Measuring muscle thickness at a few spots on the body may not correctly show how much muscle has grown overall, because the measurements might be inaccurate or have not been properly tested for reliability.

We analyzed the available evidence and found that measuring muscle thickness at just a few spots on the body may not accurately reflect overall muscle growth. The single assertion we reviewed suggests these single-point measurements could be unreliable or untested for consistency, meaning they might not capture how muscle changes across the entire body [1]. What we’ve found so far is that while muscle thickness scans are often used in research and fitness settings to track changes over time, there’s no clear proof that a single measurement point—like the thigh or biceps—can reliably stand in for total muscle gain. Without proper validation of how well these spots represent the whole body, the results could be misleading. For example, muscle might grow more in one area and less in another, but a single measurement might miss that pattern entirely. We don’t have evidence showing that these measurements are wrong, but we also don’t have evidence confirming they’re accurate enough to represent overall growth. The lack of studies testing reliability or comparing single-point readings to full-body assessments means we can’t say how much error might be involved. For someone tracking progress, this means relying on one ultrasound or scan point—like the vastus lateralis or biceps—might give you a rough idea, but it shouldn’t be treated as a complete picture. If you’re trying to understand how your whole body is changing, consider combining multiple measurement points, or using other tools like strength gains, photos, or circumference tracking alongside thickness readings.