The Study
Resistance training load does not determine resistance training-induced hypertrophy across upper and lower limbs in healthy young males.
This study found that lifting heavy weights and lifting light weights made people’s muscles grow about the same — but it only tested 20 young guys, and we don’t know if they were tricked into thinking they were lifting different weights. So we can say the two kinds of lifting seemed to work similarly, but we can’t be 100% sure it’s because of the weights alone.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
People lifted weights in two different ways—some heavy with few reps, some light with many reps—but both made muscles grow about the same, as long as they pushed until they couldn't do another rep. Some people’s muscles grew a lot, others not much, and it had nothing to do with how heavy the weights were.
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 566 / 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—this means lifting light weights to failure can build muscle just as well as heavy lifting, which could help people who can't lift heavy.
- 2Muscle growth was similar between heavy (70–80% 1RM) and light (30–40% 1RM) loads.
- 3Protein synthesis went up by 0.27% per day at week 1 and 0.10% per day at week 10.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
The Journal of physiology
Year
2025
Authors
Matthew Lees, Jonathan C. Mcleod, Robert W Morton, Brad S. Currier, Matthew D Fliss, Sean Mckellar, Rajbir S Sidhu, B. Stansfield, Erin K. Webb, C. McGlory, J. Burniston, S. Phillips
Related Content
Claims (10)
When people lift weights until they can no longer complete another repetition, the amount of muscle growth is similar whether they use light, moderate, or heavy weights.
When muscles are trained to complete fatigue, both slow-twitch and fast-twitch muscle fibers grow by the same amount, no matter how heavy the weight or how many repetitions are performed.
During the first weeks of weight training, muscle protein synthesis increases, but after 10 weeks of continued progressive training, this increase diminishes regardless of whether the weights are heavy or light.
During resistance training, the rate of muscle protein synthesis rises in the first week and decreases by the tenth week, even when the training intensity increases over time, and this pattern occurs regardless of how heavy the weights are.
When muscles are trained to the point of exhaustion, both slow-twitch and fast-twitch muscle fibers grow by the same amount, no matter how heavy the weight or how many repetitions are performed.
During resistance training, the rate of muscle protein synthesis rises initially but decreases steadily between week 1 and week 10, regardless of how heavy the weights are, showing a reduction in the muscle-building response over time.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.