Whether you lift light weights or heavy weights until you can’t do another rep, your muscle fibers don’t seem to grow significantly more with one than the other — but we can’t be sure because the results are too uncertain.

Lifting light or heavy weights until failure doesn’t clearly make your fast-twitch muscle fibers bigger in your thighs — the data is too mixed to say one is better.

Whether you lift light weights or heavy weights until you can't do another rep, your slow-twitch muscle fibers in your thighs grow about the same amount — but we can't be sure because the results are too uncertain.

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

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

Lifting lighter weights might make your slow-twitch muscles grow more than your fast-twitch muscles, according to some new ideas.