Key Takeaways

  1. Two of the most popular exercises for building the hamstrings are the lying and seated hamstring curls.
  2. In a recent study, researchers found that seated leg curls resulted in more hamstring muscle activation than lying hamstring curls.
  3. Keep reading to learn what this means for your training and the best hamstring exercises for building muscle.

What’s the best hamstring curl machine exercise for building bigger gams? 

That’s a tough question to answer. 

There are myriad different exercises and exercise variations for training every muscle group, new studies come out supporting this one or that, and every meathead in the gym and “influencer” on social media beats the drum for their pet exercises. 

This is particularly true of the hamstrings, because there are two very different ways to train them. 

Some exercises train the hamstrings using what’s known as hip extension (moving your abdomen away from your thighs), with some of the most common examples being the deadlift, Romanian deadlift, and glute bridge.

Other exercises train the hamstrings using what’s known as knee flexion (bringing your ankles closer to your butt), with some of the most common examples being seated and lying leg curls and nordic curls.

Which is better, though? 

That’s what scientists from Jobu University wanted to find out in a study published in 2020.

Let’s look at what they did.

What Did the Researchers Do?

lying leg curl machine


The researchers had 7 healthy, untrained men between the ages of 21 and 25 report to the lab on 5 separate occasions. 

The first visit was to familiarize the participants with the exercises they’d have to perform as part of the experiment. On each of the following four visits, the participants did one of four exercises:

  • Isokinetic hamstrings curls with the hips fully extended (similar to a lying leg curl)
  • Isokinetic hamstrings curls with the hips flexed at 90 degrees (similar to a seated leg curl)
  • Isokinetic hip extension with the knees flexed at 90 degrees (similar to a “donkey kick” with the knees bent at 90 degrees)
  • Isokinetic hip extensions with the knees fully extended (similar to a “donkey kick” with the legs kept straight throughout)

(In case you’re wondering, an isokinetic exercise is an exercise performed on a particular type of workout machine that only allows you to move a weight at a set speed, regardless of how hard you push. It’s often used in scientific studies, because it helps ensure the participants are all performing an exercise the same way).

During each session, participants performed two sets: one set of 3 reps, and one of 30 reps.

In each set the participants only performed the concentric portion of the exercise (the lifting portion), and were instructed to perform the reps as hard as they could. However, because they were performing the exercises on an isokinetic machine, no matter how hard they pushed they could only move the weight at a set speed.

For the set of 3 reps, they could only move the weight at a speed of 30 degrees per second, (pretty slowly), and for the set of 30 reps they were limited to 180 degrees per second, which means the reps were performed relatively quickly.

During the set of 3 reps, the researchers measured the participants’ peak torque (a measurement of how much force the participants could generate), and during the set of 30 reps, the total work performed (measured in Joules).

The participants performed all four of the exercises in a random order, completing one exercise per session, and rested three days between each session. 

Before the participants performed the exercises, and then again five minutes after completing the exercises, the researchers did MRI scans on the midpoint of the back of the participants’ thighs to measure muscle activation. 

Without getting too far into the weeds, muscle activation isn’t always a perfect predictor of muscle growth, but it is an indication that an exercise is probably effective for training a muscle.

Summary: Researchers wanted to know if knee flexion exercises like leg curls, or hip extension exercises like deadlifts, were more effective at activating the hamstrings.

2024 4th of July Sale! 2024 4th of July Sale!

The Best Hamstring Curl Exercise Is . . . 

After collecting and analyzing all of the data, the researchers found that the participants were able to generate more force and did more total work when they did seated leg curls (hips flexed) than when they did lying leg curls (hips extended).

In other words, seated hamstring curls appeared to be superior to lying leg curls for activating the hamstrings (which indicates they’re probably better for building muscle).

The researchers also found that when the participants performed hip extensions (an exercise similar to “donkey kicks”), they were able to generate more force when their knees were fully extended (straight) than when they performed the exercise with their knees flexed at 90 degrees (bent).

Finally, the researchers also found that the biceps femoris and semitendinosus muscles (which comprise a large chunk of the hamstrings) were recruited more during leg curls (knee flexion) than during donkey kicks (hip extension). 

Summary: This study found that seated hamstring curls tended to activate and train the hamstrings more effectively than lying hamstring curls or other hamstring exercises.

What Does This Mean for You?

hamstring exercises

Perhaps the most significant finding of this study is that we now have some evidence that seated leg curls are more effective for training the hamstrings than pretty much any other exercise, including lying leg curls.

And while muscle activation doesn’t always translate into more muscle growth, recent research tells us that when it comes to the hamstrings, the more active they are during an exercise, the more they grow.

Without going too far down the rabbit hole of hypertrophy science, this is likely because muscles tend to grow more when they are. . .

. . . and seated leg curls check both boxes.

In comparison, lying leg curls train your hamstrings through a full range of motion, but don’t train them in a fully stretched position, and exercises like deadlifts, Romanian deadlifts, and good mornings train your hamstring in a stretched position, but don’t train them through a full range of motion.

Does this mean that leg curls are the only hamstring exercise you should do? Does it mean you should ignore other exercises like the . . . 

 . . . no. Let’s not throw the baby out with the bathwater. 

Prioritizing compound exercises that allow you to lift heavy and effectively implement progressive overload should always be nucleus for your lower-body workouts.

However, it seems reasonable to say that when choosing accessory exercises for your lower body workouts, it’s wise to include seated leg curls much of the time. 

That’s not to say that other hamstring exercises have no utility—not only can other exercises like Nordic curls, glute-ham raises, reverse hyperextensions, cable pull-throughs, and the like effectively train your hamstrings, they can also make your workouts more enjoyable by injecting some much needed variety into your training. 

Summary: Compound exercises like the squat and deadlift should be the bread and butter of your lower body workouts, but including seated hamstring curls will improve your hamstring strength and size more than most other hamstring exercises.

Find the Best Diet for You in Just 60 Seconds

How many calories should you eat? What about "macros?" What foods should you eat? Take our 60-second quiz to get science-based answers to these questions and more.

Take the Quiz


Perhaps the most significant finding to come out of the present study is that seated leg curls are about the most effective exercise there is for targeting the hamstrings.

Don’t lose sight of the forest for the trees, though—this doesn’t mean they should be given precedence in your training over key lower-body exercises like the squat, deadlift, lunge, and all the variations of each.

Instead, you should still start your lower-body workouts with heavy, compound exercises like squats and deadlifts, and then include seated hamstring curls as an accessory exercise.

What’s your take on hamstring curl exercise? Have anything else to share? Let me know in the comments below!

+ Scientific References