LaLiga study: validation of ThermoHuman in professional soccer
In a research study on the use of infrared thermography to help football teams in injury prevention, carried out in collaboration with LaLiga, the validity of ThermoHuman was analyzed.
From the Innovation Department of LaLiga, they aimed to activate and promote technologies that help maximize the value of the teams, through collaborations, to improve the competition and the competitiveness of the teams. In this sense, tools that improve the availability of the best players will help improve fan engagement, since, as Kaplan et al. (2019) have seen, if the most important or media players in the squad are injured, the number of spectators in the stadium and the television audience are lower.
In addition, injuries affect both the performance and the economic section of the club, since, as has been investigated, a lower availability of players due to injury affects the final position in the classification (Hägglund et al. 2013), and that entails less money for television rights. Besides, the economic impact due to the days the players are absent may be very relevant (Cortê et al. 2019). As seen in previous posts, thermography helps to reduce days off due to injury, as well as to reduce injuries compared to not using the tool.
LaLiga helped identify and generate innovation projects supported by innovative technological solutions, focusing on the business objective and promoting the innovative culture and image of LaLiga and the first division clubs. During the process, LaLiga provided guidance so that the solutions were accepted and understood by professionals with the aim of measuring the degree of adoption of these technologies in sport.
Among the pilot projects that participated, ThermoHuman was one of the selected ones.
Injuries in soccer and thermography: implementation of the strategy
With the background of the use of technology for injury prevention, a 4-month study (from November 2020 to March 2021) was proposed in two LaLiga soccer teams. A double-blind methodology was proposed, that is, the thermography technicians only took the images and signaled the alarms in the appropriate players, without intervening. On the other hand, the professionals within the medical/technical staff were not aware of the thermography alarms and noted if any player had undergone any intervention, such as training adaptation, physiotherapy treatment or injury (see Figure 1):
The objective of the study was to verify the efficacy of infrared thermography for injury prevention without performing an intervention. The only tested application of thermography was the prevention of injuries, but you can find the rest of the thermography applications in this article.
A database of thermography alarms was obtained. The images were taken twice a week by two technicians, one for each team, and a weekly database of the interventions that the players had suffered. The tables were configured according to the model explained in Figure 2.
At the end of the pilot study, in the fourth month, both databases were crossed to see the correlation results of the thermography alarms that had been marked for the players and the real interventions that the professionals had carried out on a day-to-day basis. (figure 3):
Two categories (false negative and true positive) were established to see the degree of correspondence between what had really happened and what the technicians had indicated would happen (figure 4).
The results show two main variables to take into account:
The first is related to the sensitivity of the tool and is what we have called the “alarm ratio”. It is the number of alarms that occur divided by the actual interventions. Or what is the same, the interaction between the databases.
The second is related to the predictive value, that is, the success of what was identified and what later happened, which we have called “hits“. Another way to understand it is the relationship between alarms and interventions.
For the first variable, the calculation of the average alarm ratio of the two pilot projects is 2.24. This means that for each actual intervention that occurred, ThermoHuman’s methodology signaled that intervention would occur and 1.24 more (figure 5).
This ratio in a squad of 11 players would mean that out of 8 alarms indicated by the thermography, 4 players would undergo some type of intervention, from physiotherapy treatment to injury (figure 6). Put into practice, this can mean a high ratio, but it can put the correct focus on the injury that is going to occur and for this we analyze the following variable.
Concerning the second variable (the number of hits or true positives) we found that, out of the 170 correlations that occurred, 69.41% correspond to the region that was affected. This means that of those alarms that the technicians point out in the evaluation in daily practice will coincide with regions that will be affected by some type of intervention or treatment (figure 7).
To put the same example on that squad of 11 players, 8 have been identified as possible candidates and 4 have undergone an intervention. Of those 4 who have undergone an intervention, the thermography was correct in 3 of them what was going to happen and in one it failed (figure 8).
Thermography is a technology that reports the physiological state of tissues. Therefore, variation in thermal symmetry is related to an increased risk of injury. This variation is very sensitive during the training process, therefore thermography can show a high alarm ratio. As tissues react to load and generate adaptations, thermal symmetry can vary and alert us.
But this alarm system, which ThermoHuman has carried out with such a high percentage of success in relation to subsequent interventions, allows this technology to have a predictive and preventive nature of injuries.
The physiology and metabolism of the tissues react before the appearance of the injury. For this reason, we mention the overload processes and compensations that can lead to injury and that can be measured with thermography.
Thanks to this research project, in collaboration with LaLiga, ThermoHuman has been able to develop an alarm system integrated into its software that offers labels by color and region for the control and monitoring of athletes (soccer, basketball players, etc.) with the aim of improving the application of injury prevention.
Scott Kaplan, Vaibhav Ramamoorthy, Cheenar Gupte, Amit Sagar, Deepak Premkumar, Joshua Wilbur and David Zilberman. (2019) The Economic Impact of NBA Superstars: Evidence from Missed Games using ticket Microdata from a Secondary Marketplace. Conference paper: MIT Sloan Sports Analytics Conference 2019
Hägglund M, Waldén M, Magnusson H, et al. Injuries affect team performance negatively in professional football: an 11-year follow-up of the UEFA Champions League injury study. Br J Sports Med 2013;47:738–742.
Côrte AC, Pedrinelli A, Marttos A, et al. Infrared thermography study as a complementary method of screening and prevention of muscle injuries: pilot study. BMJ Open Sport & Exercise Medicine 2019;5:e000431. doi: 10.1136/bmjsem-2018-000431
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