Partial cooling of the upper body with a water-cooled vest in an environment exceeding body temperature.

OBJECTIVES: To evaluate the efficacy of water-cooled clothing that continuously cools restricted body areas to suppress body temperature increase as an anti-heatstroke measure for workers in hot environments that exceed body temperature. METHODS: Ten healthy men were placed in Room A (air temperature: 25°C, relative humidity: 50%) for 15 min. They were then transferred to Room B (air temperature: 40°C, relative humidity: 50%), where they rested for 10 min, then put on cooling clothing, and again rested for 15 min (the control group rested for 25 min). They then performed intense ergometer exercise for 40 min at 40% maximal oxygen consumption after which they rested for 10 min. The three trial conditions were CON (long-sleeved summer work clothes), VEST (cooling vest), and P-VEST (partial cooling vest). In VEST and P-VEST, water-cooled clothing continuously recirculated with 10°C water was used to cool the upper body. In P-VEST, only the neck, axillae, and heart areas were in contact with the cooled clothing. The measured indices were the rectal, esophageal, and external auditory canal temperatures; heart rate; estimated sweat volume; and subjective evaluations. RESULTS: Compared with the CON condition, the rectal, esophageal, and external auditory canal temperatures and the heart rate were significantly lower and the subjective indices were decreased in the VEST and P-VEST conditions. CONCLUSIONS: Partial cooling showed a body cooling effect similar to that of whole upper body cooling. Partial body cooling promoted the heat dissipation, suggesting that partial cooling is efficient for maintaining body cooling in hot environments.

Efficacy of ice slurry and carbohydrate-electrolyte solutions for firefighters.

OBJECTIVES: To examine the thermoregulatory and fluid-electrolyte responses of firefighters ingesting ice slurry and carbohydrate-electrolyte solutions before and after firefighting operations. METHODS: Twelve volunteer firefighters put on fireproof clothing and ingested 5 g/kg of beverage in an anteroom at 25°C and 50% relative humidity (RH; pre-ingestion), and then performed 30 minutes of exercise on a cycle ergometer (at 125 W for 10 minutes and then 75 W for 20 minutes) in a room at 35℃ and 50% RH. The participants then returned to the anteroom, removed their fireproof clothing, ingested 20 g/kg of beverage (post-ingestion), and rested for 90 minutes. Three combinations of pre-ingestion and post-ingestion beverages were provided: a 25℃ carbohydrate-electrolyte solution for both (CH condition); 25℃ water for both (W condition); and a -1.7℃ ice slurry pre-exercise and 25℃ carbohydrate-electrolyte solution post-exercise (ICE condition). RESULTS: The elevation of body temperature during exercise was lower in the ICE condition than in the other conditions. The sweat volume during exercise was lower in the ICE condition than in the other conditions. The serum sodium concentration and serum osmolality were lower in the W condition than in the CH condition. CONCLUSIONS: The ingestion of ice slurry while firefighters were wearing fireproof clothing before exercise suppressed the elevation of body temperature during exercise. Moreover, the ingestion of carbohydrate-electrolyte solution by firefighters after exercise was useful for recovery from dehydration.