If you train with weights that change resistance throughout the movement (like using bands or machines that adjust), you can do more reps and lift more total weight before getting tired than if you use the same weight the whole time — and after 20 weeks, this difference is pretty big.

Using light weights until you're exhausted or slow builds your muscle stamina better than heavy weights, but doesn't make you as strong as lifting heavy weights.

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.

Even after doing 21 sets of squats, you can still lift the same heavy weight two days later—your muscles bounce back fast.

Even though your body releases similar growth hormones after light workouts whether you rest a little or a lot, you still get stronger and bigger muscles either way.

When you do resistance training with changing resistance (like bands or machines that get harder at different points), your body sends out quick chemical signals—like ERK1/2 and hormones—that seem to help you feel less tired over time, possibly making you more endurance-ready in the long run.