I've always been very "veiny" on both my arms and legs and as i've improved my body it's become more and more pronounced ... my limited understanding of it is that the immediate "bulging" during/after exercise is a product of increased insulin in the body and over the long term it's an affect of your hearts ability to pump greater amounts of blood and your muscles requirements for greater amounts of blood ... i've never heard of any negative effects of it but :dunno: