Monday, April 5, 2010

Head Injury Risk and Artificial Turf

Head injuries are far too common in both professional and youth soccer. While most concussions occur by the head striking another object (e.g. head to head) about 10% are due to the head hitting the ground. Some have suggested that the “hardness” of artificial turf increases the risk of this type of injury by increasing the impact between the head and ground. Others, however argue that the new, third generation fields are “softer” and the rubber infill may reduce head impact forces. In a attempt to settle this issue, researchers at Cardiff University performed biomechanical analyses of both grass and artificial turf playing surfaces.

The investigators recoded impact forces on six different types of artificial turf surfaces. These surfaces varied in their design and type of infill material. The surfaces were tested as “newly installed” and after a period of wear. They also tested a heavily watered, professional grass soccer field that showed varying degrees of wear.

Impact forces were recorded by dropping 4.5 kg (10 lbs) spherical object from different heights. The device conformed to specifications of the National Highway Traffic Safety Administration for studying head impact forces. Impact forces were converted into a Head Injury Criterion (HIC). A HIC of 400 is considered a 10% risk of traumatic head injury. Higher HIC values indicate greater risk.

The HIC values varied across the types of artificial turf surfaces. The best performers (i.e. lowest HIC) were designed with an underlying shock pad and a sand-rubber infill (at a ratio of 1:1). The weakest performers lacked the shock pad and used rubber only as the infill. Thus, including a shock pad and a sand-rubber infill seems be important issues in reducing head injury risk.

Wetting the fields by saturating them with water did not alter the impact forces or risk of head injury.

A well watered, well maintained grass surface outperformed all of the artificial surfaces. In fact, HIC values recorded on this surface were well below 400 indicating a very low risk of head injury. However, areas of high use had rather high HIC values. In most cases, these were greater than what was recorded on the artificial surfaces. The increased HIC values on the worn areas are probably due to the lack of grass and/or compacted soil increasing the hardness of worn areas.

Back to the original question, is there increased risk of head injury on the new, third generation artificial turf fields compared to natural grass? The answer appears to depend on the quality of the grass field. Well kept grass fields have lower risk potential than turf but fields that are heavily used have greater risk. The important issue seems to be maintenance of a grass field. A well maintained and sparsely used grass field may be the best option. However, most soccer grass fields are HEAVILY used throughout the year and have bare spots and areas of compacted soil. In these cases, head injury risk could be reduced by installing artificial turf.

Reference:

Theobald P, Whiteleg L, Nokes LDM, Jones MD (2010) The predicted risk of head injury from fall-related impacts on third-generationartificial turf and grass soccer surfaces: A comparative biomechanical analysis. Sports Biomechanics, 9:29-37.