Performance Testing on Synthetic Turf Fields

There are many testing standards within the synthetic turf industry. One of the standards growing in popularity is the “FIFA Standard” or FIFA Quality Programme as it is officially called. FIFA implemented quality standards as far back as 2001 to ensure football (soccer) surfaces could be designated with a FIFA quality mark, meaning the surfaces were up to their standards. Revisions to these standards have occurred since then with the latest revision in 2015.

The FIFA Standard covers performance measures ranging from ball roll, ball bounce, and foot traction, to surface heat, surface planarity, and even turf yarn thickness. The commonly referenced tests within this standard are Vertical Deformation, Energy Restitution, Shock Absorption (formerly known as Force Reduction), and Rotational Resistance. These first 3 tests are completed using the Advanced Artificial Athlete (AAA – Figure 1) while the fourth test uses a mechanical torque wrench (Figure 2) attached to a weighted test foot with cleat studs (Figure 3)

USGreentech Performance Testing - Advanced Artificial Athlete (AAA) USGreentech - Performance Testing -Rotational Resistance USGreentech - Performance Testing - Cleat Studs
Figure 1 - Advanced Artificial Athlete (AAA) Figure 2 - Rotational Resistance Figure 3- Cleat Studs

Vertical Deformation is the measure of how much a surface gives underfoot. To picture this, think about planting your foot onto a concrete floor versus a trampoline. The concrete floor would have a very low vertical deformation while a trampoline would be high. Athletes want a firm surface but also some give to help protect their ankles and joints.

Shock Absorption is exactly as it says, the measure of shock absorption percentage by a surface. A lower score indicates a surface is harder and is absorbing less of the impact. This means vibration from the impact may travel back through the athlete’s legs. A higher score indicates a surface is absorbing a higher amount of the shock, with less vibration traveling back to the athlete’s legs.

Rotational Resistance is the measure of surface traction. Cleat studs are attached to a weighted device which when turned measures traction in Newton meters (Nm). A higher score indicates higher traction while a lower score indicates low traction.

Although not part of the current FIFA standard, these test are still important:

Energy Restitution is the measure of how much energy as a percentage is returned from a surface to the athlete. A good way to think about this is to imagine running on the beach…that would be nice right about now wouldn’t it? Running over compacted wet sand will have a higher Energy Restitution meaning energy is being returned to the individual. Running over dry sand that gives underfoot will return less energy because more is being absorbed by the surface, therefore causing fatigue to the individual.

G-max is a test that is effective at measuring body injury impact rather than head injury impact. This test involves dropping a 20-lb, flat-ended missile akin to a torso or body part. G-max measures how well the turf system absorbs the impact. G-max scores should not exceed a score of 200 G’s according to ASTM or a score of 165 G’s according to the Synthetic Turf Council.

HIC is a test for Head Injury Criterion. To test for HIC, a 10.1 lbs hemispherical missile is dropped from various heights and the impact of the fall is measured. The missile is designed to simulate the shape and weight of the average human head. Within the missile is a device that measures the acceleration of the missile at impact. The peak acceleration is used as a measure of impact severity. The HIC tests provide a value on a scale of 0 to 2,000 and correlates to a drop height at which a score of 1,000 is achieved. This height is called the critical fall height. World Rugby has adopted a 1.3 meter standard which means that at 1.3m the HIC score must be less than 1,000.

You may instinctively want your turf to score at the minimum or maximum for some of these tests, but in fact there is an ideal range according to FIFA. These ranges have been set based on scores from testing conducted on natural turf fields. Below are the ideal FIFA ranges for the tests mentioned above:

TEST Vertical Deformation Shock Absorption Rotational Resistance Energy Restitution
SCORE RANGE (LAB) 4 to 11 mm 57 to 68%

27 to 48 Nm

No FIFA range
SCORE RANGE (FIELD) 4 to 11 MM 55 to 77%

25 to 50 Nm

No FIFA range

According to Jeff Gentile, Director of Operations at Firefly Athletics/Sports Labs USA, “In the 2015 manual, FIFA added a wider range for several performance tests when the testing is completed in the field rather than the lab. This accounts for the variable conditions experienced in the field like that of compaction, gradation and weather which are not as controlled as in the lab. Also lab testing occurs over concrete and field testing is typically over a gravel base. The impact to the performance scores is often a slightly softer surface after installation compared with the system when tested in the lab. This wider range recognizes these differences and helps account for the associated impact.”

When reviewing test results, consider if the results are from a lab sample or an in-situ sample. Consider how new or how old the sample/field is. Age of turf/infill can play a factor in your results as your turf or infill can begin to degrade, compact, or simply migrate away. There are a lot of turf system characteristics to consider when designing a field. To learn more about what to consider for your upcoming synthetic turf field, call USGreentech and speak with one of our team members.

Picture of Ross Vocke, Operations Manager
Written by Ross Vocke, Operations Manager

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