The Study
Comparison of Muscle Hypertrophy and Strength Adaptations Induced by Back Squat and Leg Extension Resistance Exercises
This study is like a fair race between two different workouts — one group did squats, another did leg extensions. Because they were randomly assigned, we can guess that the workouts caused the differences in muscle growth and strength. But we don’t know if the people measuring the results were blind to who did what, so we can’t be 100% sure.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
Two groups of women trained for 8 weeks—one did squats, the other did leg extensions. Their thigh muscles grew in different spots, and each group got stronger in the exercise they did.
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 548 / 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—exercise choice changes where muscles grow and how strong you get in that specific movement.
- 2Leg extensions: RF grew 11.4%, 12.3%, 17.5% at top, middle, bottom.
- 3Squats: VL bottom grew 18.2%.
- 4Squats: 46.7% stronger in squat.
- 5Both: ~20% stronger in leg extension.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Journal of Strength & Conditioning Research
Year
2025
Authors
Witalo Kassiano, Bruna Costa, Gabriel Kunevaliki, Felipe Lisboa, Aline Prado, Luis Alves, Ian Tricoli, Natã Stavinski, Jarlisson Francsuel, Edilson S. Cyrino
Related Content
Claims (10)
When the total amount of work and effort are the same, exercises that use multiple muscle groups do not cause more muscle growth in the target muscles than exercises that focus on one muscle group.
Squats make the lower part of the outer thigh muscle grow more than leg extensions do, probably because squats involve more hip and knee movement together.
Which leg exercise you choose matters: leg extensions grow the front thigh muscle more, squats grow the lower outer thigh more and make you stronger at squats—but both help you get stronger at leg extensions.
Even if you only do squats, you still get almost as strong at leg extensions as someone who only does leg extensions—so squats aren’t useless for that movement.
Doing leg extensions makes the front thigh muscle grow more evenly along its length than doing squats, which don’t stimulate that muscle as much.
If you want to get stronger at squats, doing squats is way better than doing leg extensions—but if you want to get stronger at leg extensions, both exercises work about the same.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.