Manufacturers' efforts to make modern artificial turf surfaces as much like natural grass as possible have succeeded in at least one regard: Two Norwegian soccer studies suggest that overall injury rates do not differ significantly between the two types of playing surfaces.

Closer analysis of the findings did reveal some differences between the two playing surfaces, suggesting that synthetic turf is associated with higher risks of some types of injuries and lower risks of other types.

Both studies were conducted at the Oslo Sports Trauma Research Center, and presented at the second World Congress on Sports Injury Prevention, held in Tromso, Norway.

In a three-season study of 14 Norwegian male professional soccer teams, the acute injury rate for matches played on grass (16.7 injuries per 1000 match-hours) did not differ significantly from the rate in matches played on artificial turf (15.1 per 1000). Only injuries that resulted in a loss of practice or playing time were included.

However, injuries incurred during matches played on artificial turf were more likely to be severe (resulting in more than 21 days missed) than match injuries sustained on grass. Mild training injuries (less than a week missed) occurred at a significantly lower rate on artificial turf than on grass. These findings are consistent with those of an earlier Norwegian study of more than 2000 young female soccer players, which was published in the August 2007 issue of the British Journal of Sports Medicine.

Another study of youth soccer players, presented in Tromso, involved more than 3000 matches played by elite girls' and boys' teams during two Norway Cup tournaments. That study found that playing surface did not significantly affect overall injury rate, nor the rate of injury resulting in at least one day of missed play. There were, however, some differences in the details.

Players were more likely to have back and head injuries on synthetic turf. But lower extremity and ankle injuries were less likely to occur on an artificial surface. In addition, the risk of injury for male players was lower on artificial turf than on grass, while the opposite was true for female players.

The studies' common finding -- that artificial turf does not affect overall injury rate -- is also consistent with a Swedish study of 290 elite male soccer players, which was published in the December 2006 issue of BJSM. In the Swedish study, however, playing surface was also not associated with injury severity.