If you're already used to lifting weights, mixing up your routine—like changing how heavy you lift, how many reps you do, or how long you rest—won't make your muscles grow any bigger than sticking to the same routine. Both ways work about the same.

If you're already used to lifting weights, it doesn't really matter if you change up how heavy you lift, how many reps you do, or how long you rest—your muscles will grow about the same either way.

Even if you tweak your weightlifting routine—like lifting heavier, doing more reps, or resting longer—it won’t make your muscles grow bigger than a simple, steady progress plan, even if your body is making more muscle proteins.

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.

Some people think mixing up your leg workouts (like changing weights or angles) might make all parts of your quadriceps grow better than doing the same routine over and over—but right now, science hasn’t proven this for sure.

Getting stronger from lifting weights doesn’t always mean your muscles are getting bigger—and vice versa. Strength and size don’t go hand in hand.