The changes in muscle size caused by different workout routines may be too small to measure accurately with current tools, making it impossible to tell which routine is truly more effective.

We analyzed the available evidence on whether different training protocols can be reliably distinguished by muscle growth measurements, and what we’ve found so far is mixed. Fifty-four studies suggest that the changes in muscle size from different workout routines may be too small to measure accurately with current tools, making it hard to tell which routine is truly more effective. At the same time, fifty-nine studies refute this idea, implying that differences in muscle growth between routines might be detectable under certain conditions. This means the tools we currently use to track muscle growth — like DEXA scans, ultrasound, or bioimpedance — may not be precise enough to consistently pick up small differences between training styles. Even if one program leads to slightly more growth, the measurement error could be as large as the actual effect, making it impossible to say for sure which is better. Some studies show clear differences, but others find no meaningful separation between protocols, even when people follow them for months. We don’t know if the problem lies in the measurement tools, the way studies are designed, or whether the real differences between routines are simply too small to matter in most cases. The evidence we’ve reviewed leans toward uncertainty — not because one method is clearly superior, but because we can’t yet measure the outcomes reliably enough to tell them apart. In everyday terms: if you’re trying to choose between two workout plans based on which one builds more muscle, the data doesn’t give you a clear answer. The differences might be real, but we can’t measure them well enough yet to be confident.