It’s only when quality shock pads are used beneath infilled turf that the safety levels of natural grass can be achieved for players. We know this from the data collected from the GMAX test, the HIC test, and the AAA foot impact test on fields of all types. This produces a complete picture of how the field is performing from an impact safety standpoint both when newly installed and throughout its lifecycle.

The HIC test correlates with the likelihood and severity of a head injury. It has been used for decades in the auto industry and for playground surfaces, and was adopted by ASTM for athletic fields in 2018. The HIC impact test drops a 10.1 lb. hemisphere projectile (curved like a human head) multiple times from increasing heights and determines the surface’s Critical Fall Height. The higher the Critical Fall Height, the safer the surface. A good natural grass field will produce a minimum critical fall height of about 6 feet or higher.

The test method covers the measurement of surface hardness. It does not correlate with head injury. Landing on a harder surface transmits more energy to the body so common sense would tell you that a “softer” surface would be better. It’s applicable to natural and artificial playing surfaces. It drops a 20 lb flat missile from 24″. Gmax is a good measurement when used in conjunction with HIC, but as a stand alone test it is not a total measurement of safety. A quality natural grass field will produce a GMax typically below 100 G’s.

This test simulates the heel strike of an adult running athlete in stride. In other words, it measures the softness or hardness underfoot during play on a field. A great natural grass field hits the “sweet spot” of being firm underfoot while producing very low Gmax and high Critical Fall Height. This is why quality natural turf is the benchmark for quality artificial turf.