I'm not sure if this is the right place to post this, but here goes. It seems to me, that I only have localized definition. I have almost perfect ab definition, but my arms aren't really defined at all. The only time there's some good definition there is when I'm working out. Why is this? Could it be because I only weigh 144lbs and don't have enough muscle for good definition? But I've seem people even skinnier than I am that have better arm definition, I think. Any ideas?