What’s the fastest way to make your hamstrings grow? The seated or lying leg curl?
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?
The Hamstring Muscle Group
On the back of your thigh, you’ve got three muscles:
- Biceps femoris
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 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.
Seated vs Lying Leg Curl: What’s the Difference?
Seated leg curls differ from lying leg curls in that the hamstring muscles crossing the hip are put in a stretched position.
In a lying leg curl, those same muscles are challenged at shorter lengths. This, in theory at least, should lead to faster hamstring growth with the seated leg curl.
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To put that theory to the test, a team of Japanese scientists got a group of young men and women to do both exercises for three months .
When you do seated or lying leg curls in a gym, both legs are normally trained together. But in this study, subjects trained one leg at a time. This meant each leg could be trained using either the seated or lying leg curl.
When you use different groups of people to compare different exercises, the food they eat, the life they live, and the genes they were born with can skew the results.
But when the right leg is trained with one exercise, and the left leg is trained with another, genetics, lifestyle and diet are the same for both legs.
Subjects in the study trained their hamstrings twice a week for 12 weeks, doing 5 sets of 10 reps in each workout.
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.
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, with all the additional growth coming from the hamstring muscles that cross the hip.
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%
- Seated Leg Curl + 24%
- Lying Leg Curl + 19%
- Seated Leg Curl + 8%
- Lying Leg Curl + 4%
Why did some muscles grow faster when they were trained with the seated leg curl?
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.
That is, the start position of each rep places the hamstrings at full length.
As a result, those 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. Gastrocnemius, a calf muscle crossing the knee, is also involved in knee flexion.
While hip extension moves like the Romanian deadlift do hit the hamstrings hard, you need some kind of hamstring curl to fully develop the hamstrings.
And the seated leg curl is a better option for hamstring muscle growth compared to the lying or standing leg curl.
For complete hamstring development, you’ll see the best results by including exercises that involve both hip extension and knee flexion in your resistance training program.
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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