Updated

Leg Curl

Legs ['Hamstrings', 'Calves']

The leg curl is a legs movement that works the ['hamstrings', 'calves']. Two things decide whether it produces results: the load relative to your one-rep maximum, and the number of hard sets per week. For strength, three to five sets of one to five repetitions at 85 per cent or more of your one-rep max is the classic prescription; for muscle size, three to four sets of six to twelve repetitions at 65 to 80 per cent, taken close to failure; for endurance, two to three sets of fifteen or more at under 65 per cent. Ten to twenty hard sets per muscle group per week is the range most training research converges on, and progression comes from adding a little weight or a repetition rather than from changing the exercise. The calculator below estimates your one-rep max from a set you have actually completed, which is the number every percentage above refers to.

Leg Curl 1RM Calculator

Estimate your one-rep max

Enter the weight you lifted (kg or lbs)

Leg Curl Strength Standards (kg)

Body Weight Beginner Novice Intermediate Advanced Elite
120 kg 45 65 90 120 155
130 kg 45 65 95 125 160
140 kg 50 70 95 130 165
150 kg 50 70 100 135 170
160 kg 50 75 105 140 180
170 kg 55 75 105 140 185
180 kg 55 80 110 145 190
190 kg 55 80 115 150 195
200 kg 60 85 115 155 200
210 kg 60 85 120 160 205
220 kg 60 90 120 165 210

How to Perform the Leg Curl

Lie face down on a leg curl machine with the pad positioned just above your heels and your knees aligned with the machine's pivot point. Grip the handles for stability. Curl the weight up by bending your knees and bringing your heels toward your glutes. Squeeze the hamstrings at the top of the movement, then lower the weight slowly under control to the starting position without letting the weight stack rest between reps.

Muscle Activation

The leg curl isolates the hamstring muscles through knee flexion. The biceps femoris, semimembranosus, and semitendinosus are all heavily activated. The gastrocnemius (calf muscle) also crosses the knee joint and contributes to the curling motion. Unlike hip-hinge exercises that train the hamstrings through hip extension, the leg curl targets the knee flexion function of the hamstrings, making it a valuable complement to exercises like Romanian deadlifts.

Common Mistakes

  • Lifting the hips off the pad during the curl, which uses momentum and reduces hamstring isolation.
  • Using too much weight and performing partial reps instead of achieving a full range of motion.
  • Letting the weight drop on the eccentric instead of controlling the descent.
  • Not aligning the knee joint with the machine's axis of rotation, which can cause knee discomfort.

Variations

Seated leg curls place the hamstrings in a stretched position at the hip, which may provide a different training stimulus. Single-leg curls address imbalances. Nordic hamstring curls are a bodyweight alternative that eccentrically loads the hamstrings with extreme intensity. Stability ball hamstring curls can be done at home.

Programming Tips

Perform 3-4 sets of 10-15 reps, 2-3 times per week. The hamstrings respond well to both heavy loads and higher reps. Include both a hip-hinge movement like the Romanian deadlift and a leg curl variation for complete hamstring development across both functions of the muscle.

Frequently Asked Questions

Yes, deadlifts train the hamstrings through hip extension, but leg curls target knee flexion. Training both functions leads to more complete hamstring development and helps prevent injuries. In practice, the leg curl loads the hamstrings, calves and needs machine; an intermediate lifter of average bodyweight handles about 105 lbs, so judge your own numbers against that rather than against a gym record.
Both are effective. Lying leg curls allow for a stronger contraction, while seated leg curls place the hamstrings in a more stretched position, which may be better for hypertrophy. Include both if possible. In practice, the leg curl loads the hamstrings, calves and needs machine; an intermediate lifter of average bodyweight handles about 105 lbs, so judge your own numbers against that rather than against a gym record.
Stay hydrated, warm up properly, and avoid going too heavy too quickly. Cramping often indicates fatigue or dehydration. Reduce the weight slightly and focus on controlled reps. In practice, the leg curl loads the hamstrings, calves and needs machine; an intermediate lifter of average bodyweight handles about 105 lbs, so judge your own numbers against that rather than against a gym record.
Yes, strong hamstrings are critical for knee stability and injury prevention, especially for athletes. Both eccentric and concentric hamstring training through leg curls reduces injury risk. In practice, the leg curl loads the hamstrings, calves and needs machine; an intermediate lifter of average bodyweight handles about 105 lbs, so judge your own numbers against that rather than against a gym record.

Related Exercises

Squat

['Quadriceps', 'Glutes', 'Hamstrings', 'Core', 'Lower Back']

Front Squat

['Quadriceps', 'Glutes', 'Core', 'Upper Back']

Leg Press

['Quadriceps', 'Glutes', 'Hamstrings']

Romanian Deadlift

['Hamstrings', 'Glutes', 'Lower Back']

Calf Raise

['Gastrocnemius', 'Soleus']

Progressing on the leg curl

Progression on a machine movement for the legs follows the same logic whatever the exercise: add a little load or one repetition once the last set stops being hard, and change nothing else. A machine or cable stack usually moves in fixed increments, and the pin position is only part of the load: seat height and handle position change the leverage enough that the same pin can be easier or harder. Note the settings alongside the weight.

Stalling is normal and usually means one of three things: total weekly volume for the legs has drifted too low, recovery is short because sleep or calories are, or the load has been pushed while form quietly deteriorated. Filming a set from the side settles the third question faster than any cue. Ten to twenty hard sets per muscle group per week is the range most training research converges on, and a stall at the bottom of that range is a volume problem rather than a programme problem.

Common mistakes on legs work

The commonest error on leg movements is cutting depth as the load rises, which trades range of motion for a number on the bar. Squatting to a consistent depth, ideally with the hip crease below the top of the knee, makes the numbers comparable week to week. The second is letting the knees travel inward under load, which is usually weak hip abductors rather than a technique fault.

Where the leg curl fits in a week depends on how demanding it is rather than on the muscle it trains. A movement using a machine across the legs is best placed while you are fresh if it is heavy and technical, and late in the session if it is a single joint. Two sessions a week touching the same muscle group beat one for most people, because protein synthesis after a session returns to baseline within about forty-eight hours, and a muscle trained once a week spends five of those days doing nothing.

Across all of them, the same two rules apply. Warm up with the movement itself at progressively heavier loads rather than with general cardio, and leave one repetition in reserve on all but the last set: training to failure on every set raises fatigue considerably without adding much to the result.