On the heel's of Eric's article discussing one of the offseason's hot topics, I thought I'd finally throw together the science/medicine that is currently available on Fieldturf (and other third/fourth generation turfs).
I'll offer my own conclusions on the topic as well and leave my personal feelings regarding ND out of the equation (save it for the comments I guess).
I've also added the references and some extra studies' findings for those of you who want extra credit.
I'm sure there are more studies available than what I've included so if you know of any, I'd be happy to review them and add them to this review.
The scientific discussion of artificial turf can be divided into two parts: speed and injury risk. There is significantly more data available on the latter compared to the former. As with most things in science and medicine, we need more research in both.
There is really only one study (that I'm aware of) of collegiate football players assessing third-generation Fieldturf versus natural grass with respect to speed. The study was performed by Gains et al. It compared 24 redshirt freshmen D2 college football players on Fieldturf vs Natural grass in an agility drill (involving cutting) and 40 times. In the same individual 40 times did not differ between surfaces but proagility times appear to be faster on Fieldturf compared to natural grass. The authors would have to analyze more athletes to get to a statistical significance however.
The data/results: No difference in 40 times (Fieldturf: 5.34 ± 0.30 seconds, Grass: 5.33 ± 0.33 seconds). Proagility times (Fieldturf 4.49 ± 0.28 seconds, Grass 4.64 ± 0.33 seconds).
The best analysis to date looking at overall injuries across sports is a metaanalysis (study combining results/data from several studies) done by Williams et. al from Sports Medicine. Reviewing results from 20 cohorts (sets of data) in 11 studies, Williams et al found there was an increased risk of ankle injury on artificial turf compared to natural grass (data from 8 cohorts to form this conclusion). Knee injury data ranged from lower risk (0.4x risk) to higher risk (2.8x) on artificial turf so by this metaanalysis there does not appear to be a difference. In all other data sets, rates of injury were comparable between the two field types.
An important note regarding this metaanalysis is that 16 of the 20 cohorts were from soccer studies. Only 2 were football (1 high school, 1 college) with the final 2 being rugby. And the 2 football studies have a conflict of interest.
Football Injury Rates
Those two football studies were prospective studies done by Meyers published in the American Journal of Sports Medicine. Overall they're well designed but were funded by Fieldturf. That raises an eyebrow to me. Would the company fund research and allow it to be published if the data was all bad??
Meyers' first study from 2004 (with Barnhill) studied 8 high schools over 5 football seasons. Total injuries per 10 team games on Fieldturf 15.2 (13.7-16.4) compared to 13.9 (11.9-15.6) on natural grass. None of the data was statistically significant (including total injury rates) though there was a trend toward more minor and moderate injuries on Fieldturf, more severe injuries on natural grass (based on days missed as a result of injury). More noncontact injuries, skin injuries (i.e. abrasions), muscle trauma were seen with Fieldturf; More head, nerve, ligament injuries with grass.
His second study from 2010 looked at the college game. Injury rates were assessed for 24 universities' college football teams over 3 seasons (total of 465 games with 230 of those on Fieldturf). Per 10 team games, rate of total injuries was 45.7 (44.2-46.3) on FieldTurf vs 51.2 (49.8-51.7) on natural grass. The incidence of minor, moderate, and severe injuries were each lower on Fieldturf compared to natural grass. Authors also noted less time lost from injuries on Fieldturf. No significant differences in head, knee, or shoulder trauma were observed between Fieldturf and grass.
So as you can see, even with studies funded by Fieldturf, the results do not give us a very clear pictures. Only ankle injuries appear to be statistically more common on turf compared to natural grass at this point.
ACL Debate and the NFL
A hot topic that goes back and forth is ACL injuries. We have studies with data going back to the 1960s! So let's hit this in sequential order then get to the meat at the end of this subsection...
Nicholas et al followed one NFL team and analyzed injury data from 1960 through 1985 for regular season games (artificial surfaces instituted in 1968). Major knee injuries (those requiring missing more than 8 games) declined starting in 1969. It's difficult to make the leap to assume it was because of artificial turf though. They did note knee injury rates on turf vs grass were not different in comparing games on the two surfaces.
A study by Powell et al analyzing injury data in the NFL from 1980-1989 found a statistically significant increase in ACL tears and a trend toward more MCL sprains on Astroturf compared to natural grass.
A review of noncontact ACL tears was done by Scranton et al and published in 1997. 61 noncontact ACL injuries occurred in 22 NFL teams over a 5 year period (1989-1993) with 20 of these occurring on an artificial turf. Statistically, however, risk was increased on artificial turf compared to natural grass.
The last study I'll mention from the NFL comes from Bradley et al and published in Arthroscopy. Analysis was performed of injury rates in 31 NFL teams from 1994-1998. At the time 15 out of 31 NFL teams played on artificial turf. 209 ACL injuries occurred in this time frame - in practices more injuries occurred on grass than on turf but during games the number of ACL tears were equal comparing the two surfaces.
NCAA and ACL Injuries
A recent study by Dragoo et al assessed the NCAA ACL injury database to compare the two over a 5 year period through 2009.
The authors found 1.73 ACL injuries per 10000 athlete exposures (1 exposure being a game or a practice) on artificial turf vs 1.24 ACL tears per athlete exposure on natural grass. 318 total ACL tears were registered in the database over those 5 years. Or looked at another way, on an artificial surface athletes were at 1.39x greater risk of an ACL tear than on natural grass. As an aside, the study also found ACL tears were 10x more likely in games (8 tears per 10000 exposures) than in practice (0.8 per 10000 exposures) which fits with other studies done on the topic.
To look at it an even different way, assuming all 85 of your NCAA football players dressed for a game, you would have an ACL tear in one player on a team roughly once every 15 games, once every 147 practices. Assuming 120 practices/games in a year (an overestimate I'm sure), you'd have 1 additional ACL tear every 2 years if a team played exclusively on artificial turf compared to grass if the data from this study is correct.
It should also be noted only 10% of NCAA schools reported data for this study but there was enough data for a statistically significant difference. Did other schools not participate or did they not have any complete ACL tears?
CostThe third part (or parts) of the debate is really not something I'm well versed in: the costs of maintenance, installation, etc. Here is a link to a cost analysis from Fieldturf but I have to imagine this is altered for each individual school and installation.
Then the question becomes: if injury rates are mildly increased with Fieldturf and its cohorts, what kind of price do you put on injuries vs. a field holding up at the end of a game/season? I look at it like the intangibles of a football team - hard to analyze completely.
1. Players' straight line speed is not changed by Fieldturf. Speed with cutting and agility drills is likely faster on Fieldturf compared to natural grass.
2. Ankle injuries appear to occur more frequently on artificial turf compared to natural grass.
3. The jury is out on whether or not other injuries are more common with third/fourth generation artificial turf compared to natural grass (including ACL injuries).
4. My personal feeling is with more research you will likely see
a. More lower extremity injuries with Fieldturf (ankle sprains, ACL tears, other knee sprains) compared to natural grass - but will it be a negligible or slight increase? I think a minimal increase in ACL tears but a minor increase in ankle sprains.
b. More abrasions (though significantly less than Astroturf) and other skin conditions than with grass
c. Slight increase in muscle strains
d. No difference in concussions, upper extremity, back conditions, nerve injuries compared to grass
5. How do you balance a probable slight increase in injury risk against lower cost of a field and its ability to hold up at the end of a game/season?
Bradley JP, Klimkiewicz JJ, Rytel MJ, Powell JW. Anterior Cruciate Ligament Injuries in the National Football League: Epidemiology and Current Treatment Trends Among Team Physicians. Arthroscopy 18(5) 2002: 502-509.
Dragoo JL, Braun HJ, Durham JL, Chen MR and Harris AH. Incidence and Risk Factors for Injuries to the Anterior Cruciate Ligament in National Collegiate Athletic Association Football : Data From the 2004-2005 Through 2008-2009 National Collegiate Athletic Association Injury Surveillance System. Am J Sports Med 2012; 40: 990-5
Gains GL, Swedenhjelm AN, Mayhew JL, Bird HM, Houser JJ. Comparison of speed and agility performance of college football players on field turf and natural grass. Journal of Strength and Conditioning Research 2010; 24(10): 2613-7.
Meyers MC. Incidence, mechanisms, and severity of game-related college football injuries on FieldTurf versus natural grass: a 3-year prospective study. American Journal of Sports Medicine 2010; 38 (4): 687-97
Meyers MC, Barnhill BS. Incidence, causes, and severity of high school football injuries of FieldTurf versus natural grass: a 5-year prospective study. American Journal of Sports Medicine 2004; 32 (7): 1626-38.
Nicholas JA, Rosenthal PP, Gleim GW. A historical perspective of injuries in professional football: twenty-six years of game-related events. JAMA. 1988;260(7):939-944.Powell JW, Schootman M. A multivariate risk analysis of selected playing surfaces in the National Football League. Am J Sports Med 1992;20:686-694.
Scranton PE Jr, Whitesel JP, Powell JW, et al. A review of selected noncontact anterior cruciate ligament injuries in the National Football League. Foot Ankle Int. 1997;18(12):772-776.
Williams S, Hume PA, Kara S. A Review of Football Injuries on Third and Fourth Generation Artificial Turfs Compared with Natural Turf. Sports Medicine 2011; 41 (11): 903-923.
Additional Studies and Findings
These studies were included in the metaanalysis done by Williams et al. I have included the data down here for you guys...
Fuller CW. Clarke L. Molloy MG.Risk of injury associated with rugby union played on artificial turf. Journal of Sports Sciences. 28(5):563-70, 2010 Mar.
Injury risk was analyzed from 6 Hong Kong Rugby teams and 2 English Rugby teams on grass vs artificial turf over 2 seasons (only 451 total athletes). Overall injury rates and severity were not statistically different on each surface. There was a trend toward more ACL injuries on artificial turf vs grass (3.82x increased risk but not statistically significant, small sample size).
Bjorneboe J. Bahr R. Andersen TE. Risk of injury on third-generation artificial turf in Norwegian professional football. British Journal of Sports Medicine. 44(11):794-8, 2010 Sep.
14 soccer teams were followed over 4 seasons and injury data was analyzed artificial turf vs natural grass. 526 grass, 142 artificial turf injuries were recorded. Injury rates were 17.0 per 1000 match hours on grass vs 17.6 on turf. Rates for training were also similar - 1.8 on grass, 1.9 on artificial turf.
Ekstrand J. Timpka T. Hagglund M.Risk of injury in elite football played on artificial turf versus natural grass: a prospective two-cohort study. British Journal of Sports Medicine. 40(12):975-80, 2006 Dec.
290 European soccer players playing on artificial turf gathered injury data over a period of time (10 teams, range of 4-32 months of data collection) compared to 202 Swedish players playing on natural grass over > 10 months. 2.94 injuries per 1000 training hours noted on grass vs. 2.42 per 1000 training hours on artificial grass. During matches, 19.6 injuries per 1000 hours on turf vs 21.48 on grass. There were fewer ankle injuries on grass.
Dragoo JL. Braun HJ.The effect of playing surface on injury rate: a review of the current literature. Sports Medicine. 40(11):981-90, 2010 Nov 1.
More studies are needed but this review from November 1, 2010 included data from research done prior to that date. First and second generation turf were associated with significantly higher injury rates. Data suggests third-generation turf injury rates are similar to natural grass.
Fuller CW. Dick RW. Corlette J. Schmalz R. Comparison of the incidence, nature and cause of injuries sustained on grass and new generation artificial turf by male and female football players. Part 1: match injuries. British Journal of Sports Medicine. 41 Suppl 1:i20-6, 2007 Aug.
NCAA soccer teams were followed for two seasons (50+ mens, 60+ women's teams). Men's injury rates were 25.43/1000 player hours on turf, 23.92/1000 on grass. For women 19.15/1000 on turf, 21.79 on grass. Non-season ending injuries on turf lasted for 7.1 days on turf, 8.4 days on grass. For women 11.2 days on turf, 8.9 days on grass. No difference in ankle injuries or ACL injuries noted.
Fuller CW. Dick RW. Corlette J. Schmalz R. Comparison of the incidence, nature and cause of injuries sustained on grass and new generation artificial turf by male and female football players. Part 2: training injuries. British Journal of Sports Medicine. 41 Suppl 1:i27-32, 2007 Aug.
NCAA soccer teams were followed for two seasons (50+ mens, 60+ women's teams). Training injuries for men was 3.34/1000 player hours on turf, 3.01 on grass. For women 2.6/1000 player hours on turf, 2.79 on grass. Men's injury time for non-season ending injuries was 9.4 days on turf, 7.8 days on grass. For women 10.5 days on turf, 10 days on grass. Ankle injuries in men were higher on turf compared to grass though. No difference in ACL injuries.