Journal of Sports Science and Medicine
Journal of Sports Science and Medicine
ISSN: 1303 - 2968   
Ios-APP Journal of Sports Science and Medicine
Androit-APP Journal of Sports Science and Medicine
from September 2014
©Journal of Sports Science and Medicine (2005) 04, 422 - 429

Research article
Immediate Re-Hydration Post-Exercise is Not Coincident with Raised Mean Arterial Pressure Over A 30-Minute Observation Period
Bartholomew Kay1, , Brendan J. O'Brien2, Nicholas D. Gill3
Author Information
1 Massey University, Institute of Food, Nutrition, and Human Health, Palmerston North, New Zealand
2 University of Ballarat, School of Human Movement and Sport Sciences, Ballarat, Australia
3 Waikato Institute of Technology, School of Sport and Exercise Science, Hamilton, New Zealand

Bartholomew Kay
✉ Massey University, Institute of Food, Nutrition, and Human Health, Pvt Bag 11222, Palmerston North 5301, New Zealand.
Publish Date
Received: 02-05-2005
Accepted: 29-08-2005
Published (online): 01-12-2005
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This investigation assessed the effects of immediate or delayed re-hydration post-exercise, on mean arterial blood pressure (MAP) and on blood plasma volume (PV) expansion post-exercise. It was hypothesised that fluid ingestion would raise MAP and attenuate PV expansion. On two occasions separated by seven days, eight males (age 20.4 ± 1.7 years, mass 79 ± 5 kg [means ± SD]; VO2max 48 ± 11 mL·kg-1·minute-1, [mean ± SE]) cycled in the heat (35°C, 50% relative humidity) at a power output associated with 50% VO2max, until 1.0kg body mass was lost. 1L water was given either immediately thereafter, or two hours post-exercise by random assignment. On both occasions, MAP was calculated every five minutes for a period of 30-minutes post-exercise, and change in PV was calculated 24-hours post-exercise. Repeated measures ANOVA for MAP results suggested a low probability of a treatment effect (p = 0.655), a high probability of a time effect (p = 0.006), and a moderately high probability of a time x treatment interaction (p = 0.076); MAP tended to be lower when fluid had been consumed. PV expansions 24-hours post-exercise were not significant changes with respect to zero, and were not significantly different by treatment condition. In conclusion: (a) The exercise was not sufficient to elicit significant PV expansions; thus, we were unable to determine the effects of the timing of post-exercise re-hydration on PV expansion. (b) The hypothesis regarding MAP in response to drinking was not supported, rather there was a 92% probability that the inverse affect occurs.

Key words: Dehydration, re-hydration, blood pressure, plasma volume

           Key Points
  • Post exercise hypotension is perhaps the most important mediator of plasma volume expansion post exercise
  • It was hypothesised that drinking water immediately post exercise would attenuate post exercise hypotension by rapidly ameliorating dehydration
  • We found that not only was our hypothesis incorrect, but rather a 92% probability exists that the inverse is true, i.e. drinking water in fact leads to lowered blood pressure, as compared to not drinking.
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