The strategies to return to sports practice after an injury are highly relevant both in the medical area and in the sports area, since they mark the success of recovery and the good practices of both departments. Currently, the availability of the player is one of the variables that has the most influence both at an individual level, since the athlete himself benefits from better opportunities if he can compete, and at a collective level, since as shown by Hagglund et al. (2013), the teams with the best availability end up in better positions in the leaderboard.
The recurrence rate of a muscle injury is one of the markers that most affects medical services, since within the multifactorial nature of the injury, predicting it is still a utopia pursued by many investigations. Despite this, today there is already science that supports the use of different technologies, including thermography, to reduce its recurrence. The management of the injury and the return to competition (the famous return-to-play) is a process that falls directly within this department and many times calls professional work into question. The complexity of managing injuries, social expectations and sports and media pressure are more than relevant aspects to take into account.
Research indicates that the risk of recurrence in a muscle injury is 12 to 63% for the hamstring complex. In addition, a third of these recurrences occur within the first year from the first injury and are usually more severe. According to the literature, these high recurrence rates are due to poor management of the recovery process (Silvers-Granelli et al. 2017).
That is why tools that help us in return-to-play (RTP) decisions can be of great interest for monitoring injuries.
Injury management benefits from the information obtained by the means of assessment. Just as a diagnostic tool reports the severity and state of the tissue, assessment tools, such as force platforms that assess functionality or thermography that assess the physiological and metabolic adaptation of the tissue, are of great help in establishing the RTP criteria safely.
In this sense, strength assessment tests are widely used in Sports Sciences and have proven reliability in the scientific literature, where asymmetries above 10-15% indicate that there are large imbalances and that the criteria have not been met back to competition safely (Davies et al. 2017). Also, in muscle injuries it is sought that these values are equal to the non-injured leg or to pre-injury levels (Tol et al. 2014; Zambaldi et al. 2017).
In ThermoHuman, we have case studies where we relate the return to competition with thermography evaluations complemented with force platform evaluations that indicate that thermal asymmetries can be related to strength deficits, as can be seen in figure 1:
Figure 1. Evolution of a professional soccer player, from before a muscle injury in the right biceps femoris. At the time of deciding on the RTP, there was a thermal asymmetry similar to that of the injury period and still a significant asymmetry in a strength test.
In addition, within the normality of athletes, values below 0.004 ºC ± 0.66 of thermal asymmetry are considered in general, and 0.02 ºC in the biceps femoris region and 0.014 ºC in the quadriceps region, when these regions are healthy (Escamilla-Galindo et al 2022). Thus, as described in previous articles, muscle injuries present a hypothermic pattern that has to normalize during recovery until normothermia is achieved.
That is what Gonçalo Trindade did during the 2021/2022 season to reduce days off due to muscle injuries compared to the previous year.
The Clube Desportivo Nacional rehab trainer compared the data on injuries and time off from two consecutive seasons: in the first he used GPS and in the second he added thermography. He used thermography as a tool in assisting muscle injury recoveries to make RTP decisions.
As we can see in figure 2, the results show that the inclusion of a thermography protocol every 48-72h, in combination with neuromuscular tests, reduces the number of days off due to muscle injury by 31% compared to not using this tool.
Figure 2. Comparison no thermography vs. thermography of a professional soccer team in two consecutive seasons in the number of muscle injuries and days off due to injury.
On average, in the 2020-2021 season, the RTP time of a muscle injury was 26 days off. While, the following season the average was 18 days off, which means a decrease of 8 days off (a decrease of 31%).
Trindade explains these results by:
An optimization in the recovery process, largely due to the various data we had that allowed the player to train and play safely without having any recurrence. Also, those injuries were less severe.
Gonçalo Trindade, 2022
In figure 3, you can see a player of the team with a muscle injury in the left hamstring region. From the thermogram we can appreciate a significant hypothermic difference in the injured region.
The mean asymmetry metric confirms this difference (asymmetry: 0.46 ºC medial region of the posterior thigh; 0.82 ºC internal region). The coefficient of variation metric adds more specific information, flagging the mid region as cooler than usual (-1). In addition, the right side, without injury, appears to have a hot profile, since the player's biomechanics are affected during the recovery process, increasing the temperature of a large part of the regions of the healthy side:
Figure 3. Example of a player injured in the hamstring region of the left leg. Mean asymmetry and coefficient of variation metrics confirm the severity of the injury.
Thermography is a useful complementary tool that improves the results of an injury prevention protocol in a professional soccer team. It has been shown that not only the incidence (number of injuries per year) is reduced, but also its severity (average faster recovery time), while the availability of players to train and compete is increased.
Davies GJ, McCarty E, Provencher M, Manske RC. ACL Return to Sport Guidelines and Criteria. Curr Rev Musculoskelet Med. 2017 Sep;10(3):307-314.
Escamilla-Galindo VL; Fernández-Cuevas I.; Del Estal-Martínez A. Description of the thermal pattern of 950 athletes using thermography to measure skin temperature. September 2022 Conference: 27th Annual Congress of the European College of Sport Sciences (ECSS)
Hagglund M, Walden M, Magnusson H, Kristenson K, Bengtsson H, Ekstrand J. 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 Aug;47(12):738-742.
Silvers-Granelli HJ, Cohen M, Espregueira-Mendes J, Mandelbaum B. Hamstring muscle injury in the athlete: state of the art. J ISAKOS. 2021 May;6(3):170-181.
Tol JL, Hamilton B, Eirale C, Muxart P, Jacobsen P, Whiteley R. At return to play following hamstring injury the majority of professional football players have residual isokinetic deficits. Br J Sports Med. 2014 Sep;48(18):1364-9.
Zambaldi M, Beasley I, Rushton A. Return to play criteria after hamstring muscle injury in professional football: a Delphi consensus study. Br J Sports Med. 2017 Aug;51(16):1221-1226.
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ThermoHuman has had the support of the Funds of the European Union and the Community of Madrid through the Operational Programme on Youth Employment. Likewise, ThermoHuman within the framework of the Export Initiation Program of ICEX NEXT, had the support of ICEX and the co-financing of the European Regional Development Fund (ERDF).
Thermohuman has received funding from the Centre for the Development of Industrial Technology (CDTI), in participation with the European Regional Development Fund (ERDF), for the R+D activities involved in creating a new tool, based on thermography, for the prediction and prevention of rheumatoid arthritis. See project detail.
