Posted 3 November 2005. Applied Turfgrass Science.
Synthetic Turf Playing Fields Present Unique Dangers
University of Missouri
Columbia, Missouri (November 2, 2005) – Brad Fresenburg made a disturbing discovery when he took surface temperatures of artificial playing turf on a 2003 summer afternoon.
The University of Missouri turfgrass expert found that on a 98-degree day at MU's Faurot Field the surface temperature on the synthetic grass was 173 degrees. Nearby natural grass showed a temperature of just 105 degrees.
When Fresenburg took the temperature at head-level height over the faux turf, the thermometer registered 138 degrees.
Fresenburg said there's a national trend toward high schools and municipal recreation departments replacing grass with artificial turf -- once the almost exclusive purview of college and professional sports teams -- and he wants coaches and parents to know how to keep players safe.
"If they are going to have artificial fields, we need coaches, parents and players to know that temperatures on these fields are going to be anywhere from 150 to 170 degrees on some days," Fresenburg said. "You might as well be sitting in an oven somewhere."
The new generation of synthetic turfs are as safe, even safer in some ways, as natural grass, concluded Michael Meyers, a professor at West Texas A&M University. He has tracked playing field injuries in Texas high schools for eight years now.
Athletes tend to suffer injuries at roughly the same frequency on natural and synthetic turfs, but different surfaces tend to result in different types of injuries, he said. "There is more torque, more velocity and more traction" on artificial turf, Meyers said. That can lead to more muscle strains and spasms.
But natural grass has its own hazards, such as slippery mud or unseen potholes, and possibly in arid areas, harder surfaces. More concussions per games played occurred on natural grass fields.
The newer generation of synthetic turfs is "far superior," said Meyers, to previous types like the former industry standard Astroturf, which he described as basically a carpet and carpet pad laid over concrete. Now fields are built over surfaces in-filled with recycled rubber pellets and other materials that make for softer falls, mimicking natural grass and soil playing conditions.
The drawback, said Fresenburg, is that all those rubber and plastic materials amplify sunlight to cause near unbearable temperatures at certain times of the day.
Rex Sharp, MU's head athletic trainer, said he believes synthetic turf to be just as safe as grass. But he agrees that outdoor fields will get hotter under certain conditions. In his experience the artificial fields get at least 10 to 15 degrees hotter under the afternoon sun, he said. University staff constantly monitors field temperatures during practices, Sharp said.
Fresenburg suggested that sports teams schedule morning and evening practices, times when playing surfaces are cool. In the hot afternoon hours of August and September he said teams should seek out natural grass alternatives. Under any workout conditions, hydration of athletes should be closely monitored, he said.
MU has two artificial turf fields, the indoor field in the Devine Pavilion and the outdoor Faurot Field in Memorial Stadium. The older-generation turf used at Devine Pavilion is more tacky and prone to cause twisting-related injuries, Sharp said. The football players wear special cleats when practicing there. Faurot Field has the newer-generation FieldTurf brand surface. He said players can wear regular grass cleats there, and he believes that the surface is just as safe as natural grass.
Fresenburg is not so sure. Tests Fresenburg has done show increased potential pressure on joints and bones from the inability of a fully planted cleat-wearing foot to divot or twist out, an action that releases force. The traction on synthetic turf is much greater, he said.
"Grounds managers prefer artificial turf over natural because when teams play on grass, they leave divots and rip out grass," Fresenburg said. "Most people see those areas as damaged turf. I like to say those divots are a sign that the field is doing its job -- yielding to the athletes' cleats."
Fresenburg tested four turf types, three natural grasses and MU's Faurot Field using a contraption of cleats, weights to simulate an athlete's weight and a torque wrench-like tool. When a cleat was completely planted in Faurot Field, it needed an average of 110 foot-pounds -- a foot-pound is a measured unit of applied force -- of torque to twist free. That was compared to 81 to 85 foot-pounds needed on the natural surfaces.
"In some areas of Faurot Field, we maxed out the instrument at 120 foot-pounds," Fresenburg said. "The cleated foot simply wouldn't shear. That's not good."
The good news is that the difference only occurred when a cleat was fully planted in the field. When only a portion of the cleat simulating the ball of a foot was planted, the force needed to twist free was the about the same on all surfaces.
The hidden danger on an artificial field is the threat of bacterial infections, Fresenburg said. He said disinfectant should be sprayed as needed if there's a known infection risk, but Fresenburg said he doesn't know what procedures are necessary to prevent bacterial contamination in the first place.
"Natural grass has a microbial system. It's self-cleaning. These synthetic fields don't have that," Fresenburg said. "There's warmth. There's moisture. Bacteria can thrive in there. There's sweat, spit and blood."
Sharp said players need to immediately report any "turf-burns," abrasions so named for their similarity to rug burns. Turf burns are common on certain types of synthetic turf. They must be immediately washed with soap and water to prevent infection, Sharp said.
Often young athletes are inclined to ignore seemingly minor injuries, Sharp said. "We have done a good job of educating our students on turf burns," Sharp said. "We've had to educate our kids to let us clean and treat those."
Anyone interested in more tips on turfgrass safety can contact Fresenburg at (573) 442-4893.
"Many schools or communities may only look at the maintenance chores of natural grass when deciding to switch to artificial turf," Fresenburg said. "They should look beyond that. They need to look at all the differences between the two surfaces."