Yes, biking can be tremendously good for you, but it can also be tremendously bad for you, if you’re one of the tens of thousands of cyclists who suffer serious head injuries while biking each year. Anahad O’Connor, writing in the New York Times, reports that cycling accidents played a role in about 86,000 of the 447,000 sports-related head injuries treated in emergency rooms in 2009. He also points out that 90 percent of bicyclists killed in the United States in 2009 were not wearing helmets. What kind of helmet is the best kind of helmet? Read Bicycling’s 2012 Buyer’s Guide to helmets.