How much weight should I use on one leg?

Start at about half the weight you use for the two-leg seated leg curl, then adjust until you can complete 10 to 15 controlled reps with your hips staying down and level.

Which leg should I train first?

Start with the weaker leg, then do the same reps with the same weight on the stronger leg, even if it could do more. If the gap between sides stays large for several weeks or comes with pain, have a physical therapist or doctor look at it.

What should I do with the other leg?

Rest it bent under the thigh pad with the foot on the machine's base frame, and keep it relaxed. It should not push or brace; if you need it to hold yourself still, the weight is too heavy.

Is the single-leg version better than the two-leg seated leg curl?

Not by default. It works the same muscles through the same range, so the two-leg Machine Seated Leg Curl is the quicker choice for general hamstring training, while the single-leg version earns its extra time when one side is weaker, when you are returning from an injury or when you want to check each side separately.

Should I choose this or the single-leg lying leg curl?

The difference is hip position. Seated, the hips are bent and the hamstrings that cross the hip work at a longer length, which makes this version the stronger choice for hamstring size, while the Machine Single-Leg Lying Leg Curl trains them from a shorter starting length and adds useful variety.

Machine Single-Leg Seated Leg Curl

What Is the Machine Single-Leg Seated Leg Curl?

Machine Single-Leg Seated Leg Curl is an isolation exercise that primarily targets the hamstrings and also engages the calves. It is a beginner-level movement performed on a seated leg curl machine, with one leg curling the roller down and back under the seat while a thigh pad holds the hips in place.

Working one leg at a time shows how each hamstring performs on its own. In the two-leg Machine Seated Leg Curl the stronger side can quietly take more of the load, while here each leg has to move the weight alone, which makes a left-to-right gap easy to see and lets the weaker side get the same reps. It does not correct an imbalance by itself; matching sets and reps over several weeks is what closes the gap. It also suits a return to training after a hamstring or knee injury, once a clinician has cleared loaded work, because the weight can be set separately for each side.

Sitting with the hips bent puts the hamstrings that cross both the hip and the knee in a lengthened position, which is the main difference from the Machine Single-Leg Lying Leg Curl. In a 12-week study of adults new to resistance training, each participant trained one leg on a seated leg curl and the other on a lying leg curl, and the seated leg gained more total hamstring volume, about 14% against 9%, with the extra growth in the hamstring muscles that cross the hip. The calves assist with bending the knee, more so with the ankle kept neutral, since pointing the toes shortens the calf muscles and leaves them less able to help.

The exercise usually comes after the main squat or hinge of a lower-body session, for 2 to 4 sets of 8 to 15 reps per leg. Because the machine guides the path and the thigh pad steadies the hips, it suits beginners, though anyone who cannot yet keep the hips down and level on the two-leg version should build up there first. The extra time is worth spending when there is a reason to train each side separately; otherwise the two-leg version does the same job faster.

Muscles Worked

MuscleActivation

Biceps Femoris: Primary
Semimembranosus: Primary
Semitendinosus: Primary
Gastrocnemius (Lateral Head): Low
Gastrocnemius (Medial Head): Low
Sartorius: Low

Instructions

Adjust the backrest so your working knee lines up with the machine's pivot, and set the roller to rest on your lower calf just above the ankle.
Sit back against the backrest with your working leg straight out in front and the back of your lower calf on the roller.
Lower the thigh pad until it presses firmly on your thighs just above the knees.
Bend your other knee and rest that foot on the machine's base frame, keeping the leg relaxed.
Hold the handles beside the thigh pad, brace your core and keep your hips square on the seat.
Bend your working knee to pull the roller down and back under the seat, keeping your thigh pinned under the pad.
Pause briefly at the end of the curl, with your heel under the seat.
Straighten your leg slowly over two to three seconds, stopping just short of locking the knee.
Finish all reps on that leg, then switch sides, starting each set with your weaker leg.

Common Mistakes

Knee off the pivot
Sitting with the knee ahead of or behind the machine's pivot changes the resistance through the rep and stresses the knee unevenly.
Loose thigh pad
A thigh pad left loose lets the hip lift off the seat as you curl, which takes tension off the hamstrings and lets momentum help.
Twisting the pelvis
Rotating the hips or leaning toward the working side to finish a rep usually means the weight is too heavy for one leg.
Letting the weight snap back
Letting the stack pull the leg back up quickly skips the lowering phase and can jolt the knee into a hard lockout.
Cutting the range short
Stopping the curl well before the heel reaches under the seat, or never straightening the leg near the top, leaves out the most useful parts of the rep.
Leading with the stronger leg
Training the stronger leg first and giving it extra reps keeps the gap between sides the same or makes it bigger.

Injuries

Machine Single-Leg Seated Leg Curl is a low risk exercise when performed with proper technique. The machine fixes the path of the leg and the thigh pad holds the hips down, so most problems come from setup and load: a knee that sits off the machine's pivot loads the joint unevenly, and letting the weight pull the leg back to a hard lockout pushes the knee toward hyperextension.

The hamstrings work at a long length in this position, so a weight that is too heavy, or a jerky lowering phase, can strain them, particularly as the knee nears straight at the end of each rep. Calf cramps are common in the fully curled position; they are not an injury, so straighten the leg, stretch the calf and lighten the load. With only one leg working, a heavy weight also tends to twist the pelvis toward the working side, which loads the lower back and hip unevenly. The hip-bent seated position can aggravate sciatica or a lower back disc problem.

Set the roller on the lower calf just above the ankle, clear of the Achilles tendon, lock the thigh pad down firmly, and lower each rep over two to three seconds. If one leg alone is too much, go back to the two-leg Machine Seated Leg Curl with a lighter weight, or use the Band Seated Leg Curl. Progress by adding reps before weight, slowing the lowering phase or pausing in the curled position; the Nordic Hamstring Curl is a far harder step for later.

Stop the set for sharp pain or a pulling feeling in the back of the thigh, pain inside or behind the knee, or tingling or numbness running down the leg, and see a professional if it persists.

Overview

Primary Focus: Hamstrings
Equipment: Machine
Modality: Strength
Difficulty: Beginner

Alternative Exercises

Frequently Asked Questions

Q: How much weight should I use on one leg?: Start at about half the weight you use for the two-leg seated leg curl, then adjust until you can complete 10 to 15 controlled reps with your hips staying down and level.
Q: Which leg should I train first?: Start with the weaker leg, then do the same reps with the same weight on the stronger leg, even if it could do more. If the gap between sides stays large for several weeks or comes with pain, have a physical therapist or doctor look at it.
Q: What should I do with the other leg?: Rest it bent under the thigh pad with the foot on the machine's base frame, and keep it relaxed. It should not push or brace; if you need it to hold yourself still, the weight is too heavy.
Q: Is the single-leg version better than the two-leg seated leg curl?: Not by default. It works the same muscles through the same range, so the two-leg Machine Seated Leg Curl is the quicker choice for general hamstring training, while the single-leg version earns its extra time when one side is weaker, when you are returning from an injury or when you want to check each side separately.
Q: Should I choose this or the single-leg lying leg curl?: The difference is hip position. Seated, the hips are bent and the hamstrings that cross the hip work at a longer length, which makes this version the stronger choice for hamstring size, while the Machine Single-Leg Lying Leg Curl trains them from a shorter starting length and adds useful variety.