Seated leg curl
The seated leg curl trains the hamstrings with the hip flexed, which keeps them long, and in the only head-to-head trial it grew them more than the lying curl (+14% vs +9% in 12 weeks). It is the best-supported hamstring isolation exercise, though that rests on a small number of trials.
What the science says
- Grows the hamstrings more than the lying curl Moderate evidence
In Maeo et al.'s 2021 trial, 20 adults trained one leg seated and the other lying (5 × 10 at 70% of 1RM, twice a week, 12 weeks). MRI showed +14% whole-hamstring volume with the seated curl versus +9% lying, driven by the muscles that cross both hip and knee.
- Training at long muscle lengths seems to be why Moderate evidence
Maeo et al. (2024) compared a lengthened, hip-flexed eccentric leg curl on a weight stack with the Nordic curl in 42 young men over 12 weeks: the lengthened curl grew the hamstrings by 18% versus 11%, and the biceps femoris long head by 19% versus 5%.
- Where the growth appears varies from person to person Moderate evidence
In a 45-person randomized trial, Frouin et al. (2024) had participants train with seated leg curls and stiff-leg deadlifts for 9 weeks: the heavy-load group grew mainly the semitendinosus (about +27%), and the distribution of growth across the hamstring heads varied greatly between individuals.
- Protects against muscle damage as well as the lying curl Moderate evidence
In part 2 of Maeo et al. (2021), both seated and lying training reduced the damage and strength loss after hard eccentric curls compared with untrained controls, with no difference between them.
How to do it
Muscles trained: hamstrings, gastrocnemius
- Line up the knee joint with the machine's pivot point.
- Lock the thigh pad down firmly so the hips can't lift.
- Sit tall or lean slightly forward to keep the hips flexed and the hamstrings long.
- Curl as far as the machine allows, then lower over 2–3 seconds to a nearly straight knee.
- Don't cut the range short at the top, where the hamstrings are longest.
How to apply it
Use it as your main hamstring isolation exercise, with moderate reps taken close to failure and a controlled lowering, alongside a hip-hinge exercise.
Who should be careful
For healthy adults the main issues are cramping and expected soreness in the first weeks; build volume gradually. Anyone with a current or recent hamstring strain or knee problem should have a physician or physical therapist set their training.
Frequently asked questions
Why does the seated leg curl beat the lying one?
Sitting flexes the hip, so the hamstrings work at longer lengths. In Maeo et al. (2021) the seated curl grew the hamstrings by 14% versus 9% for the lying curl.
Will it grow all four hamstring muscles equally?
Not necessarily. Frouin et al. (2024) found growth concentrated in the semitendinosus, with large differences between individuals.
How many sets and reps should I do?
For size, 3–4 sets of 8–15 reps taken close to failure; the trial used 5 sets of 10 at 70% of 1RM twice a week.
Scientific references
- Greater Hamstrings Muscle Hypertrophy but Similar Damage Protection after Training at Long versus Short Muscle Lengths
- Hamstrings Hypertrophy Is Specific to the Training Exercise: Nordic Hamstring versus Lengthened State Eccentric Training
- Individual distribution of muscle hypertrophy among hamstring muscle heads: Adding muscle volume where you need is not so simple
More exercises
- Back squat Strong evidence
The barbell back squat reliably builds the quadriceps, glutes and adductors and is one of the best-studied lower-body exercises in training research.
- Front squat Moderate evidence
The front squat holds the bar on the front of the shoulders, which keeps the torso more upright and loads the knees less than the back squat while recruiting the thigh muscles about as much.
- Bulgarian split squat Moderate evidence
The Bulgarian (rear-foot-elevated) split squat trains one leg at a time and builds the quads and glutes with far less load on the bar than a back squat.
- Leg press Strong evidence
The leg press builds the quadriceps about as well as free-weight squats and also grows the glutes and adductor magnus, with no balance or spinal-loading limit.
- Hack squat (machine) Moderate evidence
The machine hack squat lets you squat deep on a fixed track with your back supported, which makes it easy to push the quads close to failure.
- Conventional deadlift Moderate evidence
The conventional deadlift trains the whole posterior chain and grip and is a core strength lift, but research on its growth effects is thin: trials either use other deadlift variants or measure strength rather than muscle size.