Synthetic Turf Field Testing HIC and GMAX
Aside from issues relating to playing dynamics and athlete performance, the risk of injuries is one of the main concerns for field owners, parents, athletes, and coaches when it comes to artificial turf. Despite this, synthetic turf has grown in popularity over the years.
Play surfaces are a critical factor in head and body impact injuries, and two of the most widely used methods for evaluating sports field safety are the HIC test and the Gmax test. But what exactly are these tests—and which one should you use?
What is the HIC Test?
The Head Injury Criterion Impact Test (ASTM F355E), or HIC test, is one of the most effective ways to measure the probability of head injury from surface impact. Multiple studies and experiments have assessed the effectiveness and limitations of HIC testing.
In 2010, World Rugby adopted HIC as the standard for impact measurement.
Concussions have become a major concern in turf-related injuries. According to the Concussion Legacy Foundation, 1 in every 5 concussions is caused by a player’s head impacting the playing surface. This highlights the importance of regular HIC testing by field owners, recreation providers, and operators to assess surface safety.
How HIC Works:
A 10.1 lb. hemispherical headform (HIC missile) is dropped from various heights.
It simulates the weight and shape of a human head.
Acceleration at impact is recorded and converted into a HIC value.
The critical fall height is the height where the HIC score reaches 1000.
For example, World Rugby uses a 1.3m standard, with a required HIC score under 1000.
What is the GMAX Test?
The Gmax test measures how well a turf surface absorbs shocks from impact. It uses a 20.0 lb. flat-ended missile, dropped at multiple field locations to evaluate shock absorption characteristics.
How Gmax Works:
Measures the maximum acceleration during impact.
Gmax is a ratio: impact acceleration vs. normal gravitational acceleration.
Higher Gmax values = worse shock absorption.
The ASTM standard limits Gmax to 200—anything higher is considered unsafe.
Some organizations, like the Synthetic Turf Council, recommend a stricter limit of 165.
Three drops are done per location; the second and third drops are averaged for the Gmax score.
Gmax testing has been used for nearly 20 years in synthetic turf, tracing back to the crash test dummies used by Ford and GM in the 1960s.
HIC vs. GMAX: Which Should You Use?
Both HIC and Gmax provide valuable insights into a field’s ability to absorb impact and reduce injury risk.
For head injury risks, the HIC test is highly recommended over Gmax.
For overall field safety, it's best to conduct both tests to ensure athlete performance and safety.
Beyond HIC and Gmax: Comprehensive Testing
To get a complete picture of turf field safety and performance, additional tests should be conducted:
- Vertical Deformation
- Energy Restitution
- Force Reduction
- Rotational Resistance
These tests are performed according to FIFA standards and offer a broader view of how the surface affects both safety and performance.
