More than 3,000 athletes are poised to take an unusual tour of New York City on Sunday when they dive into the Hudson, bike along the West Side Highway and run through Central Park for a combined 32 miles.
The grueling course starts with a 1,500-meter swim down the Hudson River with the current from 99th to 79th streets along the Manhattan shoreline.
Athletes then trade wetsuits for bicycles and head north into the Bronx to Gun Hill Road for the first leg of the 40-kilometer bike ride. There, they turn around and pedal back to 57th Street in Manhattan.
Another U-turn brings the bikers to 79th Street. There, riders put on their running shoes and head head for Central Park where they lap around the northern loop and finish a 10-kilometer run near the band shell.
Spectator viewing areas are provided along the route as well as a festival and family re-union area at the finish line.
The event is also open to four legged runners. Canine athletes who normally train alongside their human counterparts are racing in a separate five-mile run in what's called the Doggy Dash.
Last year, two participants died of cardiac arrest during the swim portion of the event, prompting organizers to provide dozens of lifeguards on boat, kayak and jetski to accompany the athletes in case they appear in distress.