The Study
The effects of hip flexion angle on quadriceps femoris muscle hypertrophy in the leg extension exercise
This study tried two different ways of doing a leg exercise and found that one way might make one muscle in your thigh grow a little more. But it only tested 22 guys who had never lifted weights before, so we can’t say it works the same for everyone.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
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.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 554 / 100
Quality score
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1Yes — if you want to grow the rectus femoris muscle more, using 40° hip flexion during leg extensions is a better choice than 90°.
- 2Rectus femoris grew more with 40° hip flexion (BF > 100).
- 3Vastus lateralis grew the same at 40° and 90° (BF = 0.07).
- 4Study lasted 10 weeks with 2 sessions per week.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
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 (7)
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.
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°).
When performing leg extensions with the hip fully extended, the rectus femoris muscle grows larger than the vastus lateralis muscle because the rectus femoris spans two joints and is stretched more during this movement.
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 span two joints grow more when trained with exercises that move only one joint, compared to exercises that move multiple joints at once, because of reduced mechanical efficiency during compound movements.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.