The Ultra-Trail du Mont-Blanc (UTMB) is one of the most prestigious and challenging ultra-marathons in the world. The UTMB race week attracts thousands of runners from around the world each year, congregating in Chamonix, France. However, not every athlete who starts the race is able to finish. 

In 2022, there were 2,795 starters in the UTMB, the 171 km event around the Mont-Blanc massif. Of the starters, there were only 1789 finishers. A completion rate of only 64%! There are many different reasons that runners don’t arrive back into Chamonix under the 46.5 hour cutoff time. Here are 5 reasons why you might DNF (Did Not Finish) the UTMB.  

1. Injuries

Injury is one of the most common reasons that runners don’t finish the UTMB. With the course covering over 171 kilometres and includes a total elevation gain of 9,600 meters (much of which is at altitude!), makes for a physically demanding event. Runners are at risk of developing injuries such as blisters, muscle strains, and stress fractures, which can prevent them from continuing the race. In the 2022 event, YouTuber Ben Parkes had a nasty fall whilst descending one of the peaks. He battled through but had to withdraw 46 kms into the race. 

2. Fatigue

Fatigue is another major reason runners don’t finish. With the race starting on Friday evening, runners have a maximum time limit of 46.5 hours to complete it. It proves too challenging for many having to run over two nights with limited or no sleep. 

Runners starting the race too fast, can also lead to fatigue and/or injury later on. In the 2022 edition, we saw Jim Walmsley in first position and moving well but faltered in the latter stages, ultimately finishing in 4th place. Fatigue often leads to runners falling behind, unable to keep a suitable pace. With checkpoint cut offs in place, this is the most likely scenario for runners being required to withdraw from the event.

3. Weather

Poor weather conditions can also be a major obstacle for runners trying to finish the UTMB. The race takes place in the French, Italian and Swiss Alps, which are subject to sudden and severe weather changes. Runners face the probability of strong winds, rain, and even snow, which makes the course even more difficult and dangerous. 

Alternatively, the UTMB has also had its share of hot years where weather conditions have been quite warm, also caused issues. These adverse conditions can also lead to weather associated injuries including hypothermia or dehydration if a runner is unable to regulate their body temperature and stay warm/cool.

4. Preparation

Lack of proper training and preparation is also a major reason that runners don’t finish the UTMB. The race is incredibly demanding, both physically and mentally, and requires a significant amount of training and preparation. Runners who are not properly prepared may find it difficult, particularly when faced with adverse weather conditions and steep terrain.

5. Equipment

Inadequate equipment is another major reason that runners don’t finish the UTMB. The race requires runners to carry an extensive mandatory kit including clothing, food, and hydration. This is carried and utilised throughout the entire event. Runners may struggle if they don’t have proper gear to keep them warm and dry during the race, or if they don’t have enough food and water to sustain them.

The UTMB is a challenging ultra-marathon that leaves many runners disappointed at the conclusion due to a DNF. It is not always from a lack of preparation or packing the wrong equipment that will lead to failure but external influences like weather or a freak misstep can also cause a DNF. Prepare as best you can to tackle the monster that is the UTMB and hope for a little luck in order to be able to run back into Chamonix, a UTMB Race finisher.