A competitor runs through fire during the Tough Guy Challenge in Telford, England. Every year, thousands of people run the eight-mile assault course, which involves freezing temperatures, fire, and ice
2 of 30David McNew/Getty Images
Ray Sanchez (left_ of Sacramento runs along highway 136 during the AdventurCORPS Badwater 135 ultra-marathon outside of Death Valley National Park, Calif. Billed as the toughest footrace in the world, competitors run 135 miles nonstop over three mountain ranges.
3 of 30Mohd Rasfan/AFP/Getty Images
Australian base-jumper Chris McDougall leaps from the top of the 421-meter Kuala Lumpur Tower during the International Tower Jump. Ninety-five professional base-jumpers from 18 countries took part.
4 of 30Oli Scarff/Getty Images
Competitors run up a hill as they take part in the National Cyclo-Cross Championships in Bradford, England.
5 of 30Romina Amato/Red Bull via Getty Images
Gary Hunt of the UK dives from the 27-meter platform at the Red Bull Cliff Diving World Series at Islet Vila Franco do Campo, Azores, Portugal
6 of 30Jean Noel Herranz/DPPI/Icon SMI
Paul Henri de le Rue snowboards down a mountain in Pyrenees, France.
7 of 30Chris Stewart/AP
A large amateur group of Ironman athletes compete in the early morning 2.4-mile swim in Kailua Bay during the Ironman World Championship in Kailua-Kona, Hawaii.
8 of 30John Vizcaino/Reuters
A rider launches off a jump during the Red Bull Devotos de Monserrate urban downhill mountain bike race in Bogota.
9 of 30Fabrice Coffrini/AFP/Getty Images
Finland's Lari Joutsenlathi (left) and Switzerland's Kim Mueller compete during the finals of the Ice Cross Downhill World Championships in Lausanne, Switzerland.
10 of 30Joerg Mitter/AFP/Getty Images
Josh Sheehan drops in on Dubai during the Red Bull X-Fighters World Tour.
11 of 30Christian Pondella/Getty Images
Alex Sorgente skates during the Skateboard Big Air Finals at the X Games in Los Angeles.
12 of 30Frederic J. Brown/AFP/Getty Images
Alana Smith, 12, competes in the Skateboard Street Final at the X Games in Los Angeles
13 of 30Romina Amato/Red Bull via Getty Images
David Colturi dives from a 27-meter platform at the Scaliger Castle Red Bull Cliff Diving World Series in Malcesine, Italy.
14 of 30Gabriel Bouys/AFP/Getty Images
Tightrope walker Andrea Loreni performs in front of the Coliseum in Rome.
15 of 30Alexandro Auler/Latincontent/Getty Images
A kite surfer competes during a free session at El Hyaque Beach in Isla Margarita, Venezuela.
16 of 30Mark Wieland/Getty Images
Brett Rheeder of Canada competes in the Mountain Bike Slopestyle Final at the X Games in Munich, Germany.
17 of 30Alex Grimm/Bongarts/Getty Images
DTM driver Mattias Ekstroem (right) of Sweden competes with the USA's Townsend Bell in the Ford RallyCross competition at the X Games in Munich.
18 of 30Shaun Botterill/Getty Images
Diego Demelchori and Simon Pavey compete in the Dakar Rally in Copiapo, Argentina.
19 of 30STR/AFP/Getty Images
Exelon Kyle walks on a tightrope extended between two hot-air balloons in Kunming, in southwest China's Yunnan province. Kyle took 38.35 seconds to complete the 'hot air balloon 18 meters fast walking' and created a Guinness World Record.
20 of 30Joe Klamar/AFP Photo
Nik Wallenda walks without any harnesses or nets on a tightrope stretched across the Little Colorado River Gorge at the Grand Canyon. Wallenda, a seventh-generation skywalker, traversed the 1,400-foot wire 1,500 feet above the ground in just under 23 minutes.
21 of 30Jorge Leal/Nazare Qualifica/Polvo Concepts/AP
Hawaii's Garrett McNamara surfs what has been determined as the tallest wave ever ridden at Praia do Norte beach near Nazare, Portugal. Portugal's navy awarded McNamara its Medalha Naval de Vasco da Gama in a ceremony in Lisbon.
22 of 30Kathleen Hinkel/Icon SMI
Jeremy Thompson competes at the World Snowboard Tour Slopestyle event at the World Ski and Snowboard Festival in Whistler, British Columbia.
23 of 30Mark Wieland/Getty Images
Jose Miralles of Spain competes during the Night of the Jumps freestyle motocross European Championships Series in Munich.
24 of 30Harry How/Getty Images
Kevin Robinson competes in the GoPro BMX Big Air Final during X Games Los Angeles in Irwindale, Calif.
25 of 30Alex Grimm/Bongarts/Getty Images
Nate Adams performs in the Moto X speed and style competition at the X Gamed in Munich, Germany.
26 of 30Gregory Boissy/AFP Photo/Getty Images
Garrett McNamara (left) and Mark Healy of the United States compete during a free session on the southern Pacific Ocean island of Tahiti.
27 of 30Doug Pensinger/Getty Images
Shaun White snowboards during practice before the Snowboard Superpipe Final at the Winter X Games in Aspen, Colo. White would go on to win his sixth consecutive Superpipe gold medal.
28 of 30Jeff Gross/Getty Images
Chaz Ortiz competes in the Skateboard Street Final during the X Games in Los Angeles.
29 of 30Robert Beck/SI
A competitor surfs at the Maverick Invitational big-wave surfing contest in Pillar Point Harbor, Calif.
30 of 30Phil Walter/Getty Images
Tristyn Kronk of Australia clears a jump in a Junior Men's event at the UCI BMX World Championships in Auckland, New Zealand.
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