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.

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.

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.

For beginners lifting weights, pushing muscles to complete exhaustion doesn't build more muscle than stopping just short of exhaustion, as long as the total amount of lifting is the same over 8 weeks.

Lifting weights until you can't do any more reps, whether with light or heavy weights, makes muscles grow bigger in fit young men after 8 weeks. It shows that pushing to your limit is what really matters for growth, not how heavy the weights are.

When young male athletes lift weights until they can't anymore, it doesn't matter much whether they use heavy weights or lighter ones—both ways build about the same amount of muscle after 8 weeks.