If you're a young adult who doesn't lift weights or do strength training for 8 weeks, your muscles won't get noticeably bigger or stronger on their own — you need to actually train to see changes.

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.

If you take a one-week break from your heavy leg workouts, your leg strength and ability to keep going during exercises won’t drop in any meaningful way — at least not if you’re already trained.

Whether you use machines that change resistance as you lift or keep the same weight all the way through, after 20 weeks of training, healthy men gain about the same strength and muscle size either way.

We don’t really know if variable resistance training works well for athletes or over long periods—most studies have only looked at beginners and for a few months at most.

Doing strength training with heavy weights for two months makes your muscles bigger and stronger, no matter when you take creatine.