For decades, they stood by safe and smiling, a fixture on America’s sporting sidelines. But today’s young cheerleaders, who perform tricks once reserved for trapeze artists, may be in more peril than any female athletes in the country.

Emergency room visits for cheerleading injuries nationwide have more than doubled since the early 1990s, far outpacing the growth in the number of cheerleaders, and the rate of life-threatening injuries has startled researchers. Of 104 catastrophic injuries sustained by female high school and college athletes from 1982 to 2005 — head and spinal trauma that occasionally led to death — more than half resulted from cheerleading, according to the National Center for Catastrophic Sports Injury Research. All sports combined did not surpass cheerleading.

New acrobatic maneuvers have turned cheerleaders into daredevils. And while the sport has retained its sense of glamour, at dozens of competitions around the country, knee braces and ice bags affixed to ankles and wrists have become accouterments as common as mascara.