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.

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 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.

If you're a guy between 18 and 40 and you start lifting weights, whether you're new to it or have been doing it for years, you probably won't gain much more muscle just because you're experienced—but the people who’ve trained the longest (4+ years) still tend to gain the most muscle, so experience doesn’t always make a clear difference.

If healthy guys between 18 and 40 lift weights regularly for at least two weeks up to a year, they typically gain about 1.5 kilograms of muscle—no matter what kind of weight routine they follow.