Documentation:FIB book/Brain/Concussion in soccer

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The biomechanics of (sub)concussive head impacts is not well understood. Therefore, the long-term effect of repeated head impacts, such as heading in soccer, causes concern. In the past years, the Belgian youth competition has banned throw ins, as the ball was often intercepted using the head, and the US has even banned heading in youth soccer altogether. However, many countries have not yet adopted this safer approach to heading in youth competitions. A definitive link between heading in soccer and negative long-term cognitive effects has yet to be established.

The exact process of concussion is not completely understood. There are many vague definitions of concussion, usually involving some kind of external insult that leads to symptoms. One working definition of concussion (also referred to as mild traumatic brain injury or mTBI) is a clinical syndrome with neurological-cognitive-behavioural signs and symptoms caused by acceleration, deceleration or rotational forces on the head (Kamins and Giza, 2016)[1]. Subconcussion is a subclinical injury that is caused by biomechanical forces but is presented without acute signs and symptoms (Kamins and Giza, 2016)[1].

Several studies have been done to quantify the magnitude of forces and acceleration acting on the head during heading in soccer. This can be related to calculated head injury criteria (HIC) and to other studies that establish limits for mild traumatic brain injury.

An example of a study that evaluated accelerations in heading impacts is by Funk et al (2011)[2]. They evaluated the mean peak values of linear acceleration and rotational acceleration caused by a soccer ball impact to the forehead. The ball was released and struck the subjects’ forehead, who did not attempt to actively head the ball. They tested at several different impact velocities (5, 8.5, 10 and 11.5 m/s). The average peak linear acceleration corresponding to the different ball velocities ranged from 6.8- 21 g and the average peak rotational acceleration ranged from 361-2217 rad/s2. This corresponded to an average HIC15 value of 1.0-6.4, which is well below the limit of 700 that is used in automobile testing.

However, such static impacts in a laboratory setting might not give an accurate impression of the head impacts that occur while actively playing soccer. Therefore, different studies have been done to assess heading impacts in real life situations. For instance, Miller et al (2019)[3] assessed head impact exposure during games and practice in youth female soccer players by measuring head kinematics using instrumented mouthpieces. Video analysis was used to describe the source of each head impact. The results showed that the average peak linear and rotational acceleration values from impacts during games were 14.6 g and 1,305 rad/s2. Table 1 gives an overview of several studies that directly correlate heading in soccer with accelerations of the head. It can be seen that there is variation between the values obtained from different studies. It is important to note that these differences can be caused by variations in the set up (such as ball speed, weight of the ball, etc) but also by different measurement methods. Since the sensors are not rigidly coupled to the skull there can be relative motion between the sensors and the skull, which leads to different values between different sensors.

Table 1: Peak linear acceleration and peak rotational acceleration measured in soccer headers.
Study Peak linear acceleration (g) Peak rotational acceleration (rad/s2) HIC15 Measurement method Situation Concussion sustained
Funk et. al. (2011)[2] 6.8 - 21 361- 2217 1.0-6.4 Tri-axial accelerometers in mouthpiece Soccer balls shot at forehead at velocities 5, 8.5, 10 and 11.5 m/s, no active heading No
Naunheim et. al. (2003)[4] 20.29 1302 NR Three triaxial accelerometers mounted to the head Mechanical soccer ball driver projected balls at subjects in a laboratory No
Miller et. al. (2019)[3] 14.6 1305 NR Tri-axial accelerometers and gyroscope in mouthpiece, video analysis Head impacts occurring during soccer games and practice No
Harriss et. al. (2019)[5] 27.35 1447.42 NR Tri-axial accelerometers and tri-axial gyroscope in headband Head impacts during regular soccer games No

The values of head accelerations are meaningless if they cannot be compared to values that correspond to mTBI. Namjoshi et al. (2017)[6] attempted to define the lower limit of mTBI using a closed impact model of engineered rotational acceleration (CHIMERA). In the experiment mice received impacts to the head at different energies, corresponding to sub-threshold, threshold and mild TBI values. The results were scaled to human values. This resulted in mean HIC15 for the sub-threshold, threshold and mTBI groups of 43.01, 91.94 and 108.4, respectively. The corresponding equivalent human head kinematics values at threshold energy were a peak linear acceleration of 38 g and a peak angular acceleration of 782 rad/s2. Many other studies have related the actual occurrence of concussive events to the head accelerations that occurred during the impact that caused the concussion. Table 2 provides an overview of several studies that describe threshold values for linear and rotational acceleration that cause concussion.

Table 2: Classification of Concussion Threshold for linear acceleration and rotational acceleration values in sports.
Study Threshold value peak linear acceleration (g) Threshold value peak rotational acceleration (rad/s2) Threshold value HIC15 Measurement method Situation
O'Connor et. al. (2017)[7] 69.7 to 145

30.7 to 31.7

30.4 to 52.2

7688

5419

4030

NR

NR

NR

Helmet Accelerometer

Helmet Accelerometer

Helmet Accelerometer

Football

Men's Hockey

Women’s Hockey

Namjoshi et. al. (2017)[6] 38 782 91.94 CHIMERA animal model for closed head impacts Mice received impacts to the head at different energies, corresponding to sub-threshold, threshold and mild TBI values.
Rowson et. al. (2013)[8] 104 4726 NR Instrumented helmets Men’s football
Broglio et. al. (2010)[9] 96.1 5582 NR Head Impact Telemetry System High school football
Greenwald et. al. (2008)[10] 96 7235 160 Six single-axis accelerometers embedded in helmets High school football
Funk et. al. (2007)[11] 165 9000 400 Head-mounted accelerometers College football
Frechede et. al. (2008)[12] 103 8022 359 MADYMO simulation Reconstructed video analysis of football and rugby players
Ommaya et. al. (1967)[13] NR 7500 NR Derived from displacement data Primates were subjected to a range of angular accelerations
Figure 1: Data from various studies showing the threshold linear acceleration required to get an mTBI.
Figure 2: Data from various studies showing the threshold angular acceleration required to get an mTBI.

The values for the threshold values of linear and angular acceleration from table 2 are visually represented in figures 1 and 2. Each coloured bar represents the value found in an individual study. Evidently, significant discrepancies arise when assessing the linear and angular acceleration magnitudes required to induce a concussion, with threshold values ranging from 30.4-165g and 782-9000 rad/s2 for linear and angular acceleration respectively. As previously discussed, the magnitude of linear and angular acceleration forces generated when heading a ball are dependent on the ball’s impact velocity, with greater velocities generating larger forces[11]. Variables such as age and gender further contribute to the likelihood of obtaining a concussion, as it was found that females as well as younger individuals exhibited higher peak acceleration and angular displacement values, likely attributed to the greater ball-to-head size ratios [14][15]. Additional characteristics such as ball pressure have been shown to influence the response of the head upon impact, with lower pressures[16]. The influence of head impact location on linear and rotational head accelerations has further been revealed to have significant effects, with the top of the head sustaining the largest linear accelerations and rotational velocities, when compared to the front, side and back regions [5]. Additional factors such as neck strength have been suggested to minimise the risk of concussion, signifying that increased strength facilitates a decrease in head acceleration[17].

References

  1. ↑ 1.0 1.1 Kamins, J. and Giza, C.C., 2016. Concussion—mild traumatic brain injury: recoverable injury with potential for serious sequelae. Neurosurgery Clinics, 27(4), pp.441-452
  2. ↑ 2.0 2.1 Funk, J.R., Cormier, J.M., Bain, C.E., Guzman, H., Bonugli, E. and Manoogian, S.J., 2011. Head and neck loading in everyday and vigorous activities. Annals of biomedical engineering, 39(2), pp.766-776
  3. ↑ 3.0 3.1 Miller, L.E., Pinkerton, E.K., Fabian, K.C., Wu, L.C., Espeland, M.A., Lamond, L.C., Miles, C.M., Camarillo, D.B., Stitzel, J.D. and Urban, J.E., 2019. Characterizing head impact exposure in youth female soccer with a custom-instrumented mouthpiece. Research in Sports Medicine, pp.1-17.
  4. ↑ Naunheim, R.S., Standeven, J., Richter, C. and Lewis, L.M., 2000. Comparison of impact data in hockey, football, and soccer. Journal of Trauma and Acute Care Surgery, 48(5), pp.938-941.
  5. ↑ 5.0 5.1 Harriss, A., Johnson, A.M., Walton, D.M. and Dickey, J.P., 2019. Head impact magnitudes that occur from purposeful soccer heading depend on the game scenario and head impact location. Musculoskeletal science and practice, 40, pp.53-57.
  6. ↑ 6.0 6.1 Namjoshi, D.R., Cheng, W.H., Bashir, A., Wilkinson, A., Stukas, S., Martens, K.M., Whyte, T., Abebe, Z.A., McInnes, K.A., Cripton, P.A. and Wellington, C.L., 2017. Defining the biomechanical and biological threshold of murine mild traumatic brain injury using CHIMERA (Closed Head Impact Model of Engineered Rotational Acceleration). Experimental neurology, 292, pp.80-91
  7. ↑ O'Connor, K.L., Rowson, S., Duma, S.M. and Broglio, S.P., 2017. Head-impact–measurement devices: a systematic review. Journal of athletic training, 52(3), pp.206-227
  8. ↑ Rowson, S. and Duma, S.M., 2013. Brain injury prediction: assessing the combined probability of concussion using linear and rotational head acceleration. Annals of biomedical engineering, 41(5), pp.873-882
  9. ↑ Broglio, S.P., Schnebel, B., Sosnoff, J.J., Shin, S., Feng, X., He, X. and Zimmerman, J., 2010. The biomechanical properties of concussions in high school football. Medicine and science in sports and exercise, 42(11), p.2064
  10. ↑ Greenwald, R.M., Gwin, J.T., Chu, J.J. and Crisco, J.J., 2008. Head impact severity measures for evaluating mild traumatic brain injury risk exposure. Neurosurgery, 62(4), pp.789-798
  11. ↑ 11.0 11.1 Funk, J.R., Duma, S.M., Manoogian, S.J. and Rowson, S., 2007. "Biomechanical risk estimates for mild traumatic brain injury." Annual Proceedings/Association for the Advancement of Automotive Medicine. Vol. 51.
  12. ↑ Fréchède, B. and McIntosh, A.S., 2009. Numerical reconstruction of real-life concussive football impacts. Medicine and science in sports and exercise, 41(2), pp.390-398
  13. ↑ Ommaya, A. K., Yarnell, P., Hirsch, A. E., and Harris, E. H., 1967, ‘‘Scaling of experimental data on cerebral concussion in sub-human primates to concussion threshold for man,’’ Proceedings, 11th Stapp Car Crash Conf., SAE Paper No. 670906.
  14. ↑ Karlin, A.M., 2011. Concussion in the pediatric and adolescent population:“different population, different concerns”. PM&R, 3(10), pp.S369-S379.
  15. ↑ Tierney, R.T., Sitler, M.R., Swanik, B., Swanik, K., Higgins M., Torg J.,2005. Gender differences in head-neck segment dynamic stabilization during head acceleration. Medicine and Science in Sports and Exercise. 37(2), pp. 272–279
  16. ↑ Shewchenko, N, Withnall, C, Keown, M, Gittens, R, and Dvorak, J., 2005. Heading in football. Part 3: effect of ball properties on head response. British journal of sports medicine, 39, pp.26-32
  17. ↑ Collins, C.L., Fletcher, E.N., Fields, S.K., Kluchurosky, L., Rohrkemper, M.K., Comstock, R.D. and Cantu, R.C., 2014. Neck strength: a protective factor reducing risk for concussion in high school sports. The journal of primary prevention, 35(5), pp.309-319.


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