If you're a healthy man between 18 and 40 years old, doing strength training will help you build muscle at about the same rate no matter your exact age in that range.

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.

Even people in their 50s and 70s can get much stronger and activate their muscles better after 12 weeks of heavy weight training — age doesn’t stop them from improving.

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 older women lift weights for 8 weeks, their muscles don’t get much bigger, but they do get stronger and walk faster—so it seems like something other than bigger muscles is helping them move better.