Tennis fans who have watched Novak Djokovic in recent competitions may have seen him donning a peculiar device on his chest as he changes shirts mid-match.
Djokovic has worn the chest patch at least since the 2023 French Open in June, where he won his record-23rd grand slam men's singles title. At the time, the Serbian star called it the "biggest secret of his career," claiming the device — called a TaoPatch — used nanotechnology to improve his game.
He also joked the device helped him emulate Iron Man, whose portrayal by Robert Downey Jr. in the namesake 2008 film saw him implant an arc reactor into his chest.
"When I was a child I really liked Iron Man, so I try to impersonate him," Djokovic told reporters at Roland-Garros. "You must know that my team gives me incredibly efficient microtechnology to help me perform at my best on the pitch. So this is the biggest secret of my career."
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But what exactly is a TaoPatch and — if it works as Djokovic claims it does — why is he allowed to wear it? The Sporting News has everything you need to know about "the biggest secret" of Djokovic's tennis career.
What is Novak Djokovic's TaoPatch?
The device Djokovic wears on his chest is called a TaoPatch, from Italian company Tao Technologies. It is uncertain whether he is merely a consumer of the product, or whether he is a paid spokesperson.
Tao Technology's English website claims the TaoPatch "contains layers of nanocrystals, which capture your body heat and convert it into impulses of very weak light, which is then emitted onto the specific points on your body." The device is purported to "stimulate" users' central nervous system, "enhancing its communication with the rest of your body."
The TaoPatch purports to provide several benefits, including "improving posture, balance and flexibility, to boosting athletic performance and focus, and reducing stress, anxiety and chronic pain."
Tao Technology offers different models on its site, including Start, Pro, Platinum, & Emotion. The company's retail website is currently working to get approval from the Food and Drug Administration.
Djokovic has faced criticism in the past for promoting pseudosciences and health fads. Among the most notable of those is his opposition to the COVID-19 vaccination. His refusal to take the vaccine caused him to miss several top ATP tournaments in 2022, including grand slam events in the Australian and U.S. opens.
MORE: Novak Djokovic admits failure to isolate despite positive COVID-19 test
Why is Novak Djokovic allowed to wear TaoPatches?
According to a report by Forbes, officials from the French Open and ATP have declined comment on the legality of the TaoPatch. Djokovic's most recent usage of the device is at Wimbledon, suggesting officials there also do not believe it provides an illegal advantage.
The ATP's 2022 rulebook does prohibit certain uses of technology that may provide an unfair advantage, including the use of a battery inside a player's racket. Per the ATP, a battery is "prohibited because it is an energy source, as are solar cells and other similar devices."
Per a June 1 tweet from TaoPatch.com, the device "is activated by sunlight and body heat."
TaoPatch backs up its claims by citing a study by peer-reviewed medical Minerva Medica, which only mentions preliminary findings.