In the world of ultrarunning, we often talk about our "why." Why run for days on end? Why endure the discomfort, the cold, and the exhaustion? For Jenny Hoffman, a Harvard physics professor and an ultrarunner of more than two decades, the answer is simple: “I ran marathons through graduate school, and then I jumped into a 100K, which was a lot of fun. It escalated pretty quickly from there.” Twenty years and thousands of racing miles later, Jenny is still breaking records and representing her country, and still appreciative of the ability she has been blessed with to run fast over incredible distances. Sometimes the answer to “why” comes not from asking questions, but simply fighting to maintain momentum when things get hard. As Jenny puts it, “You need to be lucky enough to have a physically robust body, and then you need to be stubborn enough to push when the going gets tough."
We caught up with Jenny shortly after the World 24-Hour Championships in Albi, France. While she is known for holding the Fastest Known Time (FKT) for running across the United States, and is incredibly successful in disparate fields, her attitude is strikingly grounded. There is no ego here, just a deep appreciation for the landscapes she traverses and the good fortune she feels in being able pass through them under her own steam.
The Accidental Ultrarunner
Like many successful ultrarunners, Jenny didn’t grow up dominating track meets. "I ran track in high school, but I wasn't very good at it," she admits. In fact, she spent her college years as a rower, enjoying the camaraderie of crew life and slowly callussing herself to the grind of endurance sports.
Her entry into running was almost a whim. During her senior year, a friend convinced her to drive down to the Philadelphia Marathon. Despite having almost no long distance (“I'd maybe done one or two 10-mile runs in my life at that point”), she jumped in. She was hooked immediately, not by the competition, but by the communal sense of achievement and encouragement. "It was pretty amazing to see an environment where it's not all about competition, where runners are actually rooting for each other," she says. That spirit, so central to the ultra community, became the foundation of her journey.
The Longest Haul
Jenny describes herself as a "quantity over quality" person (a quick glance at Jenny’s Strava will confirm she definitely puts in the hours). This mindset eventually led her to one of the ultimate endurance challenges: a transcontinental run across the United States. But the road wasn't linear.
In 2019, she made a heartbreaking attempt that ended after 2,600 miles, just 400 miles from the finish line in New York. "I took a misstep in Eastern Ohio... One misstep, and I was done," she says. At the time, she was six days inside world record pace.
The injury required surgery, and recovery took months, starting with learning to walk and run again. But exactly one year later, on Thanksgiving, Jenny celebrated her return with a run that perfectly encapsulates her mindset. While most runners were lining up for a local 5K, Jenny went out and ran a solo 100-miler. "That was my Turkey Trot," she jokes.
That stubbornness paid off. In 2023, she returned to the road, completing the cross-country run in 47.5 days. She ran through "27 days of cornfields," gaining a profound appreciation for the people and industries that power the country.
Of Mud and Twilight
After her success crossing the lower 48 states, Jenny turned her attention to Alaska. In the summer of 2025 she ran the length of the Dalton Highway, setting an FKT, covering the 414 miles in 5 days and 18 hours.
"There was so much mud in Alaska!" she says. “The amazing thing about northern Alaska is that it is simultaneously a desert and a wetland. The runoff from the snow makes the ground very wet, so you have this beautiful vegetation, but the actual precipitation from the sky is very low.”
The route took her from the flat, misty tundra of the Arctic Ocean, over the Brooks Range, and across the Yukon River. It was a minimalist adventure supported by a small crew, a tent, and a camp stove.
The challenge wasn't just the terrain, it was the relentless daylight. Running in "Civil Twilight", where the sun is technically set but still provides enough light for outdoor activity, blurring the lines between day and night. Yet, the wildlife made it worthwhile. She recalls being awed by grizzlies, musk ox, caribou, and porcupines along the way.
Balancing the Equation
How does a tenured Harvard professor find time for 100-mile+ training weeks? For Jenny, running isn't an extension of her work, it’s an escape from it. "I really need that blank time away from the stresses of the job," she explains. She is a morning person, often rising at 3:00 or 4:00 AM to log miles before the academic day begins.
She is also passing her love of the outdoors to the next generation. Her 16-year-old son has already completed the Long Trail and the John Muir Trail solo. They are even planning to run the Coldwater Rumble 100K together in Arizona this January.
The Next Step
Despite her accolades, Jenny remains humble about her "talent," attributing much of her success to simply loving the process. "You have to love it," she says. "To put in the big miles and run through the sleet... you have to love it".
As we look to the 2026 season, Jenny is already eyeing her next big summer race or FKT attempt. Wherever the road takes her, we know she’ll be running it with gratitude, grit, and fighting every step of the way.
Discover more about Jenny Hoffman by tuning into the full podcast.