By definition, when physical therapy is applied to any living tissue, a change in the physiology of the region will occur. Cryotherapy, massage therapy, laser or any other treatments will have effects on the symptoms, on the local hormonal and enzymatic environment or on the vascularity of the tissue. In addition, in the vast majority of cases there will be a significant change in the temperature of the skin in that particular region.
It is, therefore, to be expected that, after a local cryotherapy session on a knee, that area will significantly decrease the temperature of the skin. This change in physiology is accompanied by a reduction in most signs and symptoms, such as pain, swelling, or tissue compliance. And the opposite will happen if we apply diathermy on a muscle: we will reduce the pain, we will accelerate the recovery and contractile capacity of that tissue, due to the significant increase in the temperature of that region.
In figure 1, we can visually observe the examples we just talked about:
Figure 1. Thermal effect of different treatments, assessed with infrared thermography. Local cryotherapy in the right anterior thigh (1a) and diathermy in the left posterior thigh (1b). Images property of ThermoHuman.
Thanks to such visual examples as the previous ones, it is so interesting to observe the thermal effects of different treatments with thermography, since depending on its magnitude we can assess therapeutic efficacy, and thus assess whether the choice is appropriate.
Lubkowska & Pluta (2022), in a recently published systematic review, have reviewed the scientific literature on this subject. As results, we will see a description of the main physical therapies that have been evaluated with thermography. Specifically, they study the effects of cryotherapy, laser therapy, electrotherapy, diathermy and massage, of which we present the results below.
It is, without a doubt, the most studied treatment to date due to its great capacity for thermal modification in contact with the skin. Of the 51 results found initially, after applying inclusion and exclusion criteria, 21 individual studies were reviewed in this regard (n= 963). Among local cryotherapy studies, its use stands out in the comparison and assessment of different cooling methods, such as cold packs, ice packs, liquid nitrogen vapor or ice massage. In figure 2, we can observe the local effect of drastic reduction in the temperature of the knee region in this patient (Radecka et al. 2021), with a thermal asymmetry of -9.8º C:
Figure 2. Example of drastic reduction in local temperature in the left knee, after application of local cryotherapy. (Radecka et al. 2021)
As examples of whole body cryotherapy, cold water immersion stands out, without a doubt, in which the athlete is immersed in a bathtub or bucket containing water at between 5 and 15° C, with the aim of improving the muscle recovery, although cryo-cabines are gaining in popularity with short duration protocols (3 minutes) at extremely low temperatures (-110 to -160º C).
In general, cryotherapy causes changes in skin temperature and stimulates the skin's thermoreceptors, affecting the body's thermoregulation. Having thermography allows us to assess the magnitude of this drop in temperature.
Of the 31 studies found in the first search, only 2 were included in the review (n = 55): one on the evolution of pressure ulcers (Bilska et al. 2020) and another on the application of biophotomodulation (Stamborowski et al. 2021), represented in figure 3. More exhaustive research is necessary before a thermal effect can be attributed to this type of therapy.
Figure 3. Thermal image of a patient after the application of biophotomodulation (laser). Extracted from Stamborowski et al. (2021).
Of the 11 individual studies that were reviewed, only one (Benito-Martínez et al. 2020) met the inclusion and exclusion criteria. With n = 45, he investigated the thermal effects on skin temperature by applying square biphasic symmetric currents to one of the thighs.
The results show an increased temperature of 0.35 °C, after the application of electrotherapy, thus confirming a greater local vascularization thanks to selective muscle recruitment. In Figure 4, the thighs of a patient are shown to which electrical currents are applied at different times. We can observe the increase in temperature on the recruited side, especially 10 minutes after treatment:
Figure 4. Patient to whom square biphasic symmetric electrical currents are applied to the right thigh, analyzed by thermography before (4a), immediately after (4b), 10 minutes later (4c) and 20 minutes later (4d). Extracted from Benito-Martínez et al. 2020.
Of the 32 results found initially, after applying inclusion and exclusion criteria, 6 individual studies were reviewed in this regard (n= 186). Two thermal effects of extracorporeal shock waves, shortwave and microwave diathermy, and Tecartherapy were studied. Figure 5 shows the effects of increased skin temperature in some of the regions treated with diathermy, such as the posterior region of the knee (+0.8º C) (Kaźmierska et al. 2021).
Figure 5. Thermal effects in different regions of the body after diathermy treatment. Extracted from Kaźmierska et al. 2021.
Of a total of 20 articles found, four of them were reviewed after meeting the inclusion and exclusion criteria, adding a total of 127 patients. Wälchli y colaboradores (2014), established a temperature increase of 0.7 °C in the pre vs. post treatment, thus describing the massage as a hyperthermic therapy, due to its short-term vasodilator effect.
Figure 6. Patient before (6a), after 10 minutes of acclimatization (6b), immediately after massage treatment (6c) and 10 minutes after treatment (6d). Extracted from Wälchli et al. (2014).
Physical treatments produce therapeutic effects, through a change in metabolism in the physiology of the target tissue, which results in an increase or decrease in regional temperature.
Thermography measures the surface temperature of the skin, which makes it an easy-to-apply technology when evaluating the effectiveness of a treatment. Thanks to this review, health professionals who apply physical treatment can find in thermography a tool that gives them a baseline to assess the suitability of a specific physical therapy, based on the thermal behavior obtained after treatment.
Benito-Martínez, E.; Senovilla-Herguedas, D.; de la Torre-Montero, J.C.; Martínez-Beltrán, M.J.; Reguera-García, M.M.; Alonso-Cortés, B. Local and contralateral effects after the application of neuromuscular electrostimulation in lower limbs. Int. J. Environ. Res. Public Health 2020, 17, 9028
Bilska, A.; Stangret, A.; Pyzlak, M.; Wojdasiewicz, P.; Szukiewicz, D. Skin surface infrared thermography in pressure ulcer outcome prognosis. J. Wound Care 2020, 29, 707–718
Kaźmierska, B., Sobiech, K.A., Demczuk - Włodarczyk, E. et al. Thermovision assessment of temperature changes in selected body areas after short-wave diathermy treatment. J Therm Anal Calorim (2021).
Lubkowska A, Pluta W. Infrared Thermography as a Non-Invasive Tool in Musculoskeletal Disease Rehabilitation—The Control Variables in Applicability—A Systematic Review. Applied Sciences. 2022; 12(9):4302.
Radecka, A., Pluta, W., & Lubkowska, A. (2021). Assessment of the Dynamics of Temperature Changes in the Knee Joint Area in Response to Selected Cooling Agents in Thermographic Tests. International journal of environmental research and public health, 18(10), 5326.
Stamborowski SF, de Oliveira Spinelli BM, Lima FPS, Costa DR, de Silveira Souza GA, Lima MO, Lopes Martins RAB. The influence of photobiomodulation on the temperature of the brachial biceps during muscle fatigue protocol. Lasers Med Sci. 2021 Oct;36(8):1741-1749.
Wälchli, C.; Saltzwedel, G.; Krüerke, D.; Kaufmann, C.; Schnorr, B.; Rist, L.; Eberhard, J.; Decker, M.; Simões-Wüst, A.P. Physiologic effects of rhythmical massage: A prospective exploratory cohort study. J. Altern. Complement. Med. 2014, 20, 507–515.
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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.
