Maybe you've noticed the purple dots on some of the athletes, most notably on Michael Phelps.
They're a result of cupping - an ancient tradition found in Chinese medicine, used to draw blood to an affected area. Specialized cups are placed on the skin, which are then heated or pumped to suction the skin away from underlying fascia and muscles. This is what causes the capillaries under the skin to rupture, leaving the bruises behind.
Some western medicine practitioners explain the physiological benefits as a triggered immune response within the treated area. Psychologically speaking, the positive outcomes could also result from knowing you've taken steps to care for yourself. As an athlete, it might make you feel like you have a competitive advantage.
My acupuncturist introduced me to cupping about a year ago when I was suffering from several overuse injuries. During my first treatment, cupping gave my muscles a short break and flooded my body with emotions. I was mostly mystified by relief suction cups were providing my muscles and my psyche.
Bruises get a bad rap. Thanks to cupping, I've grown to view them in a positive light - taking care of myself with cupping is an impetus for my body to take care of itself. Thanks to Michael Phelps, perhaps the world will view bruises, and cupping, in a positive light as well.