Seated vs Lying Leg Curl: Why Hip Flexion Builds More Hamstring

In the seated vs lying leg curl debate, seated wins for hamstring size, at least in the best study we have. In a 12-week MRI trial, the seated leg grew about 14% in total hamstring volume while the leg trained on a lying machine grew about 9% (Maeo et al., 2021). The likely reason is hip position, not magic.

This article is part of our guide to range of motion and stretch-mediated hypertrophy. Here we stay focused on one question: what actually differs between the two machines, how big is the difference, and what should you do on Monday.

Seated vs lying leg curl: what the Maeo study actually did

Most gym debates run on opinion. This one has a clean experiment behind it, which is rare.

Twenty healthy adults trained one leg on a seated leg curl and the other on a prone (lying) leg curl. Same load rule (70% of 1RM), same volume (5 sets of 10 reps), twice a week for 12 weeks. Because each person trained both legs, genetics, diet and sleep were shared across conditions, which removes a lot of noise. MRI then measured the volume of each hamstring muscle before and after (Maeo et al., 2021).

The results:

• Whole hamstrings: about +14% seated vs about +9% prone.
• Biarticular heads (cross hip and knee): about +8% to +24% seated vs +4% to +19% prone.
• Monoarticular head (crosses only the knee): about +10% vs +9%, no meaningful difference.

That is roughly half again as much growth for the same sets and reps. One caveat now, so it does not get lost: this is one trial in healthy adults, 12 weeks long. It is a well-designed one, but still one.

Why hip flexion changes the exercise

Three of the hamstring muscles (semitendinosus, semimembranosus and the long head of biceps femoris) run from your sit bones past the hip to below the knee. They work at both joints. They flex the knee and extend the hip.

That matters because of a simple geometry fact. Bend your hip and the sit bone moves away from the shin, so those muscles are already pulled long before the knee even starts bending. On a seated machine, your hips are flexed. On a lying machine, your hip is close to straight, so the same muscles start out shorter.

The short head of the biceps femoris starts on the thigh bone and crosses only the knee. Hip angle barely changes its length, which fits with it growing about the same on both machines. For the deeper mechanics of two-joint muscles, see our piece on active and passive insufficiency in biarticular muscles.

Why seated feels harder

If you have ever switched from lying to seated and felt your numbers drop, that is normal. A muscle that starts stretched usually feels heavier and more demanding at the bottom of the rep, and the machine’s resistance profile differs too.

In the trial, each version was loaded at 70% of its own 1RM, so the relative effort was matched even if the plates were not. Your gym stack will not be calibrated like that, so go by effort. Drop the weight 10-20% when you switch and aim to finish sets 1-3 reps short of failure.

Is it just muscle length? What the broader evidence says

The seated result fits a wider pattern. A systematic review of full versus partial range of motion found that training through a full range benefits lower body hypertrophy compared with partial range, though evidence for the upper body was limited and conflicting, and responses may be muscle specific (Schoenfeld and Grgic, 2020). We cover that more generally in full vs partial range of motion and long muscle length training.

A later trial from the same lead author compared Nordic hamstring training with a weight-stack curl done in an accentuated hip-flexed position, in 42 healthy young men split into three groups of 14 (one of them a no-training control). The hip-flexed work produced bigger gains in total hamstrings (+18% vs +11%) and in the biceps femoris long head (+19% vs +5%), but the Nordics grew the knee flexors that do not extend the hip about 1.9-fold more (Maeo et al., 2024).

Two things to take from that. First, the direction agrees: hip-flexed knee flexion is a strong hamstring builder. Second, hamstring growth is exercise-specific, so no single movement trains every part equally.

What seated vs lying does not tell you

Be honest about the limits.

• Sample size. 20 healthy adults. Results may differ in older or highly trained lifters.
• Duration. 12 weeks. We do not know how the gap behaves over years.
• Volume. 5 sets of 10, twice a week is a lot for one muscle group. Your own program will likely use less.
• Muscle damage. After hard eccentric work, seated and prone legs showed no significant difference in damage markers, and both were far better protected than a control leg (Maeo et al., 2021). So the seated advantage is about growth, not about soreness protection.
• Injury prevention. The seated curl was not tested for injury risk. The best-known injury evidence is for Nordics: a meta-analysis of 15 studies found programmes including the Nordic hamstring exercise had about half the rate of hamstring injuries (van Dyk et al., 2019). If you play sprinting or kicking sports, that matters. See our guide to Nordic hamstring curls.

How to do a seated leg curl for hamstring growth

Some detail on each step:

1. Align the pivot. The machine’s axis should sit level with your knee joint. If it is off, the cable path and the pad will drift as you curl.
2. Pad above the heel. Resting on the lower calf, just above the Achilles tendon, is comfortable and stable.
3. Lock the thigh pad. If your thighs can lift, your hips will help, and the stretch you are paying for disappears.
4. Start from stretch. Let the weight stretch you at the top of each rep, then curl without a bounce.
5. Lower slowly. Two to three seconds on the way back is plenty. Do not drop the stack.

Many seated machines have a back pad you can tilt. A slightly reclined back is fine, but keep the hip clearly bent.

How to program it

You do not need to copy 5 sets of 10 at 70% 1RM, twice a week. That was a research protocol, not a prescription.

• Frequency: twice a week works well for most people.
• Sets: 3-4 hard sets per session, so roughly 6-8 for the week on top of hinge work.
• Reps: 8-15, finishing 1-3 reps from failure.
• Pairing: add a hip-extension movement such as the Romanian deadlift. Curls and hinges train different jobs.
• Progression: add a rep or two each week, then add a small amount of load.

For where this fits in a lower-body day, see our free leg day plan. To check your weekly volume, use the training volume calculator. To learn the anatomy behind each head, read functional anatomy of the hamstrings.

Seated vs lying leg curl: quick comparison

	Seated leg curl	Lying (prone) leg curl
Hip position	Flexed	Near straight
Whole hamstring volume change (12 wk)	About +14%	About +9%
Biarticular heads	About +8% to +24%	About +4% to +19%
Monoarticular head	About +10%	About +9%
Damage protection afterwards	Similar	Similar
Typical feel	Harder at the stretch	Easier to start

What if you only have a lying machine?

Do not panic. A lying curl still grew hamstrings by about 9% in the study. Train it close to failure with a controlled lowering phase, and add a hinge for the hip-extension side.

A cheap workaround some lifters use is to flex the hips slightly with an angled pad or bench, but we do not have trial data on it, so treat it as an experiment. If you train at home in India without machines, hip hinges with a slow lowering phase and a loaded Nordic variation are the realistic options, and a single adjustable-bench setup covers most needs.

If you have a current hamstring pain, a tear or a history of strains, check with a doctor or physiotherapist before loading the muscle hard.

The bottom line

If you have both machines, make seated your default hamstring curl. It put more growth into the two-joint hamstring muscles in the cleanest trial we have, probably because sitting loads them in a stretched position. Do not overthink it beyond that: keep the sets hard, the range full and your hips glued to the seat, and add a hinge. Consistency across months beats the choice of machine.

For coaching help building this into a full program, you can start with our free workout plans.