When men and women do strength training, men tend to build more upper-body muscle than women do, and this difference is bigger in the upper body than in the legs—probably because men start out with more upper-body muscle to begin with.

Men tend to gain a little more muscle than women from weight training, not because their muscles grow better, but because they start with more muscle to begin with.

When men and women in their late teens to mid-40s do strength training, they both gain muscle at about the same rate—men might gain a tiny bit more, but it’s so small it doesn’t really mean one sex builds muscle better than the other.

One study with women showed a much bigger muscle growth difference than the others — all of which were only with men — suggesting sex might matter, but we need more studies to know for sure.

Men and women gain muscle at about the same relative rate when they train the same way—women just start with less muscle, so they gain less in absolute numbers.

Whether you're male or female, if you lift weights, you're likely to gain muscle and strength at about the same rate — even though guys usually start with more testosterone than girls.