What is a competition tan?

In one line

A competition tan is darkening the skin with products that are applied or sprayed on before going on stage, so the borders between muscles show up well under bright lights.

What is a competition tan?
Why is the skin of people on stage so dark?
In photos of bodybuilding contests, the competitors' skin is an unusually deep brown. They put color on their skin on purpose before the contest. This is called a 'competition tan', or just a 'tan'.
In one line
Darkening the skin color before going on stage
A competition tan is making the skin darker with products that are sprayed or applied on before going on stage. 'Tan' in English means skin turned brown by the sun. It is one part of getting ready right before a contest.
Background - what 'tanning' first meant
Browning the skin in the sun
In the Korean dictionary, tanning means making the skin brown by exposing it to ultraviolet (UV) light. When skin gets UV light, a deeper layer of skin makes more of a brown pigment called 'melanin', and the skin gets darker. In this post, a competition tan means getting the color from products instead of the sun.
Why do it
To show muscle borders under bright lights
International Federation of Bodybuilding and Fitness (IFBB) rules require the contest stage to be lit evenly with very bright lights, with no shadows. Under these lights, darker skin shows the borders between muscles better. That is why competitors put on a much darker color than ordinary tanning products.
Coloring method 1 - DHA
An ingredient that reacts with the outermost skin layer
Almost all products that turn the skin brown without sun contain an ingredient called 'DHA'. DHA is a type of sugar that reacts with amino acids (the small pieces that make up proteins) in the outermost layer of skin to make a brown color. The US Food and Drug Administration (FDA) allows it for use on the outside of the body.
How long it lasts
It fades as the outer skin layer comes off
DHA makes its color in the outermost layer of skin. This layer keeps renewing itself and slowly flakes off from the surface. So color from DHA fades and disappears over several days.
Coloring method 2 - bronzer
Color that washes off
Some products do not react with the skin and just cover the surface with color. Like makeup, they give color for a short time and wash off, and are usually called 'bronzers'. The dark contest color used at US contests also comes off when it gets wet, so competitors cannot shower until the contest is over.
Federation rules 1 - a natural color
The IFBB Pro League and NPC set color rules
The rules of the IFBB Pro League, a pro organization separate from the IFBB, and the NPC, a US amateur organization, say a tan must look like a natural tan. Colors with an orange, yellow, red, green or gold hue, and metallic-looking colors, are banned. Putting on too much product is also banned.
Federation rules 2 - it must not wipe off
The IFBB bans tans that rub off
The International Federation of Bodybuilding and Fitness (IFBB) rules ban tans and bronzers that come off when wiped. If the color comes off by wiping, the athlete cannot go on stage. Contest tans sprayed on with machines by professional companies are allowed, but glitter and gold pearl are banned.
Things to watch
Keep it away from the eyes and lips
The FDA does not allow DHA around the eyes, on the lips, or on moist areas such as the inside of the nose and mouth. Spraying the whole body makes it easy to reach these areas, so the FDA advises covering the eyes and lips and not breathing it in. The FDA has also received reports of rash, coughing and dizziness after spray tans.
Common misconception
Does skin darkened by a tan block the sun?
No. The brown color DHA makes is a different substance from the melanin made when skin tans in the sun, and it has almost no power to block UV light. That is why US rules require tanning products without a sunscreen ingredient to carry a warning that they do not protect against sunburn.
Summary
Color that shows the muscles under stage lights
A competition tan is putting a dark color on the skin with products before going on stage, so muscle borders show up better under bright lights. Skin darkened by a tan still does not block the sun. Related terms: DHA, bronzer, mandatory poses.