EXERCISE-ASSOCIATED SKIN TEMPERATURE DYNAMICS BY INFRARED THERMOGRAPHY. METHODS AND APPLICATIONS.

Heat dissipation during sport exercise is an important physiological mechanism that may influence athletic performance. Therefore, monitoring skin temperature during exercise provides important physiological information about thermoregulatory processes. Skin temperature measurements through infrared thermography have the advantages to be non-invasive and to record temperature data simultaneously from different points on a wide area of the body. The aim of the present investigation were: first, to compare three methods of thermal images analysis in skin temperature evaluation, and second to study the skin temperature dynamics during two types of physical exercise. In the present thesis three studies will be presented and discussed. The analysis of thermographic images, with the goal of obtaining a temperature value representative of a specific area, is usually performed by different methods of averaging temperature values inside a selected Region of Interest (Troi and Tot). A comparison between the methods mainly used in literature in the specific case of a muscular group of calves on a population of 33 healthy subjects is presented. Here, it is presented an alternative method (Tmax) to obtain a temperature value of a specific area based on maximal temperature detection instead of considering the average temperature on the selected area. No meaningful difference in mean temperature between Troi and Ttot was found (p = 0.9), while temperature values calculated using Tmax were higher than the above methods (p < 0.001). The high correlation among the compared methods prove that they can equally represent temperature trends in cutaneous thermographic analyses. The second and the third study presented here are applicative study investigating the skin temperature response during physical exercise. The aim of the second study was to test the hypothesis that differences exist in the dynamics of exercise-associated skin temperature changes between trained and untrained subjects. Thermoregulation of a local muscle area (muscle–tendon unit) involved in a localized steady-load exercise (standing heels raise) using infrared thermography was investigated. Seven trained female subjects and seven untrained female controls were studied. Each subject performed standing heels raise exercise for 2 min. Thermal images were recorded prior to exercise (1 min), during exercise (2 min), and after exercise (7 min). The analysis of thermal images provided the skin temperature time course, which was characterized by a set of descriptive parameters. Two-way ANOVA for repeated measures detected a significant interaction (p = 0.03) between group and time, thus indicating that athletic subjects increased their skin temperature differently with respect to untrained subjects. This was confirmed by comparing the parameters describing the speed of rise of skin temperature. It was found that trained subjects responded to exercise more quickly than untrained controls (p<0.05). In conclusion, physical training improves the ability to rapidly elevate skin temperature in response to a localized exercise in female subjects. The third study presented here is a preliminary report, since the data analysis is still in progress. It aimed to investigate the skin temperature response by using infrared thermography during slow speed low intensity exercise as compared to normal speed low intensity exercise in squat trial. We hypothesized that low intensity resistance exercise with slow movement would result in a skin temperature response slower than the one of the normal speed exercise with the same intensity. 13 active males performed 2 sessions of deep squat exercise until exhaustion, with 50% of 1 RM. The pace of movement was set in 1s eccentric / 1s concentric and 5s eccentric / 5s concentric phase in the 1st and in the 2nd session respectively. Thermal images were recorded every 20s before exercise (2min), during exercise (until exhaustion), and after exercise (10min). Surprisingly, a different behaviour of skin temperature during and after exercise was observed among subjects: a decrease in skin temperature in 9 subjects (down group) and an increase in the other 4 (up group). Thus, statistics will be performed in each group separately. It was shown that the response of cutaneous circulation to dynamic exercise is characterized by a initial vasoconstriction to dissipate heat from the core through the skin followed by vasodilation driving the blood flow from inactive tissue (including the skin) to active muscles involved in exercise. We speculate that the unexpected different behaviour of the skin temperature response in the 2 sub-groups was probably due to a time-dependent predominance of vasoconstriction over vasodilation or viceversa.