As he biked through the French countryside in the middle of the night—his eyelids trying to close, his tendons still screaming from an 80-mile run the day before, and layers of his tongue sloughing off from a swim across the English Channel—one thought kept running through Sean Bannon’s mind: “How lucky am I to be able to do this?” In July, Bannon, 24, became the youngest person to complete the Enduroman Arch 2 Arc (often cited as the world’s hardest triathlon), just weeks before moving out of his parents’ home in Winchester to start medical school at Ohio State University.
“All this exercise and physical activity, it’s part of what I want to do as a physician,” he says. “Lifestyle medicine, preventative medicine, is all stuff I’m interested in. I really try to live what I want to do.” In the case of the Arch 2 Arc, living what he wanted to do meant nothing less than total commitment. Bannon dropped from full-time to part-time hours at his job at the Mass General Brigham Cancer Institute to make more time for training, swimming endless miles at Phillips Beach in Swampscott and Concord’s Walden Pond, and scheduling all-day runs that required him to stop back at his house every hour to rehydrate and refuel. With so much running and swimming to squeeze in, the bike became a relative afterthought. Bannon, whose own road bike is as old as he is, borrowed a BMC Roadmachine from a friend, and he ramped up his bike training only a few weeks before the race, counting on his fitness from the other events—and more than a little adrenaline—to get him to the finish line.
“Motivation comes and goes, but it’s the discipline that keeps you going,” he says. Bannon swam and played soccer at Winchester High School. When the COVID-19 pandemic closed gyms and public pools, he turned to triathlon, and he completed the 2021 Ironman Maryland triathlon at just 19. For many, the Ironman (which includes a full marathon) is a sort of pinnacle of endurance sports, but for Bannon, it was just the beginning. In 2024, he completed his first swim of the English Channel. The next year, he swam around Manhattan and also across the 20-mile Catalina Channel in Southern California, completing the “Triple Crown of Open Water Swimming.”
Those feats helped convince Enduroman organizers that Bannon was fit for the Arch 2 Arc. Unlike with most other triathlons, athletes face a rigorous application and selection process, and they complete the event on their own, during a set window provided by race organizers. Bannon traveled to England with a crew that included his parents, his father’s cousin, and two close friends, and he was also accompanied throughout the event by a race official. His odyssey started at London’s Marble Arch, with his support crew leapfrogging him in their vehicle along the route, first dispensing peanut butter sandwiches, and then switching to KitKat candy bars as complex foods became harder for Bannon to tolerate. After nearly 22 hours pounding the pavement, Bannon napped in Dover, and then his father and father’s cousin manned the support boat while the rest of the crew began moving equipment across to France. While swimming, Bannon consumed 500 calories of warm liquid carbohydrates each hour. The Channel is around 21 miles across at its narrowest point, but tides and currents mean that swimmers travel much farther, and Bannon estimates that his route covered about 30 miles. Favorable weather helped him finish the swim leg in under 13 hours.
In France, though, the team hit its first major logistical hurdle. The support van waiting for them turned out to be a stick shift, and Bannon’s father (who had just spent the entire Channel crossing on the support boat) was the only one who could drive a manual. The confusion meant that Bannon didn’t get a chance to sleep before starting his 180- mile bike ride to Paris. Overnight, when his vision began to “wiggle,” Bannon climbed into the van for a 20-minute catnap, which he says was enough to make him feel like a “new person.” At one point, he says, he broke down in tears, overwhelmed by gratitude for the friends and family who had traveled across the Atlantic to help him achieve his goal.
After 64 hours and 42 minutes (and nearly 300 total miles), Bannon reached the Arc de Triomphe. Traffic was at a standstill, and so his crew got out of the van and ran alongside him toward the Arc. When he crossed, Bannon held two records: the youngest person to ever finish the race, and the fastest to complete it without a wetsuit. Bannon knows that he won’t have time for three-day-long races now that he’s started medical school, but he suspects that he’s not done pushing his own limits. “I could get into mountaineering, or I could get really into pickleball,” he says. “There will always be more channels to swim, and more races to do.”