Sunday will mark the 17th annual NYC Triathlon, which will see athletes swimming the Hudson River, biking on the Henry Hudson Highway and Moshulu Parkway and then running in Central Park. But it's not all work and no play: Friday night, 500 triathletes stripped down to their underwear and ran 1.7 miles in Central Park for the annual Gildan Underwear Run.

The run has traditionally been an opportunity for participants to get very creative with very little.

This year's costume winner was a rainbow unicorn:

The top men's finisher was the Upper West Side's Benjamin Kiefer, who ran a 9:13. Corinne Fitzgerald of Hell's Kitchen was the first female finisher, at 11:17.

The 2017 2XU New York City Triathlon, begins before you probably even wake up on July 16th (the swim start access is between 4:30 a.m. and 8:00 a.m.). Triathletes swim 1.5 kilometers (.93 miles) in the Hudson River, bike 40 kilometers (24.85 miles) on the Henry Hudson Parkway, and run 10 kilometers (6.2 miles) in Central Park.