How is the kneeling leg curl different from the lying leg curl?

On the kneeling machine you rest on one knee and your forearms with your hips bent partway, instead of lying face down with your hips nearly flat. It also works one leg at a time, like the Machine Single-Leg Lying Leg Curl, while the Machine Lying Leg Curl usually trains both legs together.

Why does this machine work one leg at a time?

Training each leg alone stops the stronger side from covering for the weaker one and makes a difference between the legs easy to see. Start with your weaker leg and match its reps on the other side.

How much weight and how many reps should I use?

Pick a load you can curl through the full range for about 8 to 15 controlled reps. Plate-loaded machines jump in large steps, so use smaller plates to progress gradually rather than adding a full 45 lb plate at once.

Why do my hamstrings cramp on this exercise?

The hamstrings are at their shortest near the top of the curl, and a hard contraction there can trigger a cramp, especially late in a set. Lower the leg, let it relax, and continue with a lighter load or fewer reps; cramps that return every session are worth raising with a doctor.

Can the kneeling leg curl replace Romanian deadlifts?

No. The leg curl trains the hamstrings at the knee, while the Barbell Romanian Deadlift trains them at the hip, so most programs use one of each.

Machine Kneeling Leg Curl

What Is the Machine Kneeling Leg Curl?

Machine Kneeling Leg Curl is an isolation exercise that primarily targets the hamstrings and also engages the calves. It is an intermediate-level movement performed one leg at a time on a plate-loaded lever machine: one knee rests on a pad, the forearms rest on a chest-high pad, and the working leg curls a roller pad from a nearly straight position up toward the glutes.

The exercise trains knee flexion, the job the hamstrings share with the calves, without any hip hinge. That makes it a common accessory after hip-hinge work such as deadlifts, where the hamstrings are loaded mainly at the hip. Because each leg works alone, it also shows whether one side is weaker, and lets you bring that side up without the stronger leg taking over.

Hip position changes how stretched the hamstrings are during a leg curl. In a 12-week study of healthy adults, the leg trained with seated leg curls, hips bent to about 90 degrees, gained 14% in whole-hamstring muscle volume, against 9% for the other leg trained with lying leg curls, hips close to straight. The kneeling machine was not part of that study. It leaves the hips bent partway, so the hamstrings work at a length between those two setups.

Compared with the Machine Single-Leg Lying Leg Curl, the kneeling version supports the torso on the forearms instead of having you lie face down, which many lifters find more comfortable. The Machine Standing Leg Curl trains the same single-leg curl from a standing position. The choice between them usually comes down to which machine fits your body and which position you can hold steady.

The movement suits most lifters who can kneel comfortably and hold their hips still against the pad. If the setup is unfamiliar, the Machine Seated Leg Curl or Machine Lying Leg Curl teaches the same curl with both legs and less to adjust. Focus on feeling the back of the thigh pull the heel up, rather than the calf or a swing of the hips.

Muscles Worked

MuscleActivation

Biceps Femoris: Primary
Semimembranosus: Primary
Semitendinosus: Primary
Gastrocnemius (Lateral Head): Medium
Gastrocnemius (Medial Head): Medium
Gluteus Maximus: Low
Sartorius: Low
Erector Spinae: Minimal

Instructions

Load the plates on the lever arm and adjust the pads so the knee of your working leg lines up with the machine's pivot.
Kneel your non-working leg on the knee pad, resting the shin along the pad behind you.
Lean forward, set your forearms on the upper pad and hold the handles.
Let the working leg hang nearly straight with the front of the thigh against the thigh pad and the roller pad on the back of the lower calf, just above the heel.
Brace your core and keep your hips pressed toward the thigh pad.
Bend the knee to curl the roller up, bringing your heel toward your glutes as far as you can without lifting your hips.
Pause briefly at the top and squeeze the back of your thigh.
Lower the roller slowly until the leg is nearly straight, without letting the plates rest.
Complete your reps, then switch to the other leg.

Common Mistakes

Knee off the pivot
Setting the working knee ahead of or behind the machine's pivot makes the roller slide along the leg and stresses the knee instead of the hamstrings.
Hips leaving the pad
Pushing the hips back or arching the lower back to finish a heavy rep moves the work away from the hamstrings and onto the spine.
Swinging the lever
Kicking the heel up with momentum lets the plates carry the rep and skips the hardest part of the curl.
Cutting the range short
Stopping well short of a full curl, or never letting the leg lengthen at the bottom, trains only part of the hamstrings' range.
Dropping the weight
Letting the lever fall back instead of lowering it under control wastes the lowering phase and jars the knee at the bottom.

Injuries

Machine Kneeling Leg Curl is a low risk exercise when performed with proper technique. The machine fixes the path of the lever and supports the torso, so most problems come from a poor setup or a load that is too heavy to control.

The main strain points are the back of the knee, the hamstrings themselves and the lower back. A knee that sits ahead of or behind the machine's pivot makes the roller slide along the leg and puts uneven stress on the joint. Pushing the hips away from the thigh pad or arching the lower back to finish a rep shifts work onto the spine. Hamstring cramps are common near the top of the curl, where the muscle is shortest. The kneeling knee can also get sore if the pad is set so that the kneecap takes the weight.

Line the working knee up with the pivot before loading the machine, start with light plates, and lift and lower at a steady pace. If the hamstrings cramp, lower the leg, let the muscle relax and continue with a lighter load or fewer reps. To regress, use a lighter load on the Machine Seated Leg Curl or try the Band Standing Leg Curl. To progress once the movement is solid, add the Nordic Hamstring Curl or Glute-Ham Raise to your program.

Stop the set if you feel a sharp or pulling pain in the back of the thigh, pain behind the knee, or pain in the kneeling knee that does not ease when you adjust the pad. Sudden pain in the hamstring during a rep can signal a strain and is worth having checked before training it again.

Overview

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

Alternative Exercises

Frequently Asked Questions

Q: How is the kneeling leg curl different from the lying leg curl?: On the kneeling machine you rest on one knee and your forearms with your hips bent partway, instead of lying face down with your hips nearly flat. It also works one leg at a time, like the Machine Single-Leg Lying Leg Curl, while the Machine Lying Leg Curl usually trains both legs together.
Q: Why does this machine work one leg at a time?: Training each leg alone stops the stronger side from covering for the weaker one and makes a difference between the legs easy to see. Start with your weaker leg and match its reps on the other side.
Q: How much weight and how many reps should I use?: Pick a load you can curl through the full range for about 8 to 15 controlled reps. Plate-loaded machines jump in large steps, so use smaller plates to progress gradually rather than adding a full 45 lb plate at once.
Q: Why do my hamstrings cramp on this exercise?: The hamstrings are at their shortest near the top of the curl, and a hard contraction there can trigger a cramp, especially late in a set. Lower the leg, let it relax, and continue with a lighter load or fewer reps; cramps that return every session are worth raising with a doctor.
Q: Can the kneeling leg curl replace Romanian deadlifts?: No. The leg curl trains the hamstrings at the knee, while the Barbell Romanian Deadlift trains them at the hip, so most programs use one of each.