Infrared thermography (IRT) has been gaining in popularity in clinical and scientific research due to the increasing availability of affordable infrared cameras. This study aims to determine the similarity of measurement performance between three models of IRT camera during assessment of skin temperature before and after physical exercise. Three models of FLIR thermographic cameras (E60bx, Flir-One Pro LT, and C2) were tested. Thermal images were taken of the foot sole, anterior leg, and anterior thigh from 12 well-trained men, before and after a 30-min run on a treadmill. Image files were blinded and processed by three evaluators to extract the mean, maximum, and standard deviation of skin temperature of the region of interest. Time for data processing and rate of perceived effort was also recorded. Data processing was slower on the E60bx (CI95% E60 vs C2 [0.2, 2.6 min], p = 0.02 and ES = 0.6); vs. Flir-One [0.0, 3.4 min], p = 0.03 and ES = 0.6) and was associated with lower effort perception (E60 3.0 ± 0.1 vs. Flir-One 5.6 ± 0.2 vs C2 7.0 ± 0.2 points; p < 0.001 and ES > 0.8). The C2 and Flir-One cameras underestimated the temperature compared with the E60. In general, measuring mean temperature provided higher camera and examiner intra-class correlations than maximum and standard deviation, especially before exercise. Moreover, post exercise mean skin temperatures provided the most consistent values across cameras and evaluators. We recommend the use of mean temperature and caution when using more than one camera model in a study.

Small skin temperature asymmetries are claimed to indicate injuries, but the influence of measurement conditions and technical aspects of image acquisition are concerns for determining temperature asymmetries. This research determines whether distance and camera specifications affect thermal asymmetries detection. We simulated thermal asymmetries filling two glasses with water at different temperatures measured at two distances (0.7 and 1.5 m) using four different infrared cameras (T1020, E60BX, C2 and FLIR ONE). Linear regression verified the similarity between each camera and the T1020 camera (gold standard). The intraclass correlation coefficient assessed the inter-camera reproducibility. Linear regression reported increasing adjustment using mean temperature, with lower values at 1.5 m between the T1020 and FLIR ONE (0.7 m, r = 0.58; 1.5 m, r = 0.34), C2 (0.7 m, r = 0.90; 1.5 m, r = 0.62) and E60BX (0.7 m, r = 0.96; 1.5 m, r = 0.68). Higher inter-camera reproducibility was observed at 0.7 m than 1.5 m. It is preferable to take thermal images with shorter distances and to prioritise cameras with superior hardware characteristics. The portability of FLIR ONE and C2 may be an advantage in studies investigating expected differences greater than 0.05ºC and larger regions of interest.

Objective : Foot orthoses are increasingly used by runners despite the controversy about whether their use can reduce the risk of overuse injuries. Some authors have found modifications in plantar pressures with the use of foot orthoses, which could produce changes in the surface skin temperature of the foot soles. The aim of this study was to analyse the effects of custom-made and prefabricated foot orthoses on the skin temperature of different regions of both foot soles after running. Approach : Twenty-four participants carried out a maximal aerobic speed test as a pre-test, and three running tests at the laboratory wearing different foot orthoses conditions (control, prefabricated and custom-made) previously randomized. Skin temperature of four regions of interest of the foot soles was assessed before, immediately after and ten minutes after running. Main results : The use of prefabricated and custom-made foot orthoses did not produce changes on skin temperature of the foot soles neither in absolute temperatures ( p > 0.05), nor in temperature variations: between immediately after and before running ( p > 0.05), and between ten minutes after and immediately after running ( p > 0.05). Otherwise, higher values were found with no insoles than with prefabricated foot orthoses, 10 min after running in relation to before running, in forefoot [mean (standard deviation): 5.6 (2.4) versus 3.7 (2.7) °C; p = 0.02; effect size (ES d ) = 0.72], midfoot [3.7 (1.5) versus 2.7 (1.5) °C; p = 0.03; ES d = 0.65] and rearfoot [4.18 (2.05) versus 2.9 (1.82) °C; p = 0.02; ES d = 0.64)]. Significance : In conclusion, the use of foot orthoses, in general, does not affect the surface skin temperature of the foot soles after an intense run.