Slow-twitch muscle fibers need longer workout times to grow because they tire less easily. This can be done by lifting lighter weights until you can't lift anymore.

Lifting lighter weights with more reps might make your slow-twitch muscles grow bigger than lifting heavier weights with fewer reps.

Even if you lift light weights, if you go until you can’t do another rep, your muscles end up using almost all the same fibers as if you lifted heavy — which might be why both ways make muscles grow similarly.

Lifting heavier weights makes your fast-twitch muscle fibers grow bigger than lifting lighter weights does.

Lifting lighter weights many times in a row might help grow certain slow-twitch muscles better because they stay working longer.

Lifting heavy weights might make your fast-twitch muscle fibers grow bigger than your slow-twitch ones, according to some new research.