Seated vs. Lying Leg Curls: Which Builds Bigger Hamstrings?
Why Stretch Matters for Muscle Growth, and How You Should Be Training Your Hamstrings
If you’re serious about growing your hamstrings, it’s time to rethink your leg curl setup. New research shows that seated hamstring curls aren’t just harder, they’re also significantly more effective for muscle growth than lying leg curls. Here’s what the latest studies reveal, and how to apply it to your training.
The Research: Long Muscle Lengths Promote More Growth
For years, evidence has pointed to a simple but powerful training principle: muscles grow more when trained at longer lengths. That’s been well-documented in studies on quads and biceps, but hamstrings? Less so.. Until now.
In a groundbreaking study by Maeo et al. (2020), researchers recruited 20 untrained young adults and had them train one leg using seated hamstring curls and the other using lying hamstring curls for 12 weeks. Volume, load progression, and frequency were the same. The only variable? Hip angle.
Seated leg curls were done with hips flexed ~90° (muscles stretched)
Lying leg curls were done with hips extended ~30° (shorter muscle lengths)
After 12 weeks, MRI scans revealed that the seated leg curl significantly outperformed the lying curl in hypertrophy of the key hamstring muscles: the semimembranosus, semitendinosus, and the long head of the biceps femoris.
Meanwhile, lying leg curls only outperformed in one muscle: the sartorius, which isn’t even part of the hamstring group.
Takeaway: Training muscles in their lengthened position produces superior hypertrophy. Maeo et al., 2020
Why the Seated Curl Wins: A Biomechanical Breakdown
To understand these results, you need to know how the hamstrings function:
The semimembranosus, semitendinosus, and biceps femoris long head all cross both the hip and knee joints. When your hips are flexed (as in seated curls), these muscles are fully stretched.
The short head of the biceps femoris only crosses the knee joint. Its length isn’t affected by hip position.
The sartorius, a hip flexor and weak knee flexor, is shortened during seated curls and lengthened during lying curls.
The more you stretch a muscle under load, the more mechanical tension and muscle damage it experiences, both of which are key drivers of hypertrophy.
Activation Confirms It: Seated Curls Recruit More Muscle
A second study by Yanagisawa & Fukutani (2020) used T2-weighted MRI scans to assess muscle activation and force output during different hamstrings exercises. It compared:
Knee flexion with hips flexed (seated curl position)
Knee flexion with hips extended (lying curl position)
Hip extension with knees flexed and extended
The findings?
More force and total work were produced at longer muscle lengths
Greater muscle activation was seen in the hamstrings during seated curls vs lying curls
This backs up the hypertrophy findings with real-time muscle engagement data.
Takeaway: Long muscle lengths not only drive more growth—they increase force output and activation too. Yanagisawa & Fukutani, 2020
Training Implications: Smarter Hamstring Programming
If your goal is hypertrophy, here’s how to program smarter:
1. Prioritize seated leg curls
Make them your go-to leg curl variation. If your gym only has lying leg curls, consider alternatives like Nordic curls or glute-ham raises that load the hamstrings at long lengths.
2. Include hip-extension based lifts
Romanian deadlifts and back extensions train the hamstrings in different ways. Use both knee flexion and hip extension movements for complete development.
3. Use full ROM and slow eccentrics
Don’t rush the rep. Tension in the stretched position is the magic. Own that bottom range.
But What About Soreness?
Yes, seated curls might leave you more sore at first. That’s a natural result of placing muscles under tension while stretched. But that soreness fades as your muscles adapt, while the growth continues.
Final Verdict: Seated > Lying
Let’s summarize:
Seated hamstring curls create more growth in key hamstring muscles
They recruit more muscle fibers and generate more force
They offer greater stretch-induced tension, the holy grail for hypertrophy
You don’t have to ditch lying curls altogether, they’re still useful for variety or deload weeks, but they should take a back seat to seated curls in a serious hypertrophy plan.
Scientific References:
Maeo S. et al. Greater Hamstrings Muscle Hypertrophy but Similar Damage Protection after Training at Long versus Short Muscle Lengths. Med Sci Sports Exerc. 2020. PubMed
Yanagisawa O, Fukutani A. Muscle Recruitment Pattern of the Hamstring Muscles in Hip Extension and Knee Flexion Exercises. J Hum Kinet. 2020. PubMed
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