is a good option when there is no seated machine or for variety.
Do leg curls alone cover the hamstrings?
Not fully. Knee-flexion exercises tend to grow the muscles that do not extend the hip, while hip-extension work grows the biceps femoris long head more, so pair curls with a hip hinge.
Scientific references
- Greater Hamstrings Muscle Hypertrophy but Similar Damage Protection after Training at Long versus Short Muscle Lengths
- Impact of the Nordic hamstring and hip extension exercises on hamstring architecture and morphology: implications for injury prevention
- Hamstrings Hypertrophy Is Specific to the Training Exercise: Nordic Hamstring versus Lengthened State Eccentric Training
More exercises
- Back squat Strong evidence
The barbell back squat reliably builds the quadriceps, glutes and adductors and is one of the best-studied lower-body exercises in training research.
- Front squat Moderate evidence
The front squat holds the bar on the front of the shoulders, which keeps the torso more upright and loads the knees less than the back squat while recruiting the thigh muscles about as much.
- Bulgarian split squat Moderate evidence
The Bulgarian (rear-foot-elevated) split squat trains one leg at a time and builds the quads and glutes with far less load on the bar than a back squat.
- Leg press Strong evidence
The leg press builds the quadriceps about as well as free-weight squats and also grows the glutes and adductor magnus, with no balance or spinal-loading limit.
- Hack squat (machine) Moderate evidence
The machine hack squat lets you squat deep on a fixed track with your back supported, which makes it easy to push the quads close to failure.
- Conventional deadlift Moderate evidence
The conventional deadlift trains the whole posterior chain and grip and is a core strength lift, but research on its growth effects is thin: trials either use other deadlift variants or measure strength rather than muscle size.