Lying Leg Curl

What the lying leg curl actually trains

The hamstring group: biceps femoris with its long and short heads, semitendinosus and semimembranosus. Three of those four cross both the hip and the knee. One, the short head of biceps femoris, crosses only the knee, which means the leg curl is the only way to train it at all.

This is the argument for curls in a programme that already contains Romanian deadlifts. The hamstrings do two jobs: extend the hip and flex the knee. Hinges train the first. Curls train the second. Trained only at the hip, the knee flexion function goes underdeveloped, and the short head of the biceps femoris does not get trained at all.

Askling and colleagues, and the wider hamstring injury literature, have repeatedly linked eccentric hamstring strength to strain risk in sprinting sports. Whether or not you sprint, the leg curl is a straightforward way to load the hamstrings eccentrically at the knee.

Setting up and curling

Pad just above the backs of your ankles, knees lined up just off the edge of the bench. Get this right before the first set: the machine's pivot should roughly match your knee joint.

Lie face down with your hips flat against the pad and hold the handles. Let the legs extend fully so the hamstrings start from a stretch.

Curl the pad towards your glutes, keeping the hips pressed down, and bring it as close as the machine allows. Hold the top for a beat. Lower over about two seconds to full extension.

Toes pointed towards the shins recruits the calf a little more into knee flexion; toes relaxed does the opposite. Both are fine, and the only rule is that you pick one and keep it consistent so your loads mean something.

The mistakes that cost you the most

The hips lifting off the pad is the tell that the weight is too heavy. It borrows hip flexion to complete a knee flexion movement and arches the lower back under load. Press the hips down and drop the weight.

Half reps at both ends are the norm on this machine and worth breaking. Pallares and colleagues found longer ranges produced at least as good adaptations as shorter ones, and for hamstrings specifically the lengthened position appears to matter.

Dropping the weight back down is the biggest waste. The lowering is where the hamstring works eccentrically, and eccentric hamstring work is the part of hamstring training with the clearest evidence behind it. Roig and colleagues found eccentric training produced greater strength and mass gains overall; for hamstrings the case is stronger still.

And the programming mistake: assuming Romanian deadlifts cover the hamstrings. They cover one end of them. A lower body week built entirely on hinges and squats leaves knee flexion untrained, which is a strange gap to accept in a muscle group most people say they want to develop.

How to programme the lying leg curl

Three to four sets of eight to fifteen with 90 seconds of rest. Hamstrings respond well to a range of rep schemes, and the machine is stable enough that heavier sets of six to ten are also perfectly usable.

Because knee flexion is a separate function from hip extension, the useful weekly structure is one hinge and one curl in every lower body week, minimum. Schoenfeld and colleagues found weekly sets per muscle related to hypertrophy in a dose-response way, but the split between the two functions matters as much as the total here.

It is a safe place to train close to failure. Refalo and colleagues found modest differences from training nearer failure once volume was matched, so it is your choice, but there is no risk in taking a leg curl to the end.

Slow, controlled eccentrics deserve deliberate emphasis on this exercise more than almost any other. Three seconds down, every rep. If you want to make a light stack feel serious without adding plates, that alone will do it, and it keeps the useful part of the exercise intact when the machine you have access to only goes so heavy.

Where the lying leg curl sits in your week

Late in a lower body session, after the squats and presses. It works well immediately after a hip hinge because it hits the same muscle from the other end while it is already warm.

If your session's main lift was a squat rather than a hinge, the leg curl is not optional. A squat-only lower session with no hamstring work is one of the most common holes in an otherwise reasonable programme.

Variations and swaps

The seated leg curl is the better version if the machine is available. Sitting flexes the hip, which lengthens the hamstrings at the hip end while the knee moves through its range, loading them in a longer position throughout.

Single-leg curls are worth doing occasionally. Side-to-side hamstring differences are common and consequential.

Nordic curls are the hardest hamstring exercise there is. Kneel, anchor the ankles, lower the torso towards the floor as slowly as you can. Almost nobody can do a full one at first and that is fine: the eccentric alone is the training. Build up to them slowly, they cause serious soreness at first.

Sliding leg curls, heels on sliders with the hips lifted, are the home version and scale nicely.

What the evidence does and does not say

It says the hamstrings cross two joints and do two jobs, and that a programme covering only one of them is incomplete. It says eccentric hamstring work is associated with reduced strain injury risk in sport. It says longer ranges are at least as good as shorter ones.

It does not say leg curls will prevent your hamstring from tearing while you play football. The eccentric-strength association is real but it is one factor among several, and the strongest evidence sits with specific protocols in specific athletic populations rather than with any knee flexion machine.

Curl the pad all the way, keep your hips down, lower slowly, and pair it with a hinge. That covers the muscle properly.

Lying leg curl: common questions

Do I need leg curls if I do Romanian deadlifts?

Yes. Hinges train the hamstrings at the hip; curls train them at the knee. The short head of the biceps femoris only crosses the knee, so hinging alone never trains it at all.

Why do my hips lift off the pad?

Because the weight is too heavy and you are borrowing hip flexion to finish the rep. Press the hips into the pad and use a load you can curl without them moving.

Seated or lying leg curl?

Seated, if you have the choice. Sitting keeps the hip flexed, which puts the hamstrings in a longer position throughout the movement, and lengthened-position training appears to suit this muscle particularly well.

Should I point my toes?

Either works. Toes towards your shins brings the calf a little more into knee flexion; toes relaxed does the opposite. Pick one and stay consistent so your loads are comparable between sessions.

How slowly should I lower the weight?

About two to three seconds. Eccentric hamstring work has the clearest evidence behind it of anything in hamstring training, and letting the pad drop throws that half of the rep away.