About two years ago the United States Soccer Federation imposed tight restrictions on young players "heading" soccer balls in competition and practice in response to concerns that players hitting the balls with their heads were at risk for concussions, which are especially damaging to young brains.

Competitive swimmers, meanwhile, continue regularly bashing their heads into cement walls and other swimmer's skulls, with only the barest of protection.

Swimmers typically have only a couple millimeters' buffer of latex or silicone between their heads and another solid surface. But while contact sports like soccer are taking steps to minimize the number of risky collisions, updated guidelines for swimming published by the governing body USA Swimming simply call for athletes to be closely monitored for signs of concussion when they hit their heads.

"When my son joined [swimming], he was 8 years told. And my husband and I were really surprised at how nobody reacted when these kids hit their heads doing the backstroke or during warm-ups," said Twin Cities resident Theresa Finn. She recently left her longtime job with a branding and engagement firm in Chanhassen to co-found a company called Mako International LLC to make a new kind of swim cap.

Called the Hammer Head Swim Cap, the product includes the same 2 millimeters of silicone on the outside as a traditional swim cap. But underneath, the material is molded into a half-inch-thick layer of shock-absorbent silicone "pillars" arrayed in a honeycomb pattern to absorb and dissipate the brunt of an impact to the head.

The shock-absorber section is invisible from the outside. But the cap also includes visible innovations like a seamless compression fit that eliminates wrinkles that can cause drag in the water. And unlike traditional swim caps, the Hammer Head features a longer cut that covers more of a swimmer's ears, to prevent water from flowing in and out of the ear canal.

"When we developed this swim cap, it was because I've seen so many people hit their head," said David Burns, a longtime Twin Cities swimming instructor who also serves as Mako's co-founder and chief operating officer. "This cap had to be developed to protect the swimmers and give them the best competitive advantage as well. There is nothing on the market like this."

After years of research and design, the $34.95 caps are now available for pre-order on Mako's website, www.hammerheadswimcaps.com. Shipments are expected to begin next month. So far just under 1,000 have been ordered, but the company is forecasting sales of as many as 75,000 units this year.

Although lab research is underway to quantify the benefit of the Hammer Head cap, Finn said the concept of using a honeycomb of silicone to absorb and disperse shock makes intuitive sense and gives swimmers more confidence in the water.

"Now that we have this, it's like, I can't believe someone else hasn't thought of this," she said. (Mako International performed extensive patent work before finding that no one else had a lock on the idea. It then filed for its own patents.)

Mako's website says the caps meet USA Swimming standards and certifications for competition swimming and synchronized swimming. Although its shape is designed to eliminate drag, similar to "dome caps" already on the market, the Hammer Head's silicone shock-pad does add a bit more weight.

"When you hold the Hammer Head Swim Cap in your hand, and you have a regular swim cap in the other, ours is heavier," Finn said. "But what athletes have told us is, once you have it on your head, you really don't notice a difference."

St. Paul-born swimmer and Olympic gold medalist Tom Malchow is both a spokesman and investor in Mako International. He said the delay in recognizing a need for safer swim caps like the Hammer Head might be due in part to the fact that many people don't think of swimming as a contact sport.

The reality is that swimmers regularly hit their heads while trying to turn during the backstroke, and they collide head-to-head while swimming in the same lanes during practice.

Malchow said he can see a day when swimming programs or insurance companies might start to encourage the use of swimming caps with safety features. "My gut tells me that at some point, it could almost be mandatory for learn-to-swim programs," Malchow said.

He could also see potential applications for diving and synchronized swimming, and among Special Olympics athletes and swimmers at health club pools. The silicone honeycomb design could even have applications in helmets or athletic clothing for other sports someday.

"I'm excited to see where it goes in swimming and to see if there is an application for the technology outside of swimming," Malchow said. "I think everyone is looking to learn to make sports safer."