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Certified Gmax Testing

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Artificial Turf

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Gmax Testing Expectations

Assure the On-Going Safety Performance of Your Field

While the safety and performance of modern synthetic surfaces have improved tremendously (beginning with the use of sand and rubber infill in the 1990s), you can’t tell how hard a playing surface is just by walking on it. If the field is not performing well, there’s a real risk of head injury or other types of injuries to players. To assure the on-going safety performance of your field, it’s best to have it tested by a certified Gmax testing professional from Byrne & Jones Sports.

Gmax testing measures how many G’s of force a field can absorb upon impact, and how many are returned to the athlete. Our certified Gmax testers follow protocols set-up by the American Society for Testing and Materials (ASTM). A high Gmax test value means the field is absorbing less impact, and returning more force to the player (resulting in a potentially dangerous situation), than a low Gmax test value.

What You Can Expect From Your Gmax Test

During the test, we’ll determine a minimum of 10 test points on the playing surface of your field. Initially, we’ll take preliminary measurements at each test point, looking at the height of the turf fibers and the depth of the infill material. Next, we’ll perform three “drops” – letting a missile-like device fall onto the surface at each test point. To arrive at the final Gmax value for each test point, we average the results from the second and third drops.

The testing equipment also determines other values related to the impact –SI (severity index) and HIC (head injury criteria). However, the GMmax number is the one used to determine a field’s acceptability. According to ASTM requirements, every test point on a field should have a reported value of less than 200 G’s. (The National Football League obsoletes fields with a Gmax score of more than 165.) If you’re looking at building an all-new field, we’ll help determine what the ideal number should be based on the sports being played..

Since fields get harder over time, they should be tested at least once a year. The amount of the increase and the rate at which it occurs are tied to the original construction methods used on your field, the materials used, levels of play, environmental conditions and the frequency and types of maintenance.

Conducting Gmax testing immediately after a field is installed ensures that the initial specs were met and it also establishes a baseline. If your field’s Gmax numbers are too high, adding more infill can have a direct impact on getting the number reduced. Maintaining proper depth not only helps create safer playing conditions, it extends the life of the field because the infill helps to protect grass fibers.

An Investment in your Field’s and your Athlete’s Future

The cost of Gmax testing is a relatively small investment to be able to monitor and document the safety of your field. That investment in testing also helps in the liability department, showing that you’ve been proactive in terms of monitoring the condition of your field and doing other maintenance-related activities that are designed to keep it safe and playable.

Not every athletic field construction company will feature certified Gmax testers on staff. And the safety of your athletes is simply too important not to work with a contractor that can help assure the long-term playing performance of your field. Contact Byrne & Jones Sports today to schedule a Gmax testing for your playing field at 314-926-1888.










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