Effect of hydration state of circulatory and thermal regulations

J Appl Physiol Respir Environ Exerc Physiol. 1980 Oct;49(4):715-21. doi: 10.1152/jappl.1980.49.4.715.


To determine the influence of hydration state upon circulatory controls, we studied four relatively fit subjects during duplicate 30-min cycle ergometer exercise bouts (55% VO2max) in euhydrated, hypohydrated, and hyperhydrated conditions. Ambient temperature was 35 degrees C. Hypohydration was achieved by 4 days of diuretic administration and resulted in a whole-body weight loss of 2.2 kg and a plasma volume decrease of approximately 700 ml. Hyperhydration was achieved by ADH administration plus ingestion of 2 liters water but caused only a minor increase volume. Hypohydration resulted in a significantly reduced cardiac output during exercise; this the result of a reduction in stroke volume of 17 ml.beat-1 without adequate elevation in heart rate. the internal temperature (Tes) threshold for cutaneous vasodilation was elevated by 0.42 degree C in hypohydrated conditions; but once vasodilation occurred, the slope of the arm blood flow:Tes relation was unchanged from control. Maximal arm blood flow was reduced by nearly 50% in hypohydration. These restrictions in cutaneous blood flow served to maintain an already compromised venous return, but due to the limitation of core-to-skin heat transfer, forced Tes to nearly 39 degrees C, significantly higher than in euhydrated conditions.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Blood Circulation*
  • Body Fluids / physiology*
  • Body Temperature Regulation*
  • Cardiac Output
  • Dehydration / physiopathology
  • Heart / physiology*
  • Humans
  • Male
  • Physical Exertion*
  • Stroke Volume