Michael Phelps won his 19th gold at the Rio Olympics this weekend, but there was as much chatter about the strange circular bruises on Phelps’ skin as there was about his medals. Just what the heck were they, and why was he covered with them? Phelps uses an ancient Chinese remedy called cupping.
While there are a couple of different forms of cupping, Phelps practices what’s called “fire cupping.” A cotton ball is soaked in alcohol, lit with a match, and tossed in a glass cup. The ember is quickly removed and the cup is placed on the skin, forming a vacuum and sealing it to the skin. Yes, it is a bit like sucking a glass onto your face when you were a kid, but this is an ancient Chinese medical tradition, not goofing around in an IHOP.
Phelps has been a fan for years. In fact, in his March announcement via Under Armor that he was returning for the Olympics, you can see him undergo cupping.
Phelps isn’t the only Olympic athlete using cupping, and it’s popular with athletes across the world. The idea behind fire cupping in Chinese medicine is that it alleviates “stagnation” in blood flow and lymph, and that it can help relieve muscle pain, among other remedies. The bruising is because the vacuum bursts capillaries under the skin, but it’s not deep-tissue damage.
So does cupping actually work, or is it just a placebo effect? That’s still up for debate. An overview of studies on cupping found that the studies, while they pointed to a positive effect, also had a high risk of bias, and creating a controlled study to analyze it is tricky due to the nature of muscle pain. After all, you can’t just clone Michael Phelps a few hundred times and injure him in the exact same way every time to test it, although the Russians are probably working on that. So whether it works is an open question, but it’s clear that for now, it’s not going to stop Olympic athletes from trying it.