Concussions & The Kid-Friendly Gmax
February 16, 2010

Concussions, and their incidence in collision sports like football, have become a major news story in recent months.  The sport as a whole, and the NFL in particular, has come under fire from the media, the general public, and even US Congress, and has had to answer some tough questions about what is being done to ensure safe playing conditions, particularly as they relate to head injuries.

The NFL has acted quickly, implementing new medical standards and procedures for return to play, promoting the issue nationally through a PSA program during game broadcasts, and planning for further education of players.  However, as we approach Brain Injury Awareness Month in March, no one is talking about the role that playing surfaces may have in these types of injuries. 

Recently, the results of a study out of the University of Michigan were released that showed an increased risk of dementia and alzheimer’s in retired NFL players.  That sparked a deeper look at the issue and people were alarmed to find that the incidence of these types of injuries is fairly high, and the standard for diagnosing them is vague at best.  Concussions have been a concern in the sports medical community for years.  But because the symptoms can be so wide ranging, and reactions can be so individualized, they have always been hard to diagnose.  What we know now is that even though severe head injuries are rare, they can be life altering, as the Michigan study shows, and even life threatening.  But more concerning has been the realization that the effects of even a mild concussion can be cumulative and can have some long lasting effects.

“The NFL reaction has been positive and will definitely make inroads in how these injuries are treated,” said Grant Hendricks Jr, president of G9 Turf.  “But we feel that there are some proactive and preventative measures that can be taken towards addressing the issue.  There have been discussions about rules changes to the game of football, new equipment, improved oversight post-injury, but the one thing no one is talking about is the fields the athletes are playing on.”

Sports provide many opportunities for head to surface impact.  Striking the surface during a fall is actually the most common reason for occurrence of head injury.  Research shows that 44% of all concussions occur as the result of a fall.  A study done in 2000 involving HS and college football players in North Carolina showed that 10% of sports-related concussions were a result of impact between the head and the playing surface.  The same study found that the incidence of surface-related head injury on artificial turf was double that of natural turf, and 22% of artificial turf related impacts resulted in more serious Grade II injuries, compared to 9% on natural turf surfaces.  There are over 5,000 synthetic turf playing fields in the United States, and that number is growing exponentially.  As more and more of these fields go in the ground, our concern should be making sure that the kids who play on them are safe.

The best way to do that is through testing and maintenance.  There’s a term called Gmax that needs to find its way into the discussion about concussions.  Gmax testing is used to measure the shock-absorbing properties of sports surfaces - including synthetic turf fields.  The higher the Gmax number, the harder the surface, and the lower the shock-absorbing properties of the surface. Basically, the harder the surface, the greater the amount of impact absorbed by the body, or in the case of a concussion, the head. 

“The American Society for Testing and Materials (ASTM) established a voluntary standard in the 1930’s that said Gmax levels should be set at 200 or less, but that is a threshold for “life threatening” brain injury,” said Reed Hendricks, a vice president at G9.  “We think that number should be significantly lower.” 

More recent studies show a high correlation between Gmax levels and the severity of head injuries sustained in a fall. In fact, a Canadian study in 1995 found that falls which occurred  on playground surfaces with a Gmax exceeding 200 had an injury risk that was three times greater than falls on surfaces with a Gmax rating below 150.  The good news is that Gmax number can be managed through some simple maintenance procedures.

“There’s a common misconception that synthetic turf surfaces are maintenance free,” Reed added.  “You don’t have to water synthetic turf.  You don’t have to seed it, fertilize it, or treat it with pesticides, which are all positive aspects of synthetic turf systems.  But they are NOT maintenance free.   You have to maintain the components of the system.” 

“Over time, the infill materials within these synthetic turf surfaces become hard and compacted,” says Grant.  “This is a result of several factors, including heavy use, rainfall, and atmospheric pollution that is common in most environments.  Once compaction begins approaching that 200 Gmax number, issues of safety and field playability become a concern.  Compacted infill will also clog the drainage system under the field.  Once that happens, rain water begins to build up and puddle on the surface, which makes the field slick and unplayable in most cases.”

There are services and equipment currently available in the industry that can help decompact infill and keep fields soft.  With the right program you can decompact infill, lower Gmax, and in the end make the field safer for the kids who play there.  The same is true of many city playgrounds and parks, which have also moved towards synthetic surfaces.

“The concussion issue is an important one, and something that is going to require further study,” Grant says.  “With that, I think you are going to see a greater focus on the shock attenuation properties of synthetic turf and the best ways to manage those properties to ensure the safety of the fields.  The important thing for people to realize, both installers and the people who manage and use these synthetic surfaces, is that maintenance is an important and viable option when dealing with issues like this.  We have to think proactively and find ways to try and prevent these serious head injuries, not just find better ways to deal with the resulting effects.”

Clearly, more research needs to be done on the issue, and not just at the NFL level.  This is an issue that more directly affects over 30 million active children in our country who participate in youth sports.

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