Switching between heavy and light weightlifting every two weeks doesn't help young male athletes build more muscle or get stronger than just sticking with either heavy or light weights alone over 8 weeks.

Switching between heavy and light weightlifting every two weeks doesn't build more muscle or strength than sticking with either heavy or light weights alone in young male athletes over two months.

Lifting heavy weights until you can't lift anymore makes young male athletes much stronger than lifting light weights over 8 weeks, even if both make muscles grow about the same size.

If young men lift light weights with very short breaks between sets for 8 weeks, their upper arms grow more than if they lift heavy weights with long breaks—even if they do the same total amount of lifting—because the short breaks create more muscle-burning stress that helps muscles grow bigger.

Lifting lighter weights many times in a row helps well-trained young men do more push-ups longer than lifting heavier weights fewer times, after 8 weeks of training.

When young male athletes push themselves as hard as they can in weight training, whether using heavy or light weights, their muscles grow about the same amount after 8 weeks.