What is Gmax?
Gmax measures the shock attenuation of sports surfaces. The higher the Gmax value, the less absorption of force by the playing surface and the greater the magnitude of impact on the athlete. The Synthetic Turf Council recommends a maximum Gmax of 165 and an annual testing of stadium fields.
Who should test?
Your synthetic turf installer may be required to maintain your field to a Gmax standard specified in your warranty. Self- testing is often biased. An independent ASTM compliant test performed by The Outsiders will ensure accurate data and meaningful documentation.
At 10 designated test points, a 20 lb. missile is dropped from 24 inches three times. The average Gmax value of the second and third drops are recorded and reported along with the infill depth and turf temperature at each location. The testing is conducted in compliance with the American Society for Testing and Materials standards. www.astm.org .
Gmax testing results show areas of concern. Gmax values over 165 indicate maintenance, repair or replacement is advised. ASTM specifications state that if values equal 200 or greater the field should be taken out of use until it can be brought into compliance.
High Gmax Can Create Liability
As an owner or field manager, you have an obligation to provide safe facilities. Where standards exist, you should ensure that your facilities are in compliance and that you and your organization aren’t exposed to unnecessary liability if an injury occurs.
As an athletic director or coach, you have a “duty of care” to the athletes under your supervision. Your “duty of care” encompasses the obligation to make sure the facilities you use are inherently safe and properly maintained.
Location Gmax Data
|Goal Line, Center of Field
10 Yard Line, 63’ from Center
25 Yard Line, 40’ from Center Center of the Field
25 Yard Line, 63’ from Center
|12 Yard Line, Center of Field||136||173||172||173||1.10||115|
|50 Yard Line, 12’ Out of Bounds||155||154||154||154||1.10||116|
|35 Yard Line, 5’ Outside Hashes||134||137||144||141||1.05||117|
|6’ from Goal Line, Center of Field||159||158||163||161||1.01||114|
|6’ from Back of End Zone, Center||145||147||145||146||1.08||118|
Many Atlanta Area Schools Fail to Test for Safety of Artificial Turf
September 10, 2018
ATLANTA - A FOX 5 I-Team investigation has found many local school systems are not conducting basic safety tests on artificial playing fields.
Artificial turf fields have become commonplace throughout metro Atlanta school systems.
It is called a G-Max test. A fancy name for a simple, yet intricate device, that essentially tests how hard an artificial playing field is.
“This (test) will let you know right off the bat, if a surface is soft enough” says Daniel Edmonds of Labosport.
Edmonds says his company can do all kinds of testing of artificial turf in the lab. They can check for longevity, bounce, failing fibers, and safety issues like knee and ankle injuries.
But, he says the most common safety test, recommended by the Synthetic Turf Council, is the G-Max test.
Researchers have found 10% of all concussions happen when a player’s head hits the field. And, concussions are more serious on artificial turf, according to sports injury researchers.
An international standards organization set a failing score on the G-Max test at 200.
According to Penn State Center for Sports Surface Research, Any G-Max score over 200 could cause life threatening head injuries.
The NFL wants a score of 165 or lower.
“It is hard to fail a G-Max test. (If you fail this test) you don't want to be playing on that field, says Labosport’s Edmonds.
We surveyed metro area high schools and found most school systems do not have a regular G-Max testing plan.
Cherokee county told us they ran a G-Max test on their fields when they were installed and again every two years. But, Cherokee county is rare.
Cobb, Fayette, Forsyth County and the city of Carrollton have done no testing. Fayette and the city of Carrollton have done no G-max testing. Cobb and Clayton told us they have not done regular testing since an initial test when the fields were installed.
Fulton said they only test at the end of the field's 8 year warranty.
Atlanta Public Schools has a lot of artificial turf fields, some for more than a decade. They have never done G-max testing.
But in answer to our survey, Atlanta claimed the school board approved a new G-max testing plan at the beginning of August. We have not been able to review the contract because APS says it is still negotiating with the winning bidder, and by law, cannot release it to us until it is signed.
Then, just a few days ago, Atlanta's facilities director sent out an email to all the metro school systems asking if they knew anything about this G-Max testing.
“Does anyone have any experience / knowledge of impact testing of synthetic turf fields?
Do you test?
What test do you use?”
Simple questions that have been around the industry for years. These Atlanta parents think it is high time, the city joined the club.
“It sounds like something that’s important it needs to happen for the safety of the kids. It would be beneficial if Atlanta would take the extra initiative to do those tests, absolutely, says the father of an Atlanta Public school football player, Aaron Simpkins.
And, another father, Jay Hare adds, “If the school can't pay for it, I would think our boosters would try to do something to make sure they were at least playing on a safe field.”