As one of the biggest companies in the bike industry, Trek can always count on getting a lot of attention for its product launches. But in March, a teaser for a new technology it claimed only appears “once every 30 years” raised interest levels even higher. So what was it?

Turns out, it was a new kind of helmet. The brand’s four new lids combine conventional EPS foam with a new low-density, latticelike structure called WaveCel, which both compresses and shears laterally on impact to protect the brain. Along with the WaveCel-equipped helmets, which are now available, Trek released a study by the researchers who invented the technology. The study claims to show that WaveCel was up to 48 times more effective at preventing concussions than helmets with just standard EPS foam.

Some competitors were nonplussed by the bold safety pronouncements. MIPS, a company whose technology essentially popularized awareness of the role of rotational energy in brain injuries (and offered its own solution), responded by saying that MIPS was “unable to replicate” Trek’s performance claims in its own testing. (Trek’s headline claim failed to mention that the same testing also showed that systems like MIPS lowered the risk of concussion, if not as much as WaveCel.) A week after Trek unveiled WaveCel, Koroyd, which makes its own low-density cellular structure for use in sports helmets and other protective gear, issued a press release running down Trek’s claims and asked if Trek had been “carried away by a wave of hype.”

Faced with the Trek-said, MIPS/Koroyd-said spat, what are cyclists to make of the claims on each side? It’s a little hard to say at this point, but some context helps at least frame the issues and understand why this is such a contentious topic.

WaveCel is not a Trek invention; it’s the work of a team of researchers at Legacy Biomechanics Laboratory in Portland, Oregon, led by Michael Bottlang, a mechanical engineer with a background in biomechanics and orthopedics. Bottlang has been working on the technology for at least six years; an early version featured an aluminum honeycomb structure. Trek has the exclusive license to it for cycling applications.

Under impact, the EPS foam in a conventional helmet will compress, absorbing linear-impact energy. But EPS foam on its own does nothing to dissipate the rotational energy created when the head twists quickly under the force of impact. That energy, which causes the brain to move rapidly inside the skull, can bruise or tear delicate tissues and is widely thought to be responsible for concussions and other traumatic brain injuries that occur, even in the absence of skull fractures.

That’s where MIPS and other rotational energy systems come in: MIPS is a low-friction slip-plane liner that lets the helmet rotate independently to a limited degree and reduce some of those forces. MIPS handles only rotational energy, not linear-impact force. Trek claims that WaveCel addresses both. WaveCel doesn’t replace all the EPS foam in a helmet; Trek helmets with WaveCel still have a layer of EPS foam and the outer plastic microshell.

Bottlang’s team also led the clinical research that Trek relied on for its claims. The team included researchers from Bottlang’s lab and the University of Strasbourg’s Institute for Fluid and Solid Mechanics, in France, and its findings were published in the March issue of the peer-reviewed journal Accident Analysis and Prevention.

To test WaveCel’s ability to dissipate rotational energy, Bottlang’s team dropped helmets fitted with weighted head forms onto an angled anvil and measured the resulting forces. The research found that while slip-plane systems like MIPS reduced rotational acceleration by 22 percent on average compared to standard EPS-only helmets, WaveCel reduced rotational acceleration by 73 percent, leading to a brain-injury risk of just 1.2 percent compared to 34 percent for MIPS. (Foam-only helmets saw the highest risk, at 59 percent). Based on that, Trek claimed a WaveCel helmet could be up to 48 times more effective at preventing concussions.

Those bold claims are what attracted MIPS’s attention. “Preliminary test results of WaveCel helmets by MIPS cannot substantiate these claims,” MIPS said in its press release. The company added that further testing was needed and that MIPS “cannot see that the helmets perform in a way that [justifies] the claims Bontrager/WaveCel makes in the comparison between WaveCel and other helmets/technologies.”

Some caveats are in order here. First, while the Legacy Biomechanics research was funded by a National Institutes of Health grant (not Trek), Bottlang and Legacy have a commercial interest in the technology by licensing it to Trek. So it’s fair for competitors to question their claims. Second, the peer-review publication is a solid step, but by itself it’s no guarantee of accuracy. Legacy’s findings are fascinating, but they’re preliminary and need to be replicated by other researchers.

MIPS admits that its own research is preliminary and that it does not yet have data it can share. The company did not respond to a request for clarification on whether it was testing via the same methodology that Legacy used, which included nonstandard approaches like a flexible neck on the head form, an attempt to replicate what happens to the head in a crash. Trek, for its part, did not respond to my question on whether it was in communication with MIPS about the test protocols and data collected.

In other words, we don’t even know yet if both sides are looking at the same data or using the same test standards. There are multiple helmet-certification standards worldwide: the CE for Europe, the AS/NZS for Australia and New Zealand, and the CPSC for the United States, to name three regulatory regimes. There are also voluntary standards, such as the Snell B95 certification, and more exploratory methods like the one the Legacy team used. But there is no single widely accepted test protocol yet for examining how helmets handle rotational energy and no time line for arriving at one.

So where does that leave cyclists? Is WaveCel markedly better at preventing concussions than other technologies? Or is it overwrought hype? At this point, neither Trek nor MIPS is in a position to answer the questions about their respective claims. Perhaps the best piece of impartial data comes from Virginia Tech’s Helmet Lab and its Star methodology, which is the only independent, widely respected testing protocol to address oblique impacts and rotational energy.

One of Virginia Tech’s most valuable contributions to the helmet-safety discussion is a qualitative score rating for helmets it tests. Two of Bontrager’s new WaveCel-equipped helmets, the Specter and the XXX, are now rated first and third respectively in its rankings. The twist is that the helmet in second is also a Bontrager, the Ballista MIPS, which does not use WaveCel. Further, the aggregate test scores of all three helmets are within one full point of each other (a lower score is better).

It’s great for Bontrager that the company swept the Virginia Tech testing podium. But the fact that it did so with two different helmet technologies means it’s impossible to say at this point whether WaveCel dramatically reduces the chances of a concussion compared to MIPS (or other systems Legacy didn’t test, like POC’s SPIN or 6D’s ODS), doesn’t reduce concussion risk at all, or does so but in a more modest way than Trek claims.

If you’re shopping for a helmet, here’s the best advice I’ve got for you right now: buy one that Virginia Tech rates four stars or better and that fits you comfortably. Keep it clean, store it properly (inside your house, not the garage, and away from direct sunlight), and replace it every five to ten years (as recommended by the Consumer Safety Protection Commission), because things like UV radiation from sunlight can degrade the microshell. (And always replace a helmet after a crash; EPS foam is not multi-impact.)

Most of all, remember that bicycle helmets don’t protect against every conceivable impact. If you do hit your head in a crash, seek medical help, and be attentive to symptoms like sensitivity to light and noise or mental or emotional changes like increased anxiety, irritability, or confusion, which can be signs of a possible concussion or more severe brain injury. There’s growing evidence that mild brain injury can cause chronic health issues and is strongly linked to an increased risk for depression. As much as we are grateful that companies like Trek and MIPS are trying to improve ways to protect your head, you only get the one. Take care of it as best you can.