The Study
Electromyographic Comparison of Five Lower-Limb Muscles between Single- and Multi-Joint Exercises among Trained Men.
This study is like taking a snapshot of how hard different muscles work during three leg exercises. It shows which muscles turn on more during each move, but it doesn’t prove that doing those exercises will make your muscles grow or get stronger over time.
Analysis score
Maximum 44 for a cross-sectional study.
Where the score came from
This study checks which leg exercises make specific muscles work harder using a machine that listens to muscles.
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 534 / 100
Quality score
Snapshots of a population at a single point in time, or descriptions of small groups. Can identify correlations and prevalence, but cannot determine cause and effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1Yes, the differences are big enough to matter—especially for people wanting to grow or strengthen specific leg muscles.
- 2Leg press made the outer quad work 17.6% harder than knee extension.
- 3Knee extension made the front-middle quad work 24.3% harder than leg press.
- 4Kickback made the hamstring work 76% harder than leg press.
- 5Butt and inner quad worked the same in all exercises.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Journal of sports science & medicine
Year
2021
Authors
N. Stien, A. Saeterbakken, V. Andersen
Related Content
Claims (6)
Doing leg extensions might grow your front thigh muscle more than leg presses, even though both workouts work the other big thigh muscles just as hard.
If you're a guy who lifts weights, your front thigh muscle works way harder during leg extensions than during leg presses — probably because the movement challenges how that muscle crosses two joints at once.
For guys who lift weights, doing leg presses or kickbacks works the butt muscle just about the same — neither one gives you a bigger advantage in muscle activation.
For guys who lift weights, the inner thigh muscle works just as hard during leg presses and knee extensions — these two exercises use that muscle in a similar way.
For guys who lift weights, the leg press works the main quad muscle harder than the knee extension machine, based on electrical activity in the muscle.
If you're a guy who lifts weights, doing kickbacks might work your back thigh muscle way more than the leg press — like 76% more, according to one study.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.