But new research shows that cheerleaders, who once dazzled with their smiles and sequins, are at greater risk of serious injury than American football players.

Instead of just cheering on their team, cheerleaders are now encouraged to compete in high-stress competitions, where dangerous throws and tumbles reminiscent of gymnastics are the norm.

Because the pastime is not regulated like a sport, accidents are common and cheerleaders are swapping their pom poms for crutches, knee braces and ice packs.

Campaign groups, horrified by a growing incidence of "catastrophic injuries" which have left cheerleaders with disabilities, paralysis and even dead, are fighting to clean up the "sport", where many school coaches do not have the necessary safety training.

Figures collated by the National Centre for Catastrophic Sports Injury Research found that between 1982 and last year, 67 young women suffered devastating injuries or death, which accounts for two out of three of all serious sporting injuries among young women.

The incidence of injuries causing paralysis or disability was 2.68 per 100,000 cheerleaders, which eclipses the figure for American football, where there are more fatalities but a lower ratio of injuries to participants.

The number of cheerleaders treated at hospital accident and emergency wards increased from under 5,000 a year in 1980 to nearly 30,000 a year today.

At least three deaths and numerous cases of permanent paralysis are blamed on falls and collisions to the end of last year, and since then two more cheerleaders have died. Most recently in April, 20-year-old Lauren Chang from Massachusetts was killed by an accidental kick to her chest during a cheerleading competition at a local gym.

Dr Frederick Mueller, a sports injury expert at the University of North Carolina, who did the research, told The Sunday Telegraph: "We are getting more and more of these cheerleading injuries, and they are pretty serious head and neck injuries. They're throwing people in the air 20 to 25 feet and trying to catch them on the way down. It's really gymnastic activity. It shouldn't be called cheerleading any more.

"Right now they don't have certified coaches. You get some kids teaching each other."

A pressure group, the National Cheer Safety Foundation, is calling for federal legislation to regulate both schools and colleges but also the private cheerleading companies who run teams in national competitions.

Its founder, Kimberly Archie, said: "Cheerleading isn't really regulated at all. People make up their own rules because cheerleading is not considered sport. For years it was just seen as cute girls on the sideline, even though the injuries are outrageous.

"We have coaches without resuscitation and first aid training. I'd like to see a national youth sports safety act."

She said a further 14 cheerleaders have died suddenly after heart attacks that some believe are attributable to the stresses of their routines.

The foundation has drawn up an action plan for clubs on how to cope with serious accidents, which has already been adopted by more than one thousand school districts in the last two months.

The American Association of Cheerleading Coaches and Administrators, which represents coaches in private clubs, did not respond to a call seeking comment.