Sometimes an athlete goes to such extreme measures for performance that even his greatest fans stop and go,"Wait...what?"

World No. 1 Novak Djokovic has accomplished that feat. The Serbian is famous for his very strict diet, which includes going gluten and dairy free, as well as limiting his sugar intake. Yet, Djokovic may have taken his health obsession to a new level during this year's US Open.

According to the Daily Mail, the 32-year-old brought a personal hyperbaric chamberto Flushing Meadows, parking a trailer roughly 1,000 feet from Arthur Ashe Stadium. The pod lets users intake 100 percent oxygen, improving performance and speeding up recovery, especially from injury (yes, it is legal).

Djokovic started using a hyperbaric chamber in 2010, and buying one set him back approximately $75,000. While many athletes will jump into a pod at a facility, no one in tennis has brought a personal one along as if it's an extra checked luggage.

As luck would have it, Djokovic would end up retiring during the fourth round of the US Open against Stan Wawrinka due to a left shoulder injury after losing the first two sets. He's working hard on his return, and you can bet it includes quality time in his hyperbaric chamber.