Why are the Olympic athletes covered in spots?

BBC.com
The mark of an Olympic athlete, at least at Rio 2016, seems to be a scattering of perfectly round bruises. Swimmers and gymnasts, particularly from Team USA, are among those seen sporting the mysterious dots.
No, not paintballing misadventures – they are the result of a practice known as “cupping“; an ancient therapy where heated cups are placed on the skin.
The technique, which is a form of acupuncture, is done by lighting flammable liquid in a glass cup.
Once the flame goes out, the drop in temperature creates suction which sticks the cups to the body.
The suction pulls the skin away from the body and promotes blood flow – and leaves those red spots, which typically last for three or four days.
Athletes say they are using it to ease aches and pains, and to help with recovery from the physical toil of constant training and competing.