Like the swimming portion of a triathlon, there are many established distances for the cycling leg. The standard distance is 40 kilometers (25 miles), but sprints are half that distance and the Ironman cycling section is three times as long.
Topping the list of the most common rule violations during a triathlon is biking without a helmet [source: USA Triathlon]. In USA Triathlon races, you only have to wear your helmet when you're mounted and riding the bike. For ITU races, you have to wear a helmet for the entire time that you're "in possession" of the bike, which starts from the moment you grab your bike off the rack until the moment you hang it back up [source: ITU]. You also can't bike without a shirt on. (Triathlon rules make frequent use of the word "torso.") Failure to wear a helmet or a shirt results in immediate disqualification.
The most complicated and controversial rules in the cycling section have to do with drafting and blocking. Drafting is a cycling technique in which a racer rides very closely behind another competitor to cut down on wind resistance and expend less energy. In long-distance team races like the Tour de France, drafting is a critical strategy for success. Triathlons, on the other hand, are generally viewed as individual races, not team events, so drafting is often illegal.
In a "draft-illegal" event -- most non-elite triathlons are draft-illegal -- strict rules govern how long you can remain in another rider's draft zone. Under ITU rules, the draft zone is a large rectangle measuring three meters wide by 10 meters long (10 by 33 feet) that extends backwards from the front tire of the bike [source: ITU]. (The zone measures 12 meters long for long-distance races.)If you want to pass a rider in front of you, you can only ride through their draft zone for a total of 15 seconds [source: ITU]. Failure to do so will result in a time penalty.
Blocking is a no-no in both draft-legal and draft-illegal triathlons. Blocking is the act of willfully keeping others from passing. This usually involves riding on the left side of the course while not actively in the process of passing. Blocking will also cost you a time penalty; repeated violations could lead to disqualification or even suspension.
The running leg of the triathlon isn't immune to rules and regulations. Leave your iPod at home and learn more on the next page.