Seated or lying leg curls: which builds bigger hamstrings?

Bar chart: over 12 weeks of training, seated leg curls grew the whole hamstrings 14% and lying leg curls 9%, in the same people training one leg each way.

The short answer

Seated leg curls built more hamstring muscle than lying leg curls: about 14% versus 9% over 12 weeks, in a study where each person trained one leg each way. The likely reason is that sitting puts the hamstrings on a stretch. And because squats did not grow the hamstrings at all in another study, direct hamstring work is worth doing.

Why the position matters

Most of your hamstring muscles cross two joints: the hip and the knee. Bending the knee is what a leg curl trains, but where your hip is changes how stretched the muscle is while you do it. Sitting bends your hip, which lengthens the hamstrings across the back of the thigh. Lying face down keeps the hip straight, so the same curl happens with the muscle shorter.

That difference is the whole question: does training a muscle at a longer length build more of it?

The study that compared them

Twenty healthy adults trained for 12 weeks, twice a week, doing seated leg curls with one leg and lying leg curls with the other. Both legs did 5 sets of 10 reps at 70% of their one-rep max, and muscle size was measured with MRI before and after ¹. Training each leg differently in the same person rules out differences in diet, sleep and genetics.

Hamstring growth in 12 weeks	Seated curl	Lying curl
Whole hamstrings	Up 14%	Up 9%
Muscles crossing the hip and knee	Up 8% to 24%	Up 4% to 19%
Muscle crossing only the knee	Up 10%	Up 9%

The pattern fits the explanation. The muscles that cross both joints, the ones sitting stretches, grew more with seated curls. The one muscle that crosses only the knee, which sitting does not stretch, grew about the same either way. The authors concluded that training at long muscle lengths promotes muscle growth ¹.

Why squats are not enough

It is easy to assume heavy squats cover the hamstrings. In a 10-week study comparing full and half squats, most of the front thigh, the glutes and the inner thighs grew, but hamstring volume did not change with either depth ². If you want bigger hamstrings, they need their own exercises: a curl, and a hip hinge like the Romanian deadlift.

So which should you do?

If your gym has a seated curl, make it your main hamstring curl. It produced more growth in the one study that compared them directly ¹.

Lying curls still work. They grew the hamstrings 9% in 12 weeks, which is real progress ¹. If lying is what you have, or it feels better on your back, use it and push your sets hard.

Use both if you like. Our Leg Builder program leads with seated curls in one workout and uses lying curls in the other, alongside a Romanian deadlift.

Try this workout

A hamstring session

Who it is for: Lifters who want more hamstring size, on a lower-body day or as a short session of its own.

1Warm up. 5 minutes easy, then a light set of each exercise.
2Seated leg curl. 5 sets of 10 at roughly 70% of your one-rep max, as in the study ¹.
3Romanian deadlift. 3 sets of 6 to 10, pushing your hips back until you feel a strong stretch.
4Lying leg curl. Optional: 2 to 3 sets of 10 to 15 for extra volume.
5Each week. Twice a week, as in the study ¹. Add weight once all 5 sets of 10 feel controlled.

Want it planned week by week? Leg Builder builds on this session.

Put it into practice

Sources

All research

1Greater Hamstrings Muscle Hypertrophy but Similar Damage Protection after Training at Long versus Short Muscle LengthsMaeo et al., 2021. Medicine & Science in Sports & Exercise 53(4):825-837.
2Effects of squat training with different depths on lower limb muscle volumesKubo et al., 2019. European Journal of Applied Physiology 119(9):1933-1942.

General fitness information, not medical advice. If you have an injury or a health condition, check with a professional before starting a new kind of training.