--- title: Olympic Cupping: Why Swimmers Are Doing It description: Michael Phelps and other Olympic athletes in Rio are using cupping to deal with muscle soreness and pain canonical: https://time.com/4443581/michael-phelps-cupping-olympics/ author: Alice Park article:opinion: false article:content_tier: free article:published_time: 2016-08-09T00:21:38.000Z article:modified_time: 2026-08-04T07:55:16.369Z article:section: Health og:title: Michael Phelps Is Crazy for Cupping og:description: It leaves dark red welts on your skin, but U.S. swimmers say the temporary marks are worth it og:url: https://time.com/4443581/michael-phelps-cupping-olympics/ og:site_name: TIME og:image: https://static.time.com/v3/assets/bltea6093859af6183b/blt58e999092e8a1bed/6988a1a00b72e3a9846ea962/phelps-cupping.jpg?branch=production og:image:width: 2560 og:image:height: 1707 og:image:alt: SWIMMING-OLY-2016-RIO og:type: article twitter:card: summary_large_image twitter:title: Michael Phelps Is Crazy for Cupping twitter:description: It leaves dark red welts on your skin, but U.S. swimmers say the temporary marks are worth it twitter:image: https://static.time.com/v3/assets/bltea6093859af6183b/blt58e999092e8a1bed/6988a1a00b72e3a9846ea962/phelps-cupping.jpg?branch=production ---  # Why Michael Phelps Is Gaga for Cupping ## Video: The classic American striving of Katie Ledecky [Watch (HLS stream): The classic American striving of Katie Ledecky](https://cdn.jwplayer.com/manifests/BXGDiCWg.m3u8) (2:08)  _Published 2016-08-08. Sports Illustrated's Scott Price looks into what drives USA swimmer Katie Ledecky as she competes in the 2016 Olympics in Rio._  by [Alice Park / Rio de Janeiro](https://time.com/author/alice-park/)  ## Alice Park / Rio de Janeiro Senior Correspondent Aug 9, 2016 12:21 AM UTC  Michael Phelps competes in a men's 200-m butterfly heat during the swimming event at the Rio 2016 Olympic Games at the Olympic Aquatics Stadium in Rio de Janeiro on Aug. 8, 2016 Michael Phelps competes in a men's 200-m butterfly heat during the swimming event at the Rio 2016 Olympic Games at the Olympic Aquatics Stadium in Rio de Janeiro on Aug. 8, 2016Odd Andersen—AFP/Getty Images  by [Alice Park / Rio de Janeiro](https://time.com/author/alice-park/)  ## Alice Park / Rio de Janeiro Senior Correspondent Aug 9, 2016 12:21 AM UTC They were hard to miss — the dark, purply circles dotting [Michael Phelps](http://time.com/4442634/ledecky-gold-world-record-rio-2016-olympics/)‘ back and shoulders and running all the way down his leg. Perfectly circular, they look like some kind of rash. In Phelps’ case, they’re completely intentional. “I’ve done cupping for a while before meets,” says Phelps. “But I haven’t had a bruise like this for a while. I asked for a little help yesterday because I was a little sore and I was training hard.” Cupping is a Chinese practice of sucking the skin away from the underlying muscles for a short period of time in order to stimulate blood flow. For swimmers, you’d want to do that to promote faster recovery and to swish away the build up of any lactic acid in the muscles that can lead to soreness, not a good thing if you’re racing heats in the morning and finals in the evening of the same day and have more than one race over a week. Traditionally, cupping involves wiping the skin with something flammable like alcohol, and then lighting a match in an inverted small cup to build up heat. The match goes out, and the cup is placed over the skin, where the heat builds up pressure and starts pulling the skin away. Over several minutes, the blood vessels start to expand and tiny capillaries near the surface break, which causes the redness. The U.S. swimmers, including silver-medal winner Chase Kalisz and bronze medalist Dana Vollmer, have also adopted the practice in