Sunday morning, about 8,500 people gathered along Chicago's lakefront for the ultimate test of physical endurance.
After months of training, participants in the Life Time Fitness Chicago Triathlon ran, biked and swam on a 90-plus-degree summer day.
Mark Fretta of Portland, Oregon won the race--completing the course in 1 hour, 52 minutes, and 22.5 seconds. Fretta called Sunday's triathlon the "hardest race of [his] life," thanks to the Chicago humidity we all know and don't love.
Another triathlete summed it up perfectly to the Chicago Sun-Times:
''Chicago is weird,'' said Kevin Collington, who finished second in the race. ''It can be 70 on race day or 95.''
Photographer Eric Wynn took some amazing photos of Sunday's event, and shared them with HuffPost Chicago. See more of Wynn's work here.