Modern bike helmets far from perfect

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This article was published 07/10/2017 (3219 days ago), so information in it may no longer be current.

Whether helmet use should be mandatory for bicycle riders is a heated topic.

You’re undoubtedly better off wearing a helmet if an accident occurs, and the importance of wearing a helmet increases with the significance of the accident. But while helmets have come a long way since the strappy leather head coverings some cyclists wore before the 1970s, they still don’t do much to protect us from concussions.

Helmet experts are calling for radically new designs to improve safety.

Studies have found that in an accident, you’re much less likely to suffer a severe brain injury if you’re wearing a helmet than if you’re not, but your odds of experiencing minor brain trauma are similar. That’s because modern helmets are lined with hard foam. The design can withstand a serious impact, protecting your skull from fracturing against a hard surface such as pavement, but the rigid foam doesn’t absorb as much energy as a softer liner, such as those found in football helmets.

The best protection for a bicyclist would be a helmet made from a softer material thick enough to absorb any impact, but “nobody wants to bike around with a mushroom on their head,” said Mehmet Kurt, who studies head injury prevention at the Stevens Institute of Technology in Hoboken, N.J.

Consumer preference has often driven helmet design, and not always in the direction of safety.

Randy Swart, director of the Bicycle Helmet Safety Institute, a non-profit based in Arlington, Va., said the transition from round helmets to elliptical or oval-shaped ones in the 1990s was “certainly not an improvement” safety-wise. But people wanted to look like Lance Armstrong.

According to Roy Burek, a visiting professor at the Concussion and Traumatic Brain Injury Prevention Group at Cardiff University in Wales, cyclists can face four basic types of brain injury: skull fractures, interior brain bruising and swelling, brain bleeding, and twisting or distortion of the brain.

Skull fractures and brain bruising result from direct impact and linear energy — the sort you would experience if you fell and hit your head on a curb.

Bike helmets protect from these injuries quite well. The hard-to-crack polycarbonate layer on the outside of helmets prevents skull fractures. Microscopic air pockets in the hard foam lining inside helmets burst in a crash, allowing the lining to compress to about 25 per cent of its volume and absorbing much of the impact that would send the skull smashing into the brain.

When a rider goes flying and skids to a stop, the brain experiences the effects of rotational energy, which can produce internal bleeding and contortion.

“The brain is a little bit like an orange in a glass of water,” Burek said.

“If you twist the glass quickly, the orange won’t follow immediately behind.”

Now imagine that the orange is attached to the glass by little vessels. Those vessels will tear when the glass moves but the orange doesn’t (or when the orange moves much more slowly).

That’s what happens with the brain inside the skull.

As the skull whips around, the small blood vessels that stretch from the brain to the skull break, causing bleeding in the brain.

In addition to tearing blood vessels, the brain itself also twists.

Helmets do a pretty good job of protecting riders from skull fractures and brain bruising. They don’t do much to prevent injuries resulting from rotational energy.

Helmet design could go in many directions. Swart envisions a smooth, round helmet with a softer material that survives more-dramatic impacts but wouldn’t need to be impractically thick.

Burek noted that most bicycle accidents occur at low speeds, so an ideal material for a helmet would be soft when you land at low speeds, to allow the brain to move and thus decrease damage from rotational energy. But that material would also be “smart” — firming up when a high-speed crash occurred, thus preventing a skull fracture.

Helmets are not designed to move when you crash, because you really don’t want them falling off.

“We need to come up with materials that don’t collapse head on, but twist and move in different directions like a second scalp,” Burek said.

It’s a bit like landing on a water bed instead of a firm mattress.

— Special to The Washington Post