Bike helmets were designed to protect against catastrophic head injuries like skull fractures, lacerations or contusions on the brain, which they do.
However, as the understanding of concussions has advanced significantly in recent years, basic helmet design has not, and the standard that North American helmet manufacturers follow has not changed since 1999.
If a cyclist falls and his head hits the pavement or an automobile, the brain could undergo what scientists call linear acceleration – moving in the direction of the impact. And by moderating that, helmets can reduce the risk of skull fractures, neurosurgeon Charles Tator told CBC News.
- Listen to CBC Radio Ideas' host Paul Kennedy interview Dr. Charles Tator
Tator is a surgeon at Toronto Western Hospital and a professor of neurosurgery at the University of Toronto. He founded ThinkFirst Canada, an injury prevention group, and is now a board member of its successor organization, Parachute Canada.
However, at impact the brain may also undergo rotational or angular acceleration.
"The evidence from science is that concussion is more related to rotational acceleration, which in laymen's terms is really a jiggle of the brain. It's like the movement of Jell-O in a bowl when you jiggle it," Tator explains. And the result of that jiggle can be cellular damage to the brain, which can affect neurons and their connectors.
He says "it is time that our standards include measures of angular acceleration."
- Check out an interactive map of the human brain
Current bike helmets, Tator says, "are pretty well useless in attenuating" rotational acceleration.
University of Ottawa kinesiologist Blaine Hoshizaki concurs. He told CBC News, "Bicycle helmets are not really providing a great deal of protection, if at all, in regards to concussions."
Concussions on the rise
When it comes to bike crashes, concussions are on the rise.
For example, U.S. hospital emergency room data shows that the number of cycling-related concussions increased 67 per cent between 1997 and 2011.
A 1996 study found that more than half of U.S. riders who sustained concussions were wearing a helmet.
Different helmet designs aimed at reducing the risk of concussion are in the works.
Randy Swart, director of the all-volunteer Bicycle Helmet Safety Institute in the U.S. says, "It's tricky for a helmet designer to try to design a helmet that will help prevent an injury that isn't completely understood, guarding against a mechanism that isn't completely understood."
But Hoshizaki says the mechanism of a concussion is well enough understood now and he feels a new helmet can be designed.
The key, he says, is a design that reduces rotational acceleration. In his Ottawa lab, his team has introduced systems that substantially decrease rotational acceleration.
However, the lab isn't about helmet design, it "focuses more on reconstruction and understanding the mechanism of injury."
Understanding the mechanism of head injuries in sport is the focus of Hoshizaki's research.
He chairs the ice hockey equipment committee of the International Organization for Standardization and also sits on Canadian, American and European standards committees for sports equipment.
And he also acknowledges that there is little incentive for manufacturers to "develop a different paradigm" when it comes to protective equipment.
The cost of new design likely means a higher price tag and in the bike shops such a helmet would be competing against other helmets, of lower price, that also meet the current safety standards.
So to make a new helmet accessible would mean revising the standard to address rotational acceleration, in the expectation this would reduce the number of cycling-related concussions.
No mandatory standard in Canada
Bike helmets sold in the U.S. must meet the mandatory standard set by the U.S. Consumer Product Safety Commission, and since 1999 there has been no change to the standard.
Canada does not have a mandatory standard. There was one developed by the Canadian Standards Association, but its use by manufacturers has waned because of free trade, so it's the CPSC standard that really matters.
In a detailed look at helmets and concussions in the June 2013 issue of Bicycling magazine, journalist and author Bruce Barcott looked at the difficultly in getting a CPSC standard revised. Even CPSC commissioner Robert Adler described it as "almost impossible," during congressional testimony in 2012.
Nevertheless, according to Barcott, "National Institutes of Health (NIH) scientists warned that 'existing helmets are not protecting the brain adequately' because their design was based on a paradigm that ignored data on rotational forces. Revising the existing standards was deemed an 'urgent task.'"
Hoshizaki says it wouldn't be difficult to develop a test to measure the ability of a helmet to manage rotational acceleration and "it's pretty clear you can develop a standard for [rotational and/or] angular acceleration, no question about it."
New designs claim to address concussion
There are now helmet designs out there that claim to lower the risk of concussion by reducing rotational acceleration of the brain.
One is known as MIPS, an acronym for Multi-directional Impact Protection System.
This Swedish design uses a liner inside the helmet that attaches to it with a pin and on impact allows the rest of the helmet to rotate a bit, thereby absorbing some of the rotational energy. There are now helmets on the market with MIPS.
Hoshizaki, who has visited the MIPS lab in Stockholm, calls the Swedish company's mechanism for measuring rotational acceleration "very narrow," but acknowledges it does have one and "it's valid and other people have replicated it."
Swart, who is also the co-vice chair of the American Society for Testing and Materials' subcommittee on headgear, cautions that he doesn't "think the MIPS technology is proven in the field to really mitigate concussion."
Another design, by the Legacy Biomechanics Laboratory in Portland, Oregon, "employs an elastically suspended aluminum honeycomb liner to absorb linear acceleration in normal impacts as well as angular acceleration in oblique impacts," according to a study.
The study's authors claim their Angular Impact Mitigation (AIM) system reduced peak angular acceleration by 34 per cent, and predict a 27 per cent reduction in the risk of concussion.
Study co-author Michael Bottlang told CBC News that they have recently secured funding to introduce AIM to the market.
"Further research is required," the study states.
Hoshizaki says bike helmets designed to protect against concussions are a priority now.
"It doesn't mean you are going to make the helmet less protective in terms of catastrophic injury, but you have to start opening up the opportunity to encourage the manufacturers to become more innovative in terms of managing concussive injuries and for sure it can be done, we're right on the cusp of this."