Leg Extensions with Bent Hips Grow Thigh Muscle Better
The effects of hip flexion angle on quadriceps femoris muscle hypertrophy in the leg extension exercise
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
When doing leg extensions, bending your hips a little (40°) makes the front thigh muscle (rectus femoris) grow more than bending them all the way (90°). The side muscle (vastus lateralis) grows the same either way.
Surprising Findings
The rectus femoris grew dramatically more at 40° hip flexion, while the vastus lateralis showed no difference.
Most assume all quadriceps muscles respond similarly to isolation exercises — but this shows biarticular muscles (crossing hip and knee) respond differently to joint positioning than single-joint muscles.
Practical Takeaways
If you want to maximize growth in your front thigh muscle (rectus femoris), try doing leg extensions with your hips bent to about 40° instead of fully upright.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
When doing leg extensions, bending your hips a little (40°) makes the front thigh muscle (rectus femoris) grow more than bending them all the way (90°). The side muscle (vastus lateralis) grows the same either way.
Surprising Findings
The rectus femoris grew dramatically more at 40° hip flexion, while the vastus lateralis showed no difference.
Most assume all quadriceps muscles respond similarly to isolation exercises — but this shows biarticular muscles (crossing hip and knee) respond differently to joint positioning than single-joint muscles.
Practical Takeaways
If you want to maximize growth in your front thigh muscle (rectus femoris), try doing leg extensions with your hips bent to about 40° instead of fully upright.
Publication
Journal
Journal of Sports Sciences
Year
2024
Authors
Stian Larsen, Benjamin Sandvik Kristiansen, P. Swinton, Milo Wolf, Andrea Bao Fredriksen, Hallvard Nygaard Falch, Roland van den Tillaar, Nordis Østerås Sandberg
Related Content
Claims (6)
For the outer thigh muscle (vastus lateralis), bending your hip to 40 or 90 degrees during leg extensions doesn’t seem to make a difference in how much the muscle grows in guys who haven’t lifted before.
If you're a guy new to lifting and want your front thigh muscle to grow as much as possible, doing leg extensions with your hip more bent (40°) is probably better than keeping it straighter (90°).
Doing leg extensions with your hip bent at 40 degrees instead of 90 degrees probably makes the front thigh muscle (rectus femoris) grow more in guys who haven’t lifted weights before.
If you stretch your hips back while doing leg extensions, your quad muscle gets longer and grows more—especially in the middle and upper parts—than if you do the exercise with your hips bent.
Muscles that cross two joints (biarticular muscles) exhibit preferential hypertrophy with isolation exercises that target a single joint action, due to mechanical disadvantage during multi-joint movements.