Seated leg curl: proper form, muscles worked and common mistakes

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How to do it

Set the pad on the Achilles tendon and the lap pad on the thighs. Flex the knee bringing the heel toward the glutes and control the return without letting the weight drop.

Muscles worked

Main muscle: hamstrings. When it plans weekly volume, every set of this exercise counts in full for hamstrings: the generator does not split it with other muscles.

Seated leg curl vs. lying leg curl: hip position changes how the hamstring is stretched

The seated and lying leg curls do the same thing at the knee, but the hip sits in a different position. Seated, the hip is flexed, and the hamstrings, which cross both the hip and the knee, start each rep more stretched. Lying down, the hip is near neutral and that pre-stretch is smaller. In practice, many people feel the seated version more in the early part of the range. In addition, the backrest and the pad over your thighs give a very stable posture: no pelvis that rises, no lower back that arches.

It's the best option if your back arches or your hips lift when you lie down, if you're just starting, or if you want to load up without worrying about balance. Combine it with a Romanian deadlift or a lying curl in the same block to cover different hip angles. It fits after your heavy lifts, for 8 to 15 reps.

Before starting, adjust the backrest so the knee axis lines up with the machine's, and make sure the pad holds your thigh without crushing it. To progress, stretch the lowering to three seconds, add a brief pause with the knee bent, and add weight only if you control the whole range.

Recommended sets and reps

As an isolation exercise, it works best in 3–4 sets of 10–15 reps with 0–2 RIR. Use it at the end of the session to add volume without systemic fatigue.

Common mistakes to avoid

• Lifting your hips off the pad as the weight comes up: it shortens the hamstring range and the lower back takes over.
• Not adjusting the seat and pads to your body: your joint should line up with the machine's pivot.
• Cutting short the part of the range where the muscle is stretched: that is exactly where this exercise gives the most stimulus.

What the research says

This is an isolation exercise. For beginners, adding it on top of compound lifts does not always help: in the trial by Gentil and colleagues (2013), people who only did lat pulldowns gained as much arm size as those who also did curls. It earns its place with experience, and for muscles the big lifts leave short.

Its peak tension comes with the muscle stretched, and that matters: in the trial by Maeo and colleagues (2021), seated leg curls, which stretch the hamstrings more, built more muscle than lying curls, and Pedrosa and colleagues (2022) saw something similar in the quads when training the long end of the range.

On how hard to push: the meta-analysis by Refalo and colleagues (2023) found no clear advantage in going to failure over stopping just short of it. That is why the generator programs it with reps in reserve (RIR) instead of asking for failure on every set.

Why the seated leg curl grows the hamstrings more

Three of the four hamstring muscles cross two joints: the knee and the hip. Seated, the hip is flexed, which leaves them more stretched throughout the curl than lying face down with the hip extended. Maeo and colleagues tested it in 2021 in Medicine and Science in Sports and Exercise: twenty adults trained for twelve weeks with one leg on the seated curl and the other on the lying curl, with the same relative load, sets and reps.

The seated-curl leg gained more muscle volume, measured by MRI (Maeo et al., 2021). The difference showed up exactly where anatomy predicts: in the biarticular muscles. The short head of the biceps femoris, which only crosses the knee and is not stretched further by hip flexion, grew the same with both.

If your gym has both machines and your goal is hypertrophy, this is the one to prioritise. Make the most of it by lowering to full knee extension on every rep: that stretched position is where the advantage lies.

Related guide

Best leg exercises for the gym and at home

Alternative exercises

• Lying leg curl
• Standing cable leg curl
• Romanian deadlift
• Single-leg RDL
• Glute-ham raise

More isolation exercises

• Lying leg curl
• Incline dumbbell curl
• Reverse barbell curl
• Hammer curl
• Band hammer curl

Add it to your routine

Progrevia can generate a personalized routine that includes Seated leg curl based on your level, goal and available days.

Frequently asked questions

What muscles does Seated leg curl work?

Seated leg curl mainly works the hamstrings muscle group, plus synergist and stabilizer muscles depending on the variation.

How many sets of Seated leg curl should I do?

Between 3 and 5 sets per session, adjusting the total weekly volume for hamstrings to your level (about 10–20 sets per muscle per week).

Is the seated leg curl better than the lying one for hamstrings?

Not necessarily. With the hip flexed, the hamstring starts more stretched, which is why many people prefer it. But the lying curl works well too, and choosing one or the other comes down to the machine you have and your comfort. Using both in different weeks is a simple way to vary the stimulus.

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