If you're someone who works out casually, lifting weights with your muscles stretched might give you slightly bigger arms compared to mixing stretched and shortened positions — but the difference is small and we're not sure if it really matters in real life.

Doing arm exercises that shorten and lengthen the muscles might help build arm size a little, but the evidence isn't super strong—there's only about a 55% chance it's better than just lengthening exercises.

If regular gym-goers train their biceps by lifting in a way that stretches the muscle more, they’ll likely gain more muscle size over two months.

Even though muscles might grow a tiny bit more at the far end when stretched more, it’s so small that it doesn’t really matter in practice — all parts grow about the same.

Doing strength exercises with your muscles stretched more or less doesn’t seem to make much difference in how much each part of the muscle grows — all parts grow about the same.

Working your muscles through a fuller range of motion during weight training might make them grow a little bigger than training with a shorter range, but it’s not always clear or the same for every muscle.