The Study
The Effect of Unilateral and Bilateral Leg Press Training on Lower Body Strength and Power and Athletic Performance in Adolescent Rugby Players
This study is like a fair race between two kinds of leg workouts — one using both legs at once, and one using each leg separately. It found that both workouts made the players stronger with their legs, and using one leg at a time made each leg even stronger. But neither workout made them run faster or jump higher. So we know which workout made legs stronger, but not if it helps them play better in games.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
Kids trained one leg at a time or both legs together on a leg press machine for 5 weeks. Both ways made them stronger when pushing with both legs, but pushing one leg at a time made that one leg even stronger.
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 get stronger on one leg (like for rugby tackles or kicks), training one leg at a time works better.
- 2But getting stronger doesn't automatically make you faster or higher jumpers.
- 3Both-leg strength up by ~10%.
- 4One-leg strength up by 20% with one-leg training, 12% with two-leg training.
- 5Sprinting and jumping didn't get better.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Journal of Human Kinetics
Year
2023
Authors
Xiang Zhao, A. Turner, J. Sproule, Shaun M. Phillips
Related Content
Claims (6)
For small muscle groups, unilateral and bilateral resistance training produce equivalent hypertrophic adaptations when volume and effort are matched.
When teenage rugby players train one leg at a time on the leg press machine, they get much stronger in that single leg than when they train both legs together at the same time.
Even though the players got stronger from doing leg presses, they didn’t run any faster after five weeks — meaning just getting stronger on a machine doesn’t automatically make you sprint better.
Training one leg at a time makes that leg much stronger than training both legs together — even though both methods make you equally strong when using both legs at once.
Doing leg press exercises twice a week for five weeks makes teenage rugby players much stronger when pushing with both legs at once, whether they use one leg or both legs at a time.
Even though the players got stronger, their ability to jump higher or more powerfully didn’t improve after five weeks of leg press training — meaning strength on the machine doesn’t automatically make you jump better.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.