Guardians of Your Galaxy
Cycle Analysis by Mark Barnes, Ph.D.
Concussions have received increasing media attention, raising awareness of insidious long-term consequences of head injuries, ranging from subtle cognitive and emotional problems to profound global impairments. It’s no surprise that brain damage is problematic. What is surprising is the extensive impact (pun intended) minor blows can have on our body’s delicate control center, and therefore all our functions.
It’s not enough for helmets to keep our skulls from being crushed. Given modern neuroscience’s revelations, athletes, soldiers and motorcyclists all need helmets to cushion a much broader range of strikes. That includes minor contact that may previously have been considered trivial, as well as glancing contacts that generate rotation inside our heads.
Our brains are gelatinous organs comprised of 100 billion neurons, about the same number as stars in an average galaxy. While our skulls provide substantial armor for that fragile circuitry, they can’t protect our brains from sloshing and twisting in response to shocks. Bouncing back and forth against the skull’s interior can injure brain tissue on opposite sides.
Sudden rotation can shear nerves and tear blood vessels, yielding catastrophic damage, even though the impact causing it may appear less dramatic than a direct hit. Accumulating evidence shows even mild brain injuries can produce life-changing consequences, especially when repeated.
Motorcycle helmets haven’t changed much in decades. A fiberglass or polycarbonate shell protects the helmet’s contents from penetration or abrasion and distributes impact forces across a broader area, dissipating energy through its own deflection and destruction.
This shell houses a layer of expanded polystyrene (EPS) foam, akin to that of a cheap picnic cooler, which is lined with lightly cushioned fabric for comfort against the head. The EPS layer gets crushed (mostly from inside) during impact, absorbing some energy as it slows the skull’s travel toward the shell.
Even slightly collapsed EPS no longer provides effectively controlled resistance, rendering a helmet compromised after a single hit, though it may not be outwardly apparent. After multiple shocks (common in motorcycle crashes), EPS performance is reduced where, and to the extent, it’s already been deformed.
Design and testing have historically focused on mitigating the extreme forces generated by high-speed collisions. It was incorrectly believed that something that protects from horrific impacts will surely also protect from lesser knocks.
The stiff EPS and rigid shell construction required to absorb high-energy forces don’t compress or flex adequately under lighter loads. Most of the energy from minor- to moderate-level impacts is still relayed directly to the head. Ironically, these are the impacts motorcyclists encounter most often.
This realization prompted helmet engineering for better performance in less extreme collisions, with dual-density (two-layer) EPS cushioning both moderate and severe impacts. But this didn’t address tangential forces that easily cause brain rotation inside the skull, the foremost source of brain damage, not to mention neck and spine injuries. Motorcycle crashes subject helmets to exactly such abuse, rather than, or in addition to, the high-velocity linear impacts traditionally used in standardized lab testing.
Recent advances include more sophisticated provisions for abating rotational energy by allowing an inner layer to swivel within an outer layer. Rotational shock is thus reduced independent of liner compression, which still absorbs direct strikes. As the head rotates within the helmet, the impact load is spread over more compressible material, further dissipating energy.
Multidirectional Impact Protection System (MIPS), is a third-party technology that facilitates 10-15mm of internal rotation via a low-friction zone between the comfort liner and EPS. More elaborate systems developed by helmet manufacturers carry brand-specific names.
Helmet shape is another important factor, because a larger shell exerts more leverage in a fall, and more irregular and angular shapes have more catch-points to initiate rotation. Brain damage from related forces increases on a curve, so small reductions in helmet size may yield meaningful safety gains.
Leading manufacturers, such as Arai (which currently doesn’t employ the technologies discussed), tout their smooth, spherical shells as minimizing such problematic contours. Many helmet makers have designed break-away vent housings and visors to reduce their contributions to rotation.
We hope exposure to emerging technologies stimulates interest in acquiring a new helmet. It could prolong your tenure as a motorcyclist, preserve your quality of life, and prevent injuries an old lid might not. While pricy, every helmet in our tech analysis (Page 24) is cheaper than an emergency room visit. That’s not counting the costs, financial or otherwise, of sustaining a brain injury.
Your conventional helmet is obsolete and may not protect you from the impacts you’re most likely to experience; those which are also most likely to damage your fragile brain. MCN
Dr. Mark Barnes is a clinical psychologist, in private practice, and author of “Why We Ride,” excerpts from 20 years of MCN columns.