Thermal resting pattern and acute skin temperature response to exercise in older adults: Role of cardiorespiratory fitness

Background: Infrared thermography is a growing area of interest in sports science due to the potential of skin temperature (T-sk) measurements to provide valuable information from rest to exercise. However, limited research exists on T-sk in older adults and the impact of factors such as sex and cardiorespiratory fitness (CRF) on T-sk. This study aims to investigate T-sk at rest and after acute exercise in older adults and assess whether sex or CRF influences T-sk. Methods: Ninety-two participants (41 women, 68.48 +/- 3.01 years) were examined with a thermographic camera in a conditioned room (23.02 +/- 3.01 degrees C) at rest and after a graded protocol. The T-sk of 25 regions of interest (ROIs) were extracted and analysed. Results: Men had higher overall T-sk at rest in 76% of ROIs, showing significant differences (p < 0.010) in six specific ROIs, independent of CRF. Both sexes had similar T-sk responses after graded exercise, with increases in distal parts (1.06 +/- 0.50 C-degrees), decreases in proximal parts (-0.62 +/- 0.42 degrees C), and stable central T-sk (0.23 +/- 0.59 degrees C). Increases in lower limb T-sk were significantly associated with CRF in men and women (beta = 0.438, p = 0.001, and beta = 0.535, p < 0.001, respectively), explaining 17% and 27% of the variance, respectively. Conclusions: This study demonstrates a sex-specific effect on resting T-sk in older adults, suggesting that sex-specific T-sk patterns should be considered when analysing T-sk in this population. Additionally, the association between increases in lower limb T-sk and CRF suggests that T-sk could be a promising predictor of CRF in older adults.