Twenty Year Performance Trends In The Arrowhead 135 Winter Ultra-Endurance Race

PURPOSE: Human locomotion over snow covered terrain can pose extreme physiological challenges. The Arrowhead Ultra 135 is one of the coldest ultra-endurance races in North America. Competitors travel 217 km (~2,000 m elevation gain) via bike, xc-ski, or foot in temperatures that can reach -40 °C while carrying survival gear. To date, a comprehensive analysis of successful finish rates and finish times from the Arrowhead Ultra 135 has not been reported. Our purpose was to compare race completion and performance trends across exercise modes (bike, xc-ski, foot) for the 20-year history of the event. METHODS: Race results from 2005-2025 were obtained from the Arrowhead Ultra 135 website. For each year, the number of race starters, finishers, and non-finishers in each exercise mode (bike, xc-ski, foot) were compiled and the finish times of the top three participants in each category were identified. Odds ratios were calculated to determine the association between exercise mode and finish rate (did finish vs. did not finish). A two-way ANOVA was used to assess the effect of exercise mode and event year on finish times. RESULTS: Over the 20-year event history, a total of 2,304 racers started the race and 1,361 finished the race (59%). Of racers that started, 68% (848 of 1,234) of bicyclists, 47% (47 of 101) of skiers, and 46% of foot participants (466 of 969) finished. Accordingly, racers who traveled via bike had greater odds of successfully finishing the race compared to those who traveled via ski (OR = 2.5, 95% CI [1.7-3.8], P < 0.001) or foot (OR = 2.4, 95% CI [2.0-2.9], P < 0.001). Finish times for bike (18.6 ± 5.8 hrs) were faster than those for ski (38.5 ± 12.9 hrs) and foot (41.3 ± 6.5 hrs) (p < 0.001) whereas finish times for ski and foot did not differ (p = 0.15). CONCLUSIONS:For the Arrowhead Ultra 135, traveling via bike consistently yielded the most participants and finishers, fastest finish times, and greatest odds of finishing compared to ski and foot travel. Together, these findings imply that traveling via bike offers distinct advantages for this self-supported winter ultra-endurance race. These findings may have implications for individuals who travel long distances over snow covered terrain, including ultra-endurance athletes, polar explorers, and military personnel.