jeudi 27 novembre 2014

Does Soccer shoe cause Injury ?

Nowadays, with technology, information is easily and quickly available. However, as a down side, it is also easy to come across a brief overview of a subject and apply it as if it was truth. The topic of soccer shoes and injuries has been discussed more on the news this years with various event such as the Word Cup in Brazil, the women U20 Word Cup here in Canada and the potential law suit against FIFA for the senior women Word Cup of 2015. A good example of this phenomenon is the research by Drakos et.al. (2010) which states that the playing surface (turf vs grass),  not shoe type, may increase risk of injuries. With that information, one could state that turf increases risk of injuries. However, if we take a closer look at the paper by Drakos, we find out that the study was done on cadaver specimens with an average age of 57 years. Drakos et.al. (2010) did show an increased ACL strain with friction on turf surface, but the limitation of having cadavers without muscle contraction to stabilize the knee seem important. Using cadavers  does not provide a realistic picture of the situation of injuries in relation with surfaces of play and shoe design. This is why I decided to have a closer look at the topic of cleats and injury in soccer.

First of all, there has been a good amount of research on the subject, in soccer, handball and america football. The oldest study I found on the topic is from Lambson et.al. (1996), which looked at « Edge Design » (ED) soccer cleats. They statistically showed more injury happening with the ED shoes (0,017%) compared with regular round studs (0,005%). 56% of those injuries where non-contact ACL injuries, which are believed to be caused by increase torque from the shoes. That is, at first, coherent with the study of Drakos. However, another interesting finding about the research of Lambson et.al. (1996) is that full-foot stance developed about 70% more torque than toe stance. What I see here is that torque is position dependent. As such, it would be possible to change torque by teaching proper technique when player changes direction, for example. An other research by Queen et.al. (2007), shows that « turf shoes » where the only one reducing force and pressure under the metatarsal head. Even if researchers concluded that it could lead to a decrease in injuries, but that there is no conclusive evidence that the choice of shoe can help minimize risk of injury. This is another good example of research where one could have stated that shoes, other than turf specific shoes, increase the risk of injuries. However after looking at limitations and conclusions of the authors, it seem too early to do such a statement. A third paper by Smeets et.al. (2012), looked at different turf fields and showed higher torque when using sand-filled turf (Varioslide Excellence) as compared to the latest generation of turf field (Champion Infinity). They also showed that torque was higher in dry conditions compared to wet conditions. Consequently, the sand-filled turf (Varioslide Excellence) in dry conditions was considered as the most hazardous surface to play on. 

Gehring et.al. (2007) state that « low knee flexion angles, a highly activated m. quadriceps femoris is generally associated with increased ACL strain ». They also point out evidence that hamstring action is essential to knee stability. However the most interesting information Gehring et.al. (2007) have found is that increased ground force reaction (GFR) does not transfer to knee joint moment. If higher GFR does not transfer to the knee, then the increased torque between shoe and surface of play is not a risk factor for knee injuries. Gehring et.al. (2007) concluded that no indicator of non-contact increase injuries come from bladed cleats. On the applied side of things, researchers stated that « activation of m. biceps femoris peaked in the pre-activation phase and during foot strike, this could be associated with an injury preventing strategy. » In other words Gehring et.al. (2007) message is that the right muscle activation at the right timing is a greater factor to consider in injury prevention. Luckily is it also more coachable, as you can work on increasing muscle strength, activation and coach better movement patterns. Another paper by Galbusera (2013) comes to the same conclusion, showing no difference in the torque of cleats and playing surface.  Finally, Hennig (2011) published an extensive review on soccer shoes, looking at injuries, comfort and performance. The authors point out that « There is surprisingly little or no evidence that there is a relationship between traction properties and injury risk. » His review also showed no difference in injury rate on different playing surfaces.

In conclusion, it seem to be that there is no significant evidence that playing surface and shoe design lead to increased risk of injuries. As a professional in coaching, I think those result show that better training, strengthening and injury prevention strategies could lead to reduced injuries. If one is to make a public statement about a topic based on research results, I think it is a professional duty to take an extensive look at the available literature on the subject beforehand.
References


  • Lambson R.B., Barnhill B.S., Higgins R.W., (1996). Football cleat design and its effect on anterior cruciate ligament injuries. The American Journal of Sport Medecine, 24: 2, 155-159.
  • Gehring D., Rott F., Stapelfeldt B., Gollhofer A., (2006). Effect of soccer shoe cleats on knee joint loads. International Journal of Sport Medecine, 28: 1030-1034.
  • Queen R.M., Charnock B.L., Garrett W.E., Hardaker W.M., Sims E.L., Moorman C.T., (2007). A comparaison of cleat types during two football-specific tasks on field turf. British Journal of Sports Medecine, 42: 278-284.
  • Drakos M.C., Hillstrom H., Voos J.E., Miller A.N., Wickiewicz T.L., Warren R.F., Allen A.A., O’Brien S.J., (2010). The effect of the shoe-surface interface in the development of anterior cruciate ligament strain. Journal of Biomechanical Engineering, 132: 1-7.
  • Smeets K., Jacobs P., Hertogs R., Luyckx J.P., Innocenti B., Corten K., Ekstrand J., Bellemans J., (2012). Torsional injuries of the lower limb: an analysis of the frictional torque between different types of football turf and the shoe outsole. British Journal of Sports Medecine, 46: 1-7.
  • Galbusera F., Tornese D.Z., Anasetti F., Bersini S., Volpi P., Barbera L.L., Villa T., (2013). Does soccer cleat design influence the rotational interaction with the playing surface? Sport Biomecanics, 12: 3, 293-301.
  • Hennig E.M., (2011). The influence of soccer shoe design on player performance and injuries. Research in Sport Medicine, 19: 186-201.

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