As we all know, concussions have become a major — if not THE major — issue in competitive contact sports, from the pros down to the peewees. And concussions aren’t limited to football, of course — just about every contact sport is dealing with the increase, including other field sports like rugby, lacrosse and soccer.

“Research using sensor devices has revealed that each year in the United States, there are over 1.5 billion impacts to the heads of youth and high-school football players,” says Chris Nowinski, founding executive director of the Sports Legacy Institute (SLI), who launched the Hit Count initiative in 2012 with SLI medical director Dr. Robert Cantu.

While a number of factors come into play when it comes to concussions, one that we have some control over as field designers and owners is the field surface itself. By properly maintaining and monitoring a field’s turf, we can at least minimize any concerns the playing surface could pose for player safety.

Putting Turf to the Test

Turf safety is measured by what’s called a G-max test, which measures the shock attenuation of a surface by dropping the equipment’s “missile” onto the turf and measuring the resistance and absorption rate. The resulting G-max value represents the ratio of deceleration upon impact to acceleration due to gravity. In other words, it measures how well the turf absorbs and slows the impact.

Right now, the American Society for Testing and Materials (ATSM) recommends keeping the G-max level below 200, with a vote scheduled in May to lower that standard to 165 — the maximum also recommended by the Synthetic Turf Council (STC). [Ed. Note: Results of the vote had not been published as of press time.] The NFL is requiring teams to maintain their fields below 165 as well. These lower numbers stem from growing research on concussions showing that any safety enhancements can help. So the lower the turf’s G-max value, the greater safety buffer the surface can help provide.

Typical native topsoil and natural grass turf systems, whether they’re USGA or ASTM sand, Kentucky bluegrass or Bermuda grass, inherently have a lower G-max value — usually in the 80–110 range. As such, synthetic turf manufacturers are trying to create turf systems that get closer to those naturally lower levels, which typically involves designing a field with a padded turf system. 

Historically, however, natural grass fields have not been tested. While, again, their numbers will be lower by nature, the variety of soil profiles in a field area, particularly in a city, make the safety level of natural grass fields harder to predict. While the NFL now tests its fields before every game — synthetic or natural — lower levels of competition don’t have the capacity or resources to maintain that same kind of rigorous program to ensure the turf is at safe levels. 

Keeping the G-Max Low

The best course for keeping G-max levels under the recommended standard, particularly on synthetic fields, depends on the level of play and the field system in place. Padded systems on fields reserved for only one sport per season, for instance, will be easiest to keep in the lower G-max value range. But for many schools, cities and organizations, that kind of exclusivity isn’t reality. In all cases, the most effective means for keeping a field in its best and safest playing condition is aggressive, field-specific maintenance. 

Depending on the field — most are sand rubber over a stone base — and the level of play, a maintenance schedule should include a series of checks and improvements throughout the year. For a synthetic field, that could include regularly checking infill depths to make sure the infill is uniform across the field as originally intended by the turf vendor. This check could be conducted in conjunction with grooming. Conducting a G-max test at least once a year is also recommended. But a field’s shock resistance may lessen over the course of a season, depending on play and the type and compatibility of the rubber and sand, so testing it more frequently ensures the levels stay in that lower range.

Maintenance is just as important for natural turf, too. Annual aeration is critical to decompacting the soil for the turf plants and helps the attenuation level of the natural grass level. Maintaining sufficient grass cover is also critical in providing a safe field. 

After conducting these sorts of regular field investigations, you get to know how the field reacts to your level of play and how attenuation levels change, so you can tweak the maintenance frequency to help the G-max levels stay consistently within the acceptable safety range over the course of a season or two. If that isn’t working, that’s a clue that another factor may be the issue. For synthetic fields, it could mean more aggressive maintenance is necessary, indicating that you should consult your vendor and design professional. 

Getting Started

If you haven’t yet developed a schedule or program for testing your fields for safety, the first place to start is with your field vendor. Not only are they most familiar with the field systems in place, but they will likely be able to coordinate G-max testing for you. In fact, for new fields, owners may want to consider making field safety testing a part of the installation contract or warranty. The contract or warranty language can ensure the turf stays below a G-max value of 165 for the length of the warranty. 

If your athletic department hosts a variety of turf systems, you may want to consider contacting a testing lab to devise an annual contract since the complexity and variety of surface materials may go beyond the scope of the original installation company’s work. Or, a good field design consultant can certainly assess your fields and recommend a plan for regular testing throughout the year.

The issue of safety, and concussions in particular, will only continue to get more scrutiny at all levels of play. While the field system and regular testing can help, maintenance is truly the best means for keeping your turf in the safe zone and doing your best to ensure the field is one less safety issue for players, coaches and parents to worry about.

David Nardone is a Principal and Athletic Field Specialist at design firm Stantec.