21 Aug 2018
Biomechanical Analysis of Concussion Risk in Soccer
The following text is from one of the finalists in the 2017 SARA Abstract Contest. The author was awarded a special participant prize for the clarity and quality of her research project presentation. The other texts submitted in the SARA Contest are also available.
The author also presented her research on the television show Électrons libres.
Header image purchased on Istock.com. Protected by copyright.
Like any other sport, soccer involves a risk of injury. Concussion is a particularly common injury in most sports. One of the most significant injury mechanisms of concussion is head acceleration. In soccer, head acceleration is generated by heading techniques and involuntary impacts. However, the data on head kinematics in soccer are scant in the current literature. Thus, the main objective of this research project was to assess risks of concussion during soccer games. The participants in this study wore an instrumented headband to measure various kinematic parameters of the head. These parameters were then matched with head injury criteria to identify concussion risk. The results identified game-related concussion risks, even though soccer is considered a non-contact sport.
Since the early 2000s, there is awareness in the sports world of the significant consequences of concussion. It has been shown that concussions can cause minor temporary distractions in attention and memory, but can also lead to death [1, 3, 8]. Concussion studies have focused mainly on contact sports like American football . However, non-contact sports like soccer are not spared. For example, at the university level, the number of concussions reported among female soccer players equals the number reported for hockey players . In Canada, between 2012 and 2014, the number of concussions reported by female soccer teams, with players aged 10 to 19, was greater than the total concussions caused by hockey, rugby and cheerleading .
In Canada, soccer is popular with young people. Players can be exposed to concussions over a long period of time. Concussion statistics show that they are increasing yearly. In fact, the reported number of concussions among young players aged 5 to 18 increased by more than 40% between 2004 and 2014 . This is why understanding the injury mechanisms of concussions in soccer is essential.
Head acceleration is the most important injury mechanism of concussion . In soccer, head acceleration is caused by involuntary impacts and specific heading techniques, such as the voluntary action of redirecting the ball with the head. In current literature, there are not a lot of data on head acceleration in soccer players during games. This lack of data is due to the fact that measuring instruments generally require the use of wires, restricting the players’ movements. Recent technological development has made it possible to overcome this restriction but, based on current knowledge, only three studies have been conducted in real time since 2010 [5, 7, 9]. The lack of data on head acceleration limits the understanding of injury mechanisms and the identification of concussion risk in soccer. Thus, the main objective of this research project is to assess concussion risks while playing soccer.
The specific objectives (SO) are:
SO1: to measure linear and angular head acceleration in soccer players during games;
SO2: to determine concussion risks associated with the amplitude of measured acceleration;
SO3: to identify types of involuntary impacts and heading techniques that could lead to a risk of concussion.
Participants in the research project had to be over 18 years of age. Also, they could not have upper body injuries or a concussion without presenting medical advice allowing their return to the game. Eight male players from the provincial league and sixteen female players from the regional league participated in the research project.
The measuring instrument used is the SIM-G  and consists of a gyroscope and two triple axis accelerometers. It was inserted in the headband worn by the participants as shown in Figure 3. A linear acceleration greater than 10g detected by the SIM-G triggered the recording of data. The data were then sent directly to an acquisition system. All games were filmed to validate the SIM-G activations.
In order to identify concussion risks, the participants’ head acceleration was matched with Zhang’s injury criterion for concussion . This criterion consists of risk thresholds that quantify the probability of concussion in relation to head acceleration measurements. The three risk thresholds are 25%, 50% and 80%; they correspond to the linear acceleration of 66g, 82g and 106g, and to the angular acceleration of 4,600 rad/s2, 5,900 rad/s2 and 7,900 rad/s2, respectively.
Acceleration data measured during the study are summarized in the following table.
Table 1 Participant head acceleration measured during soccer games
Heading techniques generated the highest incidence of acceleration, exceeding the risk of concussion by 50% for both male and female players. Specifically, the type of heading that caused the highest risk of concussion was jumping in male players, and redirecting the ball (head spin) in female players. As for unintended impacts, contact between male players and between female players caused the highest risks of concussion.
Heading technique: jumping and redirecting the ball
This research project made it possible to quantify head acceleration frequency and magnitude caused by unintended impacts and heading techniques in soccer players. It identified the presence of concussion risk while playing soccer and the higher risk potential when performing heading techniques. This is a significant advancement in the knowledge on concussions in non-contact sports like soccer. This project also identified the types of impacts and heading techniques that can lead to concussion when playing soccer, which is the first step in reducing such risks in this sport. Finally, this research project demonstrated the urgency of making players aware of the risk of concussion while playing soccer.
Caroline Lecours is a PhD student in the Mechanical Engineering Department at ÉTS. The objective of her PhD project is to determine concussion risks and frequency in soccer practice.
Program : Mechanical Engineering
Éric Wagnac is a professor in the Department of Mechanical Engineering at ÉTS. His research interests include biomechanics, computer design, finite element simulation, protective devices and surgical tools.
Program : Mechanical Engineering
Research laboratories : LIO – Imaging and orthopedics research laboratory
Yvan Petit is a professor in the Department of Mechanical Engineering at ÉTS. His research interests include computer-aided design, biomechanics, medical and protective devices, and additive manufacturing techniques.
Research chair : Canada Research Chair in Biomechanics of Head and Spine Injuries