In physiotherapy, various physical agents are applied in order to combat pain, inflammation and to maximize the movement possibility of the treated person. Many physical modalities influence the body temperature; therefore, the therapy results may be directly visualized in terms of thermovision. The therapeutic doses and duration of treatment should be personalized according to the patient needs, feelings during the therapy, and the observed therapeutic results. Thermal imaging allows to visualize the skin temperature, as well as the temperature changes due to the physiotherapeutic procedures, and it is a helpful tool for therapy outcomes monitoring. In this paper, we analyzed the body response to therapeutic cooling (local cryotherapy) and heating (red and near infrared irradiation with special lamp) in two groups of volunteers: students (mean age 20.4) and older people (mean age 68.7). The physical agents were applied on the right thigh area. The mean temperatures in this areas were determined from thermal images before treatment, just after, and then 15 and 30 min after the therapy. The new MATLAB-based software was developed for image processing and analysis in selected regions of interests (ROI). The analysis revealed that in the case of heating the mean temperature returns to the initial one after 30 min in younger persons, whereas in elderly persons after 30 min it was still higher than that before the treatment. In the case of cooling, in older people the decrease of the mean temperature was smaller than in juniors. The analysis of temperature distribution in ROI in the untreated left leg revealed also that there is a systemic response to the physical agents, which was more visible after the application of cryotherapy. The thermovision allowed to find out the different responses to the physiotherapy in younger and older persons, what should be taken into account by therapy planning.