Influence of body dimensions and sex on cold-induced vasodilation.

Cold-induced vasodilation (CIVD) is a physiological response characterized by cyclic vasodilation occurring within 5-10 min of cold exposure, predominantly in the fingers and toes. This study aimed to determine the roles of body dimensions, specifically surface-to-mass (SM) ratio and sex in modulating CIVD responses. Thirty-nine participants (mean ± SD age: 24 ± 3 yr; height: 174 ± 28 cm; weight: 75.3 ± 15.2 kg; 20 males & 19 females) completed a 30-min immersion of the digits in ice water while sitting in a thermoneutral room (22 °C). Skin temperature was measured continuously on the anterior pads of the index, middle, ring, and little finger to assess CIVD parameters (onset time (t_onset), minimum finger temperature (T_min), maximum finger temperature (T_max), mean finger temperature (T_mean), and CIVD_waves). A negative relationship was observed between T_max and SM ratio (r =  - 0.39, p = 0.001) and T_mean and SM ratio (r =  - 0.32, p = 0.001), indicating that individuals with smaller SM ratios exhibited enhanced CIVD responses. A subgroup of 7 males and 7 females with identical anthropometrics from the original cohort showed no differences between any CIVD parameter: T_mean (Males: 8.0 ± 1.9 °C; Females: 8.9 ± 1.6 °C, p = 0.36), T_max (Males: 11.2 ± 3.1 °C; Females: 13.1 ± 1.2 °C, p = 0.16), T_min (Males: 5.9 ± 1.4 °C; Females: 5.0 ± 1.7 °C, p = 0.31), and t_onset (Males: 12.0 ± 4.4 min; Females: 9.6 ± 3.6 min, p = 0.28). Therefore, body dimensions seem to play a crucial role in modulating CIVD responses, whereas sex does not.