This individual sport requires endurance, core strength and balance, bike handling skills (time in the saddle) and self-reliance. Advanced riders exhibit extreme risk taking performing aerial manoeuvers and steep technical decents. It can be performed almost anywhere from a back yard to a gravel road, but the majority of mountain bikers ride off-road trails, whether country back roads, fire roads, or singletrack (narrow trails that wind through forests, mountains, deserts, or fields). There are aspects of mountain biking that are more similar to trail running than regular bicycling. Because riders are often far from civilization, there is a strong ethic of self-reliance in the sport. Riders learn to repair their broken bikes or flat tires to avoid being stranded miles from help. This reliance on survival skills accounts for the group dynamics of the sport. Club rides and other forms of group rides are common, especially on longer treks.