Eagles running back Darren Sproles is using cryotherapy to stay fit during the offseason

The following is an actual photo that Darren Sproles posted to his Instagram feed, and not a scene from a science fiction movie:

As Sproles prepares for his final season in the NFL, he has become the latest of more than a few NFL players to use cryogenics as a way to stay in shape. Players from the Denver Broncos, Green Bay Packers and Minnesota Vikings, among others, have turned to the technology in recent years.

Cryotherapy involves standing in a full-body-sized chamber in nothing more than one's underwear as liquid nitrogen surrounds the torso and limbs. The temperature of the chamber is dropped to levels that seem impossibly low, as far as minus-300 degrees Fahrenheit, for up to three minutes.

Although the procedure is not officially approved by the FDA, it has been used for long enough now that it has become a relatively common practice among professional athletes. It first became well-known in the United States when it was used by the Dallas Mavericks team that won that year's NBA championship.

Here are some details from a 2015 Denver Post story on cryotherapy:

Professional soccer and rugby players had long been using it in Europe and Asia, where it was first developed in 1978 to help treat arthritis and inflammatory diseases. But the use by professional athletes in the U.S. was in its infancy. Now LeBron James and the Cleveland Cavaliers turn to it regularly. Major League Baseball players have used it. Floyd Mayweather incorporated it in his training before his fight with Manny Pacquiao. Olympic sprinters Usain Bolt and Justin Gatlin often take mobile cryotherapy units with them to races.

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The treatment claims to rely on deception, lowering the temperature of the skin by 30 to 50 degrees to trick the brain into thinking the entire body is freezing. The mind game leads to a fight-or-flight response and the release of endorphins, the body's natural painkillers, to help reduce soreness and inflammation.

Unlike traditional ice baths that require painful submersion in ice and water for about 15 minutes, cryotherapy sessions are said to be painless and more effective.

"We'll actually use it with a lot of the guys Sunday morning before they go to the stadium, so about three hours before kickoff we'll go through and use the cryotherapy on them because it cleans out any inflammation, soreness that they have, but it also kind of dumps endorphins back into the body," said Dr. Ryan Tuchscherer, a chiropractor and the co-founder of Cherry Creek Spine and Sport Clinic. "It really gets them amped up and ready to go, versus the old, traditional way of doing an ice bath or an ice tank."