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.

We analyzed the available evidence and found that people who start with thinner thigh muscles tend to grow them bigger faster after resistance training compared to those who start with thicker thighs [1]. However, the initial thickness of the muscles doesn’t strongly predict how much total growth a person will achieve over time. This suggests that while there may be a faster initial response in those with less muscle mass at the start, it doesn’t mean they’ll end up significantly larger in the long run. The evidence we’ve reviewed so far leans toward this pattern, but it doesn’t show that muscle thickness at the beginning determines final results. We don’t have enough data to say whether this applies to other muscle groups or if factors like training experience, diet, or genetics play a larger role. What we’ve found so far is limited to thigh muscle growth and doesn’t confirm a universal rule. For someone starting out, this might mean that if your legs are leaner now, you could see noticeable changes early on—but that doesn’t guarantee you’ll outgrow someone else in the end. Progress depends on many things, and initial muscle size is just one small piece.