The Trans Pyr - Spain1 of 9
Trans Pyr 2012 ? Marc Roca
Anyone who's ridden in the Alps and Pyrenees will tell you the Pyrenees inflict the most pain. Trans Pyr starts on the shore of the Mediterranean Sea and finishes eight days later on the other side of Spain in San Sebastian. The course sends mountain bikers 509 miles on rugged paths through the entire length of the Pyrenees, with an estimated 66,601 feet of total climbing. If that number is too hard for you to wrap your head around, it's the same as climbing Mount Whitney in California more than four times. The winning rider usually spends around 45 hours in the saddle, with others almost doubling that.
Race Across America - United States2 of 9
Another race that boasts to be the toughest, RAAM totals 3,000 miles point to point from Oceanside, California to Annapolis, Maryland. That's about 1,000 miles longer than the Tour de France, and the winners often do it in half the number of days compared to the Tour's three-week trek. Participants aren't required to sleep, and many of the top competitors only get an average of two hours a day. For solo riders, it's estimated that nearly 180,000 calories were burned by top finishers, making this race just as much of an eating contest as it is a cycling race.
La Ruta de los Conquistadores - Costa Rica3 of 9
La Ruta 2012 ? Jose Andres Vargas Lead Adventure Media
Dubbed one of the most feared and respected of all races, La Ruta is a mountain bike race that supplies the World's very best endurance athletes with a course that traverses the American land mass from Pacific to Atlantic. Though the race starts and finishes literally on the beach, the in-between is where things get tough. The terrain is so grueling (over 29,000 feet of climbing) that it took the Spanish conquistadores a century ago more than 20 years to cross. The course spans five mountain ranges and has riders head up a 12,000-foot volcano once they've sweated through jungles, rain forests and river gorges. Make no mistake, this three-day race is only for professionals, and even they might want to think twice.
The Tour de France - France4 of 9
Mark Cavendish, 2010 Tour de France, stage 5, AP Photo/Laurent Rebours
You really can't have a list without the Tour. Why? Because of the speed. While most other races have no set time limits for each day of racing, those lucky enough to make it onto a pro tour team are challenged by a daily average speed in excess of 25 mph for 21 days and more than 2,100 miles. This intensity puts the body consistently on the edge of lactate threshold, promising to crush those cyclists with flaws in their arsenal. The last rider must finish within a pre-determined percentage of the winner's time (depending on the difficulty of the course) or else they are not allowed to continue. Crash or lose contact with the peloton for a second and your race could be over.
The Tour Divide - Canada/United States5 of 9
The Tour Divide is the Grand Tour of Mountain Biking. Unlike RAAM where participants often have two support vehicles trailing behind, the Divide is a self-supported race across the country for 2,745 miles, starting on the border in Banff, Canada, and ending in Antelope Wells, New Mexico. Ridden on the forgotten passes of the Continental Divide, the route climbs nearly 200,000 feet vertically through Montana, Wyoming, Colorado and New Mexico over extremely mountainous terrain. The race has no entry fee and offers no medals, but if you finish you'll be in the record books, which is reward all by itself.
The Iditarod Invitational - United States6 of 9
Iditarod Invitational ? Katharina Merchant
If you want my pick for world's toughest race, this is it. It isn't the longest race at 1,110 miles, nor is it the steepest, but the trail from Anchorage, Alaska, to the finish in Nome during the dead of winter is the most challenging. There is no set course and racers are allowed to make their on way on bike, ski or foot. Extreme weather conditions often makes the visibility limited and trails indistinguishable, forcing racers to trek through their own paths. Conditions often range from freezing rain in the low 30s to temperatures plummeting as low as negative-56 degrees Fahrenheit. Even the race organizer's page states that this race "is not for everyone. A mistake at the wrong time and place in the Alaskan Wilderness could cost you fingers, toes and even your life." With an average speed of just over 3 mph and with only 42 participants in the history of the race have able to finish, this is one adventure race that isn't even fair to classify.
Cent Cols Challenge - Europe7 of 9
The field is limited for the Cent Cols Challenge to 30 lucky riders. Lucky, that is, if you like to experience a tremendous amount of pain. The course varies from the Dolomites of Italy to the Pyrenees of France, but the challenge remains the same: Bike up 100 of the toughest mountain passes in the world in 10 days for an experience your legs will never forget. This is a race of survival.
The Death Ride - United States8 of 9
For a single day race in the United States, it doesn't get much more difficult that the Tour of the California Alps. The course totals 129 miles, and for most of it you are either going up or coming down. Total climbing is over 15,000 feet, which includes five mountain passes that each reach well over 8,000 feet in elevation. The scenery is stunning, but it is the pain that will be a long-lasting memory.