Lying Leg Curl

The lying leg curl — also called the prone leg curl — is the classic machine exercise for isolating the hamstrings. Because the hips are pinned to the bench, all of the work happens at the knee, letting you load the back of the thigh directly without the lower back or glutes taking over. It's a staple accessory after squats, deadlifts or Romanian deadlifts, when the hamstrings need direct work the main lift didn't fully provide. This guide covers exact setup and technique, the muscles trained, common mistakes, how it compares to the seated leg curl, and how to program it for strength or size.

What muscles does the lying leg curl work?

The lying leg curl trains the hamstrings — biceps femoris, semitendinosus and semimembranosus — through pure knee flexion, with the body prone so the hip stays fixed and the hamstrings work only at the knee. The gastrocnemius, which also crosses the knee, assists especially as the pad approaches your glutes. Because the hip doesn't move, the lying leg curl trains the hamstrings in a shortened position compared with the seated leg curl, which flexes the hip and stretches the hamstrings further before the knee even bends.

How grip and angle change muscle activation

EMG research on knee-flexion exercises shows the two long hamstring muscles trade off dominance as the knee bends. Treat these as general patterns rather than a reason to change your setup.

• Shallow knee flexion (around 30°): Biceps femoris (outer hamstring) shows relatively higher activation.
• Deeper knee flexion (90° or more): Semitendinosus (inner hamstring) becomes more dominant.

Based on EMG research. [1]

How do you do the lying leg curl?

To do the Lying Leg Curl: adjust the machine so the pivot point lines up with your knee joint and the ankle pad rests just above your heels; lie face down with your hips flat on the pad and grip the handles (or bench edge) to keep your body still; extend your legs fully to start, keeping your hips pressed into the bench; curl the pad up and in toward your glutes by bending your knees, keeping your hips down the whole time.

1. Adjust the machine so the pivot point lines up with your knee joint and the ankle pad rests just above your heels.
2. Lie face down with your hips flat on the pad and grip the handles (or bench edge) to keep your body still.
3. Extend your legs fully to start, keeping your hips pressed into the bench.
4. Curl the pad up and in toward your glutes by bending your knees, keeping your hips down the whole time.
5. Squeeze your hamstrings hard at the top of the movement for a full second.
6. Lower the pad back to the start under control — don't let it drop.

What are the key lying leg curl form cues?

Hips down

Keep your hips glued to the bench for the entire set — lifting them shifts the load to your lower back and glutes.

Toe position

Pointing your toes toward your shins (dorsiflexed) shifts more work onto the hamstrings; pointing them away brings the calves in more.

Controlled negative

Lower the pad over 2–3 seconds instead of letting the weight stack drop — this is where most of the muscle-building tension happens.

Full contraction

Curl all the way until your heels are near your glutes, then pause and squeeze before releasing.

Breathing & tempo: Exhale as you curl the pad up toward your glutes, inhale as you lower it back down. A 2–1–2 tempo (2s up, 1s squeeze, 2s down) keeps tension on the hamstrings and prevents momentum from taking over.

How should you warm up for the lying leg curl?

Do a light set of 12–15 reps at roughly half your working weight before your first working set, focusing on the full range of motion. If the lying leg curl follows a squat or deadlift variation, your hamstrings are likely already warm — one ramp-up set is usually enough.

What are the most common lying leg curl mistakes?

• Letting the hips rise off the bench — Brace your core and press your hips down throughout the set; if you can't keep them down, reduce the weight.
• Using momentum to swing the weight up — Slow the rep down and use a weight you can control through the full range without jerking.
• Stopping short of full contraction — Curl all the way until your heels approach your glutes rather than stopping halfway.
• Dropping the weight on the way down — Lower the pad for a full 2–3 count instead of letting the stack fall.
• Misaligned knee pivot — Reset the machine so the pivot lines up with your knee joint before you load it — a mismatched pivot creates knee strain.

Why does the lying leg curl hurt — and how do you fix it?

Pain during the lying leg curl is almost always a setup or loading issue. Match your symptom below, and stop and see a professional if pain is sharp or doesn't resolve.

How many sets and reps should you do?

Choose your sets and reps by goal: heavier and fewer reps for strength, moderate for muscle size, lighter and higher for endurance.

RPE / RIR: Leave 2–3 reps in reserve (RPE 7–8) on most sets — the lying leg curl is an accessory movement, so chasing failure every set adds fatigue without much extra benefit. Save an all-out set (RPE 9–10) for your last set only.

Place the lying leg curl after your main compound lift (squat, deadlift, or hip-hinge variation) as an accessory to finish off the hamstrings. Progress by adding a rep or two before adding weight, and keep the tempo controlled rather than chasing heavier loads.

How often should you lying leg curl and where does it fit?

Train the Lying Leg Curl 1–2 sessions per week, placing it after compound lower-body lifts, as an accessory.

• Frequency: 1–2 sessions per week
• Best split days: Leg day, Pull day (if hamstrings are grouped with posterior chain), Upper/lower split — lower day
• Where to place it: After compound lower-body lifts, as an accessory

Because it's a single-joint accessory, the lying leg curl tolerates higher rep ranges and closer-to-failure training without the systemic fatigue of a heavy compound lift.

How do you progress the lying leg curl?

Add a rep or two each week within your target range before adding weight, and prioritize a full, controlled range of motion over loading up with partial reps.

What's the right range of motion?

Start from a fully extended knee and curl until your heels are close to your glutes — a full stretch-to-contraction range builds more hamstring size than partial reps. If a knee injury limits full flexion, work within a comfortable, pain-free range instead of forcing it.

What are the benefits of the lying leg curl?

• Isolates the hamstrings without loading the spine — useful for lifters wanting extra hamstring volume without more axial fatigue
• Simple to learn and safe to train close to failure since there's no balance or spotting requirement
• Builds knee-flexion strength that supports sprinting, jumping and change-of-direction movements
• Easy to progress in small increments on a machine's weight stack

Who should do it: Beginners wanting a low-skill way to add hamstring volume, bodybuilders chasing balanced leg development, and any lifter whose squats and deadlifts leave their hamstrings under-trained relative to their quads.

Is the lying leg curl safe?

The lying leg curl is a safe, low-back-friendly exercise for most people when the machine is set up correctly and the hips stay pinned to the bench.

Knee pain or a knee-injury history

Use a lighter load, keep the pivot aligned, and work within a pain-free range of motion.

Lower-back sensitivity

Keep your hips glued to the bench and choose a weight you can curl without arching or lifting your hips.

Spotting: No spotter is needed — if a rep gets too heavy, simply lower the weight under as much control as you can and reset.

How do grip and stance change the lying leg curl?

• Toes dorsiflexed (pulled up): Biases the hamstrings by reducing gastrocnemius assistance.
• Toes plantarflexed (pointed): Brings the calves in more; useful as a light variation but slightly reduces pure hamstring isolation.

Lying Leg Curl variations

How does the lying leg curl compare?

Lying Leg Curl vs. Seated Leg Curl

The lying leg curl trains the hamstrings in a shorter, hip-extended position, while the seated leg curl stretches them further by flexing the hip first. Research shows the seated version tends to build more hamstring size, but both are effective — use whichever machine you have access to, or include both for variety.

Lying Leg Curl vs. Romanian Deadlift

The RDL is a compound hip-hinge that loads the hamstrings and glutes together under heavier weight; the lying leg curl isolates the hamstrings alone with less lower-back demand. Use the RDL as your main hamstring builder and the leg curl as an accessory finisher.

Lying Leg Curl alternatives

Estimate your lying leg curl 1RM

Enter a weight and the reps you hit with it to estimate your one-rep max (Epley formula), then see your training percentages.

How many calories does the lying leg curl burn?

Calories depend on your bodyweight and how hard you train. Resistance training has a MET value of about 3.5. Enter your bodyweight and minutes to estimate the burn (calories = MET × kg × 3.5 ÷ 200 × minutes).

Lying Leg Curl strength standards

Approximate lying leg curl working weight as a multiple of bodyweight for a set of 8 reps — treat these as general benchmarks, since machines vary in resistance and leverage.

By age: Strength on isolation machines declines more gradually with age than on heavy compound lifts; lifters over 50 can typically still work within 80–90% of these figures with consistent training.

What counts as a good rep?

A full rep starts with the knee extended, curls the pad until your heels approach your glutes without the hips lifting off the bench, and returns under control to the starting position.

References

1. The task-dependent differences in electromyography activity of hamstring muscles during leg curls and hip extensions. PLOS ONE / PMC, 2021
2. Biceps Femoris Activation during Hamstring Strength Exercises: A Systematic Review. Sports (MDPI) / PMC, 2021
3. Muscle Activation Patterns of the Proximal, Medial and Distal Biceps Femoris and Gluteus Maximus Among 6 Hip Extension and Knee Flexion Exercises in Trained Women. NIH / PMC, 2022
4. Greater Hamstrings Muscle Hypertrophy but Similar Damage Protection after Training at Long versus Short Muscle Lengths. NIH / PMC, 2021
5. Lying Leg Curl: How to Use It, Form & Benefits. NASM Exercise Library
6. How to Do Lying Leg Curl: Muscles Worked & Proper Form. StrengthLog
7. Lever Lying Leg Curl. ExRx.net