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.

Lifting weights until you're tired, whether with light or heavy weights, makes your muscles bigger and stronger in the same way for beginners.

When untrained men lift weights until they can't do any more reps, they get more tired over time compared to stopping earlier, meaning their muscles wear out faster.

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.

Lifting weights at different effort levels (from light to heavy) all made muscles bigger and stronger in men over 12 weeks, but the lightest effort wasn't as good as heavier ones.