10th August 2015

Last month saw the FIFA Women’s Football World Cup come to a close, with the USA winning the tournament for a record third time. Like many, I enjoyed watching competitive football which was largely bereft of play acting diving and shouting profanities at the referee. However, few may be aware of the controversy leading up to the tournament, with a number of high profile players raising major concerns around the playing surface. Indeed, unlike the men’s competition, all of the FIFA World Cup games in Canada 2015 were played, not on grass, but on synthetic surfaces. The first synthetic pitch I remember was that of Luton town FC in the 1980s which was commonly referred to as the ‘plastic pitch’. Synthetic pitches have developed significantly since then and we are now talking about 5th and even 6th generation pitches. These latest innovations are a far cry from the concrete-esque, sand dressed prototypes.

At a basic level, grass offers a number of advantages – for one it smells better (particularly when freshly cut) and you don’t have to spend two hours shaking rubber crumbs from your kit. Also, if you have ever had the misfortune of sliding on a synthetic pitch, you will know that friction burns are taken to a new level of pain. But in reality, the players at the Women’s World Cup were raising concerns with much more important issues than these – that of equality (as the men’s tournament has never and will never be playing on an artificial surface) and player welfare (is grass safer?).

There has always been a concern that artificial surfaces increase the risk of serious joint injury in footballing codes. Researchers in Sweden have been analysing patterns of football injuries over a decade. As such we have a clear understanding of the areas of the body most at risk of injury and the most important risk factors. Ankle sprains and knee sprains account for almost 40% of all injuries in professional soccer. Indeed, a typical team in the English Premiership will incur approximately 10 such injuries per season, meaning that at least one player will be side lined for around 25 weeks of the season. This incurs significant cost when salaries are in excess of £100K per week. Of further note is that the incidence of serious knee injuries such as anterior cruciate ligament injuries is 2-3 times higher in women’s sport; and there is evidence to show that younger female athletes have the highest rate of ankle sprain across any sporting population.1

Interestingly a large percentage of knee injuries in footballing codes are non-contact, so we can’t blame the opposition, or the ref. But can we blame a synthetic playing surface? Although there are multiple risk factors associated with any injury (warm up, strength, fatigue level, flexibility etc), there is evidence to show that the interaction between the shoe and the playing surface is very important. This interaction relies on optimal friction: too little friction and we will slip and fall over (try running on ice); but excessive friction prevents any interplay between the shoe’s outsole and the playing surface which can cause high loads to transfer up the kinetic chain which the ankle and knees have to ‘soak up’. If these loads are large enough, then ligaments (which are important stabilisers of joints) will tear. So in reality we are looking for the Goldilocks effect – we need to get the amount of friction ‘just right’. Get it wrong and recent evidence suggests that the risk of injury increases two fold. That said, excessive friction can occur on either surface (grass or artificial) and a meta-analysis (which is the highest level of scientific evidence) found that athletes are essentially at no greater risk of injury playing on artificial turf compared to natural grass.2 However, very few of these studies involved female athletes, and this debate is far from being over.

Perhaps a more fundamental problem at the recent World Cup in Canada was the lack of consistency in the type of synthetic surface players were exposed to. Sport, particularly at the highest level is reactive and unaccustomed or unanticipated changes in external factors such as playing surface can increase injury risk. So whether it is grass or artificial, tournament officials should do their best to keep the surfaces consistent so that players can be accustomed to its feel, its friction, and adopt an appropriate playing style.

On a related note, Rory McIlroy raised some eyebrows after he sustained a complete rupture of his anterior talofibular ligament (a nasty ankle sprain) during a five a side soccer game. This is a far cry from Rory’s day job (walking on grass and swing a golf club at very high speeds) and the injury eventually forced him to miss the Open Championship. This left many people questioning whether someone involved in such a high stakes, top level professional sport, should be partaking in a kick around with his mates? It did make me think whether playing surface was a factor in this injury, or whether Rory selected his five a side shoes as carefully as he does his golf spikes?? On average males sustain 1 ankle sprain for every 143 sporting exposures1. But we must also think about the benefits associated with a casual kick about, such as the social outlet and psychological down time from intense competition. Making a judgment on the value of this trade is off is made at an individual level and only Rory can judge whether the value of social sport trumps the risk of injury.

Review Article

  1. Doherty C, Delahunt E, Caulfield B, Hertel J, Ryan J, Bleakley C. The incidence and prevalence of ankle sprain injury: a systematic review and meta-analysis of prospective epidemiological studies. Sports Med. 2014;44(1):123-40.
  2. Jay H. Williams, Emmanuel Akogyrem, and Jeremy R. Williams. A Meta-Analysis of Soccer Injuries on Artificial Turf and Natural Grass. Journal of Sports Medicine Volume 2013: 1-6. doi:10.1155/2013/380523
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