The Study
Repeated Resistance Training Reveals the Reproducibility of Muscle Strength and Size Responses Within Individuals
This study is like a fair science experiment where some people did strength training and others didn’t. It shows that, on average, training really does make muscles bigger and stronger. But it can’t perfectly predict how any one person will respond if they train again later.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
This study checked if people’s muscles grow and get stronger the same way when they do the same training twice.
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 555 / 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, the results are meaningful: most people benefit from training, and if you responded well before, you likely will again.
- 2After 10 weeks of training, leg strength went up by 22%, arm strength by 25%, and muscle size by about 16–17%.
- 3When people trained again, their results were similar.
- 4Only one person didn’t improve much, and no one failed both times on more than one thing.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
European Journal of Sport Science
Year
2025
Authors
Aapo Räntilä, Eeli J. Halonen, Esko J Tiainen, Sasu O Kaasinen, J. Hulmi, J. P. Ahtiainen
Related Content
Claims (8)
Everyone can lose fat, get stronger, and build muscle with the right diet and exercise — how much they gain might differ, but the ability is there for all of us.
Everyone can build muscle with consistent strength training over time — if you didn’t gain muscle once, it’s probably not your genes, just that specific training phase didn’t work for you.
Just because someone doesn't gain muscle in one workout phase doesn't mean they never will—everyone eventually gains muscle with enough training over time.
When people stop training, their muscles don't get weaker as fast as they shrink — strength sticks around more than size, maybe because the brain and nerves keep working well even as muscles get smaller.
If you respond really well (or not so well) to a weight training program, you’ll probably have a similar result if you do the exact same program again after taking a break.
If you gain more muscle and strength when working out, you might also lose more when you stop — your gains and losses seem to go hand in hand.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.