The full study can be read here.
Tell us more about yourself and the author team.
This study is the result of a collaboration between myself (a teaching and research academic at the University of Sydney, Australia), Andreas Serner (Medical Research Lead at FIFA), Filip Orest (a final-year medical student from Linköping University, Sweden, who completed a full-time research placement with me in Sydney during 2023), and Julia Georgieva (a PhD student that I co-supervise at Curtin University, Perth, Australia).
What is the story behind your study?
I am currently contracted by FIFA to work as an injury spotter during their organised tournaments. So far, I have worked at the u17 and u20 men’s FIFA World Cups, FIFA Women’s World Cup, FIFA Club World Cup and the recent Olympic Games. It was during the build-up to the FIFA Women’s World Cup in Australia/ New Zealand last year that I seriously started to think about the differences in heading technique between men and women as well as the mechanism of potential head injury events. This led to an editorial that was recently published in BJSM. However, this editorial was largely theoretical, and I remember talking with Andreas during an informal de-briefing session after the World Cup and discussing some of the differences that I was observing between men and women while injury spotting and asking him if I could access match videos to conduct further research in this area. The study progressed very quickly once Andreas was on board because Filip was coming to Sydney to complete his research placement. Julia had just submitted her PhD study, in which she coded headers from the previous FIFA Women’s World Cup in 2019. Access to HD match footage, including the broadcast footage and all the other camera angles, was key to completing this study. We then used a purposive sample of matches from the men’s and women’s World Cups, where the same national teams competed against each other, to collect data on head impact type as well as descriptors related to the technical performance of headers.
In your own words, what did you find?
Initially, we developed a couple of hypotheses that we wanted to explore. The first was to see whether professional women would perform fewer headers than men, as it is often reported in the literature that women do not head the ball as much as men. Our data did not support this hypothesis, as the number of headers was statistically very similar (women 409 headers v men 436 headers; incidence rate ratio 1.07). Our second hypothesis then focused on whether there would be differences in the technical performance of headers between women and men. Our data showed that women performed fewer controlled headers than men, were less likely to head the ball using their foreheads and were less likely to use their upper body when compared with a similar sample of men. Additionally, women were more likely to head the ball from corners and goal kicks, whereas men were more likely to head the ball during free play and long balls. Women were also more likely to head the ball to intercept play, with men more likely using headers to pass the ball. Finally, we found that women closed their eyes earlier before the header than men.
What was the main challenge you faced in your study?
The main challenge was locating each header in the multiple camera angles and having a clear enough view to code each technical descriptor, particularly the timing of eye closure. Filip did a fantastic job; it took him at least 8 hours per match to code every descriptor. It was time-consuming in and of itself without the additional time to complete intra-rater and inter-rater reliability. Additional time was also spent developing the coding methodology at the beginning, including creating the data dictionary for all the descriptors and definitions and the final auditing process once data had been collected. Data collection, therefore, was a very painstaking and challenging process.
If there is one take-home message from your study, what would that be?
If readers only take away one thing from this study, I hope it will be that heading in football is a very complex skill that involves so much more than head-to-ball contact. I would love our findings to stimulate further discussion and research into the potential role that coaching and the development of technical proficiency might play in heading-related injury risk mitigation, particularly in women and girls, who are the fastest-growing demographic of players across the world but remain under-resourced and under-researched.