Rewinding a bike crash shows how helmets protect

What if you could go back in time and see exactly what would have happened if only you had done things differently?

That’s what researchers at KTH Royal Institute of Technology in Stockholm did with three actual bike crashes in which the riders wore no helmets. This squirm-inducing video shows the impact on an adult male’s brain when he lost control of his bike and crashed.

Then the video does something extraordinary: it reenacts the same crash and shows what would have happened if the rider had worn a helmet.

The visualization is based on computer-simulated motion recreation done by neuronics researcher Madelen Fahlstedt and colleagues at KTH Royal Institute of Technology in Stockholm (with the help of researchers at Leuven University). In order to show how much the brain’s tissues are stretched in each instance, they used a detailed computer model of the head (KTH head model) and reconstructed accidents. Then they compared their simulations against actual CT images of the damaged brains.

We know from epidemiology that helmets are more likely to protect people, but up until now, we could only guess at how much protection your brain tissues really get. Few studies have gone beyond epidemiological surveys to accurately map the cause-and-effect relationship between helmets and protection, she says.

“We can see how much the brain tissue is stretched in the collisions, and that the tissue is stretched most in those areas where the impact occurred,” Fahlsted says.

In the reenactments, an ordinary bicycle helmet reduced the brain tissue’s stretch rate between 33 to 43 percent in the three accidents studied, she says. “Given the factors in our study, we have also been able to see a reduced risk of 54 percent for concussion when using bicycle helmets.”

Not only do helmets decrease stress on brain tissue, they also reduce the risk of skull fractures, she says.

“We saw a great reduction of stress on the bones, as a result of wearing a bike helmet, from 80 megapascals down to 10 megapascals. This figure indicates how much load you put on a given surface, and translated into more understandable terms, this means a reduction from 100-percent risk of skull fracture down to 10 percent for those wearing helmets.”

David Callahan

David Callahan
David Callahan is editor for international news and media at KTH Royal Institute of Technology.

3 thoughts on “Rewinding a bike crash shows how helmets protect”

  1. Then the video does something extraordinary: it reenacts the same crash and shows what would have happened if the rider had worn a helmet. Not only do helmets decrease stress on brain tissue, they also reduce the risk of skull fractures. Really informative post.

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