The Importance of Aid-Station Efficiency in Ultra-Endurance Sport

Ultra-endurance sport is extremely fascinating due to the unique aspects beyond physiology that can hugely impact race performance, with one of those factors being aid-station efficiency. Even for the top 3% of finishers at Ultra-Trail du Mont Blanc in 2025, time spent not moving accounted for almost 20 minutes of total race time. For some athletes in that top 3%, almost 2.5% of the total race was spent sat down at a major aid-station. I’m not fully convinced that physiological capacities are the ultimate factor in ultra-endurance success - the ultimate factors are those that allow for the athlete’s physiological capacities to be 1) maximised and 2) sustained for as long as possible, and aid-station efficiency is one of those major factors.

Finishing position (top 50 finishers)/time spent at aid-stations at UTMB 2025.

Above is a graph showcasing the total time spent in major aid-stations by the top 50 finishers at the 2025 Ultra Trail du Mont Blanc. I’ve conducted similar analysis of previous editions of this race, and the same results appear. The fastest finishers tend to be the most efficient at aid-stations. Being a fast runner is not sufficient in achieving a fast finishing time at UTMB - the athlete must have completed extremely thorough plans on what physiological state they want to be in when approaching, using and departing each aid-station. For extra proof of its importance, the difference between Emma Stuart finishing 11th and breaking into the top 10 women (subsequently beating one of the greatest ultramarathon runners of all time in Courtney Dauwalter) was 7 minutes of aid-station time (equating to 0.45% of her total race length). Of course, enhancing aid-station efficiency by 25% - which would’ve been enough to beat Dauwalter and break into the top 10 - is a lot easier said than done, but it does highlight the extremely fine (but impactful) margins associated with aid-station efficiency.

As touched upon above, the athlete must have completed detailed plans on how they want their body to be performing at each station as well as how (and for how long) to utilise each station. However, it’s very important that these plans do not cause confusion. If the plans are complex, then the athlete (and their crew) must ensure they’ve rehearsed the process. If unable to rehearse, plans must be simple enough that they’re extremely easy to follow. Unnecessary confusion, or being forced to complete mental mathematics deep into a 100 mile race will likely result in incorrect calculations alongside an additional (and often avoidable) cognitive demand also risks increasing the athlete’s rate of perceived exertion.

Following Kilian’s win at UTMB in 2022, he underwent neurological evaluation using measurements of the pupils, a methodology most commonly used in clinical settings. Following this evaluation, Alvarez-Herms and Jornet (2024) found that UTMB (at least when completed at Kilian’s intensity) caused levels of cognitive impairment that’s often reflected in those suffering from traumatic brain injuries. Creating an aid-station plan that’s so complex it demands the athlete - who’s likely in an extreme form of cognitive impairment - to attempt mental maths on the run is not sensible and far from beneficial to performance. Additionally, Marcora, Staiano and Manning (2009) found that mental fatigue (induced by 90 minutes worth of the AX-continuous performance task) reduced time to exhaustion by 15% compared to when in a “fresher” neurological state.

There exists a clear interrelation between physiological and psychological fatigue. Physiological fatigue reduces cognitive performance and psychological fatigue reduces physiological performance. It is therefore extremely important to limit any additional cognitive work, and one of the biggest threats to increased cognitive work during a race like UTMB is calculating factors relating to aid-stations (nutrition or hydration calculations, the weight of the running pack or pacing).

Eszter Csillag at Western States. Image by Luke Webster.

I believe that one of the most important factors in ultra-endurance sport success is the extent in which the athlete is able to fully concentrate on physiological performance. The athletes that are able to direct the vast majority of attention to the running may be better placed to either 1) achieve closer to their physiological limits or 2) sustain a specific intensity for a prolonged period. The goal is to take care of logistics in a way that allows the athlete to maximise their physiological abilities, and ensuring that the aid-station process is efficient plays a huge role. It can also be concluded that aid-station performance doesn’t just effect ultra-endurance performance in isolation, but also effect running performance between aid-stations, especially if the aid-station process is messy or complex.

When working with ultra-endurance athletes on race specifics, aid-station efficiency is one of my priorities. It’s important not to lose sight of the definition of efficiency: ‘achieving maximum productivity with minimum wasted effort or expense’. It’s very important to strike the correct balance between fuelling (or resting) sufficiently and being fast through the process. An over-emphasis on speed will compromise the athlete’s needs, and an over-emphasis on the athlete’s needs will compromise speed. Returning to the graph, it can be seen that the race winner (Tom Evans) was 6th fastest at aid-stations. This is further evidence that solely focusing on reducing time spent at aid-stations (or missing aid-stations altogether) is not sensible - when a measure becomes a goal, it ceases to be a good measure.

An athlete I work with recently competed in a 50 mile race. A number of the aid-stations were slightly off-course and as a result were optional to attend. In pre-race planning, we decided to be conservative with our aid-station approach and not overemphasise speed. As a result, we agreed to attend every aid-station. Many of his competitors opted to skip early aid-stations, but despite this early advantage this athlete’s cumulative aid-station time exceeded the vast majority of his competitors. A guideline for aid-station efficiency is to spend all necessary time at each station, but not a second longer. There are specific psychological interventions that may be beneficial in improving aid-station efficiency, which is a topic I aim to discuss in the future, either as an article or on one of my social media platforms (@TomasBlackRun).

References

Álvarez-Herms, J., & Jornet, K. (2024). Physiological Data of Kilian Jornet During the Victory of UTMB 2022: An Exceptional Report of Maximal Metabolical Limits. Sports medicine (Auckland, N.Z.), 54(12), 3211–3214. https://doi.org/10.1007/s40279-024-02091-4

Marcora, S. M., Staiano, W., & Manning, V. (2009). Mental fatigue impairs physical performance in humans. Journal of Applied Physiology, 106(3), 857–864.