Running Modalities

Off-road running events are described as races in unsealed surface and natural environments. They are increasingly popular, but the terminology is confusing, and often is difficult to differentiate among them.

Races are usually differentiated by distance, terrain, elevation change and sometimes time. For example, an ultramarathon is usually defined by its distance, longer than 42k, but depending on the terrain or elevation change the ultramarathon could also be described as a trail, hill or skyrunning race.

A recent article with the collaboration of the Ultra Sports Science Foundation (USSF, has reviewed the nomenclature of these disciplines. In accordance with the many governing bodies they have offered recommendations to classify and describe races properly and avoid future confusions.

We will focus this post and the next one in explaining the main characteristics of each off-road running type, and finish with a series of recommendations for better understanding future events.


Trail running

Trail running is the most popular discipline in off-road running.

The main characteristics are:

  • Course on a natural environment with a maximum of 25% on paved roads.
  • Route properly marked.
  • Commonly in self-sufficiency between aid stations.

ITRA (International Trail Running Association) is the international governing body since 2013 (recognised by World Athletics in 2015).

In 2018 it was established a category system in “km-effort”, considering the distance in kilometres plus a hundredth of the gain in meters:

[km-effort] = distance (in km) + (vertical gain (in m) / 100)

Therefore, seven categories exist, from XXS (easiest course) to XXL (hardest course). Depending on the course effort a classification system was introduced by ITRA to rank athletes. For elite runners ITRA organises annually world championship races.


Mountain running

Mountain running has the same rules than trail running regarding the terrain, surface and course markings. Although most of the races are off-road, they can use paved roads if there is large elevation change on the course.

Other characteristics:

  • Distance ranks from 1k to 42k.
  • Average incline should include a minimum of 5% and not exceed 25%.
  • Additional support equipment is not allowed (bags, sticks, ropes or compasses).

WMRA (World Mountain Running Association) is the governing body since 1984.

Races are classified in one of the following categories: uphill, uphill & downhill, vertical (incline no less than 25%) and long-distance.



Skyrunning races take place in mountainous environments, usually above 2000m above sea level, and using highly technical trails. If the average inclination is higher than 6% races can happen at lower altitudes.

ISF (International Skyrunning Federation) regulates this discipline, still unrecognised by World Athletics.

Races are categorised in three categories:

  • Sky: 20-49k with 1300m vertical climb.
  • Ultra: 50-99k with 3200m vertical climb.
  • Vertical: uphill race up to 5k with 1000m vertical climb.

The main difference with mountain and trail running is that skyrunning involves highly technical mountain environments.

Photo by Asoggetti (Unsplash)

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