The Study
Biomarkers associated with low, moderate, and high vastus lateralis muscle hypertrophy following 12 weeks of resistance training
This study looked at a group of young guys who lifted weights and found that some grew bigger muscles than others. It noticed that people who started with thinner muscles and had more RNA in their muscles after training tended to grow more—but it didn’t prove that RNA made them grow. It’s like noticing that people who eat more ice cream also get more sunburns—both happen in summer, but ice cream doesn’t cause sunburn.
Analysis score
Maximum 72 for a cohort study.
Where the score came from
Everyone who lifted weights got stronger and gained some muscle, but some people grew way more muscle than others — even though they all did the same workout.
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 540 / 100
Quality score
Groups of people are followed over time to see who develops an outcome. Strong for identifying risk factors and associations, but cannot prove causation as firmly as RCTs.
Key takeaways
Summary
Based on the study abstract and findings.
- 1Even if you start with bigger muscles, you might not grow much — and if you start smaller, you might grow a lot.
- 2No single biological clue tells you who will grow the most.
- 3Low responders gained 0.11 cm in thigh thickness; moderate gained 0.40 cm; high gained 0.69 cm.
- 4Baseline thickness explained only 11% of the difference.
- 5Ribosome levels explained 8%.
- 6Inflammation drop didn't link to growth.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
PLoS ONE
Year
2018
Authors
C. Mobley, Cody T Haun, Paul A. Roberson, Petey W. Mumford, Wesley C. Kephart, M. Romero, Shelby C. Osburn, C. Vann, Kaelin C. Young, Darren T. Beck, Jeffrey S. Martin, Christopher M. Lockwood, M. Roberts
Related Content
Claims (6)
Even if you don't get noticeably bigger from lifting weights, resistance training still helps you build muscle and get stronger in your legs and lower body. Everyone benefits, no matter how little they grow.
Even the muscles that are built for endurance can get bigger—like, over 10% bigger—if you do the right kind of strength training for a few months. This goes against what people used to think.
People who got bigger from weight training didn't necessarily have bigger changes in their muscle cells than those who didn't grow as much — so these classic cell measurements can't explain why some people build muscle faster than others.
People who start working out with thinner thigh muscles tend to grow them bigger faster than those who start with thicker thighs—but how thick your muscles are at the beginning doesn’t tell you much about how much they’ll grow overall.
People who gain more muscle from weight training also tend to have more RNA in their muscles, but this only explains a tiny part—about 8%—of why they got bigger. So while RNA levels go up, they’re not really the main reason muscles grow.
Working out with weights can lower a specific inflammation signal in your muscles, especially in people who respond really well to exercise—but that drop in inflammation doesn’t seem to explain why some people get bigger muscles than others.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.