Generally speaking, what you are referring to is termed "vascularity" if it is reference to healthy subcutaneous blood vessels. Body builders get those from larger - than - average musculature (which requires increased blood flow) and reduced subcutaneous (under the skin) fat. On the other hand, a sedentary person who gets pronounced surface blood vessels may well have varicose veins or an equivalent malformation of the blood vessels due to their lack of physical health.
