Vascularity refers to the appearance of one's veins through the skin. The veins are not just visible through the skin, but often also protrude up from the rest of the body, forming little channels that can be easily seen. Male bodybuilders often strive to achieve this look when competing. This is because vascularity can give the perception of muscle fitness.

The vascular system is the highway for blood traveling through the body. The vascular system also includes arteries and capillaries. Vascularity occurs when the veins, arteries, and capillaries become engorged.

While genetics and environmental temperature can affect a person's level of vascularity, so do other, more controllable factors. Perhaps the most important of these is body fat. People who have an extremely small amount of body fat tend to be more vascular than those with moderate to high amounts of fat. This explains why bodybuilders often have protruding veins.

Another factor that can affect how vascular a person appears is low water retention. For this reason, bodybuilders often lower their water intake in the days before a competition, despite the fact that this self-imposed dehydration can have negative health consequences. Decreasing or eliminating one's intake of salt can also lead to increased vascularity, because salt intake promotes water retention; this is another frequently used technique of bodybuilders seeking to maximize their vascularity for competition. Lifting weights also increases the appearance of veins, albeit temporarily, by delivering more blood to the muscles being worked. This is why bodybuilders will often pump iron just before they are to pose for judging at competitions.

Topical solutions can also be used to increase vascularity. Bodybuilders often used menthol-based vasodilators, which work by increasing blood flow to the area of the body where they are applied. Topical vasodilators are often sold as sexual dysfunction aids, because they help send blood to the sexual regions, resulting in engorgement.

While it may seem like vascularity is a condition to aspire to, this is not always the case. It can signal high blood pressure, which can lead to a stroke or heart attack. In addition, vascularity can result from a condition called arteriosclerosis, in which the arteries thicken and stiffen. This is dangerous because if vessels become clogged, blood can't flow to the two main organs responsible for sustaining life — the heart and brain. This sometimes results in internal bleeding.

Decreased vascularity can point to danger as well. Some conditions which can cause this decrease include acidosis, in which toxins build up in the blood; severely low blood pressure; low blood sugar levels; and serious mitochondrial diseases.