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 (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 (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 (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 (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 (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 (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 (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 (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 (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 (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.

  • 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.

jeudi 16 janvier 2014


We live in a society of convenience. Cell phones are disposable, computers work at light speed, everything needs to be fast and expendable. Even in healthcare, there is a pill for everything! Unfortunately, this mentality has tainted athletes' development. I have seen young athletes being pushed to win to a point of verbal abuse. This kind of behaviours favours athletes dropout, sport injuries and even burnout. Thankfully for my profession, there is still no pill that makes you stronger or more efficient. Performance comes from good work ethic and motivation to improve. 

New York Times recently published an article about American ski racer Mikaela Shiffrin. At 17 years old, she is second youngest USSA athlete to win a world cup race. The article is about how her well rounded development made her into a champion. I was pleasantly surprised to find a story not about parents pressuring and overworking their children, instead I read about supportive parents and a well rounded childhood. The Shiffrin children learned that one of the most important things to be successful in sport and in life is a good work ethic. To quote Eileen (Mikaela's mom) :
“It was 90 degrees and she was 10 years old and she worked so hard without complaining. So she’s a good ski racer because she did all kinds of different developmental things — like learning a good work ethic — but none of them were part of a plan to make a world champion.”

Mikaela's parents focused on having their children developing essential skill for life through sport. Through support and encouraging their children to practice various sports and activities (outside of skiing), Mikaela and her brother learned motor control more efficently (unicycle riding) and were able to develop their work ethic (doing house maintenance work). They was no magic formula, they fostered a very important condition to success : Motivation. Intrinsic Motivation Theory (Deci & Ryan, 1985) illustrated below:

(Deci & Ryan, 2000)

For example, if you say to yourself "I have to do the dishes" your motivation is Extrinsic, you are experiencing Introjected Regulation. Knowing the consequences of not doing the task, you "have to" do it but perceive it as a "punishment". If you're doing the dishes because you're getting paid to do it, there is external motivation. You are receiving an external reward. This theoretical model illustrate separate levels of motivation which should to be seen as a continuum. Practicing an activity regularly and having a positive experience as well as receiving positive feedback, may entail internal motivation (Identified, Integrated and Intrinsic). These levels of motivation are an essential part of what it takes to become an expert in any domain. Having Mikaela say “I will want to win. But the result of the race will not motivate me. I can honestly say that I am motivated by improvement, not results. That’s a core principle.” is a sign that she is Intrinsically motivated, not only to do her sport, but to improve in it.

In order to help young athletes become motivated, parents and coaches should focus on 3 elements to help increase motivation : Competency, Autonomy and Belonging. Helping turn focus to the child's strengths or on one particular skill in his sport for example. This will help foster their motivation to practice that particular sport. Being more intrinsically motivated will help them focus on making regular progress and strive for improvement. As John Wooden said "Seek small improvements on day at a time. That's the only way it happens - and when it happens, it lasts."