A few weeks ago, Trek and their subsidiary company Bontrager dropped what they described as a game changer: their new WaveCel helmet design. Their claims certainly sounded amazing, with Bontrager stating that WaveCel is 48 times more effective than standard foam helmets at reducing concussions caused by cycling accidents.

We had many questions: how does the WaveCel act to reduce concussions and traumatic injuries? What do these claimed numbers mean? Is this technology the real deal?

A basic understanding of head injuries was key to unpacking how this helmet technology has been developed and assessed. In this article, we explore head injury physiology, look at existing technologies and how WaveCel seeks to overcome some of the limitations of existing products. We dive into some literature produced by Bontrager, and the resulting helmet wars between Bontrager and competing helmet protection heavyweight, MIPS; look at what the gaps may be in their testing and claims; and finally what this means for your head and helmet choices.

Head injuries and traumatic brain injuries

Head injuries and brain injuries are distinct, but overlapping terms describing damage occurring to the external head (skull, scalp) and the internal brain and structures respectively (oedema or swelling, diffuse axonal injuries, subdural bleeds and concussions). Head injuries such as lacerations and skull fractures require the head to be struck by an external force to damage the head and skull directly. Helmets have long been used as a safety measure to mitigate these type of injuries, however reduction of internal traumatic brain injuries (TBI) occurring inside the head has been highlighted as a potential area of improvement for cycling helmet safety.

Why the distinction? Well this is because of the nature of the brain itself. The brain and it’s vasculature exists within the rigid outer bucket of the skull: essentially like a slightly gelatinous baked custard in a rigid baking dish. The case of a rapid deceleration, head strike, and repeated shaking (or dropping the custard…) results in the soft, squishy brain striking the outer shell of the skull resulting in injuries to the brain.

Previous studies have shown the even when the custard remains in the bowl…errr skull, the brain is highly susceptible to damage from shearing strains induced by angular head acceleration. In the instance of a bike crash, it’s rare that one crashes directly onto one’s head, and hence the head is subjected to both oblique and linear forces in the case of a bike crash.

Extensive research on helmets have long focused on external damage from linear accelerations, however, the development and use of a standardised oblique testing matrix in order to test for internal head injury litigation through helmets in a lab setting has been largely ignored until recent years.

Outcomes of a traumatic brain injury can range from a mild concussion to death, and the chance of acquiring a brain injury when on the bike directly relates to impact height and speed, impact location and the peak linear acceleration. Lab-based testing seeks to translate these forces into brain-injury risk using the Abbreviated Injury Score (AIS) and Brain Injury Criterion (BrIC)1.

With the discovery of repeated concussions or mild sub-concussive hits being linked to a degenerative brain condition called chronic traumatic encephalopathy (CTE)2, concussions and head injuries have come into mainstream consciousness, as we now understand even ‘mild’ concussions can have devastating long-lasting effects.

1 Takhounts, E. G., Craig, M. J., Moorhouse, K., Mcfadden, J., & Hasija, V. (2013). Development of Brain Injury Criteria (BrIC). SAE Technical Paper Series. doi:10.4271/2013-22-0010

2 Stein TD, Alvarez VE, McKee AC. Concussion in Chronic Traumatic Encephalopathy. Curr Pain Headache Rep. 2015;19(10):47. doi:10.1007/s11916-015-0522-z