Head impact differences in blind football between Rio 2016 and Tokyo 2020 Paralympic Games: video-based observational study

Discussion

This study aimed to identify differences in head impact characteristics of blind football players at the Rio 2016 and Tokyo 2020 summer Paralympic Games. The results demonstrated that the head impact situation differed between the Rio 2016 and Tokyo 2020 Paralympics Games, thereby supporting our hypothesis. This is the first study to investigate the head impact situation of blind football players at the Paralympic Games throughout these two events and to clarify the changes in head impact situations that occurred along the time course.

Compared with the Rio 2016 competition, the overall score nearly doubled at the Tokyo 2020 event and significantly increased with respect to the average score per game. Additionally, the number of drawn games in Tokyo 2020 was lower than in Rio 2016. These results are interesting despite the fact that the time per game was reduced in Tokyo 2020. There are two main possible reasons for this, the first being the increasing of competition-level Paralympians. Blind football has been adopted as an official Paralympic competition since 2004.1 Additionally, considering that the Paralympics began in 1960,19 blind football is a discipline with a short history, and the number of players remains small. The Paralympians who competed in blind football at the Tokyo 2020 event were significantly older than who competed at the Rio 2016 event, possibly indicating less turnover in the national team players from each country and that many of the players competed in two consecutive Paralympic Games. This suggests that the increase in the number of years of continuous competition may have contributed to the increase in competitiveness. Second, there have been some changes to the rules. The goal width was expanded at the Tokyo 2020 compared with that at the Rio 2016.12 13 This suggests that an environment in which scoring was easier was brought about from the rule’s perspective.

In the present study, the headgear wearing rate in Rio 2016 was 30.2%, which was higher than previously reported in the Tokyo 2020 competition (23.4%).4 There was a 5-year gap between Rio and Tokyo due to the COVID-19 pandemic.20 21 The fact that headgear wearing is not mandatory and is optional may be a reason why less than one-third of the para-athletes wore headgear in two Paralympic Games. However, since headgear is at least effective in preventing superficial head injury,22 it is important to educate the field about its use. Head impact exposure was high in Rio 2016 compared with that in Tokyo 2020, possibly due to the difference in the number of head impact cases, that is, the playing time, with 1105 cases of head impact in Rio 2016 and 931 cases in Tokyo 2020. The head impact exposure rate was higher in Rio 2016 than that in previous studies of able-bodied football players18 23; a similar trend was observed in Tokyo 2020. Thus, in both of the two tournaments, the head impact exposure was higher in blind soccer than in able-bodied soccer, highlighting that visual limitations are the most relevant.

The results of present study showed that the number of normalised head impacts (average per min) was not significantly different between the Paralympic Games, whereas the characteristics were different. This is a main finding, and we need to discuss why it differed between the Paralympic Games, focusing on characteristics of head impact that appear to be of high intensity. In Tokyo 2020, the rate of head impact when the score is draw accounted for 41.0%, which was a lower percentage compared with that in Rio 2016 (63.7%). This is due to the fact that the number of goals scored doubled in Tokyo 2020, resulting in a relatively short length of draws. Among the results obtained in this study, the most notable features were the situation, impact object, site of impact and fall or not. Residual analysis showed the following characteristics that resulted in a high percentage of head impacts in Tokyo 2020: dribbling, impact with the opponent, face impact and falling. Previous research on head impact areas and objects during blind football games has demonstrated that a higher percentage of impacts to the face occur during contact with the opponent.4 Furthermore, 44.2% of head impacts without falls reportedly occurred during dribbling, compared with 55.9% with falls.4 The results of the comparison of the two Paralympic Games revealed that the Tokyo 2020 had a higher probability of head impacts that could be expected to be of high intensity, although the number of occurrences per game was not significantly different. As shown in figure 2, the percentage of falls during dribbling in Tokyo 2020 was more than three times higher than that in Rio 2016. Despite the shorter game time, the total number of goals scored at Tokyo 2020 nearly doubled, suggesting increased opportunities for aggressive situations during the game. This may lead to the occurrence of dangerous head impacts, and preventive measures need to be considered from an early stage. Specifically, there is a thorough enforcement of the vocalisation (Voy) rule on the defence side, and physical contact with the upper limbs prior to the head and face.

However, gaps exist between research findings and field awareness, as evidenced by the decline in headgear wearing rates. First, education for athletes and coaches is important to improve this issue. With the addition of rules regarding head injury assessments beginning in January 2021,13 there is a trend of beginning to recognise the risk of head injuries, such as concussions in blind football players. Nevertheless, this is only secondary prevention, with much room for improvement in primary prevention. Athletes and coaches must be aware of how dangerous impact is, rather than just taking collisions for granted because of visual deprivation. The second priority is to improve the evaluation system. This is expected to include an expanded video review as part of the sideline screening process.7 As in the present study, the first step is to define what is presumed to be particularly dangerous head impacts and promote a common understanding. When such impact occurs during play, a screening assessment should be performed on the athlete to determine whether he can continue to play. However, the baseline differs for able-bodied and para-athletes using the screening method for concussion. In addition, because some disabilities make it difficult to use conventional screening methods for some evaluation items, establishing a competition-specific evaluation system and following up with individual athletes is essential.24 In fact, new evaluation tools for athletes with lower limb or spinal cord disorders have already been validated, and a multifaceted evaluation capability is required in the future.25 Thus, future research on the application of the system to athletes with visual impairments is also expected. Nine concussion occurrences were reported at the Tokyo Games, although it is highly likely that concussions are under-reported.9 Furthermore, zero cases were reported in blind football competitions, which remains a concern.9 As mentioned in the sixth International Conference on Concussion in Sport in Amsterdam, further research is needed for further evaluation and knowledge for para-athletes.26

This study had some limitations. First, the actual occurrence of head and neck injuries is unknown. Since we only analysed head impact in this study, caution should be exercised in overinterpreting the results. Second, the definition of the intensity of head impact was that it depended on information obtained from the match video. Since we interpreted the impact based on situations, such as impact involving a fall or during dribbling, low-impact cases might have been included in the analysis. Simulation studies and shock measurements during actual games are expected in the future.