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 (tonset), minimum finger temperature (Tmin), maximum finger temperature (Tmax), mean finger temperature (Tmean), and CIVDwaves). A negative relationship was observed between Tmax and SM ratio (r =  - 0.39, p = 0.001) and Tmean 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: Tmean (Males: 8.0 ± 1.9 °C; Females: 8.9 ± 1.6 °C, p = 0.36), Tmax (Males: 11.2 ± 3.1 °C; Females: 13.1 ± 1.2 °C, p = 0.16), Tmin (Males: 5.9 ± 1.4 °C; Females: 5.0 ± 1.7 °C, p = 0.31), and tonset (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.