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.

We analyzed the available evidence and found that ribosome biogenesis—meaning the production of cellular structures called ribosomes that help build proteins—is linked to muscle growth after resistance training, but it doesn’t explain most of the change. In people who gain more muscle from weight training, we see higher levels of RNA in their muscles, which is a sign that ribosome production is increasing [1]. However, this increase only accounts for about 8% of the total muscle growth observed. That means while ribosome biogenesis is happening alongside muscle growth, it’s not the main driver behind why muscles get bigger. The evidence we’ve reviewed so far leans toward ribosome biogenesis playing a small, supporting role rather than a central one. We don’t have data showing what else might be more important, and we haven’t seen any studies that contradict this pattern. Right now, the picture is incomplete: we know ribosomes are involved, but we don’t yet understand the bigger picture of what’s actually causing most of the growth. For someone lifting weights, this means building muscle isn’t just about making more ribosomes—it’s likely about a mix of signals, processes, and adaptations we’re still learning about.