A Need For New Bicycle Helmet Standards

Consumer Reports. June 2015.

I was excited when I skimmed a Consumer Reports (2015) on bicycle helmet safety to see a mention of ventilation and rotational injury. However, I was disappointed that no attempt was made to measure either factor. 

The article mentioned that most helmets today protect against linear impact injuries, but don't protect against brain injuries. Then it used the fact that the medical profession has a lot of difficulty quantifying brain injury, and used that issue as an excuse for not testing the effectiveness of helmets in preventing brain injuries.

While the medical consensus is that rotational acceleration of the brain is the cause of injury (Condi, 2015), there is no consensus about how or even whether a traumatic brain injury can be diagnosed at the time of an accident. Capillaries can be sheared, decreasing oxygen supply, without causing enough bleeding to be detected by CAT scans or MRIs. Axons can be stretched and damaged, but memory may not be affected by these losses until weeks after an accident.

However, it is relatively simple to create an inexpensive and disposable brain analog that can be included in a helmet to detect conditions likely to cause brain injury. These devices consist of a set of ink drops, enclosed in permeable membranes, and suspended in a liquid gel. If ink stains the gel, it may be assumed a brain would have been damaged. The depth of color indicates the amount of damage. (needs documentation)

The Kingston Impact Simulator (KIS) test (2013) has been used to test how helmets protect against angular impacts, which is assumed to cause rotation, but it does not directly measure rotation, nor does it consider impact from all possible angles.

The 1960's style leather helmets were criticised because they were not effective against impact injuries, which are the main cause of immediate death after an accident, but the old leather helmets actually prevented more brain injuries than most hard helmets, because most bicycle injuries do not involve high impact danger, but they do cause rotational motion that causes the most shearing of axons and capillaries in the brain.(Condi, 2015)

Clearly a bicycle helmet greatly improves the likelihood of surviving an accident. That fact is not in doubt.

However, I wonder how many of those bicycle accidents were caused by wearing a helmet? Helmets can cause accidents by causing heat build-up, by distracting the rider, and by blocking the rider's vision.

I know that all three of my bicycle accidents as an adult (prior to the "big one," when I wasn't wearing a helmet), happened because I passed out due to heat exhaustion because my bicycle helmet didn't allow adequate ventilation.

I've learned my lesson. I will never ride a bicycle without a helmet. But proper fit, and ventilation will be priorities in selecting a helmet. I'll also be aware of the temperature along the way, and I'll have a back-up plan to get out of the heat in case the temperature rises too quickly. (I already carried three bottles of ice water with me.)

I won't be satisfied that my helmet is providing the most important kind of protection until manufacturers start publishing Kingston Impact Simulator test results, which measure a helmets ability to shield riders from angular impacts that cause rotational injury. Most bicycle accidents happen at under 30 mph, and most brain damage under 30 mph is due to rotational injury, not impact injury. Helmet manufacturers argue that impact protection provides rotation protection, but that is an often repeated conjecture that conflicts with the results of angular momentum helmet studies (2004), because those studies demonstrated significant differences in the amount of protection based on the angle of impact. (Angle of impact translates into direction and degree of rotation.)

* When shopping for a helmet, I would like to know the Kingston Impact Simulator rotational impact test results, including whether test helmets were cracked during testing, and not just the degree to which the impact was reduced by the helmet
* I would like to see an airflow rating with best and poorest ventilation when riding into and away from a 20 mph wind at 20 mph. Vents must be designed with baffles that cause some airflow even when riding with the wind.
* I would like helmets equipped with heat alarms: a simple metal coil mounted inside a helmet expands with heat, and sets off an alarm when the temperature inside the helmet exceeds a safe temperature.
* I would like to see all helmets (bicycle, motorcycle, football, hockey, etc) designed to hold a cheap disposable dye capsule that responds to jarring and rotation the way the brain does, so dye beads suspended in a gel capsule stain the surrounding gel causing the gel to go through a range of color changes to indicate the likelihood and degree of brain injury after an accident. Emergency personnel could take a glance at this capsule and immediately know whether the individual has experienced a sub-concussive injury (because a series of "mild" injuries can cause serious brain damage), a concussion, or a more serious brain injury.
* I would like to see two-vector rotation impact test results showing the simulated level of brain injury (using disposable dye capsules) when a helmet protecting that capsule is dropped 4 feet onto a conveyor belt running at 30 mph (simulating a bicycle accident).


References:

The Best Bike Helmet for You: The bottom line on protecting your brain. (2015). Consumer Reports. Retrieved from http://www.consumerreports.org/cro/magazine/2015/06/best-bike-helmet-for-you/index.htm

Cai, X. (2015). A prototype helmet fitting system. Retrieved from http://qspace.library.queensu.ca/.../Cai_Xingcheng_201501...

Camarillo, D. B., Shull, P. B., Mattson, J., Shultz, R., & Garza, D. (2013). An instrumented mouthguard for measuring linear and angular head impact kinematics in American football. Annals of Biomedical Engineering, 41(9), 1939–49. doi:10.1007/s10439-013-0801-y
http://www.ncbi.nlm.nih.gov/.../PMC39.../pdf/nihms470591.pdf

Condi, F. X. (2015). Helmets, Sensors, and More: A Review. Practical Neurology, 15(2), 32–36. Retrieved from http://practicalneurology.com/.../helmets-sensors-and...

Foster, T. (2013, January). The helmet wars. Popular Science, 282(1), 50-77. Retrieved from
http://web.ebscohost.com/src/pdf...

Karton, C., Rousseau, P., Vassilyadi, M., & Hoshizaki, T. B. (2014). The evaluation of speed skating helmet performance through peak linear and rotational accelerations. British Journal of Sports Medicine, 48(1), 46–50. doi:10.1136/bjsports-2012-091583
http://www.researchgate.net/.../00b7d5203928b50ff8000000.pdf

Kis, M., Saunders, F., ten Hove, M. W., & Leslie, J. R. (2004). Rotational acceleration measurements--evaluating helmet protection. The Canadian Journal of Neurological Sciences. Le Journal Canadien Des Sciences Neurologiques, 31(4), 499–503. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/15595255

Kis, M., Saunders, F. W., Irrcher, I., Tator, C. H., Bishop, P. J., & ten Hove, M. W. (2013). A method of evaluating helmet rotational acceleration protection using the Kingston Impact Simulator (KIS Unit). Clinical Journal of Sport Medicine, 23(6), 470–7. doi:10.1097/JSM.0b013e318295a80f