When is the best time to do a thermography evaluation?

Thermography is a useful tool to assess tissue response to interventions. Depending on the behavior of the resulting thermal pattern, one can quickly and intuitively understand whether a tissue has been heated or cooled, and what our purpose was. In addition, it is an ideal tool if you seek to improve education in the patient or athlete.

Human tissues, depending on their vascularization, their connection to the central nervous system and their functional physiology, will respond to stimuli in a very different way. As a general rule, when we evaluate with thermography we look for two objectives (and four applications):

• Evaluate the state of the athlete to understand their basal thermal profile, detect regions with an abnormal signal and/or be able to support the diagnosis in the event of a pathology. Given all these applications, we hope that, either in a healthy athlete or in an injured athlete, thermography will inform us of the temperature, and hence the physiology, of the different regions.

• On the other hand, we can generally look for the response of how an athlete or patient behaves before an intervention or a planned stimulus, to understand what the intervention produces. What in research is known as pre-post quasi-experimental studies.

Therefore, when faced with these types of objectives, we look for three types of response: normothermia, hyperthermia or hypothermia.

When the result of the evaluation is normothermia.

We always look for a state of balance or homeostasis, that the tissues are in accordance with normal thermal patterns, in a state of normothermia between both extremities without generating asymmetries, it is the ideal result.

In scientific research, the thermoregulatory system tries to keep a state of equilibrium for the whole organism, researchers such as Uematsu et al (1989) and Vardasca et al. (2012) verified that healthy subjects maintain this state of balance. In the same way, from the ThermoHuman department, it was investigated with more than 950 healthy athletes, establishing an average asymmetry of 0.004 ºC.

When the result of the evaluation is hyperthermia and hypothermia.

We can observe in Sillero-Quintana et al. (2015) that depending on the tissue affected, the thermal response is different. While the tissues most dependent on the arthrokinematic system such as bones, joints, ligaments and fascia tend to respond to injury with hyperthermia; tissues dependent on the neuromuscular system (nerve and muscle) tend to respond with hypothermia to its involvement.

In addition, when there is an injury to the skin or to the more superficial layers of the fascia, such as a burn, a scar, or even an infection after an operation, the tissue also tends to respond with hypothermia. In the case of burns, the response is hypothermic and will depend on the degree. However, burns from sun exposure tend to be hyperthermic.

The study by Sillero-Quintana et al. (2015) is one of the most complete in this regard, since it analyzes almost 250 people in a screening in hospital emergencies. However, it only provides us with information about the tissue when it is already injured, so knowledge of the moments prior to the injury, and even of the different responses to interventions, is still a field to be explored.

There is some research into the response to classical physiotherapy treatments measured by thermography, and except for topical ice application, most are aimed at increasing blood flow and tissue oxygenation with subsequent hyperthermic response of the region (Lubkowska et al. 2022).

Something similar occurs with the application of training stimuli, most have a hyperthermic response, not acutely, but after 8 hours of stimulus application (Fernandez-Cuevas et. al 2014). Besides, recently a line of research has been opened according to the type of fatigue generated, the thermal response and the presence of discomfort, which according to our first results is linked to a hypothermia response.

For all these reasons, it seems interesting to determine when are the best moments to take a thermographic image and why.

When is the best time to do the evaluation?

When implementing thermography in different sports and clinical environments we have to take into account the objective of the evaluation:

Before the intervention: if your objective is to generate a thermal profile to assess the behavior of the athlete or patient in a basal state, it is advisable to standardize the intake before any type of intervention, in a controlled environment and allowing the subject the relevant acclimatization time. Furthermore, if your objective is to identify anomalies or possible pathologies, before any diagnostic test it will also be recommended.

During the intervention: if your objective is to measure the behavior of the thermoregulatory system during an intervention due to its relationship with the other systems, during the test it is ideal to establish markers with other technologies. For example, the relationship with the lactate threshold.

Immediately after the intervention: if what is wanted is to obtain a measurement of the acute effect of the intervention and how it has affected the thermoregulation system and the other related systems, this measurement allows us to know the post-intervention result. It could be useful to check the changes in the tissue caused by a treatment at the local level or by training and its activation of the musculature to evaluate the efficacy.

24/48h after the intervention: If what we want is to establish the assimilation of the chronic effects of an intervention or identify possible regions that respond atypically to the intervention. such as a region that suffers a functional overload due to compensation (hyperthermia) or a tissue that suffers a reciprocal inhibition linked to a painful response (hypothermia). This moment allows the generation of a follow-up pattern of the asymmetries found through the ThermoHuman metrics.

From ThermoHuman we recommend two moments that we understand as key in a thermographic evaluation. The evaluation before in a basal state to identify the individualized patterns of the athlete and the evaluation 24/48 hours after the intervention because it allows us to understand how the athlete reacts and identify regions with a different from normal behavior.

Conclusions

To carry out a thermography analysis we have to take into account the purpose of the evaluation. Depending on our objective, each moment provides us with unique advantages of the physiology analysis of the tissues by means of thermography. This allows healthcare and sports professionals to assess the efficacy of an intervention at any time and make informed decisions about its use.

References

Fernández-Cuevas, I., Sillero-Quintana, M., Garcia-Concepcion, M. A., Serrano, J. R., Gomez-Carmona, P., & Marins, J. B. (2014). Monitoring skin thermal response to training with infrared thermography. New Stud Athl, 29(1), 57-71.

Lubkowska, A., & Pluta, W. (2022). Infrared Thermography as a Non-Invasive Tool in Musculoskeletal Disease Rehabilitation—The Control Variables in Applicability—A Systematic Review. Applied Sciences, 12(9), 4302.

Sillero-Quintana, M., Fernández-Jaén, T., Fernández-Cuevas, I., Gómez-Carmona, P. M., Arnaiz-Lastras, J., Pérez, M. D., & Guillén, P. (2015). Infrared thermography as a support tool for screening and early diagnosis in emergencies. Journal of Medical Imaging and Health Informatics, 5(6), 1223-1228.

Uematsu, S., Edwin, D. H., Jankel, W. R., Kozikowski, J., & Trattner, M. (1988). Quantification of thermal asymmetry: part 1: normal values and reproducibility. Journal of neurosurgery, 69(4), 552-555.

Vardasca, R., Ring, E. F. J., Plassmann, P., & Jones, C. D. (2012). Thermal symmetry of the upper and lower extremities in healthy subjects. Thermology international, 22(2), 53-60.

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