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.

When men and women who are healthy and in their 20s to 40s do strength training, they both gain about the same amount of muscle relative to how much they started with—men might gain a tiny bit more, but it’s so small it doesn’t really matter.

When men and women do strength training, men tend to gain a little more muscle size than women—not because they work harder, but because they usually start with more muscle to begin with.

When men and women do strength training, men tend to gain more muscle in their arms and chest than women, but both genders gain about the same amount of muscle in their legs and glutes.

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.