Treadmill accidents like the one that apparently killed Sheryl Sandberg's husband, Dave Goldberg, send thousands of people to American emergency rooms every year. Extremely few are anywhere near as dire as the fall that caused Goldberg's fatal head trauma, but treadmills can cause significant injuries.

Serious injuries involving exercise equipment, including treadmills, are among the most common seen in emergency rooms, according to the US Consumer Product Safety Commission. Hospitals treated some 24,400 treadmill-related injuries last year alone, commission spokeswoman Kim Dulic told USA Today. Treadmills also accounted for 30 deaths from 2003 to 2012.

Treadmill injuries in the commission's database include broken bones, abrasions, rectal bleeding and people developing chest pain while working out on the machines. A report by CBS in 2011 also recounted broken bones, and amputated fingers and concussions. Almost a third of those with treadmill-related injuries in emergency rooms in 2009 were children.

In 2009, the four-year-old daughter of former heavyweight boxing champion Mike Tyson died in a treadmill accident at the family home in Phoenix. She was strangled by a cord connected to the treadmill.

Almost 460,000 people were sent to the hospital in 2012 for injuries related to exercise equipment, according to commission data. The vast majority were treated and released, but about 32,000 were hospitalised or were dead on arrival.

Officials believe Goldberg, 47, lost his grip on a treadmill while he was working out at a resort near Puerto Vallarta while on vacation with his family. He fell backwards and struck his head. His brother found him hours later lying in blood. He was still alive but died later of severe head trauma and blood loss in hospital.

It's not clear what caused Goldberg to fall from the treadmill. He could have slipped or tripped, or may have experienced a heart problem which caused him to lose consciousness, Dr. Michael Jonesco, a primary care sports medicine physician at The Ohio State University Wexner Medical Center, speculated to Live Science.