Fatigue is required to mediate adaptations after exercise, which drive performance enhancement (Noakes, 2000). However, excessive fatigue through insufficient recovery may increase susceptibility to non-functional over-reaching, injury, and illness of the athlete (Nimmo and Ekblom, 2007).
Nowadays, recovery strategies are used in high performance sports to compensate the excess of fatigue, which serve to restore homeostasis on a physiological and psychological level (Kellmann, 2002). Beyond the fundamental strategies (sleep, nutrition, hydration and joint range of motion), Robin Thorpe focuses on various temperature-based modalities (cooling and heating), which are the most used and promising (although still scientifically inconclusive)
"...A better understanding of the exact physiological systems and mechanisms of fatigue may provide a clearer landscape into unraveling recovery from exercise, performance, and injury..."
Robin Thorpe (2021)
Robin Thorpe highlights the importance of identifying the type of fatigue, which can be described as metabolic fatigue or structural damage. Interestingly, both types might be understood as "general fatigue" but they have totally different physiological mechanisms.
Thorpe (2021) suggests that depending on the origins of fatigue, an individualization of recovery strategy can be prescribed. So, metabolic fatigue should be compensated using heating therapies and structural damage using cooling ones. The proposal is nicely described in figure 1.
Figure 1: Practical framework to enhance recovery in athletes from Thorpe (2021) Post-Exercise Recovery: Cooling & Heating, a Periodized Approach.
Robin Thorpe describes different monitoring processes to identify fatigue, such as self-reported perceived ratings, heart rate-derived autonomic nervous system, neuromuscular functional jump/eccentric/concentric/isometric protocols, biochemical/immunological/endocrine, and joint range of motion (Thorpe et al., 2017).
"...We highly believe that the measurement of skin temperature, and therefore infrared thermography, should be considered as another monitoring technology to identify the fatigue origine and the individualized recovery strategy prescription..."
Ismael Fernández Cuevas
Besides the main applications of injury prevention, diagnosis support and injury monitoring (return to play), we have been exploring other promising applications of thermography to enhance performance (internal load).
We have been working and researching together with individual athletes and teams (mainly soccer ones). For them, we have used metrics to track the thermal tendency over the time without depending that much on absolute temperatures (what we call coefficient of variation). Based on that, we have been able to classify the global thermal responses of individuals after competition into three main types (based on their historical data):
We have observed a correlation between those global thermal responses and the fatigue and overload perception after competition.
The description of fatigue origin made by Thorpe (2021) perfectly fits into our preliminary hypothesis that a hypothermic trend might be more related to metabolic fatigue, and a hyperthermic one is more linked to a structural damage. Therefore, we suggest that infrared thermography might help to identify fatigue and guide the individualization of the recovery strategy to choose.
This is the case of a soccer team that has been assessed with thermography once a week for more than 3 months. The evaluations were performed before training the day after competition (MD + 1, Match Day). Each player had more than 4 evaluations and coefficient of variation was used as metric to describe the individual thermal trend.
Figure 2. Thermal responses of a football team in MD + 1.
As can be seen in figure 2, we find different thermal trends within the same group of players after the "same" stimulus (match). Surprisingly, among players with high values of external and internal load (distance and intensity perception) we find totally different thermal trends (hyperthermic and hypothermic coefficient of variations).
Based on those results, we recommend cooling strategies for players with a hyperthermic tendency, while for players with a global hypothermic profile, warming strategies would be better.
We are currently researching in order to bring more scientific evidence to confirm this hypothesis. Nevertheless, it is clear that thermography is a very interesting technology to quantify and monitor the internal load, which is extremely interesting and necessary to reduce injury incidence and enhance performance.
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REFERENCES
MAIN REFERENCE > Thorpe, R. T. (2021) Post-exercise Recovery: Cooling and Heating, a Periodized Approach. Front. Sports Act. Living 3:707503. doi: 10.3389/fspor.2021.707503
Kellmann, M. (2002). Enhancing Recovery: Preventing Underperformance in Athletes.
Nimmo, M. A., and Ekblom, B. (2007). Fatigue and illness in athletes. J. Sports Sci. 25 Suppl 1, S93–102. doi: 10.1080/02640410701607379
Noakes, T. D. (2000). Physiological models to understand exercise fatigue and the adaptations that predict or enhance athletic performance. Scand. J. Med. Sci. Sport. 10, 123–145. doi: 10.1034/j.1600-0838.2000.010003123.x
Thorpe, R. T., Atkinson, G., Drust, B., and Gregson, W. (2017). Monitoring fatigue status in elite team sport athletes: implications for practice. Int. J. Sports Physiol. Perform. 12, 1–25. doi: 10.1123/ijspp.2016-0434
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.
