Injuries on Grass vs. AstroTurf

Since its inception more than 40 years ago, artificial turf has become a popular playing surface for numerous sports in a variety of different venues. The concept of artificial turf was brilliant--a synthetic, nylon grass substitute that was easy to maintain and could be used in indoor sports facilities. Unfortunately, the use of AstroTurf became a subject of controversy when it appeared that, relative to grass, more athletic injuries were sustained while playing on the artificial surface.

AstroTurf and FieldTurf

• AstroTurf gained notoriety in 1966, when it was installed in the Houston Astrodome. The original artificial turf was little more than a padded carpet laid over a base of asphalt. It wasn't long before athletes began blaming their injuries on the new playing surface. Discontent with the original AstroTurf led to the development of FieldTurf, an artificial surface consisting of individual blades of synthetic grass separated by finely ground silica sand and rubber. The new and improved artificial turf was advantageous because it would absorb shock and give under impact similarly to natural grass.

Coefficient of Friction

• According to Dr. Mark Drakos, a sports medicine physician at the Hospital for Special Surgery, scientists claim there are two specific factors attributed to turf, be it natural or synthetic, that can affect injury rates. One is the coefficient of friction. The coefficient of friction represents the degree to which the surface "grabs" the foot and how much force is required for the foot to slip. When the coefficient of friction is high, more force is required for the foot to slide and players complain of their feet getting "caught in the turf." The original AstroTurf had a high coefficient of friction, which might explain the higher incidence of ACL injuries.

Coefficient of Restitution

• As stated by Dr. Drakos, the coefficient of restitution is the second factor influencing turf-related injuries and is simply the surface's ability to absorb shock. He explains that G-Max values are ratings assigned to describe the shock absorbency of different materials. The higher the G-Max value, the harder the surface. For instance, concrete has a very high G-Max value, while the G-Max value of grass is relatively low. The United States Consumer Products Safety Commission regards fields having G-Max values greater than 200 as unsafe because they cause higher injury and concussion rates.

Original AstroTurf Injuries

• The original AstroTurf appeared to be responsible for increased incidence in injuries among athletes. The most frequently encountered injuries included anterior cruciate ligament (ACL) tears, concussions, and ankle sprains. Injuries specific to the artificial turf also surfaced, including turf burns and turf toe--a condition of pain at the base of the big toe that results from playing on hard surfaces. Athletes complained of increased muscle soreness relative to that experienced after playing on a grass.

FieldTurf vs. Grass

• According to the NFL's Injury and Safety Panel, players were 27 percent more likely to experience lower limb injuries when games were played on the new and improved FieldTurf instead of natural grass. ACL tears and ankle sprains represented the most frequently encountered injuries. Knee sprains were also a common occurrence. Other studies indicate that fewer head injuries occur on the artificial turf because it is softer than natural grass surfaces, which tend to become quite hard when dry or frozen. In fact, the playing surface with the highest G-Max rating is frozen grass.