Appeared in The Helios, a Wayne State University College of Engineering newsletter. Summer, 2002
Wayne State University Bioengineering researchers are proposing adjustments to the inside padding of football helmets that they believe will reduce the instances and severity of concussions on the playing field.
Dr. Liying Zhang, a researcher with the WSU Bioengineering Center in collaboration with Professors King H. Yang and Albert I King, has developed a brain model that will give helmet designers a much better idea on how much padding to use at different areas of the head. The human brain has different tolerance levels depending on the direction of the "hit" (tackle), say the researchers, and current helmet design does not consider this directional difference.
Despite new tackling rules and the mandatory use of helmets, there are still more than 100,000 football players in this country who sustain brain injuries every year ranging from mild concussions to death. Dr. Zhang began studying the problem in 1998 after the National Football League Charity approached the center with its concern about head injuries to NFL players, particularly quarterbacks sacked by very large defensive tackles.
To improve the helmet, Dr. Zhang needed to know the force levels at various locations the head can sustain without experiencing injury, as well as the thresholds necessary for serious long-lasting ones. To quantify these differences as well as other factors that cause concussion, Dr. Zhang performed studies using a three-dimensional finite element human head model -- an update of the previously developed Wayne State University Brain Injury Model. The computer model has all the essential anatomical features of a human head, and using it, researchers can calculate internal stress, strain and pressure at all locations, at any given instant during an impact.
Dr. Zhang studied directional sensitivity and calculated how a helmet reduces brain injury risk, then developed and validated a three-dimensional model of a football helmet.
Next, Dr. Zhang analyzed data of head-to-head collisions based on reconstruction of hits suffered by players in the actual game, which was well documented on high-speed video taken at NFL games. Dr. Zhang then applied the speed and direction of impact of all 12 cases involving 24 players to the human head model. The stress and strain levels were used to correlate concussion suffered by these players.
Ideally, for the helmet to be effective, it should absorb most of the force delivered to the head and distribute the remaining energy over a large area at lower force levels. The helmet padding (or lining) is designed to protect the head and to provide comfort at the same time.
To protect against side impacts (the most vulnerable kind), the helmet lining may need to offer more protection around the temporal regions, says Dr. Zhang. The brain model she developed will give helmet designers a much better idea on how much padding to use at all locations in the helmet.
Unfortunately, rotation of the head cannot be eliminated because football players need to be able to rotate their heads during the course of a game.
Dr. Zhang will continue her research to recommend further adjustments in padding thickness, taking into account comfort and practicality -- the material shouldn't weigh too much, and the padding shouldn't be too thick. Additionally, she is developing a new brain injury tolerance surface that will take into account both linear and rotational impacts.
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