Extreme sports (also called action sports or adventure sports) are any sports featuring speed, height, danger, a high level of physical exertion, highly specialized gear, or spectacular stunts.
According to the United States Parachute Association (USPA), as of 2005, there are 34,000 members of the sporting association in the U.S. alone. Skydivers participate in other adventure sports. Ten percent of USPA members also engage in snow skiing, nine percent are SCUBA divers, six percent motorcycle and 5.6 percent engage in another sort of flying activity like free-fall or gliding.
A thrill-seeker is someone who enjoys an adventure sport for the adrenaline rush each dangerous activity gives them. Each sport produces a brush with death that creates, in the participant, a surge of excitement.
In 2009, Vanderbilt University psychologist David Zald conducted a study linking thrill-seeking behavior with differences in specific regions of the dopamine in the brain. Dopamine is a neurotransmitter formed in the brain essential for a healthy central nervous system effecting emotion, perception and motion.
As Zald reported in the Journal of Neuroscience low thrill-seekers have "brakes" that limit their desire for pleasure-inducing dopamine chemicals. High thrill-seekers, however, have few brakes allowing them to crave, and reward themselves, with natural pleasure-pumping chemicals.
The adventure sport, or extreme sport, industry is booming. According to Britannica.com's feature report on adventure sports, extreme sports--including skydiving, rock-climbing, bungee jumping, parachuting, and dirt-bike racing--ask participants to tackle speed, danger, and physical prowess to accomplish the sport.
Extreme sport activities run by a company require a participant to undergo training or to learn on-site training about how to accomplish the dangerous sporting task. Rock climbers, for instance, receive professional instruction about which rocks to aim for what to do in case of an emergency. They are routinely strapped into a harness with a professional rock-climber, or an experienced climber, anchoring them and coaching from the rock base. The climber also learns which rock paths are novice and which are more difficult.