Do We Really See More Injuries On Artificial Turf Compared To Natural Grass?

By Dev K. Mishra, M.D., President, Sideline Sports Doc

One of the most common questions I’m asked by parents at the start of high school football and fall club soccer seasons is “do you see more injuries on artificial turf compared to natural grass”?  Many of the high schools in the San Francisco Bay Area where I live have installed artificial turf fields and the same is true for prominent soccer complexes.  From the standpoint of field maintenance, the cost-benefit analysis seems to favor the artificial turf.  You can get many years of excellent function from a turf field, whereas grass takes a lot of money and effort to keep up especially in wet weather.

The quality of the artificial turf has improved tremendously over the past several years.  The “blades of grass” are much softer and cause far fewer abrasions on sliding than older versions; the rubberized undersurface seems to be forgiving; and the roll is true and reliable.  For these and some other reasons I happen to like the newer varieties of artificial turf a lot.

But the question of injury rates is not fully answered.  I revisited a study presented at a prominent orthopedic meeting in 2010.  The study has not been published in the medical literature but it did have some alarming statistics that should have us asking more questions.

The study has a somewhat confusing title: “American professionalfootball games played on FieldTurf have higher lower extremityinjury rates.”  If you stare at it a while you’ll figure it out.  The NFL Injury Surveillance System was used to compile statistics on injuries primarily to the knee and ankle from the 2002 through 2008 seasons.  The particular type of artificial turf used was a brand called FieldTurf.  Some NFL teams started using FieldTurf in 2000 and by 2008 there were 10 NFL stadiums with this surface. (I believe 13 stadiums have artificial turf fields in 2011, and several brands of turf are used.)

The injury rates on FieldTurf were dramatically higher than the authors found for games played on natural grass.  The injury rate overall per team-game was 27% higher on FieldTurf, the ACL injury rate was an amazing 88% higher, and the lateral ankle sprain rate was 48% higher.  All of those differences were statistically significant.

So what can we take away from this study, and does it help to answer the question I get asked?  First of all, this was a highly select group of elite professional athletes and it’s difficult to apply the results to youth sports. Other factors besides the surface may have contributed, such as the type of shoe. The type of turf used in 2011 is quite a bit different than that used in 2002, which could also change the results.  So this is just one study and we can’t get the answer to our question from it.  But at the very least a study like this should cause sports medicine professionals to ask additional tough questions.

My opinion is that from a practical standpoint it’s the quality of the field that counts most. There’s nothing better than a perfectly manicured grass field as a playing surface for most outdoor team sports- but that’s incredibly expensive. I can’t imagine there are many youth leagues or high schools with the kind of budget an NFL team has to maintain a beautiful grass field.  If the typical youth field gets soggy and ripped up by cleats it resembles a city of gopher holes. It’s an injury-creating nightmare.  If that’s our option I would favor one of the newer varieties of artificial turf without question.

This entry was posted in Ankle, Football, Knee, Prevention, Science, Soccer, Sports Science, Tips and Training. Bookmark the permalink.

16 Responses to Do We Really See More Injuries On Artificial Turf Compared To Natural Grass?

  1. scotty baxter says:

    While the injury rate for professional american football players show an ncrease in this report, it does not look at the whole status of professional sport on artificial turf. The speed of play has changed significantly with artificial turf. Everything is manufactured for increased speed; the specialized shoes, the absolutely smooth surface and the temperature control added by watering the surface prior to a game. If a player gets hit at 5 mph faster because of this technology, would you not expect an increase injury rate? Before the death knell is given, studies of other sports on turf should be included.

    • Dev Mishra says:

      Scotty, thanks for your insightful comments. The speed of play issue is interesting, and clearly more research is needed into this. There’s a definite place for high quality artificial turf fields in youth sports, we’re just trying to get a handle on where the risks and benefits are.

      • bradley says:

        Have you played on new Fieldturf? It’s almost exactly the same speed as real grass. Because you need to clean outdoor Fieldturf surfaces regularly; bird droppings create a great habitat for staff infection, the cost of maintaining a high end grass field and Fieldturf field is identicle. It just requires less manpower to do so.

  2. Michael C. Meyers, PhD FACSM says:

    Although I find the comments in the article interesting, one would encourage looking at studies that have actually been published in medical/scientific-peer reviewed journals. At this time, there are only two studies at the high school and collegiate level (published in the top orthopedic sports medicine journal) that have looked at the relationships between football injury rates and severity and these newer generations of artificial turf versus natural grass surfaces are limited. Meyers and Barnhill, conducted the first long-term, independent injury study comparing FieldTurf to natural grass (American Journal of Sports Medicine, 32: 1626-1638, 2004) involving eight high schools and 240 games over 5 competitive seasons. Our findings indicated significant higher incidences of minor time loss injuries, noncontact injuries, surface/epidermal injuries, and muscle-related trauma reported on FieldTurf– but a significantly higher incidences of serious 22+ days time loss injuries, head and neural trauma, and ligament injuries reported on natural grass. The only other longitudinal investigation on football, a more recent study by our group (American Journal of Sports Medicine, 38(4): 687-697, 2010) on college football injuries following a span of 465 games, involving 24 universities over 3 competitive seasons, indicated significantly lower total injury incidence rates, as well as significantly lower minor, substantial, and severe incidence of trauma on FieldTurf versus natural grass. Findings also indicated significantly less trauma on FieldTurf when comparing injury time loss, injury situation, grade of injury, injuries under various field conditions, and temperature. The article concludes that FieldTurf is in many cases, safer than natural grass. In summary, there are numerous studies presented at conferences–very few ever pass muster when subjected to medical/scientific-peer review.

  3. Jeff says:

    Hi – you mention ACL injuries and ankle, but what about overall knee pain, tendonitis, etc? With three kids playing year round soccer on mostly turf now, I have seen an increase in knee pain and my oldest developed tendonitis and had to have surgery. I am sure it was not all turf related, but over a few years it seems like they have more knee pain after playing on turf.

    • bradley says:

      Turf is bad. Marketing would tell you otherwise. All turf is on a concrete base. Put whatever you want on top of concrete and you still won’t get concrete to give any.

      • Bradley, the newer artificial turf surfaces have some form of soft infill rather than concrete. Sometimes this is a rubberized substance, and sometimes a mixture of sand and rubber.

      • Gordon Bevis says:

        Good grief, what a ridiculous comment. You drive to work on a concrete road, don’t you? Are you injured every day by the concrete road? Of course not; there’s soft cushioning and suspension (tires, springs, seat) between you and the road. Artificial turf has about 2 inches of soft cushioning infill between the base (which is virtually NEVER concrete any more) and the players. Impact attenuation is regularly tested according to published ASTM standards and fields are closely monitored to maintain acceptable Gmax levels over the entire life to the turf system.

  4. Glenn says:

    Some observations:

    o A turf field does not tend to induce the injuries caused by a poor grass field. A turf field remains uniformly as it is.

    o A turf field offers better traction than a grass field. This can reduce the injuries caused by poor traction on grass, notably collisions, despite any increase in the speed of play. But better traction can increase tear and strain tissue injuries (ACL!) on turf when the player can not escape or tear free from a bad position made worse by being locked in by excellent traction.

    o A turf field can seem soft on the surface but it can have a secondary hardness that does not absorb impact forces like a grass field… even a hard surface grass field. And this secondary hardness only increases with field age/compaction. Impact forces on turf can accumulate to cause soreness and related fatigue injuries. Play on turf can wear you down more than play on grass. Also, the primary softness of a turf surface can offer less support to foot muscles over time, again leading to fatigue injuries in the foot.

    o Turf is hotter than grass. Some will suffer dehydration on turf more than on grass.

    o Turf is degrading synthetic particles and gases. It remains to be discovered how these affect the athlete.

    On balance, I feel that turf vs. grass injuries is a practical wash. I’m glad to be playing on turf. But there are clear health and safety downsides to turf… I would take a pristine grass field over a turf field any clear day.

    • Glenn says:

      Example: Land unbraced on your shoulder on a turf field with its secondary hardness and good traction, and you may experience a bit more compressive force transmitted to your collar bone than would occur sliding outward on a softer grass field, causing your collar bone to break when it might not have on a grass field.

  5. I find the article and the comments to be intelligent and the points made are all well-taken. I only wish those who research and publish studies, or those we review publisehd research studies, would disclose the source of any economic benefit that they may, if at all, derive from the synthetic turf industry, sports field consultants, manufacturers, installers, etc.

    It is poor “medicine” to rely on lack of longitudinal studies as an excuse to endorse playing on artificial turf surfaces. The NFL Players’ Association, year after year, publishes surveys of players’ views on artificial turf v. grass surfaces. Nothing is more timely and longitudinal than that – year after year, the same gripe against artificial turf – more injuries, more career-ending injuries, etc.

    I would like to call your attention to yet aother study. The research study is by Mark R.Villwock, Eric G. Meyer, John W. Powell, Amy J. Fouty, and Roger C. Haut and it is entitled “Football playing Surface components may affect lower extremity injury risk.” The study was presented at the 2008 North American Conference on Biomechanics, August 5-9, Ann Arbor, MI (http://www.x-cdtech.com/nacob/Session5.html ). Funded by a grant from the NFL Charities Foundation, the study was published as “The effects of various infills, fibre structures, and shoe designs on generating rotational traction on an artificial surface,” in Journal Proceedings of the Institution of Mechanical Engineers, Part P: Journal of Sports Engineering and Technology, Vol. 223, No. 1 (2009), pp. 11-19.

    This little-known research paper by a group of biomechanical researchers at Michigan State University may have found the answer to why professional athletes disdain playing on artificial turf fields, with so many of them in NFL annual surveys believing that artificial turf fields injures them more than natural grass.

    The purpose of this study was to investigate the role of infill material and fibre structure on the rotational traction associated with American football shoes on infill-based artificial surfaces. A mobile testing apparatus with a compliant ankle was used to apply rotations and measure the torque produced at the football shoe–surface interface.

    This group of biomechanical researchers at Michigan State University may have found the answer to why professional athletes disdain playing on artificial turf fields, with so many of them in NFL annual surveys believing that artificial turf fields injures them more than natural grass. The purpose of this study was to investigate the role of infill material and fibre structure on the rotational traction associated with American football shoes on infill-based artificial surfaces. A mobile testing apparatus with a compliant ankle was used to apply rotations and measure the torque produced at the football shoe–surface interface.

    Full text: http://journals.pepublishing.com/content/g51027g43j450472/

    Excerpts:

    Injuries to the lower extremity are among the most frequent injuries in all levels of sports and often account for more than 50% of reported injuries (Fernandez et al., 2007). While translational friction is necessary for high-level performance during any athletic contest, it is generally accepted that excessive rotational friction results in high forces being transmitted to vulnerable anatomic structures which may then precipitate ankle and knee injuries.

    In the current study a mobile testing apparatus was developed to measure the torque produced at the shoe/surface interface on sixteen surface systems. It was hypothesized that the size and structure of the infill would affect the rotational resistance of cleated shoes.

    Infill material, fibre structure, and shoe design were all found to significantly affect rotational traction. The cryogenically processed styrene–butadiene rubber (SBR) infill yielded significantly higher peak torques than the ambient ground SBR and extruded thermoplastic elastomer (TPE) infills. An artificial surface with a nylon root zone yielded significantly lower peak torques than similar fibre surfaces without a nylon root zone. The size of infill particles and the presence of a nylon root zone may influence the compactness of the infill layer. These features may act to alter the amount of cleat contact with the infill, thereby influencing rotational traction. The amount of cleat contact with the surface may also be determined by the shoe design.

    Peak torques were significantly affected by playing surface…. FieldTurf and the native soil natural grass system produced significantly different torques than all other surfaces. This was in agreement with the trend in a comparable study performed by Livesay et al (2006). In the … analyses, all three infills were found to be significantly different from one another. The highest torques were associated with the cryogenic SBR infill. This infill consisted of fine crumb rubber particles capable of packing into a dense structure thought to increase a cleated shoe’s resistance to rotation. The lowest torques were associated with the extruded infill, a larger rounded cylindrical particle made of TPE, incapable of packing as tight as the cryogenically processed infill. The open structure of the extruded infill layer was thought to reduce the frictional resistance.

    Generation of excessive torque at the shoesurface interface was a factor of both the infill particle size and fiber spacing. The peak torques measured in the current study exceed injury levels based on cadaveric studies (Hirsch and Lewis, 1965). However, muscle stiffness has been shown to protect the lower extremity at similar torques

    (Shoemaker, 1988). Future studies using a more biofidelic ankle may help establish relationships between shoe-surface interfaces and the potential for ankle injury.

    Additionally, epidemiological studies of shoe and surface injury rates will be important for validating the injury risk potential of various shoe-surface interfaces.

  6. Dev Mishra says:

    These are all valid points. From the standpoint of scientific studies, Dr. Meyers correctly points out that the published scientific literature actually has evidence that some injury rates are lower on synthetic fields as compared to natural grass. And on the other side, the NFL Injury Surveillance System data does seem to show higher injury rates on turf. There are many, many factors involved in injury rates, and the playing surface is just one of those factors that deserves continued research.

  7. Jim says:

    I don’t think it’s a fact that a natural turn field will always be a destroyed if there’s a lot of rain. If it drains property, I think it holds up pretty well. Does it require care, yes, but I think people would rather help someone get rich selling artificial turf than pay some people to care for a grass field. Ultimately, you choose…your kids’ safety or the financial well being of some company. If you don’t stand up for your kids’ safety, you’ll be at the mercy of the marketing by some company. Plastic grass over a rubber base is not going to give the way grass does. Common sense means more injuries. It’s like a hard tennis court vs. clay. Clay is safer and not that much work to take care of, but it does take some effort to care for. But the payoff is playing injury free. If you don’t care about safety, you don’t care about safety.

  8. edcoil says:

    Should cleat length be considered on turf fields and different then grass? Say a 3/4 cleat on grass and use a 1/2 on turf?

  9. kiley strickland says:

    88% or more-there’s no comparison between natual grass and artificial turf.haven’t you seen how world class athletes are stumbling tripping and tearing their legs in half! How many men women boys and girls must be lamed before that failed invention is outlawed? Wes welker dan marino jerry rice antonio cromartie santonio holmes my sister and me an hundreds more have been hobbled after being in great shape then losing years dreams and quality of life and for what? Ask any athlete which is better and 99% will say grass. Just because you can do something doesn’t mean you should. The problem is turf causes you to bounce plus it grabs the edges of your shoe. Grass is the only surface football and other outdoor field sports should be played on. Please tell everyone and let’s save our people. So what if it costs more!

  10. Many scientists and sports analysts have already studied sports injuries and its correlation with artificial grass but the truth is, we always have contradicting findings that often mislead the users. I think that the decision is up to the consumer–whether they purchase it or not–based on the information that they’ve gathered and their financial capabilities.

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