Heat dissipation evaluation in exercise by infrared thermography

INTRODUCTION Heat dissipation during sport exercise is very important to improve athlete performance. An help to physiological mechanism of generation and transport of heat in the muscle under stress and in surrounding districts, is given by IR thermography to evaluate the surface heat dissipation locally. Thermography is useful because of its high sensitivity (0.05°C) and global representation of thermal process. Its use is recommended for the athletic evaluation because it is a non-invasive technique that doesn’t need any contact with the skin, avoiding physic and psychologic conditioning (Merla et al., 2010). METHODS We tested two groups of female subjects: 9 athletes and 9 sedentaries (mean age 19.39±3.26 y, weight 53.82±5.36 kg, height 1.64±0.06 m). They performed an exercise (standing calf raise with both feet) that limits the work to one group of muscle (gastrocnemius and soleus) and allows a perfect visibility for a correct thermographic shoot. It consists to raise and lower heels (rate 1 s) without over load (N.S.C.A., 2010). Thermal images was recorded (1 Hz frame-rate) during 14 minutes (2 min. of pre-exercise to determinate basal temperature, 2 min. of exercise, 10 min. of recover). Two Regions of Interest (ROI) were selected following anatomical and functional correspondence with the muscles involved in exercise, one on each calf (Zaidi et al., 2007). The data were analyzed with a dedicated software for thermal images. The considered parameter was the mean temperature over an area of 2mmq of the hottest spot in the calf. RESULTS Both groups show a minimum in temperature after few seconds of the exercise. The calves temperatures increase with linear trend during the whole exercise and in the first minutes of recover, but with a different slope. Temperature variation in 2min. recovery-time of the athletes is 1.07°C, while for the group of sedentaries is 0.76°C. DISCUSSION From these preliminary results is clear that IR thermography is a valid diagnostic method in evaluation of heat dissipation during and after physical exercise. The different slopes of the temperature trends during exercise and the two minutes post exercise indicate that calves of athletes dissipate more heat than calves of sedentaries. It can be explained with a better muscular efficiency in trained subjects, used to do exercise, and probably due to a less fat mass in the calves of athletes than in calves of sedentaries (Merla et al., 2010). REFERENCES Merla, A., Mattei Peter A., Di Donato L., Romani G. (2010). Ann. Biomed. Eng. 38:158–163. N.S.C.A. (2010). Esercizi per l’allenamento in palestra. Calzetti-Mariucci. Zaidi H., Taiar R., Fohanno S., Polidori G. (2007). Acta Bioeng. Biomech. 9:47-51.