European Journal of Applied Physiology

, Volume 113, Issue 4, pp 1027–1034 | Cite as

Hypohydration and acute thermal stress affect mood state but not cognition or dynamic postural balance

  • Brett R. Ely
  • Kurt J. Sollanek
  • Samuel N. Cheuvront
  • Harris R. Lieberman
  • Robert W. KenefickEmail author
Original Article


Equivocal findings have been reported in the few studies that examined the impact of ambient temperature (T a) and hypohydration on cognition and dynamic balance. The purpose of this study was to determine the impact of acute exposure to a range of ambient temperatures (T a 10–40 °C) in euhydration (EUH) and hypohydration (HYP) states on cognition, mood and dynamic balance. Thirty-two men (age 22 ± 4 years, height 1.80 ± 0.05 m, body mass 85.4 ± 10.8 kg) were grouped into four matched cohorts (n = 8), and tested in one of the four T a (10, 20, 30, 40 °C) when EUH and HYP (−4 % body mass via exercise–heat exposure). Cognition was assessed using psychomotor vigilance, 4-choice reaction time, matching to sample, and grammatical reasoning. Mood was evaluated by profile of mood states and dynamic postural balance was tested using a Biodex Balance System. Thermal sensation (TS), core (T core) and skin temperature (T sk) were obtained throughout testing. Volunteers lost −4.1 ± 0.4 % body mass during HYP. T sk and TS increased with increasing T a, with no effect of hydration. Cognitive performance was not altered by HYP or thermal stress. Total mood disturbance (TMD), fatigue, confusion, anger, and depression increased during HYP at all T a. Dynamic balance was unaffected by HYP, but 10 °C exposure impaired balance compared to all other T a. Despite an increase in TMD during HYP, cognitive function was maintained in all testing environments, demonstrating cognitive resiliency in response to body fluid deficits. Dynamic postural stability at 10 °C appeared to be hampered by low-grade shivering, but was otherwise maintained during HYP and thermal stress.


Thermal sensation Skin temperature Profile of mood states Postural stability Dehydration 



The authors would like to thank Mary Pardee, Laura Palombo, and Michael Stanger for their technical assistance. We also thank the 32 research volunteers who participated in this study. The opinions or assertions contained herein are the private views of the authors and should not be construed as official or reflecting the views of the Army the Department of Defense. The experiments comply with the present laws of the country in which they were performed.

Conflict of interest

The authors report no conflicts of interest.


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Copyright information

© Springer-Verlag Berlin Heidelberg (outside the USA) 2012

Authors and Affiliations

  • Brett R. Ely
    • 1
  • Kurt J. Sollanek
    • 1
  • Samuel N. Cheuvront
    • 1
  • Harris R. Lieberman
    • 1
  • Robert W. Kenefick
    • 1
    Email author
  1. 1.Thermal and Mountain Medicine DivisionUnited States Army Research Institute of Environmental MedicineNatickUSA

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