Dave Goldberg, a beloved Silicon Valley executive and the husband of Facebook COO Sheryl Sandberg, suffered a fatal accident on vacation in Mexico last weekend. According to a spokesman for the local prosecutor’s office, the 47-year-old Goldberg “fell off the treadmill and cracked his head open” while exercising, and died of head trauma and blood loss.

Treadmills are notorious for causing accidents—occasionally fatal ones. The machines’ powerful motors and fast-moving belts can punish any momentary loss of balance with bruises, sprains, broken bones, friction burns, or worse. Distractions like watching TV or reading while running increase the likelihood of an injury.

Statistics from the US Consumer Products Safety Commission are not currently available because of an outage to its injury surveillance database. But a CBS News report in 2011 that cited the commission’s data said treadmills caused about 19,000 emergency room visits in the US in 2009—more than any other kind of exercise equipment—including about 6,000 by children.

Treadmills are especially dangerous to children: Exodus Tyson, the 4-year-old daughter of boxer Mike Tyson, died in 2009 after choking on a treadmill cord. And several medical journal articles have detailed the risks of friction burns if kids’ hands, fingers, or other body parts come into contact with the belt, often when an adult is using the machine.

Consumer Reports has some tips about treadmill safety that are well worth reading, whether you own a treadmill or use one at the gym. They include clearing the area around a treadmill in case of accidents; using a safety key which stops the belt if you fall; and avoiding looking down at your feet while you run, which can make you lose your balance. To avoid accidents involving children, keep them well away from the treadmills during use, and remove the safety key from home machines so they cannot use the treadmills on their own.

Treadmills, incidentally, were originally created as a way to reform convicts in the 19th century—they were used to mill grain, hence the name. They are the best-selling fitness machines in the United States, accounting for about 25% of the industry’s $77 billion in sales in 2012, according to the Sporting Goods Manufacturers Association.