Thermosensory mapping of skin wetness sensitivity across the body of young males and females at rest and following maximal incremental running

Humans lack skin hygroreceptors and we rely on integrating cold and tactile inputs from Atype skin nerve fibres to sense wetness. Yet, it is unknown whether sex and exercise independently modulate skin wetness sensitivity across the body. We mapped local sensitivity to cold, neutral and warm wetness of the forehead, neck, underarm, lower back, and dorsal foot in 10 males (27.8±2.7y; 1.92±0.1m 2 BSA) and 10 females (25.4±3.9y; 1.68 ± 0.1m 2 BSA), at rest and post maximal incremental running. Participants underwent our quantitative sensory test where they reported the magnitude of thermal and wetness perceptions (Visual Analogue Scales) resulting from the application of a cold (5°C below skin temperature) wet (0.8ml water), neutral wet, and warm wet (5°C above skin temperature) thermal probe (1.32cm2 ) to 5 skin sites. We found that: 1) females were ~14 to ~17% more sensitive to cold-wetness than males, yet both sexes were as sensitive to neutral- and warm-wetness; 2) regional differences were present for cold-wetness only, and these followed a cranio-caudal increase that was more pronounced in males (i.e. the foot was ~31% more sensitive than the forehead); 3) maximal exercise reduced cold-wetness sensitivity over specific regions in males (i.e. ~40% decrease in foot sensitivity), and it also induced a generalised reduction in warm-wetness sensitivity in both sexes (i.e. ~4 to ~6%). For the first time, we show that females are more sensitive to cold wetness than males, and that maximal exercise induce hygro-hypoesthesia. These novel findings expand our knowledge on sex differences in thermoregulatory physiology.