American Trail Running Association was only founded in 1996 to represent trail races in the US. In the United Kingdom, the Trail Running Association was formed in 1991. The International Trail Running Association (ITRA) was founded in 2013, and was first recognized by the IAAF in 2015. Distances in races vary widely, from 5 km, to over 100 miles (161 km). Many trail races are of ultramarathon (ultra) distance. Ultras are generally accepted as having a distance of greater than 26.2 miles (42.16 km) though 50 km races are the most common 'standard' ultra distance greater than a marathon. Races of similar distances often differ significantly in terms of terrain. This makes it difficult to compare performance across different courses. This is in contrast to times over standard distances in road running, such as 10 km or marathon. The International Triathlon Union conducts an annual Cross triathlon Championship race annually. Additionally, the XTERRA Triathlon is a private off-road series that concludes with a championship each year in Maui. Aid stations Aid stations supplying food and beverages are commonly located every 5 to 10 kilometers along the course. Ultramarathon aid stations are often stocked with dessert foods that provide runners with quickly digestible sugars that can provide a needed boost as their glycogen levels begin to drop. Most trail races only have a single stage, where competitors are timed over the entire duration of their run, including stops at aid stations. However, trail running stage races also exist. These multiday stage races usually offer complete support and runner amenities between stages. There are, however, stage races that provide no support apart from water and medical aid, and require competitors to carry all their equipment (food, sleeping bag, change of clothes, compass). The best-known example of such races is the Marathon des Sables, which was first held in 1986. Trail Etiquette (Trail Ethics) As with hiking and other activities that share trails in often sensitive wilderness environments, trail runners should comply with common leave no trace practices and other trail etiquette (aka Trail ethics). While trail etiquette and customs vary by country, season and outdoor (recreational) area, the common purpose of trail etiquette is to preserve the wilderness environment while ensuring the safety and enjoyment of all trail users (including people, animals, and sometimes motorized vehicles). Trail vs. road race participation limitations Compared to road races, there are often fewer participants as