HELMET NEWS ARTICLE FOR DECEMBER 2004
THE HELMET, PART IV
by Dr. Ken
The November article of HELMET NEWS raised a question from a reader who
did not understand a statement made regarding the size of the impact area of
the helmet. Our reader noted that in earlier HELMET NEWS articles about
helmet safety and injuries, that I had stated that the shape of the helmet
was designed to deflect contact blows and that the goal was to have the time
of contact reduced as much as possible in order to protect the head and neck
areas. He assumed that if contact was made with "the smallest possible area"
on the helmet and then "glanced off", to use a phrase I had written, the
shorter the time of contact. He was thus confused when in the November
HELMET NEWS, I stated that "applied force to a smaller area, the greater the
pressure; the same applied force to a larger area, the less the pressure."
If a singular pressure is applied to a helmet as the running back smashes
into the line of scrimmage, we want that force to be dissipated over a large
area and we want it "off of the helmet" and thus off of the involved
bodyparts, as quickly as possible. The helmet's shape allows for this. In
layman's terms, the force is "spread out" over a wide area. If instead, the
pressure from the force that is applied to the helmet is very concentrated,
the pressure transferred to the underlying bodypart is greater. While it is
safest to have the smallest possible helmet strike the smallest portion of
the helmet of the wearer, we want that force to be "spread out around the
rest of the helmet shell" as much as possible, if that makes for an
understandable statement. However, we want to avoid transferring force
through the helmet and its lining in a manner that concentrates that force
in a very small area of the head, for example. Again, think of a nail. The
point is as small and as "sharp" as possible because this allows for the
most concentration of the force of the hammer hitting it to be transferred
and thus, the greatest penetration into the wood. We don't want that type of
pressure directed into our heads! Thus, we have a helmet shell shape that
deflects the blow and "spreads it out" as much as possible. While saying
that, remember that we don't want our running back to suffer a hit to the
helmet that covers a large area (picture Gene "Big Daddy" Lipscomb's helmet
smashing into a sixth grader's youth model) as that would increase the
chance of injury.
The helmet's ability to transfer or in our example, dissipate force, lies
in part to its rigid nature which allows it to absorb the blow as a singular
unit. This reduces the pressure at the point of contact, making for a
"safer" hit. If the helmet shell was not rigid and did not act as a singular
unit, the force would not be dissipated as well and the actual pressure of
the hit, of each contact, would be more concentrated and greater with more
injury causing potential. The inner lining of the helmet however, is a
"different story" because we want the force to be dissipated over a longer
period of time and the compression of the helmet's liner materials allows
for this. That will be discussed next month in HELMET NEWS.
