Lifting heavy weights for fewer reps and lighter weights for more reps both build muscle about the same in young men when you push yourself to the max, showing that the total work done matters more than how heavy you lift.

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.

When you lift weights, how much total work you do matters more for getting stronger and bigger than whether you use heavy weights with few reps or light weights with many reps.

When young women lift weights until they can't anymore, they do more total work with lighter weights than heavier ones, but this extra work doesn't make their muscles grow any more, showing that just doing more reps isn't what makes lifting effective.

Whether you lift light weights with lots of reps or heavy weights with few reps—so long as you push until you can’t do another rep—you’ll build muscle about the same amount.

If you lift weights until you can’t do another rep, it doesn’t matter if you’re using light, medium, or heavy weights—you’ll still grow your muscles about the same, as long as you push yourself hard and do enough total work.