ISSN:
1439-6327
Keywords:
Key words Exercise
;
Glycerol hyperhydration
;
Heat exposure
;
Dehydration
;
Plasma volume
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract This study examined plasma volume changes (ΔPV) in humans during periods with or without changes in body hydration: exercise-induced dehydration, heat-induced dehydration and glycerol hyperhydration. Repeated measurements of plasma volume were made after two injections of Evans blue. Results were compared to ΔPV calculated from haematocrit (Hct) and blood haemoglobin concentration ([Hb]). Eight well-trained men completed four trials in randomized order: euhydration (control test C), 2.8% dehydration of body mass by passive controlled hyperthermia (D) and by treadmill exercise (60% of their maximal oxygen uptake, V˙O2max) (E), and hyperhydration (H) by glycerol ingestion. The Hct, [Hb], plasma protein concentrations and plasma osmolality were measured before, during and after the changes in body hydration. Different Hct and [Hb] reference values were obtained to allow for posture-induced variations between and during trials. The ΔPV values calculated after two Evans blue injections were in good agreement with ΔPV calculated from Hct and [Hb]. Compared to the control test, mean plasma volume declined markedly during heat-induced dehydration [−11.4 (SEM 1.7)%] and slightly during exercise-induced dehydration [−4.2 (SEM 0.9)%] (P 〈 0.001 compared to D), although hyperosmolality was similar in these two trials. Conversely, glycerol hyperhydration induced an increase in plasma volume [+7.5 (SEM 1.0)%]. These results would indicate that, for a given level of dehydration, plasma volume is dramatically decreased during and after heat exposure, while it is better maintained during and after exercise.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s004210050550
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