Most sports involve some level of physical risk, and Olympic contests are no exception. Although the injury rate is lower than that for some professional sports such as American football and soccer, about 10 percent of Olympians get hurt during their days at the games, either while training on site or in actual competition.

A total of 1,055 injuries were reported during the 2008 Summer Games in Beijing, according to a thorough study of injury reports by Lars Engebretsen of the University of Oslo in Norway. The insults ranged from fractured feet, dislocated shoulders and ruptured Achilles tendons to less traumatic but more prevalent ankle sprains and head contusions.

Of course, the circumstances that inflicted pain varied considerably. Engebretsen found that the fraction of injuries that took place during training was highest in table tennis, tennis, swimming, gymnastics, beach volleyball, equestrian, modern pentathlon and athletics. Injuries most often occurred during competition in boxing (no surprise), water polo, hockey, handball, weight lifting, baseball and judo.

Although we tend to think of collisions and falls as likely culprits, overuse of an athlete's muscles or joints caused more than 40 percent of the injuries in rowing, modern pentathlon, sailing, shooting, tennis, beach volleyball, triathlon, athletics, weight lifting, swimming and badminton. Contact with another athlete did cause more than half the injuries in boxing, judo, water polo, handball, taekwondo, wrestling and soccer.

Severity varied, too, of course. Fractures were highest among taekwondo injuries (4.8 percent). The same sport also had the highest rate of dislocations or ruptures to tendons and ligaments (3.2 percent).

The Winter Olympics have fewer athletes overall, so fewer injuries were reported during the 2010 Games in Vancouver: 287. But the injury rate was 11.2 percent, a little higher than the 9.6 percent for the summer games.

The distribution of injuries varied much more widely among winter sports, too. In short-track speed skating, 28 percent of men were hurt but only 9 percent of women were. In snowboard cross, however, which involves frequent contact between boarders in a free-for-all downhill race, only 11 percent of male racers were hurt but an incredible 73 percent of female athletes were. Oddly, a surprisingly high proportion of injuries occurred during training runs, when a boarder was alone on a course, without competitors to raise the stakes. The high rate may just have been the result of fast slopes, according to Engebretsen.

Legs and arms and everything in between were compromised during the past two Olympics. But hockey players suffered by far the most facial damage, caused by flying pucks, swinging sticks and the occasional fight. Downhill skiers and snowboarders had the most head injuries. Concussions affected 7 percent of all winter athletes—twice as high as in the summer games.

Engebretsen will see how the statistics hold up in 2012. He is at the London Games, and he will be studying rates of illness as well.