Full disclosure: I’m a vehemently pro muscle. It keeps your metabolism revved, takes up less space than fat, protects your joints, and allows you to lift heavy objects without the help of a guy. Full disclosure number two: I almost never weight train. Like most women, I typically choose cardio (my go-to workout is Bikram yoga) over strength training, not because I’m afraid of bulking up, but I’m a sweat addict and hate figuring out the correct weights, reps, muscle groups to target, and so on. But I should. I really really should, for the reasons listed above, as well as the surprising muscle-related facts that follow.