When Michael Phelps won a gold medal in the 4 x 100 meter freestyle relay at the Rio Olympics, he was covered with red circles on his back and shoulders from cupping. Many of the U.S. swimmers and gymnasts at the Olympics are using cupping, along with massage, saunas, ice baths and compression garments, to help them recover faster after a race or a hard training session. Top college swimming and gymnastics teams are also using cupping before competitions.

What is Cupping?
A flexible cup is placed on the skin over sore muscles and squeezed, then released, to form a vacuum which sucks the skin up into the cup. Some of the cups come with air pumps to give more suction. The suction pulls the skin away from the body, stretches and bursts small capillary blood vessels to cause bleeding into the area around muscles and into the skin. This causes the red circles on the skin.

Cupping causes slight damage to the skin, muscles and blood vessels. Your immunity responds to this damage in the same way that it responds to infections, producing large amounts of the same cells and proteins (called cytokines) that attack and kill germs. The cells and cytokines brought on by cupping have been shown to:
• increase blood flow to the damaged area (BMC Comp and Alt Med, June 12, 2012)
• decrease pain and soreness (BMC Comp and Alt Med, June 12, 2012;12(Suppl 1):P74), and J Trad Chinese Medical Sciences, July 1, 2014;1(1):49–61)
• increase the rate of healing of the muscles and tendons damaged by hard exercise (BMC Comp and Alt Med, November 16, 2010; Chinese Acupuncture & Moxibustion, 2007;27(1):6-8; Journal of Acupuncture and Tuina Science. October 2012;10(5):281–286).

The soreness you feel after intense exercise is caused by damage to the muscle fibers. Cupping can help athletes' muscles to heal faster, relieving soreness and muscle damage as they go from one competition to another, often in the same day.

Why Your Muscles Feel Sore after Training and Racing
The only way that you can enlarge a muscle and make it stronger is to exercise intensely enough to damage it. See Making Muscles Stronger. That is why athletes take a hard workout that causes their muscles to burn and be damaged. They feel sore on the next day and take less intense workouts until the soreness goes away. Then they take their next intense workout.

Questionable Benefits of Cupping
Many massage salons offer cupping and often make extravagant claims about its benefits. These salons advertise cupping as a treatment for high blood pressure, headaches, insomnia, indigestion, diarrhea, constipation, arthritis, depression, fatigue, anxiety, cellulite and so forth. Its proponents explain that cupping "breaks up adhesions and draws toxins to the surface." There is no evidence for any of these claims, yet Gwyneth Paltrow, Justin Bieber, Victoria Beckham, Jennifer Aniston and Lena Dunham have all been photographed with cupping marks.

The only indications for cupping that I can think of are:
• athletes who need to recover very fast from a previous competition on the same day. The increased rate of muscle recovery from cupping is so small that it has not been shown to improve training regimens.
• chronic headache, joint pain or other pain that does not respond to other treatments.
No good data exist to encourage athletes to cup regularly in their training or for cupping to be a first-line treatment for pain.