What’s the fastest way to make your hamstrings grow? The seated or lying leg curl? Here’s everything you need to know.
While the hamstrings are involved in compound lifts like the barbell squat and leg press, their contribution is relatively small.
If you want to maximize growth in the hamstrings, you’ll need exercises that train them directly.
One of the more popular ways to work the hamstrings is with an isolation exercise like the leg curl, which you can do in a seated, lying or standing position.
But which leg curl variation works best when it comes to making your hamstrings grow?
Seated vs Lying Leg Curl: Hamstring Hypertrophy Compared
To answer that question, a team of Japanese scientists got a group of young men and women to do both exercises for three months .
Subjects in the study trained their hamstrings twice a week for 12 weeks, doing 5 sets of 10 reps in each workout. In each training session, one leg was trained with seated leg curls, while the other was trained with lying leg curls.
Each rep lasted a total of 4 seconds – 2 seconds for the concentric (knee bending) and 2 seconds for the eccentric (knee straightening) phase of the exercise. Two minutes of rest was taken between each set.
Training load was gradually increased at the first, second, and third sessions from 50% to 60%, then 70% of 1-rep max.
The load remained at 70% of 1 rep-max for the duration of the study, and was increased only when subjects were able to complete the prescribed number of reps in all five sets.
Magnetic resonance imaging scans, the gold standard for measuring changes in muscle size, were used to assess growth in the hamstrings.
So what happened? If you had to choose between the seated and lying leg curl, which one should you pick, and why?
Is the Seated Leg Curl Better Than the Lying Leg Curl?
After 12 weeks of training, the seated leg curl stimulated around 55% more muscle growth than the lying leg curl. All the additional growth came from the hamstring muscles that cross the hip.
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In the short head of biceps femoris, the hamstring muscle that doesn’t cross the hip, there was no significant difference in growth between the seated and lying leg curl.
- Seated Leg Curl + 14%
- Lying Leg Curl + 9%
Biceps Femoris (Long Head)
- Seated Leg Curl + 14%
- Lying Leg Curl + 7%
Biceps Femoris (Short Head)
- Seated Leg Curl + 9.6%
- Lying Leg Curl + 9%
- Seated Leg Curl + 24%
- Lying Leg Curl + 19%
- Seated Leg Curl + 8%
- Lying Leg Curl + 4%
What’s the Difference Between the Seated and Lying Leg Curl?
Why did some muscles grow faster when they were trained with the seated leg curl?
The main difference between the seated and lying leg curl is that the seated version loads the hamstrings at long muscle lengths, which leads to a greater hypertrophic response.
In other words, when you sit down on a seated leg curl machine and get yourself into the starting position, it has the effect of stretching the hamstring muscles that cross the hip.
Because the starting position of each rep places the hamstrings at full length, the muscles are challenged at longer lengths compared to the lying leg curl.
One of the things that stimulates muscle growth is putting your muscles under a high level of tension in a stretched position. And that’s exactly what you get with the seated leg curl.
Here’s how the researchers sum up the results:
“In summary, we demonstrated that hamstring muscle hypertrophy was greater after seated than prone leg curl training, exclusively for the biarticular hamstrings that were in more lengthened positions during the seated leg curl. Based on these findings, the seated rather than prone leg curl is recommended if training aims include increasing or maintaining muscle size of the hamstrings.”
Knee Flexion and Hip Extension
In general, if you want your hamstrings to grow, I think it’s a good idea to incorporate exercises that involve both hip extension and knee flexion in your resistance training program.
Because the hamstring muscles cross two joints, you can train them with exercises like the Romanian deadlift (which involves hip extension) and the leg curl (which involves knee flexion) .
Other research to measure muscle growth in the hamstrings shows that weighted hip extensions are a very effective way to target the long head of biceps femoris .
That is, if you don’t have access to a seated leg curl, combining the lying leg curl with an exercise that emphasizes hip extension, such as the Romanian deadlift, will help to stimulate more growth across the whole of the hamstrings.
Exercises targeting the hamstrings via hip extension also hit a number of other muscle groups, including the glutes and spinal erectors.
Frequently Asked Questions
What muscles do leg curls work?
On the back of your thigh, you’ve got three muscles:
- Biceps femoris (long head and short head)
Collectively, those three muscles are known as the hamstrings.
The majority of muscles making up the hamstring muscle group are biarticular, which means they cross two joints, the hip and the knee.
This gives the hamstrings two main roles:
- Knee flexion
- Hip extension
The semitendinosus, semimembranosus, and the long head of biceps femoris cross two joints (the hip and knee joints) rather than one.
Unlike the other hamstring muscles, the short head of biceps femoris doesn’t extend the hip, and only gets involved in flexing the knee.
What’s the difference between the seated leg curl and leg extension?
The seated leg curl and leg extension work a completely different set of muscles. The leg extension hits the muscles on the front of your thighs, known as the quadriceps. The seated leg curl targets the hamstrings, found on the back of your thigh.
Do seated hamstring curls work your glutes?
Seated hamstring curls don’t work your glutes in any meaningful way. If you analyze the movement, all that’s happening during the seated hamstring curl is knee flexion and extension. Because the glutes don’t cross the knee, they’re not trained by the seated leg curl.
Do hamstring curls work the glute-ham tie-in?
There’s no muscle connecting the glutes and hamstrings. They’re two separate muscles. You’ve got the glutes, and you’ve got the hamstrings. Leg curls are an effective way to train the hamstrings, but not the glutes.
Do leg curls work the calves?
There are two calf muscles, gastrocnemius and soleus. Gastrocnemius crosses the knee, and assists the hamstrings in flexing the knee, which means that it is worked (to a degree at least) by the leg curl. Soleus, however, crosses the ankle but not the knee, so isn’t worked by the leg curl.
SOURCE: Greater hamstrings muscle hypertrophy but similar damage protection after training at long versus short muscle lengths. Medicine and Science in Sports and Exercise, 53, 825-837
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