ESPN Magazine's Body Issue 2015 Behind the Scenes: How Athletes Are Chosen

"Nightline" went behind the scenes at the magazine's headquarters.

— -- On the field, U.S. women's soccer star Ali Krieger turned heads with her team's jaw-dropping win at Sunday's World Cup final.

Off the field, she will be turning heads for a totally different reason because Krieger is among 24 athletes who stripped down and bared it all, tastefully, for the annual ESPN The Magazine's "Body Issue."

The rules for every athlete is the same -- they all shoot entirely in the buff. Gronkowski's 2012 shoot is legendary among the Magazine's staff because the NFL star ditched the robe entirely and walked around the set nude for the majority of the day.

ESPN The Magazine's team inspects every photo and decides which ones make the cut.

“We have a lot of athletes who come to us and say, ‘we’re dying to be in the “Body Issue,”’ which is a great thing, a great position to be in,” said the Magazine’s Deputy Editor Neely Lohmann. "You would always like to get your Lebron, people like Venus Williams, who is someone I always wanted and she did it last year."

For the first time in the seven-year history of the 'Body Issue,' ESPN Magazine allowed outside cameras to go behind the scenes at a photo shoot with one of the coveted cover athletes. Watch the full story HERE

After multiple shoots and thousands of photos, only six athletes are chosen for the 'Body Issue' cover.

“We have 10 possible covers,” said the Magazine's Editor-in-Chief Chad Millman. “We’ll choose six covers, and we’ll be upset about all the ones that we don’t get to choose.”

“It's a lot of fun,” he said. “I've been wanting to do that since I was 15 years old so its really cool to me. God gave me a body so I'm gonna show it off."

To prepare for the photo shoot, Harper said he turned to organic juices.

"Being able to get those nutrients get those supplements inside your body is huge, and it really helps you out," he continued.

Although the athletes are completely nude during their "Body Issue" photo shoots, the Magazine says it's not pornography, but rather an artistic expression of the athletic form and the athletes' private areas are not shown.

“That’s the experiment,” said photographer Peter Hapak. “Basically we have to find the right angle, the right light, just to stay on the right line. When we are not showing too much but also showing something that makes the body look good and makes the image different from the rest when the talents are completely dressed up.”

Harper did his photo shoot at a closed set at the University of Nevada, Las Vegas, and said stripping down for the shoot didn’t bother him.

“I guess I’m just very comfortable in what my body looks like, and I’m not scared to do anything,” he said. “I’m not scared to show it off in that aspect. ESPN’s great with the stuff that they do and I trust them fully with the stuff that they do.”