Up until that day, my top priorities for a helmet were that it look fly and be so comfortable that I didn't even know it was there. After all, the rivers I paddled were all deep and high volume. I thought the chances of hitting my head were about as likely as monkeys flying out of my butt. Sure, I had encountered the occasional scrape and bump when unavoidable rocks were parked right below choice play holes, but nothing like this.
The rapid--if you could call it that--was a shallow, innocent-looking Class II drop on a local play river. I never even gave drops like this a second thought after scaring myself silly on difficult rivers throughout my life. To top it off, the day was perfect--the sun was out, the companionship was stellar, and everyone was moving with fluid ease. One concussion, one cracked carbon-fiber helmet, and two compressed vertebrae later, I became a believer in bombproof head protection and felt a little less invincible.
Helmets, first and foremost, protect your gray matter. You might as well face it. You have only one brain, and damaging that one unit--regardless of whether you are paddling or riding a bike--could result in your being turned into a vegetable and taking meals through a tube stuck in your arm for the rest of your miserable life.
Helmets function by spreading the force of an impact from a relatively small point of contact over a larger area. They also provide cushioning in the event of a collision between your head and some harder object. They "manage" the impact into a sustainable force.
The first line of defense is the helmet's shell. It is generally agreed that a stiffer shell manages impact better by doing a better job of distributing the force over a larger area. Stiffer means materials such as carbon fiber and Kevlar; a few manufacturers are also playing with polycarbonate prototypes.
The lining of your helmet is the next, and last, line of defense before the force of impact is transferred to your body. Cushioning is important both for comfort and for protection. It permits a relatively small area of impact to be more evenly distributed to a larger surface area. Cushioning also aids in deceleration. When the head comes to an instant stop, the brain might not--it might slosh around within the skull. That's not good for it. Cushioning helps to provide a more gradual deceleration of your brain's movement.
Finally, the stiffest shell and the most energy-deadening foam can only work if your helmet stays on your head and doesn't ride up, down, or around an about-to-be-impacted head. A proper fit, which means that the helmet is snug throughout with no tight spots and that it resists movement while unbuckled, will allow the helmet to do its job.
It is important to note that in most product reviews, the gear can actually be tested as you might use it. Playboats are paddled on play rivers, camp stoves are cooked on, and so on. Lacking a volunteer who would allow me to drop rocks on his head, we based this review on observations of a helmet's comfort right out of the box, the degree of coverage it provides, and notes on the "outfitting." Fit is paramount, and in this case we used the guideline of how it fit out of the box with the manufacturer's provided fitting material. Keep in mind that you can make any helmet fit reasonably well given enough time, foam, and adhesive.
Selecting the perfect helmet is a little like selecting the perfect baseball cap. However, unlike a baseball cap, a helmet is protecting your most valuable asset, and the helmets listed are only a starting point. When selecting and trying on a new helmet, ask yourself if the piece of equipment that you are about to purchase is adequate protection. If any doubt exists, you are better off to continue your search.