Do You Need a MIPS Helmet? A Craniofacial Trauma Surgeon Shares What Cyclists Need to Know
This article originally appeared on Outside
Cycling is the leading cause of sports-related head injuries in the United States. It has been estimated that head injuries related to cycling accidents caused approximately 80,000 emergency department visits in 2015. 13,000 of these visits included a diagnosis of concussion and traumatic brain injury (TBI). Moreover, a recent study found that only 22% of cyclists who sustained head and neck injuries were wearing helmets during the accident.
Of all the gear you buy for triathlon, the helmet might just be the most important. Your bike helmet is the main (and most) effective strategy to prevent traumatic brain injury in cycling accidents. Cyclists are vulnerable road users, and therefore, the necessity of wearing protective equipment cannot be overemphasized. More often than not, the sequelae from a severe collision are permanent.
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Traditional Bike Helmet Design
Traditional helmets are designed to dampen the impact and reduce head impact force. A typical bicycle helmet consists of the shell, the liner, and the straps. The liner is used to absorb most of the impact energy and reduce the wearer's risks of sustaining head injuries.
Helmets have routinely used a rigid shell of EPS (expanded polystyrene foam), which diminishes the impact force and mitigates the impact. Basic cycling helmets have been designed in a way that during an impact, they crush and rupture, absorbing the shock so your skull doesn't have to.
The Consumer Product Safety Commission (CPSC) standard is mandatory for bicycle helmets in the United States, and dictates that helmets must limit peak linear acceleration (PLA) to less than 300g--a level associated with greater than 50% risk of skull fracture or severe brain injury.
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Testing the Effectiveness of Bike Helmet Protection
Before, scientists studied the effectiveness of helmets using only the vertical drop of some sort of mannequin head (head form) against a rigid surface. However, thanks to scientists in the lab, new tests are taking into consideration head rotational kinematics.
Why? Because bike accidents and impacts rarely occur in a full vertical manner, and it has been proven that real life impacts occur mostly at oblique angles of about 30 to 60 degrees. Oblique impacts induce head rotation, which is known to be a key mechanism of several distinct types of head injury, such as diffuse axonal injury, or the tearing of the connecting nerve fibers in the brain.
Studies using this new and improved multi-directional testing strategy have demonstrated that new helmet technologies can provide better protection under oblique impacts than conventional helmets. These new technologies are aimed towards mitigating the head's kinematics through rotation-damping systems.
What Is MIPS?
As we've established, rotational forces are a dominant factor causing brain injury in cycling accidents. Because of this, modern cycling helmet designs now include "anti-rotational technologies."
Multi-Directional Impact Protection System, or MIPS, consists of a thin slip liner that covers the inside of the helmet. This technology seeks to reduce rotational acceleration of the head by permitting sliding between the helmet and head during impact.
In fact, as expert scientists have stated, MIPS aims to reduce rotational head acceleration caused by an oblique impact in order to further improve protection from rotational traumatic brain injury. So basically, MIPS is oriented towards reducing rotational head kinematics by enabling sliding between the helmet and the head during a given impact.
As of 2019, MIPS technology helmets have been used by over 100 brands. There are other new technologies to address rotational protection in bike helmets, such as WaveCel and Koroyd, which utilize a collapsible cellular structure that absorbs the force of impact and minimizes the energy transferred to the cyclist's head. Shearing Pad Inside, or SPIN for short, is another rotation damping system used by some cycling helmet manufacturers.
Is a MIPS Bike Helmet Safer?
Experts in the field of biomedical engineering developed a study in order to evaluate the effects of MIPS on peak head form kinematics. They evaluated 3 head form conditions: bare, stocking-covered, and human hair, in three impact orientations over a range of impact speeds. They conducted a total of 72 freefall drop tests of a single helmet model, with and without MIPS, onto a 45deg angled anvil and measured many variables, such as peak linear (PLA) and angular acceleration (PAA), as well as the brain injury criterion. Conclusively, MIPS reduced peak angular kinematics across 3 head form conditions, 3 impact orientations, and 4 impact speeds.
But the lab is not the real world. It's important to objectively interpret these findings and extrapolate the results in the context of real-world head impacts. How substantial would a difference be between a long-haired cyclist versus a bald one?
For that matter, another group of researchers have proposed that head forms used in the lab should be better designed by incorporating artificial skin layers that can better resemble scalp's behavior, that way, a much more reliable insight could be obtained from the design of helmet technologies against rotational acceleration.
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Studying Spin, WaveCel, and More
MIPS and SPIN rotation damping systems demonstrated significant improvement in mitigating rotational head kinematics and in consequence, brain injury risk. For instance, a study was conducted in the UK and Sweden in order to assess the brain injury prevention effects of 27 bicycle helmets in oblique impacts, including helmets fitted with MIPS, SPIN, WaveCel (a wavy cellular liner), Hovding (an airbag helmet) and a number of conventional helmets.
For each bike helmet technology, a detailed computational model of TBI was used to determine strain distribution across the brain and in key anatomical regions, namely the corpus callosum and sulci. The Corpus callosum is the largest white matter tract in the human brain and a common location of axonal injury after severe traumatic brain injury.
The assessment of 27 commercially-available helmets showed that the vast majority of helmets with new technologies like MIPS or SPIN do have the potential to reduce peak rotational acceleration and velocity, and maximal strain in corpus callosum in oblique impacts.
This is further confirmed with a 2022 study by Canadian researchers, where two helmet technologies were evaluated to determine the ability to on decrease peak rotational acceleration in cycling helmets.
The findings of this study demonstrated significant reductions, compared to a traditional helmet, for peak rotational acceleration for MIPS technology and thermoplastic urethane bladders containing a low-viscosity fluid. The former showed significant reductions in rotational acceleration for the front and side impact sites, while the latter showed significant reductions in rotational acceleration for the front, side and crown impact sites. As stated by the scientists, each technology demonstrated unique performance characteristics depending on the impact condition.
Is it Worth Investing in a MIPS or SPIN Helmet?
Yes. We are not talking here about aero helmets or technology to make you faster here. Instead, we're talking about the most fundamental job of the bike helmet - something that will actually protect your head during an accident on the road.
New helmet technologies cost more, but investing in your health means you care about yourself, your significant other, your family and your sports community.
How to Wear a Bike Helmet (the Right Way)
If you want to get the most out of your bike helmet, you've got to wear it the correct way - and many are making helmet mistakes without even realizing it. Let's review the basics:
Buy the correct size by measuring your head circumference before purchasing. Then use the ratchet system to fine-tune the fit. When a helmet fits well, it does not move much when you shake your head (but it shouldn't be so tight that it causes headaches or discomfort, either).
The front of the helmet should rest just above your brow. If you see a significant amount of forehead skin, your bike helmet is higher than it should be.
When the helmet is on your head, the straps should be snug, but not tight enough to distract. You should not be able to fit more than two fingers between your skin and the chin strap. The strap dividers (the "Y" straps on your bike helmet) should sit just below your earlobe.
Based on current evidence, it is not advisable to wear thick layers between your hair (or your scalp for that matter), and the inner surface of any given helmet. For instance, a very thin and traditional cycling cap would probably not have a detrimental effect during an accident, but wearing thick layers (such as a beanie or a winter toque) is definitely discouraged, as they might alter the beneficial and protective effects of a regular cycling helmet.
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Can I Still Wear My Bike Helmet After a Crash? It Looks Fine.
Some cyclists continue to use a helmet even after the helmet has been involved in collisions, falls or road accidents. Why? For starters, the helmet "looks fine." Besides, helmets can be expensive and most cyclists simply like the helmet they already have and don't want to go through the process of fitting a new one.
But guess what? Science has demonstrated that effectiveness of head protection might be compromised even after one collision. A study was conducted in order to investigate this. Researchers used 2 types of helmets (both without MIPS technology). After several experiments (involving drop tests with different accelerations and impacts), they concluded that although macroscopic (visible) damage was not observed after the first tests, the helmet structure might have been irreversibly changed, lowering the effectiveness of the head protection in the second tests. Thus, helmets may not be safe after a collision or a fall, even if there is no visible damage.
So yes, in real-life situations, helmets subjected to an impact should be discarded. It is a matter of safety.
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Dr. Damian Palafox is a board certified plastic and reconstructive surgeon, a member of the American Society of Plastic Surgeons (ASPS) and an enthusiastic amateur triathlete
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