- IOC paves way for transgender athletes
- Chris Mosier to compete on world stage
- Qualified for men's duathlon championships
- Says he is now "fully-formed human being"
(CNN)The transgender athlete had heard it all before.
From the side of the road, someone uttering "was that a guy or girl?" as Chris Mosier ran past in full stride.
"I can't remember when that one was," he says of the kind of comments he's had to endure during a groundbreaking career. "Either just before or just after transition. I've heard comments consistently like that in races.
"Fortunately it's not the norm, but it wasn't a surprise to me when it happened. At the time, each time, of course it's hurtful. But it's just people are challenged by something they can't fit into a box, society likes to label things."
For as long as he can remember, the 35-year-old has known he didn't fit into that "box" -- that he didn't subscribe to society's traditional definition of male and female.
But life might be about to get a little bit easier for this trans-athlete trailblazer.
Last month's guidelines from medical chiefs at the International Olympic Committee suggested trans athletes be allowed to compete at the Games without having to undergo gender reassignment surgery.
Although he won't be at Rio 2016 -- his event, the duathlon, does not have Olympic status -- Mosier can still celebrate a victory for the wider trans community.
"I'm not going to Rio and I'm fine with that. I'm just happy about what this means in a broader sense for the sport in helping young athletes," he tells CNN during a telephone interview from his New York home.
"What I like is that a young, skilled athlete will now have the opportunity to go to the Olympics without a problem."
The IOC guidelines have already had a positive personal effect for Mosier, who has qualified for the U.S. men's team in his age group for June's World Duathlon Championships in Aviles, Spain.
"I'm just excited I'll be able to represent my country," adds Mosier, a silver medalist at the 2014 Gay Games.
He was also voted athlete of the year at the Complete Sports Diversity Awards and named in Advocate Magazine's 40 under-40 list, while in 2011 he was invited to the White House in recognition of his efforts in the LGBT community.
"I never imagined life would be like this," Mosier admits. "I'm now the person that I wanted to be and still want to be.
"I feel good in my own skin and confident and happy. It's amazing to see myself go from a shell of a person to being a fully-formed human being."
If the journey to get here hasn't been easy, Mosier is keen to stress his childhood as a girl was a very happy time despite the early question marks in his own mind and those of others.
"Children have an innate sense of who they are from a very young age," he explains.
"I loved sports and skateboarding from the very start. I remember different people saying 'but little girls don't do that.' That's when it became an issue, and those are my earliest memories."
The barbed comments continued through high school and college but not, Mosier insists, in the bullying sense that has perhaps been portrayed in retelling his story in the media in the past.
"People want to paint it as a time of bullying but it wasn't really that," he says.
"Yes, at high school people said things, but that was in the context of me being an athlete like, 'Good jump shot, is that a guy or a girl?' So in some ways it was more about being sexist towards female athletes than anything.
"For a long time I didn't have the language for what I was feeling about my identity so it took a voyage of self-discovery to find out what that was for me.
"I never really identified as a woman but there was an issue that society had presented me one way. I felt like, 'I'm not a man but I don't feel like a woman,' so that was a struggle."
Finally in 2010, Mosier started transitioning from female to male, which included a course of testosterone.
There were fears how the transition might affect him as a person and his relationships with his partner -- now wife -- Zhen, family members and wider friends as well as his sporting career.
"I was nervous about how that transition would impact me as an athlete. Would I still be competitive?"
Mosier was used to being at the head of events against female athletes and the stereotypical view -- one he shared to a certain degree -- was that he would be considerably less competitive against male opponents.
"I've not found that a disadvantage," he says. "There are races I've won and people wrongly assume that a (transitioned male) is not going to be competitive versus men."
Crucial to his transition has been Zhen, who supported him in his quest to understand his identity and encouraged him to undergo therapy.
He says it has made him "a better athlete, a better person and a better husband," and he has become a role model for trans athletes. He is contacted by children as young as fifth grade to share their own experiences and lean on him for advice.
"I've never had a trans person to look up to, so this is an amazing opportunity for me," says Mosier, who works as a college administrator in New York and also coaches athletes.
He knows the future will not always be easy. After the new IOC guidance he received unpleasant messages on social media, but Mosier is unperturbed.
"I think it's partly a lack of understanding and partly people who just stir the pot on social media whatever the subject," he says.
"I think most people understand that it's a basic human right for a trans athlete to be able to participate fairly."