Thermoregulatory Responses to Air Temperature of −5 o C at Different Wind Speeds: Significance of Strong Wind in a Mild Cold Environment

Abstract Background Air temperature that is considered as cold varies according to individuals. For most people temperatures below 0oC is considered ‘cold’. Urban people who live in temperate climates are accustomed to mild cold with varying wind speeds, but relatively few studies have examined the effects of wind speed in mild cold on individuals wearing winter clothing, especially compared to studies conducted in severe cold environments. We examined thermoregulatory responses to varying wind speeds in mild cold, considering anthropometric characteristics of individuals. Methods Ten healthy males (23.9 ± 3.3 y in age, 175.8 ± 4.9 cm in height, 74.4 ± 7.0 kg in body weight) participated in the following four wind conditions (0, 2, 4.5, and 7 m·s⁻¹) at an air temperature of − 5°C (Wind chill temperature: -5oC ~ -12oC). Subjects wore winter clothing (IT, 2.1 clo) and every trial consisted of 80 min (10-min rest, 60-min walking, and 10-min recovery). Results Rectal and gastrointestinal temperatures remained stable across all the conditions, suggesting sufficient insulation from the winter clothing. However, peripheral skin temperatures, particularly on the hand, foot, and finger significantly decreased with higher wind speeds (all Ps < 0.05). At 7 m·s⁻¹, the temperature of the fingers dropped to an average of 12.7°C. Overweight subjects showed less frequent shivering compared to normal-weight subjects, while body surface area (BSA) and body mass index (BMI) negatively correlated with overall thermal comfort (all Ps < 0.05). Subjective thermal and wind sensations also increased with wind speed (all Ps < 0.05). Conclusions While typical winter clothing (2.1 clo) effectively maintains core temperature in wind chill conditions down to − 12°C, extremities, particularly the hands, require better insulation. Peripheral skin temperatures and thermal comfort, provide reliable indicators for assessing cold stress. Physical properties of the body also influenced cold responses, with overweight individuals exhibiting less frequent shivering and larger body surface areas correlating with greater cold sensitivity. These findings offer insights into optimizing winter clothing design to improve comfort and safety in windy conditions in mild cold.