by Sara Behn, Boone County Hospital Foundation Director
Experienced, careful bike riders crash every 4,500 miles on the average. Head injury causes 75% of our 600+ annual deaths from bicycle crashes. Medical research shows that a bicycle helmet can prevent 85% of cyclists' head injuries.

A helmet reduces the peak energy of a sharp impact. This requires a layer of stiff foam to cushion the blow by crushing. Most bicycle helmets do this with expanded polystyrene (EPS), the white picnic cooler foam. Once crushed, EPS does not recover. Another foam, expanded polypropylene (EPP), does recover, but is much less common. A stronger EPS called GECET appeared in 1992 and is widely used now. Another foam called EPU (expanded polyurethane) is used in Taiwan. It has a uniform cell structure and crushes without rebound, but is heavier and requires a manufacturing process that is not environmentally friendly. The spongy foam inside a helmet is for comfort and fit, not for impact.

The helmet must stay on your head even when you hit more than once--usually a car first, and then the road. So it needs a strong strap and an equally strong fastener. The helmet should sit level on your head and cover as much as possible. Above all, with the strap fastened you should not be able to get the helmet off your head by any combination of pulling or twisting. If it comes off or slips enough to leave large areas of your head unprotected, adjust the straps again or try another helmet. Keep the strap comfortably snug when riding.

Most helmets are made of EPS foam with a thin plastic outer shell. The shell helps the helmet skid easily on rough pavement to avoid jerking your neck. The shell also holds the EPS together after the first impact. Some excellent helmets are made by molding EPS in the shell rather than adding the shell later.
Beware of gimmicks. You want a smoothly rounded outer shell, with no sharp ribs or snag points. Excessive vents mean less area contacting your head, which could concentrate force on one point. "Aero" helmets are not noticeably faster, and in a crash the "tail" could snag or knock the helmet aside. Skinny straps are less comfortable. Dark helmets are hard for motorists to see.

A sticker inside the helmet tells what standard it meets. Helmets made for U.S. sale after 1999 must meet the US Consumer Product Safety Commission standard, so look for a CPSC sticker.

Coolness, ventilation, fit and sweat control are the most critical comfort needs. Air flow over the head determines coolness, and larger front vents provide better air flow. Most current helmets have adequate cooling for most riders. Sweat control can require a brow pad or separate sweatband. A snug fit with no pressure points ensures comfort and correct position on the head when you crash. Weight is not an issue with today's helmets.

Check Consumer Reports for the most up-to-date standards for helmets, at http://www.consumerreports.org or at http://www.bhsi.org/guide.htm


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