One Piece Movie 7

[ChaosK]

Also, it doesn't really explain WHY it happens. Apparently, when Luffy's legs get compressed, he gets a burst of strength. But how come? What does compressing legs have to do with power? It's not been explained.

The legs were used like a spring and when you compress molecules they become more active, for Luffy, it was pretty much like the pressure from his legs flowed through to his arms in order to create a more powerful blast, something that can probably only happen if you happen to be made of rubber.

[DarthEnderX]

Pfft, I'll take that bet.

I'm off to go compress my legs in a vice, I'll let you know how it turns out.