5 ways wearing a bicycle helmet can result in injuries

We tend to be less cautious

Wearing a safety device creates a feeling of safety. This makes us less cautious. This well documented behavior is called risk compensation. We tend to take more risks when wearing safety equipment.

risk-compensationRisk compensation is the tendency to take more risks when wearing safety equipment.

The New York Times reported an odd increase in injuries after bicycle helmets became popular in the US:

the rate of head injuries per active cyclist has increased 51 percent just as bicycle helmets have become widespread. …

the increased use of bike helmets may have had an unintended consequence: riders may feel an inflated sense of security and take more risks. …

The helmet he was wearing did not protect his neck; he was paralyzed from the neck down. …

”It didn’t cross my mind that this could happen,” said Philip, now 17.

”I definitely felt safe. I wouldn’t do something like that without a helmet.” ”

Safety experts recognise the role of risk compensation.
From the New York Times article:

”People tend to engage in risky behavior when they are protected,” he said. ”It’s a ubiquitous human trait.”

Even cyclists who discount the daredevil effect admit that they may ride faster on more dangerous streets when they are wearing their helmets.”

A study in Accident Analysis and Prevention found that children are also affected by risk compensation:

“Results indicated that children went more quickly and behaved more recklessly when wearing safety gear than when not wearing gear, providing evidence of risk compensation.”

A 1989 study found that helmet wearers were 7 times more likely to have accidents.

Risk compensation is an unconscious phenomenon.
We may not be aware of it.
Yet it affect the way we ride, the way we approach risks.

We are more likely to be hit by cars

Risk compensation also affects motorists.
Motorists tend to be less careful around helmeted cyclists. Drivers assume helmeted cyclists are “protected”.

A study published by the University of Bath in the UK reported that cars leave less room to helmeted cyclists:

“Bicyclists who wear protective helmets are more likely to be struck by passing vehicles”

Injuries tend to be more severe

Another subtle aspect of risk compensation is that we tend to ride faster.
A study in the Risk Analysis international journal found that:

“those who use helmets routinely perceive reduced risk when wearing a helmet, and compensate by cycling faster

In case of an accident, the higher speed results in more severe injuries.

There is a greater risk of the head hitting the road

In the event of an accident, helmets increase the risk of the head hitting the road.  Helmets increase the volume/size of contact area of the head. Helmeted riders are more than twice as likely to hit their head in an accident, with more impacts to the sides. Post-crash studies found that most helmets show impacts to the side,where a bare head is protected by the shoulders.

helmet-head-size-2Helmets increase the volume of the head, doubling chance of the head hitting the road in an accident;

A 1988 study reports that helmeted riders hit their heads seven times more often than un-helmeted riders.

We can suffer severe brain injury

In 1960, people believed that brain injury was due to linear acceleration, from the head hitting a wall for example. This belief has shaped the design of bicycle helmets.

Since, scientific research has shown that the main cause of brain injury is diffuse injury, caused by the head turning quickly. The skull may be intact, but there can severe internal brain injury. This article reports from a surgeon who operates on cyclists:

” “The ones with brain swelling, that’s diffuse axonal injury, and that’s bad news” …

the whole brain is shaken up, creating many little tears in its inner structure …

Such patients undergo personality change, can contract epilepsy and have difficulty controlling their anger. They might become unemployable. Depression is a common accompaniment to brain injury. Rosenfeld sees patients’ families shattered, too. “They’re never the same. It often leads to marriage disharmony and family breakdown.” …

Rosenfeld’s opinion is candid. “I don’t know if [helmets] do much to protect the inner part of the brain,” “

Research has found that helmets can increase rotational acceleration:

“The non-shell helmet did in all trials grab the asphalt surface, which rotated the head together with the helmet. The consequences were in addition to the rotating of the head, a heavily bent and compressed neck, transmitted on through the whole test dummy body after the impact.  …

This gives an average angular acceleration of 20800 rad/s² for rotating the head from 0 to 0.26 rad during the 5 ms. Löwenhielm proposes 4500 rad/s² to be the maximum angular acceleration that can be tolerated for a limited time period”

Helmets were found to amplify rotational acceleration to four times higher than the tolerable maximum.

The larger head volume amplifies rotational acceleration. A 3cm increase in helmet circumference increases rotational acceleration by 150%:

“the 3000rad/s² to 8500rad/s² measured during abrasive and projection oblique tests with size 54cm (E) helmeted headforms. However, for the most severe cases using a size 57cm (J) headform, rotational acceleration was typically greater than 10,000rad/s² and increased to levels of 20,000rad/s², a level at which a 35% – 50% risk of serious AIS3+ injuries is anticipated.”

The volume of a bicycle helmet amplifies rotational acceleration to dangerous levels where severe brain injury can occur.

A New Zealand doctor reports:

“cycle helmets were turning what would have been focal head injuries, perhaps with an associated skull fracture, into much more debilitating global head injuries”

In Canada, the length of stay in hospital increased increased following helmet laws, from 4.3 days to 6.9 days. The number of serious head injury admissions increased by 46%.

Contrary to popular belief, helmets are not designed to protect against brain injury.
However, they can increase rotational acceleration, causing severe brain injury.

What a load of rubbish!

This might sound like a load of rubbish to cyclists who wear helmets. Some believe their helmet saved their life. Few consider they may have fewer accidents without a helmet.

Cycling injuries rose dramatically after a helmet law was introduced in Australia.

cycling_injury_rateThe rate of cycling injuries tripled after Australia introduced a helmet law.

You might feel safer wearing a helmet.
However that doesn’t mean you are safer.

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