"He laid on the ground for a while," recalls Mr. Stephany, who has been coaching his three children in soccer for more than a decade. "I think he said he hated me." Since then, Austin has been trying to ward off such knocks by wearing a padded headband that wraps around his temples and his forehead. Austin says he will be playing with the soccer headgear for the rest of the season.

He won't be alone. Starting in the spring, about 40,000 New York soccer players will take the field with the extra piece of gear on their heads. The New York State West Youth Soccer Association, which governs players in the state from Buffalo to Binghamton, has ruled that all participants under 14 years of age must wear head protection during games and practices, the first mandate of its kind in the country.

The decision is a boon for headgear makers like Full90 Sports Inc., which has been trying since its inception in 2002 to get the sometimes-stodgy soccer world interested in its products. Despite some initial pushback, the San Diego-based company has made headway in the last year, gaining acceptance from the Federation Internationale de Football Association, or FIFA, soccer's governing body; the U.S. Soccer Federation; and the National Federation of High Schools. Full90's headgear is one in a small group of head-protection products in the industry, including soccer helmets for young goalies.

As soccer participation continues to grow, so has concern about soccer-related injuries. Doctors treat more than 200,000 children a year for soccer-related injuries, including concussions, according to the Centers for Disease Control and Prevention. A study by Scott Delaney of Canada's McGill University in the Clinical Journal of Sports Medicine found that the rate of head injuries for soccer players was similar to rates for football players.

The mandate to use the headgear, while pioneering, is also controversial because it is still unclear what types of activities cause soccer-related concussions, and, therefore, what types of equipment would lessen impacts from collisions in the game. For instance, the debate is still raging whether "heading" -- when a player hits the ball intentionally with his head -- causes concussions or whether concussions are primarily caused by player-to-player or player-to-ground contact.

New York State West Executive Director Omer Doron says he believes that wearing headgear will reduce the likelihood and intensity of head-related injuries in soccer. "We believe this provides a safer environment," he says. "We're going to do whatever we can to pull this product forward and save one kid from getting another concussion."

Full90's product claims to reduce impact from player-to-player collisions by about half and doesn't affect heading. "We want to help prevent concussions by designing a product that would protect the player but not prevent the play of the game," says Jeff Skeen, chief executive of Full90. Mr. Skeen says he was inspired to start Full90 after watching his daughter receive three concussions on the soccer field before her 18th birthday.

But while many doctors agree with Full90 that concussions are caused by incidental collisions rather than by heading the ball, some are reluctant to endorse the product without more evidence. "You need proper data before endorsing anything like that," says Jim Morehouse, spokesman for the U.S. Soccer Federation.

Others, like Gary Green, a medical consultant to the U.S. Soccer Federation and clinical professor at UCLA division of sports medicine, worry that head protection will empower players to play more aggressively than usual. "It's going to dramatically change the nature of the game," says Dr. Green. "Our feeling is if they enforce the rules correctly, you'd avoid most head injuries that occur."

Still, there is a market for protective gear, says John Lococo, who owns four Soccer Post specialty stores on the West Coast. Mr. Lococo, who does about 60% of his business with players who are high-school age or younger, says headgear appeals to two kinds of clients: those who want the "latest" item and the protective parent who "wants the biggest shin guard" for his kids.

That is Mr. Stephany's reasoning. "You can get into all the arguments you want, but if you pass up on the opportunity to use the best possible technology and something horrible happens, you're going to feel horrible about yourself," he says. "You have to have the sense that you did the best you can for your kids."