Trail running is a sport-activity which combines running, and, where there are steep gradients, , that is run "on any unpaved surface".[It is similar to both mountain and running (also known as hill running). Mountain running may, however, include paved sections. Trail running normally takes place in warm climates, or on good paths, or tracks which are relatively easy to follow, and does not necessarily involve the significant amounts of ascent, or need for navigating skills, normal in fell running. Unlike road running and track running it generally takes place on hiking trails, often in mountainous terrain, where there can be much larger ascents and descents. It is difficult to definitively distinguish trail running from cross country running. In general, however, cross country is an IAAF-governed discipline that is typically raced over shorter distances. The number of organized trail races grew 1,000% from 2008 to 2018, from 160 to more than 1,800 globally.] Runners often cite less impact stress compared to road running, as well as the landscape and non-urban environment, as primary reasons for preferring trail running.This move to nature is also reflected in a large increase in competitors in non-traditional/off-road triathlons and adventure racing in the 201