Effects of sex and heating rate on skin blood flow oscillations during local heating in young adults.

The objective of this study was to explore sex and heating rate effects on frequency-domain indicators of the mechanisms modulating cutaneous vasodilation during local heating. In 30 young adults (21 ± 3 yr, 15 females), wavelet analysis of skin blood flux was assessed from laser-Doppler flux signals at the chest, abdomen, arm, forearm, thigh, and calf during rapid (33-42°C; 1°C·20 s-1) and gradual (33-42°C; 1°C·5 min-1) local skin heating. A wavelet transform using a Morlet mother wavelet was computed over the entire signal for each heating protocol (minimum 90 min), and 5-min time windows were subsequently isolated to determine responses during baseline and the 42°C heating plateau. Wavelet data were decomposed into metabolic, neurogenic, myogenic, respiratory, and cardiac frequency bands and presented as absolute and relative (normalized) amplitudes. There was a significant sex by heating rate interaction for relative wavelet amplitude in the metabolic frequency band (P = 0.003), which was 0.89-fold [0.82, 0.98] lower (P = 0.006) during rapid heating compared with gradual heating for females only. There were no significant interactions for the other frequency bands (all P ≥ 0.054). Males showed greater absolute and relative amplitudes for neurogenic and myogenic bands compared with females (all P ≤ 0.022). Rapid heating resulted in significantly lower absolute amplitudes for metabolic, neurogenic, and cardiac bands compared with gradual heating (all P ≤ 0.004). However, there was a significantly greater relative amplitude for the respiratory band during rapid heating compared with gradual (P = 0.030). These exploratory findings highlight important sex and heating rate effects on wavelet-based indicators of the mechanisms modulating cutaneous vasodilation during local heating.NEW & NOTEWORTHY Wavelet analysis showed males relied more on neurogenic and myogenic mechanisms than females to modulate skin blood flow during local heating. Rapid heating produced lower absolute wavelet amplitudes for metabolic, neurogenic, and cardiac frequency bands compared with gradual heating. Frequency-domain responses showed weak discrimination between skin sites across the torso and limbs. Our findings highlight sex and heating rate effects on cutaneous vasodilator mechanisms during local heating using noninvasive wavelet-based approaches for understanding microvascular control.