@2016 by  S.A.F.I.R. Hockey. All rights reserved.

Force

The force we are talking about when a body or head hits the dasher is represented by the Force = Mass x Acceleration formula. It was interesting to learn the different ways force is defined in various industries. In sports it seems "G-force" is commonly used. The "G" in G-Force stands for Gravity. 1G is the acceleration of a 1kg mass at the surface of the earth. At the surface of the earth, a 1kg mass has an acceleration of 9.8 meters per second squared.


Much of the research on force as it relates to the head and the neck of a body is measured in Newtons (N). One newton is the force needed to accelerate one kilogram of mass at the rate of one meter per second squared.

​​​Science and Engineering - A Layman's Education ​and Explanation

                                                                                                           by Marc Kapsalis, Founder

Probability of Injury

One thing I realized as I studied and learned about the problem we faced and the solution, was that it didn't matter how much "safer" our product was if it wasn't safe enough to keep the vertebrae in the neck from fracturing. This is the reason that although our testing shows we already have what would be the safest product on the market today, we haven't taken that step. For us its not about having the best product on the market, its about solving the problem of catastrophic injuries.


Mechanisms of injury

During my research I began to understand that the body is a unique "mass" to understand. For instance, as the head impacts the surface of the dasher, how the body, head and neck are all positioned or aligned will impact the likelihood and extent of injury.  There are many ways forces to the neck are described..."Axial", "Compression", "Translational", "Shearing", "Flexion" and "Extension" to name most of them. It appears that the majority of the injuries we see in hockey are to a large degree caused by "pure compression to the crown of the head". I further learned that it is not the initial impact of the head and the force the head places onto the spine that causes the injury. It is actually that the head has stopped and the mass of the body continues forward causing the neck to buckle. Typically this occurs in or around C4-C7. It's also interesting to note that a large majority of the catastrophic injuries are to players between the ages of 15 and 21. One must surmise that this due to three primary factors. First, the mass of their bodies, second, the speed/accelerations they can achieve, and third, the relative strength of their neck muscles to the other two aforementioned factors.


The Curve

I needed to either establish or find an existing, probability of injury curve for the cervical spine. Why the cervical spine? Because in every documented case in which a hockey player suffered paralysis we've found, it has been caused by catastrophic injury of the cervical spine. More specifically, it is typically what's called compression forces to the crown of the head. So what the injury curve will tell us is...what is the likelihood and extent of injury to the cervical spine at various levels of force.  There are a number of articles published on the subject and I have included some links at the bottom of the page. In the end, we know in order to significantly reduce the chance for a catastrophic injury to the spine we must get the forces to the neck upon impacting the dasher below 4000 N. Obviously, this would also have the potential to reduce every injury and eliminate many.

Click on name to be directed to article

Bishop and Wells - “Cervical Spine Fractures: National survey of neck injuries related to hockey, 1976 to 1983

Blackmore - Chancey  -  Cervical Spinal Injuries and Risk Assessment - InTech

IIHS Injury Ratings - Highway Safety Data (Will download on your computer)



For most of us, it's a challenge to understand the science and engineering behind many new innovations. Although our project is inspired by tragedy, it does give all of us an opportunity to learn more about how our bodies respond when forces are applied. I'd like to share with you what I've learned as our team has worked to solve the problem and significantly reduce the forces the body experiences when it hits the dasher.