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Artificial turf in elite soccer, new finding give rise to new questions ~ Karolina Kristenson, MD PhD

Does artificial turf (AT) affect injury rates in football (soccer)? It is a question widely debated. Robust data states that artificial turf does not affect the general injury rate for acute injuries. Few studies, however, have included overuse injuries when comparing injury rates with AT and natural grass (NT).  Also, the aspect of rapid change between surfaces is often discussed among football players, trainers and clinicians, but no previous studies have evaluated whether this actually affect injury rates.

With this background, our research group (Football Research Group, Linköping Sweden) and The Oslo Sports Trauma Research Group (Oslo, Norway) initiated a research project. We thought that a study setting in the Swedish and Norwegian first male leagues was appropriate since a) artificial turf is common in the Nordic countries, and b) the leagues are similar in climate and standards. In this way, we could collect a larger data set, which is a prerequisite to be able to analyze injury pattern, such as the injury rate for different specific muscle groups.

Photo by See-ming Lee. Used with permission. All rights reserved. Source: flickr

Photo by See-ming Lee. Used with permission. All rights reserved. Source: flickr

During two full football seasons (2010 and 2011), we recorded injuries that led to absence from football as well as player’s individual exposure to football on grass and AT. In November 2011, we could sum up that 32/37 clubs playing in the first leagues during this period had participated for the full study period. This resulted in 1063 match injuries and 1178 training injuries registered during 48,922 match and 318,568 training hours.

We compared the acute injury rates on AT and NG at the individual player level (to see if this study would replicate the findings from previous studies). Also, in this study setting we were able to compare acute and overuse injury rates between clubs that have artificial turf at their home venue (AT clubs) and clubs that have natural grass (NG clubs).

Interestingly, the result we found was that professional football clubs with AT installed at their home venue had a higher acute training injury rate and overuse injury rate compared to clubs with NG. In particular, AT clubs had a higher rate of overuse injuries to the hip/adductors (60% increase) and calf (four-fold increase).

Also, AT clubs had a higher match injury rate during the competitive season, while no differences between AT clubs and NG clubs were found during pre-season. Still, at the individual level, no differences in acute injury rates were found when playing on AT compared to NG in the total cohort analysis.

Consequently, our study replicated the findings from previous research that there is no difference in the acute injury rate at the two surfaces, yet clubs playing home matches on AT have a higher injury rate. Why is that?

Our hypothesis is that the AT clubs´ higher injury rates could be due to a rapid switching between playing surfaces and inadequate adaptation to a new surface. Since there were fewer AT clubs than NG clubs in this cohort, players from AT clubs had to alternate between surfaces more often when playing away matches.

It is possible that such frequent shifts between surfaces could lead to a greater load on musculoskeletal tissues and an increased overuse injury rate. This could explain why a higher match injury rate for AT clubs was only evident during the competitive season when switching between surfaces at away matches occurred frequently, while match injury rates were similar during the pre-season, when most friendly matches were played on AT.

Of course, many questions still remain to be answered. Sweden and Norway are located in the northern part of Europe and cross several climate zones. It is possible that clubs with AT installed at their home venue could have chosen this surface because of the rough climate conditions, i.e. a generally colder climate, which itself could influence injury rates. It is also possible that clubs chose AT turf at their home venue because of the saving in costs. Therefore, the role of climate and clubs economy as a potential risk factor needs to be addressed in future studies.

For more detailed information: Kristenson K, Bjørneboe J, Waldén M et. al. The Nordic Football Injury Audit: higher injury rates for professional football clubs with third-generation artificial turf at their home venue. Br J Sports Med. 2013 Aug;47(12):775-81.

Dr Karolina Kristenson is a PhD graduate in Football Research Group (FRG), Linköping University, Sweden. FRG has conducted injury studies since 2001 in cooperation with the Union of European Football Associations (UEFA). These cohorts include clubs playing in the UEFA Champions League, English Premier League and the Nordic top leagues. Her thesis focus on injury rate in elite football related to playing surface.

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