Extreme sports involve a high level of danger and include activities with many uncontrollable variables related to weather and terrain. They tend to be more solitary than traditional sports and athletes often do not have coaches. Extreme sports can be divided into five groups: board sports like snowboarding and skateboarding; motorsports such as motorcross and rallying; mountaineering like rock climbing and ice climbing; freefall activities like parachuting and bungee jumping; and outdoor action sports including mountain biking and cliff diving. The largest extreme sports event is the annual X Games held in the United States.