Karnazes has completed a number of endurance events, mostly running events, but also a swimming event. Most notably, he ran 135 miles nonstop across Death Valley in 120°F (49°C) temperatures, and a marathon to the South Pole at ?40°F(-40°C). In 2006, he ran 50 marathons, in all 50 US states, in 50 consecutive days, finishing with the New York City Marathon, which he completed in three hours and thirty seconds.
Other highlights are:
- Overall Winner, 4 Deserts Race Series, 2008
- Competitor magazine Endurance Athlete of the Year Award winner, 2008, 2006, 2005
- ESPN ESPY Award winner, “Best Outdoor Athlete,” 2007
- Winner, Vermont Trail 100 Mile Endurance Run, 2006
- Two-time Emmy Award winner, 2005, 2007
- American Ultrarunning Team, World Championships, 2005, 2008
- Men’s Journal, Adventure Hall of Fame, 2005
- Winner, Badwater Ultramarathon, 2004
- in 80 hours and 44 minutes without stopping (2005)
- in 24 hours on a treadmill, 2004
- single-handedly completed the Providian Saturn Relay six times
- Eleven-time 100-Mile/1 Day Silver Buckleholder at the Western States Endurance Run (i.e., better than ten twenty-four hour finishes), 1995-2006
- Outside magazine, Ultimate Top 10 Outdoor Athletes, 2004
- Swimming across the San Francisco Bay
50 marathons in 50 states on 50 consecutive days
The 50/50/50 was fifty marathons in fifty states in fifty consecutive days, beginning with the Lewis and Clark Marathon in St. Louis on September 17, 2006, and finishing with the New York City Marathon on November 5. Eight of the fifty races were conventional marathons. Since marathon races are typically held only on Saturdays and Sundays, on the other days Karnazes (accompanied by between 1 and 50 runners) ran the course of a marathon in each state using the help of the Race Director and staff of each event to officially run the certified course, but on a different day than the “live” event. (For example, as part of the 50/50/50, Karnazes ran the
official course of the Boston Marathon, but not the race itself, which is held in mid-April.)
Karnazes overcame the endurance and logistical difficulties of this goal, and Karnazes finished the final marathon, the NYC Marathon on the official race day, in 3 hours and 30 seconds. He weighed 154 lbs at the start, and 153 lbs at the end.
After finishing the 50/50/50, Karnazes decided to run home to San Francisco from New York City. He was expected to finish the trip in January 2007. However Karnazes chose to end this trek on December 15, 2006, in St. Charles, Missouri, to spend more time with his family.
The adventure was the primary subject of film director JB Benna's 2008 film entitled
UltraMarathon Man: 50 Marathons - 50 States - 50 Days, which was the first feature film about Karnazes. The film was produced by Journeyfilm, had a national theatrical release in 300 screens in 2008 and was released on DVD and Blu Ray in 2009.
A similar project, undertaken by Sam Thompson to raise money for victims of Hurricane Katrina, was finishing as Karnazes began his project. Thompson ran 51 marathons (all 50 states and D.C.) in 50 days.