British eventing rider Oliver Townend broke his sternum, four ribs, his collarbone and the tips of his shoulder bones when his horse tumbled on top of him at the Rolex Kentucky Three-Day Event in April.

But it could have been much worse.

"I walked out of hospital the next day," Townend said in a recent telephone interview.

Townend was wearing an air-bag vest at the time, a simple safety innovation that was virtually unheard of in the equestrian world until last year and now is standard issue for the world's top riders.

Without the vest, "I would be in a box or in America for a month," Townend said. "It's certainly the biggest step forward in the safety of our sport, ever."

In a similar accident, spectators gasped and expected the worst when the horse ridden by Karim Florent Laghouag somersaulted over a fence and fell on top of him at a September competition in France.

Laghouag had taken a so-called rotational fall, a dreaded spill in the Olympic sport of eventing. At least 13 riders in the past four years have been killed and several others seriously injured in such tumbles.

But soon after his horse jumped to its feet, Laghouag stood up, too. He had a dislocated elbow but no broken bones. "Today, I wear it all the time — even when I'm training," Laghouag, 35, said in French during a recent telephone interview.

Leaders in eventing — a three-phase competition involving dressage, show jumping and a cross-country obstacle course — have long expressed frustration over attempts to make the cross-country portion safer. They have tried imposing stricter rules on riders and building fences designed to break apart more easily on impact.

But the arrival of the airbag vests has generated the most excitement, even though some say the technology is too new to be wholly embraced.

Several national teams, including that of the United States, will be wearing the air-bag vests at the Alltech FEI World Equestrian Games Sept. 25 to Oct. 10.

Following motorcyclists

Inflatable vests have been sold to motorcyclists for about a decade, but few equestrians used them until a British company, Point Two Air Jackets, adapted them for use on horses and began distributing them at top European competitions last year. Hit Air, a Japanese company that says it has been selling motorcycle vests since 1999, also sells an equestrian version.

They each rely on similar technology. The 2-pound vest is attached by a cord to a rider's saddle and is worn over a traditional protective vest made of high-density foam. When a rider is thrown from a horse, the cord is yanked, puncturing a cartridge of carbon dioxide and inflating the vest. The vest can be reused after the cartridge is replaced.

Despite their relatively high cost — from about $390 to $700 — the vests have sold well. About 6,000 eventing riders now wear the Point Two vests, according to the company, and Hit Air said it had sold about 10,000 vests for equestrian use worldwide.

Lee Middleton, director of Point Two, said his product was worn by the top 40 U.S. riders. He provides some vests free to riders like Townend and Laghouag, who are not paid to be spokesmen.

"Anything like that, that can minimize the effects of an injury during a fall, is going to be great," said David O'Connor, president of the U.S. Equestrian Federation and an Olympic gold medalist.

Until recently, he also headed the international federation's eventing safety subcommittee.

"I think they've proven themselves already — and certainly with the people that have had falls with them — they swear by them," O'Connor said.

'Softer landing'

Eventing rider Doug Payne, who is sponsored by Hit Air, said he had fallen four times while wearing the vest.

"It's an interesting thing," he said. "As you're falling, everything sort of slows down. You do notice a pop sound, and that's the canister. The next thing you realize, it's a significantly softer landing than you would ever expect."

The vests have become so common on the competition circuit that it has become a common courtesy to warn other riders to unhook their cords before dismounting.

"When you arrive, everyone says: 'Your vest! Your vest!'" Laghouag said.

Inevitably, someone forgets.

"It's always a source of amusement," O'Connor said. "You hear a pop and somebody's looking like a marshmallow."

Giuseppe Della Chiesa, chairman of the eventing committee for the international governing body for equestrian sports, known as FEI, said the group recommends using the vests but does not require them because there is so little safety data.

The Point Two jackets were independently tested by the Transport Research Laboratory, a nonprofit group in Britain, which found that the air bag improved protection of the spine by 69 percent when worn over a protective vest. The air-bag vest also reduced the risk of rib fractures and underlying organ damage by as much as 20 percent, the laboratory found. Kenji Takeuchi, president of Mugen Denko, which manufactures the Hit Air vest, said by e-mail that he had conducted testing at the nonprofit Japan Automobile Research Institute.

Point Two's Middleton said he had also spoken about the vests with representatives from the mountain bike and all-terrain-vehicle industry.

Rolling to safety

Aside from the expense, some equestrian riders have expressed concern that the loud pop created when the vest is activated can spook horses. Others report feeling restricted after a fall, and worry about being able to roll to safety in an inflated vest.

Some have raised questions about the effectiveness of the vests during rotational falls similar to those of Laghouag and Townend, in which the rider somersaults with the horse and frequently does not become separated from the horse until the last moment.

According to statistics kept by the FEI, about 25 percent of riders involved in rotational falls in international competitions from 2004 to 2009 were either killed or seriously injured.

Reed Ayers, an amateur eventing competitor who holds a doctorate in engineering, is skeptical about the benefit of the vests. He said he had heard of several riders whose vests failed to inflate in falls.

"When you rely on a mechanical design, there's always a possibility that it won't work," said Ayers. "That's why you can't rely on those vests as the sole protective component."

Laghouag and Townend consider the vests lifesavers, and Middleton said that even if they failed to inflate, they would cause no harm.

"You've got to remember they've got what they've got underneath anyway," he said, referring to the stiff protective vest. "This is an added bonus."