The Study
Effects of rest intervals and training loads on metabolic stress and muscle hypertrophy
This study is like a fair race between two groups of people doing different kinds of weightlifting. One group lifted light weights with short breaks, the other lifted heavy weights with long breaks. After 8 weeks, the light-weight group got bigger arms — so we can say this kind of lifting probably made their arms grow more. But we can’t say it’ll work the same for everyone.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
Two groups lifted weights with the same total effort, but one used light weights and short breaks, the other heavy weights and long breaks. The light-weight group ended up with bigger arms.
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 — a 9.93% arm increase is noticeable and meaningful for someone training to build muscle, even if they don’t lift heavy.
- 2Light-weight group: arms grew 9.93% bigger.
- 3Heavy-weight group: arms grew 4.73% bigger.
- 4Light-weight group had huge hormone spike (7704%) and muscle swelling (35.2%), but hormone spike didn’t predict arm growth.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Clinical Physiology and Functional Imaging
Year
2018
Authors
J. Fink, N. Kikuchi, K. Nakazato
Related Content
Videos (2)
Claims (6)
If you lift light weights for more reps or heavy weights for fewer reps—but do the same total amount of work—you’ll grow your muscles just as much either way.
Even if your muscles get a big burst of growth hormone right after lifting weights, that doesn’t mean you’ll grow bigger muscles over time—some people who got way more of this hormone didn’t grow more muscle than others.
If young men lift light weights with very short breaks between sets for 8 weeks, their upper arms grow more than if they lift heavy weights with long breaks—even if they do the same total amount of lifting—because the short breaks create more muscle-burning stress that helps muscles grow bigger.
If two groups of young men lift weights with the same total effort but one rests longer with heavier weights and the other rests briefly with lighter weights, they both get just as strong after 8 weeks—even though you’d think the heavy weights would win.
Lifting lighter weights with very short breaks between sets makes your muscles swell up more right after working out than lifting heavy weights with long breaks—so if you want that pumped feeling fast, go light and quick.
If young men lift weights with the same total effort—whether they use heavy weights with long breaks or light weights with short breaks—they’ll still grow about the same amount of muscle. So, different ways of lifting can both work.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.