For some, the marathon is the ultimate athletic test of mental and physical limits. For others, however, the marathon distance of 26.2 miles is simply not far enough for lacing up their running shoes. And with around 180 annual ultra events in the UK alone, ultrarunning can no longer be viewed as a niche sport.

In a recent wide-ranging review of the topic, Dr Nicolas Berger and colleagues note that ‘the most common distances are in the range of 50–160km (50 km being the most popular)’. Between 1798 and 1969 there were fewer than 20 ultras, but in 2022 there were 7,000 ultras worldwide, with over 338,000 participants. 

Interestingly, whereas in 1980 there were around 22 men for every woman participant, by 2019 that had dropped to around three men for every woman. And although ‘older athletes perform better (peak performance at 35-45 years of age)’, it’s a sobering thought to learn that according to this I’m officially past my peak.

Hydration and thermoregulation in ultrarunning

Among the many variables that can influence performance during ultrarunning events, thermoregulation and hydration deserve serious consideration. While Dr Berger and colleagues provide a historical context, whereby participants were once warned that losing around 2% of body mass would adversely affect performance, the authors make the vitally important observation that ‘more recently, recommendations to rely on thirst have become more common, in part to minimise the risk of fluid over consumption and exercise-associated hyponatremia.’

In terms of thermoregulation, heat acclimatisation (HA) is one way of prolonging one’s capacity to withstand excessive heat: ‘This form of preparation is recommended for athletes entering events where there is a significant thermal load. HA requires serial exposures to the heat (i.e., a minimum of 5 consecutive days) …’ Outcomes of HA include ‘improved sweating efficiency (higher rate and more dilute sweat), improved cardiovascular stability and lowered core body and skin temperatures for a given work rate and thermal load. It also leads to increased self-belief, lower perceived exertion and lower anxiety.’

Gut issues in ultrarunning

Perhaps unsurprisingly, ultrarunners’ gastrointestinal (GI) tracts are prone to degrees of, let’s say, flux. In the review, Dr Berger and colleagues cite the example of the 100-mile Western States Endurance Run in California in which 96% of 272 participants reported GI-related symptoms, and although belching and flatulence were common, ‘more troublesome symptoms like nausea, bloating and stomach cramps/pain were reported by 60.3%, 48.7% and 31.9% of respondents, respectively.’ 

Although nutritional and psychological aspects will also have a bearing on success in an ultrarunning event, the review points out that ‘[a] recurring theme running through this article is the absence of controlled experimental studies. There are clear practical reasons why this is the case, including recruiting suitable motivated participants.’

Despite the many factors demanding the attention of an ultrarunner who’s preparing for a race, I can say that having trained for, competed in, and finished a 38-mile ultra, the immense satisfaction just about made up for the utter exhaustion.