A detailed shot of Phelps’ lower body could mislead someone to believe that the noticeable red spots are bruises on his skin. He took one of these pictures while competing in the men’s 200-meter butterfly heat.He was pictured again after winning the Men’s 4 × 200m Freestyle Relay Final, embracing with Conor Dwyer, Townley Hass, and Ryan Lochte. One more picture showed Phelps’s muscular torso with the eye-catching red discs. During the last leg of the 4×100-meter freestyle relay, he was seen supporting his colleague with a determined expression on his face. Naddour, AlexanderAt the Rio 2016 Olympic Games, American gymnast Alexander Naddour was another competitor with a noticeable, sizable red circle mark. When he got ready to participate on the pommel horse during the qualifying round for the Artistic Gymnastics Men’s Team, the mark was clearly visible on his right arm.

Meilutyte Ruta Ruta Meilutyte, an Olympian swimmer, was competing in the women’s 100-meter breaststroke semifinal at the Rio 2016 Olympics when she also had a noticeable red circle on her right arm.