Sports Medicine Research: In the Lab & In the Field: Playing Surfaces May Influence the Risk of Football Injuries (Sports Med Res)


Friday, October 12, 2012

Playing Surfaces May Influence the Risk of Football Injuries

The Effect of Playing Surface on the Incidence of ACL Injuries in National Collegiate Athletic Association American Football
Dragoo JL, Braun HJ, & Harris AHS. The Knee. 2012. Epub ahead of print doi:10.1016/j.knee.2012.07.006

An Analysis of Specific Lower Extremity Injury Rates on Grass and Field Turf Playing Surfaces in National Football League Games: 2000 – 2009 Seasons
Hershman EB, Anderson R, Bergfeld JA, Bradly JP, Coughlin MJ, Johnson RJ, Spindler KP, Wojtys E, & Powell JW. American Journal of Sports Medicine. 2012, Epub ahead of print.  doi: 10.1177/0363546512458888

Artificial playing surfaces are frequently used in athletics due to their cost-effectiveness and all-weather benefits.  However, the question remains whether or not these surfaces affect injury rates.  Several studies have demonstrated an increased rate of injury on artificial turf, where others have shown that there is no difference.  These two papers by Dragoo and Hershman investigate this concept, and pay particular attention to “third generation” or infill artificial surfaces which have a mat of artificial fibers that is filled with rubber particles.  The Dragoo et al. study used the NCAA Injury Surveillance System to gather anterior cruciate ligament (ACL) injury incidence data in football players across divisions and various playing surfaces from the 2004-2005 to 2008-2009 seasons.  This study demonstrated significantly higher ACL injury incidence rate on artificial turf (1.73 per 10,000 athletic exposures) when compared to natural grass (1.24 per 10,000).  This incidence rate is even higher when comparing infill surfaces (1.77 per 10,000) to either grass or other artificial surfaces without fill (1.43 per 10,000).  Most of these injuries were non-contact ACL tears, however, the study did not report if they were first time ACL tears or not. The Hershman et al. article examined lower extremity injury rates (i.e., knee and ankle sprains) on playing surface types in National Football League games between 2000–2009.  At the conclusion of the 2009 season, of the 6612 games played, approximately 60% of all games were played on natural grass, approximately 10% on older-generation turf, and 30% were played on infill artificial turf.  This study found that the injury rate for ACL sprains was 67% higher on infill artificial turf than on natural grass (injury rate was not normalized) and that there were significantly greater rates of eversion ankle sprains on infill artificial turf than on natural grass. 

Clinically, it appears that the artificial infill turf seems to have a higher ACL injury incidence rate; however, it is difficult to determine the cause of the higher injury rates.  As the manufacturing of artificial turf has evolved, it is important to look at the subdivisions and specific types of artificial surfaces as these two articles have.  The newer generation infill artificial turf is intended to be more like natural grass, yet clearly has different injury rates.  Manufacturers of the artificial turf will naturally combat this due to financial interests, yet two independent groups are echoing that infill artificial turf has higher ACL injury incidence rates.  As health care professionals, this may indicate a need to look closer at the possible reasons as to why ACL injury rates are higher.  Some people think it may have to do with the shoe/surface interaction, possibly looking at things like friction, torque, and stiffness.  Players likely wear cleats or spikes in natural grass, and wear some sort of turf sneaker on artificial surfaces.  Do you think that the playing surface can affect injury rates, or do you attribute these higher rates to other reasons?  Has anyone seen ACL injuries or any other injuries that seem to be more prevalent with athletes on artificial infill turf? 
Written by: Nicole Cattano
Reviewed by: Stephen Thomas

Related Posts

Dragoo JL, Braun HJ, & Harris AH (2012). The effect of playing surface on the incidence of ACL injuries in National Collegiate Athletic Association American Football. The Knee PMID: 22920310 

Hershman EB, Anderson R, Bergfeld JA, Bradley JP, Coughlin MJ, Johnson RJ, Spindler KP, Wojtys E, Powell JW, & for the National Football League Injury and Safety Panel (2012). An Analysis of Specific Lower Extremity Injury Rates on Grass and FieldTurf Playing Surfaces in National Football League Games: 2000-2009 Seasons. The American Journal of Sports Medicine, 40 (10), 2200-2205 PMID: 22972855


Alyson said...

Do you think that the playing surface can affect injury rates, or do you attribute these higher rates to other reasons?

I do believe that playing surfaces can affect injury rates, but it isn't an independent factor. The increased injury rate on infill turf field is a little bit concerning to me, because at the University I am a GA for, we have both an infill turf for practice, and then games are played on grass. Now, to me that brings up a whole new set of ideas. The players get used to the environmental constraint of infill turf and rubber while at practice and learn how to effectively move and accomplish movement goals with precision and consistency, but then have to carryover those skills, and learned movements to a different field type day. I realize there is a notion of being a highly skilled athlete and allowing for adaptation to occur and being able to adjust accordingly, but there is a disconnect somewhere, causing increased injury rates between the two surfaces. Is it stiffness, interaction of equipment, friction, or different force production, not sure. The shoe equipment change for athletes depending on surfaces playing on was interesting to me as well, and may contribute substantially to the increased injury incidence. Different shoes, surfuce, and atmosphere can all play a role in creating constraints to the body that will not allow for optimal movement capabilities. If the constraints are too much, injury may occur regardless.

Has anyone seen ACL injuries or any other injuries that seem to be more prevalent with athletes on artificial infill turf?
Unfortunately yes, we have some anecdotal evidence that supports this paper's discovery with our infill turf for practice for this football season.

Nicole Cattano said...

Alyson-Thank you for your comment. It is fascinating that your team practices on infill turf, yet plays on natural grass. I think you bring up an extremely valid point about this changing of surfaces possibly leading to more susceptibility to injury. Although I would almost expect athletes to suffer more severe injuries on game day, rather than practice days, due to the limited exposure to natural grass. If you were to work out injuries per contact hours on the field, do you still think that the rate is higher on the infill turf? Where I work, our football team practices on natural grass, then plays game day on infill turf. Your post has intrigued me and I am going to talk to our football AT to see what patterns he is noticing. This is a very interesting concept that definitely warrants a closer look. Has anyone else had clinical exposure to this notion of practicing on a different surface then where the team is playing games?

Kate said...

I do think that infill or turf fields can cause an increase in injuries, especially ACL tears due to the fact that they can get more traction when cutting and my athletes constantly report that when they tore their ACL on turf they felt like their foot was "stuck" but their body kept turning. However, I think what field they practice on makes a difference. For intense, like Alyson, my recent team practices on infill but plays on natural grass and this year all my ACL athletes have been injured on grass. I believe it is possible that if you practice on turf then your body and biomechanics may adapt to that setting and develop appropriate movements to decrease injury on that field. Therefore, the question could be asked, is it the playing surface in general or is it the playing surface that most teams aren't used to practicing on. As Hershman et al. found that 60% of games were played on grass so it can be assumed that most teams are more familiar with grass, which would be a possible explanation as to why more injuries occur on turf-they haven't developed the proper biomechanics to adapt to that environment.

Kirsten Miner said...

I work at a high school as a GA and our football team plays on infill turf and practices part of the week on that field if there aren't other games and part of the week on grass. This is my only year at this particular school so I can't speak on injury rates compared to past years or compared to when the school didn't have the turf field. This year we have had only 1 ACL injury so far and that occurred on infill turf during a game. I have noticed that the athletes wear cleats and not turf shoes when they play. Those of you who work at higher levels than high school do you notice if your athletes change shoes between the surfaces? I would be interested to see a breakdown of injuries between turf and grass based on shoe. Turf shoes were designed for use on turf and I wonder how many athletes wearing turf shoes on turf have a lower extremity injury and how many of those same athletes report feeling like their foot was stuck in the field. Should we be making more of an effort to not only practice on surfaces that we compete on but also changing footwear based on the playing surface?

Nicole Cattano said...

Kate and Kirsten-you both bring up really good points. I definitely think that there needs to be some sort of biomechanical adaptation period. But I kind of assumed that people chose footwear that was appropriate for be surface type. Most players at our institution change footwear based on surface type. I think that you both bring up a great point about this.

Kate said...

Kirsten- My football team does not change shoes based on surface. They wear the same cleats for both infill and grass fields.

Nicole Cattano said...

Kate-do your players report feeling any difference between surfaces with the same footwear, with or without injury?

William T. said...

Addressing the issue about footwear choice depending on surface:

I've noticed more so position specific for who chooses what. I've seen offensive linemen wearing turfs while skilled players will wear cleats. As once being an "athlete" I think the concept of having more traction and ability to change direction and stop on a dime is desirable for the skilled players. On that note I also think that since offensive linemen, if performing proper technique and not getting beat, will be able to keep their feet under them thus possibly having less an issue with traction and what not. Plus the extra weight they carry and decreased occurrence of trunk movement (shifting the line/center of gravity during play) may alter add to the feeling that one would need an extra edge to maintain traction.

The Sportsmedicine approach is that too much traction is not a good thing however I feel that given my situation you think about "you play like you practice" and if you're practicing on turf then playing on grass why change your footwear as well.

Since Alyson's last post, we finished the season with a total of 5 traumatic non-contact knee injuries; 1 being on grass during a game and 4 on turf in practice with 3 occurring in preseason.

Nicole Cattano said...

Thanks William. I couldn't agree with you more in your sentiment to practice how you play.

Very interesting about your jnjuries. Do you recall if your preseason injuries were towards the beginning or end of practice? Surface has been a primary suspect , but so has fatigue. Also, has anyone worked with some other turf/grass sports such as lacrosse or soccer that may reinforce or counter what has been found? I know football is very distinct, but I am just curious.

Brittany Cavacloglou said...

I think several factors listed above can play into ACL injuries especially when it comes to the field they are playing on and the shoe wear on their feet. Do you think athletes who play on different types of fields interchangeably experience more problems than athletes who stick to one field?

Jenna Robinson said...

I believe that artificial infill turf could have an effect on ACL tears but as far as injuries go I don't think it's an independent factor. I think it would be easier to sprain an ankle in grass, especially if the field isn't even throughout but at the same time slipping around on the turf during the rain or other harsh weather conditions can be crucial for performance. Like said, the friction and shoe style has a lot to do with injuries as well. Wearing regular running sneakers on turf is a lot harder to perform in considering no friction at all is being made. Turf shoes and cleats cause for a much greater amount of friction making it easier to run

Morgan Hooven said...

This study was very interesting to me. I would of thought that regular grass would cause more ACL injuries then the artificial infill turf. Regular grass has more holes and ditches while the turf is much more even. When playing on grass to turf, athletes need to wear different shoe wear. Do you think this change in shoe wear is causing injuries? Also, do you think that athletes should wear regular spikes on the turf field instead of wearing turf shoes?

Nicole Cattano said...

Great conversation from Brittany, Morgan, & Jenna. I've read a few articles that focus more on traction issues-which I think ultimately may be where this issue lies. Which is a great point bright up by Jenna. However there are different types of traction (lateral, rotational, & translational).

Morgan and Brittany, I don't think it's so much the issue of changing shoe wear. My opinion is that the body neuromuscularly adapts to training and practice on a certain surface with certain footwear. So the body expects certain amount of give during a cut, sprint, etc. Certain muscle firing patterns are made, and a change in friction coefficient can have adverse outcomes.

But I do think different shoes for appropriate playing surfaces would be a good thing.

Brandon Green said...

As a soccer player, I have to play with turf shoes on turf and firm ground cleats on grass to prevent ankle injuries. I tend to get lateral ankle sprains when wearing firm ground cleats on turf because of the excess traction from the studs. As an observing AT, I see more acute ankle injuries due to surface than any other injury. But I definitely believe playing surface plays a role in injury risk.

Joseph Russo said...

This study was extremely fascinating to me. I would of believed that consistent grass would bring about more ACL wounds then the manufactured infill turf. Consistent grass has more openings and trench while the turf is a great deal more even. At the point when playing on grass to turf, competitors need to wear diverse shoe wear. Do you think this adjustment in shoe wear is bringing about wounds? Likewise, do you imagine that competitors ought to wear customary spikes on the turf field as opposed to wearing turf shoes?
Seattle artificial turf

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