title: Influence of osmotic stress on thermal perception and thermoregulation in heat is different between sedentary and trained men.
abstract: Hyperosmolality in extracellular fluid in humans attenuates autonomic thermoregulation in heat, such as sweating and blood flow in the skin. However, exercise training minimizes the attenuation. The aim of the present study was to clarify the influence of hyperosmolality on thermal perception and to assess the training effect of exercise. Ten sedentary (SED) and 10 endurance-trained (TR) healthy young men were infused with 0.9% (normal saline [NS]) or 3% NaCl (hypertonic saline [HS]) for 120min on two separate days. After infusion for 20min, heat stimulus to the skin of the whole body was produced by a gradual increase in hot water-perfused suit temperature (33°C, 36°C, and 39°C), which was first used in the normothermic condition and then in the mild hyperthermic condition (0.5-0.6°C increase in esophageal temperature) and controlled by immersion of the lower legs in a water bath at 34.5°C and 42°C, respectively. Thermal sensation and comfort were rated at the time of each thermal condition. Plasma osmolality increased by ~10mosmL/kg·H2O in the HS trial. In the mild hyperthermic condition, increases in sweat rate and cutaneous vascular conductance were lower in the HS than in the NS trial in both the SED and TR groups (p<0.05). In the SED group, thermal sensation in the mild hyperthermic condition was lower in the HS than in the NS trial (p<0.05); there was no significant difference between the trials in the TR group. These results might indicate that hyperosmolality attenuates thermal sensation with heat and that exercise training eliminates the attenuation.
authors.affiliation: Sport Science Center for Active Life, Faculty of Sport Sciences, Waseda University, Tokorozawa, Japan; Body Temperature and Fluid Laboratory (Laboratory of Integrative Physiology), Faculty of Human Sciences, Waseda University, Tokorozawa, Japan.
authors.forename: Ken
authors.initials: K
authors.lastname: Tokizawa
authors.affiliation: Body Temperature and Fluid Laboratory (Laboratory of Integrative Physiology), Faculty of Human Sciences, Waseda University, Tokorozawa, Japan.
authors.forename: Mayumi
authors.initials: M
authors.lastname: Matsuda-Nakamura
authors.affiliation: Body Temperature and Fluid Laboratory (Laboratory of Integrative Physiology), Faculty of Human Sciences, Waseda University, Tokorozawa, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Tanaka
authors.affiliation: Body Temperature and Fluid Laboratory (Laboratory of Integrative Physiology), Faculty of Human Sciences, Waseda University, Tokorozawa, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Uchida
authors.affiliation: Sport Science Center for Active Life, Faculty of Sport Sciences, Waseda University, Tokorozawa, Japan; Body Temperature and Fluid Laboratory (Laboratory of Integrative Physiology), Faculty of Human Sciences, Waseda University, Tokorozawa, Japan.
authors.forename: Cheng-Hsien
authors.initials: CH
authors.lastname: Lin
authors.affiliation: Sport Science Center for Active Life, Faculty of Sport Sciences, Waseda University, Tokorozawa, Japan; Body Temperature and Fluid Laboratory (Laboratory of Integrative Physiology), Faculty of Human Sciences, Waseda University, Tokorozawa, Japan; Institute of Applied Brain Sciences, Waseda University, Tokorozawa, Japan. Electronic address: k-nagashima@waseda.jp.
authors.forename: Kei
authors.initials: K
authors.lastname: Nagashima
mesh_terms: D000328:Adult; D001127:Arginine Vasopressin / Q000097:blood; D001833:Body Temperature Regulation / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D050884:HSP72 Heat-Shock Proteins / Q000097:blood; D064368:Healthy Volunteers; D006358:Hot Temperature; D006801:Humans; D008297:Male; D009997:Osmotic Pressure / Q000502:physiology*; D010101:Oxygen Consumption / Q000502:physiology; D010465:Perception / Q000502:physiology*; D012083:Renin / Q000097:blood; D012462:Saline Solution, Hypertonic / Q000008:administration & dosage; D012867:Skin / Q000098:blood supply; D012881:Skin Temperature / Q000502:physiology; D013546:Sweating / Q000187:drug effects; D013697:Thermosensing / Q000502:physiology*; D013997:Time Factors; D055815:Young Adult
chemical_list: D050884:HSP72 Heat-Shock Proteins; D012462:Saline Solution, Hypertonic; D001127:Arginine Vasopressin; D012083:Renin
keywords: Exercise training; Hyperosmolality; Thermal sensation