Thermal sensation and cell adaptability

Thermoregulation and thermal sensation during whole-body water immersion at different water temperatures in healthy individuals: A scoping review

BACKGROUND

Severe thermal discomfort may increase risk of drowning due to hypothermia or hyperthermia from prolonged exposure to noxious water temperatures. The importance of using a behavioral thermoregulation model with thermal sensation may predict the thermal load that the human body receives when exposed to various immersive water conditions. However, there is no thermal sensation "gold standard" model specific for water immersion. This scoping review aims to present a comprehensive overview regarding human physiological and behavioral thermoregulation during whole-body water immersion and explore the feasibility for an accepted defined sensation scale for cold and hot water immersion.

METHODS

A standard literary search was performed on PubMed, Google Scholar, and SCOPUS. The words "Water Immersion," "Thermoregulation," "Cardiovascular responses" were used either as independent searched terms and MeSH terms (Medical Subject Headings) or in combination with other text words. The inclusion criteria for clinical trials terms to thermoregulatory measurements (core or skin temperature), whole-body immersion, 18-60 years old and healthy individuals. The prementioned data were analyzed narratively to achieve the overall study objective.

RESULTS

Twenty-three published articles fulfilled the review inclusion/exclusion criteria (with nine measured behavioral responses). Our outcomes illustrated a homogenous thermal sensation in a variety of water temperatures ranges, that was strongly associated with thermal balance, and observed different thermoregulatory responses. This scoping review highlights the impact of water immersion duration on human thermoneutral zone, thermal comfort zone, and thermal sensation.

CONCLUSION

Our findings enlighten the significance of thermal sensation as a health indicator for establishing a behavioral thermal model applicable for water immersion. This scoping review provides insight for the needed development of subjective thermal model of thermal sensation in relation to human thermal physiology specific to immersive water temperature ranges within and outside the thermal neutral and comfort zone.

Adventurous tourism: acclimatization problems and decisions in trans-boundary travels

As the twenty-first-Century Maritime Silk Road tourism program aims on development of new tourist routes with special interest on the polar regions of the Arctic and the Antarctic, as well as the Tibetan Plateau, management of climate risks in travels and their reduction is an important issue for achievement of its goals at national and local levels. Acclimatization is crucial for adventurous tourists, and especially for those traveling to extremely cold and highly elevated environments, when climate and weather in tourist destination differ significantly from those at home. The Acclimatization Thermal Strain Index for Tourism (ATSIT) is designed and used to measure numerically the physiological expenses a traveler pays during the acclimatization process. The purpose of the present study is to examine acclimatization consequences for travels from Beijing, capital of China, to destinations at the Arctic, the Antarctic, and the Tibetan Plateau, collectively referred to as the 3Polar regions, during the main seasons of winter and summer, and back. The results show that acclimatizing to cold involves greater physiological strain than adjustment to heat. Acclimatization load in winter is low for all travels from Beijing and back home. ATSIT projections detect the most harmful degree of discomfort for summer travels from Beijing. The greatest acclimatization impact comes when changing locales from hot and humid to cold and dry climatic conditions, which might cause high and very high physiological strain. Moreover, as many destinations in the 3Polar regions, mostly in the Tibetan Plateau, are located in mountains, a special acclimatization plan is required to weaken the threat of mountain sickness. The results will be helpful for warning stakeholders and the decision makers in the tourism sector of economies, and are expected to be translated into action for the development of proper intervention procedures in health control, to minimize population loss.

Body mapping of cutaneous wetness perception across the human torso during thermo-neutral and warm environmental exposures

Sensing skin wetness is linked to inputs arising from cutaneous cold-sensitive afferents. As thermosensitivity to cold varies significantly across the torso, we investigated whether similar regional differences in wetness perception exist. We also investigated the regional differences in thermal pleasantness and whether these sensory patterns are influenced by ambient temperature. Sixteen males (20 ± 2 yr) underwent a quantitative sensory test under thermo-neutral [air temperature (Tair) = 22°C; relative humidity (RH) = 50%] and warm conditions (Tair = 33°C; RH = 50%). Twelve regions of the torso were stimulated with a dry thermal probe (25 cm(2)) with a temperature of 15°C below local skin temperature (Tsk). Variations in Tsk, thermal, wetness, and pleasantness sensations were recorded. As a result of the same cold-dry stimulus, the skin-cooling response varied significantly by location (P = 0.003). The lateral chest showed the greatest cooling (-5 ± 0.4°C), whereas the lower back showed the smallest (-1.9 ± 0.4°C). Thermal sensations varied significantly by location and independently from regional variations in skin cooling with colder sensations reported on the lateral abdomen and lower back. Similarly, the frequency of perceived skin wetness was significantly greater on the lateral and lower back as opposed to the medial chest. Overall wetness perception was slightly higher under warm conditions. Significantly more unpleasant sensations were recorded when the lateral abdomen and lateral and lower back were stimulated. We conclude that humans present regional differences in skin wetness perception across the torso, with a pattern similar to the regional differences in thermosensitivity to cold. These findings indicate the presence of a heterogeneous distribution of cold-sensitive thermo-afferent information.