If you're trying to figure out how much muscle you build from each workout, you need to account for how long you've been training and how long the program has been going—otherwise, the numbers won't make sense.

If you work out more often, your muscles grow bigger — but only if you keep increasing your workouts, because your body gets used to the same routine and stops responding as well.

If you’ve been lifting for a while, doing more workouts over time will help you build more muscle than just lifting heavier weights.

If you're already strength-trained and do upper-body workouts for 8 weeks, it doesn't matter much if you lift all the way up and down or just do part of the motion—your muscles grow and get stronger about the same either way.

To test if rest time matters, researchers made sure both groups did the exact same amount of total lifting—so any differences (or lack of them) must be due to rest time, not how much they lifted.

Whether you push your muscles to complete exhaustion or stop a few reps short doesn’t change how much rest you need between sets to grow muscle.