AVILES, Spain -- Chris Mosier of Team USA made sports history Sunday by becoming the first out transgender athlete to compete in an International Triathlon Union championship when he ran and biked in the world duathlon championship.

Competing with the age 35-39 men's group sprint, Mosier, 35, finished 144th among 434 competitors across all ages with an unofficial time of 1:06:29. He finished 26th among the 47 men in the age 35-39 group and second among the U.S. men in his group.

"It was an amazing experience to see other teammates out there on the course and to have people yelling 'USA' as I went by," Mosier said after a quick postrace rubdown, relaxing and reflecting on competing for Team USA for the first time.

Mosier's performance was lauded as remarkable by Scott Endsley, a USA Triathlon veteran going back to the first triathlon in 1978.

"That's a great time, and he's going to get so much faster the longer he competes and gets training," Endsley said.

Mosier's eligibility for this year's duathlon championship after he qualified in the U.S. national championship was initially the subject of some doubt. The ITU uses the same rules for transgender athletes as the International Olympic Committee. Under the old governing rules, there were qualifying surgical criteria that Mosier did not fulfill.

Mosier and the ITU avoided a potentially costly legal fight over his participation when the IOC adopted new guidelines governing the participation of transgender athletes over the winter.

"Triathlon [and duathlon] is very different from any other sport," Endsley said. "Why would I look at Chris any other way than to say, 'Wow, that's amazing. How did your challenges match up today for you? How did my challenges match up for me? That's cool!' You have something in common."

Chris Mosier finished 26th in his age group as he became the first known transgender athlete to compete in the ITU world duathlon championship. Nuria Sambade Nieto

Sunday's sprint race was broken into three segments: a 5-kilometer run, a 20.55-kilometer cycling segment and a final 2.5-kilometer run to the finish at the Niemeyer Center on the bank of the Ria de Aviles opposite the Asturian port city.

"I feel great. I had such a good race. I did everything that I wanted to do," Mosier said. "It was an amazing time."

As a first-time competitor at this level, Mosier also confronted a first-time challenge: Sunday's race was draft-legal in the cycling segment, meaning that, just as in triathlon and Olympic events, riders are allowed to exploit the wind drag created by a lead cyclist. That creates tighter packs of cyclists and faster speeds as riders exert less effort to remain close to the leaders.

Afterward, Mosier was unfazed by the experience, noting, "I think that I went a little bit faster than I probably would have done otherwise. It was a really fun, fast experience. I've never done it before. It was a great opportunity to do it the first time here."

"I am proud to have him as a teammate," said Paul Bloom, a Team USA triathlon and duathlon veteran for most of the past 12 years. "I am very sympathetic to the challenges faced by transgender individuals, especially since I live in North Carolina and have seen firsthand what kind of discrimination they can face. I applaud what Chris is doing and hope he helps to create a climate where transgender athletes are allowed to compete and excel everywhere."

Mosier is already eligible to represent the United States at this level in 2017 after qualifying at the Long Course National Duathlon Championship in Cary, North Carolina, on May 14. Mosier had to compete last month knowing that he could be subject to House Bill 2, the state's recently passed "bathroom bill." Despite that concern, Mosier instead guaranteed that his first qualifying attempt for an international championship race would not be his last.