U.S. Olympian Adam Rippon is known for his gravity-defying moves on ice, but he also took a chance when he chose to come out publicly as gay.

The figure skater said he understood why many sports stars will stay in the closet on National Coming Out Day on Thursday.

"I thought it could be a risk," he told the Thomson Reuters Foundation as he discussed his own decision to come out in 2015.

"It can be scary because you think maybe I could be judged differently for being an out athlete, but I also know that as an out athlete I was my best.

"I wanted to show every single part of me and I wanted to be honest with who I was."

A growing number of high-profile athletes have come out in recent years, including Rippon, U.S. swimmer Abrahm DeVine and the British Olympic gold-winning boxer Nicola Adams.

But even as public acceptance of LGBT people grows in much of the world, especially the West, sport is commonly seen as one area where homophobia and gender stereotypes persist.

John Amaechi, a psychologist and former basketball player who came out in 2007 after retiring from sport said many players feared being known as a "caricature" based on their sexuality.

"They're afraid that their lifetime of effort and work and their legacy [will just be] 'That's that gay guy'," he said.

"Plus, they know there will be consequences."

It is not just an issue for elite players. More than three-quarters of gay, lesbian and bisexual people in a major study of more than 9,000 people in 10 countries said they had remained at least partially in the closet while playing youth sport.

Almost 80 percent of those surveyed said an openly gay, lesbian or bisexual person would "not be very safe" as a spectator at a sporting event in the 2015 study, the largest of its kind.

Sporting culture often reinforces gender stereotypes, said Guylaine Demers, an expert in homophobia at Laval University in Canada.

Gay and bisexual men often avoid coming out due to fear of losing their bond with team-mates, while women face pressure to hide their sexuality in public due to stigma of being seen as a "lesbian team", she said.

"Athletes will confess that some will just quit the sport because they feel it's too much pressure to pretend to be someone you are not," she said.

ROLE MODELS

Some experts think sport is no longer a hostile environment for lesbian, gay and bisexual people.

"It used to be in the 1980s if you were an adolescent that homophobia was accepted and homosexuality was stigmatised," said professor and former U.S. high school coach Eric Anderson. "In the late 1990s things started to change."

Anderson said by late 2000s the culture in the United States and Britain had turned around, with young sports players overwhelmingly supporting gay rights.

However, most say that while attitudes are improving, more must be done.

Representation varies hugely between sports, said Sarah Townsend, general secretary of the European Gay & Lesbian Sport Federation, with football standing out as one in which it remains "taboo" for male players to come out.

A few high-profile footballers have publicly said they are gay, among them British player Justin Fashanu, who later took his own life aged 37, and German midfielder Thomas Hitzlsperger.

But many players are thought to remain in the closet.

"The big thing is to get role models," said Townsend. "If I can see it I can be it: for youngsters, football is so important, and it is such a popular sport.

"If there are not any role models then you can't see yourself; you're not included in it."

For Rippon, who felt the lack of other out LGBT+ athletes in figure skating, coming out meant offering a lifeline to younger sports fans.

"I knew it was necessary because I didn't have anyone to look up to growing up," he said.

"That's why I felt like I needed to be that person."