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Watanabe H, Kadokura Y, Sugi T, Saito K, Nagashima K. Influence of sustained mild dehydration on thermoregulatory and cognitive functions during prolonged moderate exercise. Eur J Appl Physiol 2024:10.1007/s00421-024-05548-6. [PMID: 38985305 DOI: 10.1007/s00421-024-05548-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2024] [Accepted: 07/04/2024] [Indexed: 07/11/2024]
Abstract
PURPOSE The current study investigated whether sustained mild dehydration affects thermoregulatory function and cognitive performance during prolonged exercise. METHODS Twelve young adults performed a test consisting of three sets of 20-min exercise with 2-min intervals under euhydrated (control, CON) and mildly dehydrated conditions (MDEH) at an ambient temperature of 30 °C and 60% relative humidity. MDEH was established by restricting water intake for 24 h, resulting in urine specific gravity of ≥ 1.020. Heart rate (HR), mean arterial blood pressure (MAP), skin blood flow (SkBF), sweat rate (SR) on the chest and forearm, and ear canal and mean skin surface temperatures (Tear and mean Tskin, respectively) were continuously recorded. For each exercise set, thermal and humid sensations and thermal discomfort were assessed using visual analog scales (VAS), and the rating of perceived exertion (RPE) was estimated. Cognitive performance on the Go/No-Go (easy) and incongruent Stroop (difficult) tasks was assessed before and after the test. RESULTS No differences were observed in HR, MAP, SkBF, SR, Tear, and mean Tskin between the CON and MDEH. Thermal and humidity sensations, thermal discomfort, and RPE were higher in MDEH than in CON. Moreover, response time to the Stroop task was prolonged in MDEH. CONCLUSION These findings suggest that sustained mild dehydration does not affect autonomic thermoregulation during exercise. Augmented thermal perception and perceived exertion, which are necessary for behavioral thermoregulation, were noted; however, cognitive function may be attenuated under MDEH.
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Affiliation(s)
- Hironori Watanabe
- Institute for Energy and Environmental System, Sustainable Energy & Environmental Society Open Innovation Research Organization, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo, 1698555, Japan
- Advanced Research Center for Human Sciences, Waseda University, 2-579-15 Mikajima, Tokorozawa, Saitama, 3591192, Japan
- Body Temperature and Fluid Laboratory, Faculty of Human Sciences, Waseda University, 2-579-15 Mikajima, Tokorozawa, Saitama, 3591192, Japan
| | - Yuma Kadokura
- Infrastructure Systems Research & Development Center, Toshiba Infrastructure Systems & Solutions Corporation, Kawasaki, Kanagawa, 2129595, Japan
| | - Taisuke Sugi
- Body Temperature and Fluid Laboratory, Faculty of Human Sciences, Waseda University, 2-579-15 Mikajima, Tokorozawa, Saitama, 3591192, Japan
| | - Kiyoshi Saito
- Institute for Energy and Environmental System, Sustainable Energy & Environmental Society Open Innovation Research Organization, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo, 1698555, Japan
- Department of Applied Mechanics and Aerospace Engineering, School of Fundamental Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo, 1698555, Japan
| | - Kei Nagashima
- Institute for Energy and Environmental System, Sustainable Energy & Environmental Society Open Innovation Research Organization, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo, 1698555, Japan.
- Body Temperature and Fluid Laboratory, Faculty of Human Sciences, Waseda University, 2-579-15 Mikajima, Tokorozawa, Saitama, 3591192, Japan.
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Takamata A, Oka A, Nagata M, Kosugi N, Eguchi S, Sakagawa N, Takahashi A, Nishimoto Y, Nishimaki M, Morimoto K, Takihara T. Effect of fluid replacement with green tea on body fluid balance and renal responses under mild thermal hypohydration: a randomized crossover study. Eur J Nutr 2023; 62:3339-3347. [PMID: 37594507 DOI: 10.1007/s00394-023-03236-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2023] [Accepted: 08/08/2023] [Indexed: 08/19/2023]
Abstract
PURPOSE Maintaining an appropriate hydration level by ingesting fluid in a hot environment is a measure to prevent heat-related illness. Caffeine-containing beverages, including green tea (GT), have been avoided as inappropriate rehydration beverages to prevent heat-related illness because caffeine has been assumed to exert diuretic/natriuretic action. However, the influence of caffeine intake on urine output in dehydrated individuals is not well documented. The aim of the present study was to examine the effect of fluid replacement with GT on body fluid balance and renal water and electrolyte handling in mildly dehydrated individuals. METHODS Subjects were dehydrated by performing three bouts of stepping exercise for 20 min separated by 10 min of rest. They were asked to ingest an amount of water (H2O), GT, or caffeinated H2O (20 mg/100 ml; Caf-H2O) that was equal to the volume of fluid loss during the dehydration protocol; fluid balance was measured for 2 h after fluid ingestion. RESULTS The dehydration protocol induced hypohydration by ~ 10 g/kg body weight (~ 1% of body weight). Fluid balance 2 h after fluid ingestion was significantly less negative in all trials, and the fluid retention ratio was 52.2 ± 4.2% with H2O, 51.0 ± 5.0% with GT, and 47.9 ± 6.2% with Caf-H2O; those values did not differ among the trials. After rehydration, urine output, urine osmolality, and urinary excretions of osmotically active substances, sodium, potassium and chloride were not different among the trials. CONCLUSION The data indicate that ingestion of GT or an equivalent caffeine amount does not worsen the hydration level 2 h after ingestion and can be effective in reducing the negative fluid balance for acute recovery from mild hypohydration. TRIAL REGISTRATION ISRCTN53057185; retrospectively registered.
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Affiliation(s)
- Akira Takamata
- Department of Environmental Health, Nara Women's University, Nara, Japan.
| | - Ayano Oka
- Department of Environmental Health, Nara Women's University, Nara, Japan
| | - Mayuna Nagata
- Department of Environmental Health, Nara Women's University, Nara, Japan
| | - Natsumi Kosugi
- Department of Environmental Health, Nara Women's University, Nara, Japan
| | - Sayaka Eguchi
- Department of Environmental Health, Nara Women's University, Nara, Japan
| | - Nanako Sakagawa
- Department of Environmental Health, Nara Women's University, Nara, Japan
| | - Aoi Takahashi
- Department of Environmental Health, Nara Women's University, Nara, Japan
| | - Yuki Nishimoto
- Department of Environmental Health, Nara Women's University, Nara, Japan
| | - Mio Nishimaki
- Department of Environmental Health, Nara Women's University, Nara, Japan
| | - Keiko Morimoto
- Department of Environmental Health, Nara Women's University, Nara, Japan
- Department of Health and Nutrition, Kyoto Koka Women's University, Kyoto, Japan
| | - Takanobu Takihara
- Central Research Institute, ITO EN, Ltd., Makinohara, Shizuoka, Japan
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McKinley MJ, Martelli D, Pennington GL, Trevaks D, McAllen RM. Integrating Competing Demands of Osmoregulatory and Thermoregulatory Homeostasis. Physiology (Bethesda) 2019; 33:170-181. [PMID: 29616878 DOI: 10.1152/physiol.00037.2017] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Mammals are characterized by a stable core body temperature. When maintenance of core temperature is challenged by ambient or internal heat loads, mammals increase blood flow to the skin, sweat and/or pant, or salivate. These thermoregulatory responses enable evaporative cooling at moist surfaces to dissipate body heat. If water losses incurred during evaporative cooling are not replaced, body fluid homeostasis is challenged. This article reviews the way mammals balance thermoregulation and osmoregulation.
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Affiliation(s)
- Michael J McKinley
- Florey Institute of Neuroscience and Mental Health, University of Melbourne , Parkville , Australia.,Department of Physiology, University of Melbourne , Parkville , Australia
| | - Davide Martelli
- Florey Institute of Neuroscience and Mental Health, University of Melbourne , Parkville , Australia.,University of Bologna, Bologna , Italy
| | - Glenn L Pennington
- Florey Institute of Neuroscience and Mental Health, University of Melbourne , Parkville , Australia
| | - David Trevaks
- Florey Institute of Neuroscience and Mental Health, University of Melbourne , Parkville , Australia
| | - Robin M McAllen
- Florey Institute of Neuroscience and Mental Health, University of Melbourne , Parkville , Australia
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