Michael Phelps of the U.S. is seen with red cupping marks on his shoulder and back as he competes in the men's 4 x 100m freestyle relay final at the 2016 Rio Olympics in Rio de Janeiro, Brazil, Aug. 7, 2016. Phelps has adopted a “cupping” strategy that has become popular among swimmers and other athletes. It uses suction cups to help improve blood flow for muscles that have become sore. (Photo/Agencies)
