When you lift a weight you can do 15 times, for 5 sets of 10 reps, your body’s energy burn depends mostly on how much muscle you use and how tired you get—not how fast you lift or how heavy the weight is relative to your max.

What matters most for burning calories during weightlifting is whether you’re using big muscles like legs or small ones like chest—not how long you rest or how fast you lift.

Whether you lift heavy weights for fewer reps or light weights for more reps—as long as you push until you can’t do another rep—your muscles grow about the same amount.

You can make your workout feel harder and your muscles burn more by resting less between sets—but you can still lift the same total weight without getting weaker.

If you're already trained in lifting weights, whether you use free weights or machines, you'll get about the same strength gains after 8 weeks—as long as you're lifting the same amount, at the same intensity, and moving through the same range of motion.

Whether you lift heavy weights with fewer reps or light weights with more reps—as long as you push until you can’t do another rep—your muscles grow about the same amount.