Acute Topics in Sport Nutrition

Editor(s): Lamprecht M. (Graz) 
Table of Contents
Vol. 59, 2012
Section title: Hydration and Fluid Balance
Lamprecht M (ed): Acute Topics in Sport Nutrition. Med Sport Sci. Basel, Karger, 2013, vol 59, pp 113–119

Salt and Fluid Loading: Effects on Blood Volume and Exercise Performance

Mora-Rodriguez R. · Hamouti N.
University of Castilla-La Mancha, Exercise Physiology Laboratory, Toledo, Spain

Individual Users: Register with Karger Login Information

Please create your User ID & Password

Contact Information

I have read the Karger Terms and Conditions and agree.

To view the fulltext, please log in

To view the pdf, please log in


During prolonged exercise, fluid and salt losses through sweating reduce plasma volume which leads to heart rate drift in association with hyperthermia and reductions in performance. Oral rehydration with water reduces the loss of plasma volume and lessens heart rate drift and hyperthermia. Moreover, the inclusion of sodium in the rehydration solution to levels that double those in sweat (i.e., around 90 mmol/l Na+) restores plasma volume when ingested during exercise, and expands plasma volume if ingested pre-exercise. Pre-exercise salt and fluid ingestion with the intention of expanding plasma volume has received an increasing amount of attention in the literature in recent years. In four studies, pre-exercise salt and fluid ingestion improved performance, measured as time to exhaustion, either during exercise in a thermoneutral or in a hot environment. While in a hot environment, the performance improvements were linked to lowering of core temperatures and heart rate, the reasons for the improved performance in a thermoneutral environment remain unclear. However, when ingesting pre-exercise saline solutions above 0.9% (i.e., > 164 mmol/l Na+), osmolality and plasma sodium increase and core temperature remain at dehydration levels. Thus, too much salt counteracts the beneficial effects of plasma volume expansion on heat dissipation and hence in performance. In summary, the available literature suggests that pre-exercise saline ingestion with concentrations not over 164 mmol/l Na+ is an ergogenic aid for subsequent prolonged exercise in a warm or thermoneutral environment.Copyright © 2012 S. Karger AG, Basel

Copyright / Drug Dosage

Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher or, in the case of photocopying, direct payment of a specified fee to the Copyright Clearance Center.
Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in goverment regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug.
Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.


  1. Buono MJ, Ball KD, Kolkhorst FW: Sodium ion concentration vs. sweat rate relationship in humans. J Appl Physiol 2007;103:990-994
  2. Brown MB, McCarty NA, Millard-Stafford M: High-sweat Na+ in cystic fibrosis and healthy individuals does not diminish thirst during exercise in the heat. Am J Physiol Regul Integr Comp Physiol 2011;301:R1177-R1185
  3. Fortney SM, Wenger CB, Bove JR, Nadel ER: Effect of hyperosmolality on control of blood flow and sweating. J Appl Physiol 1984;57:1688-1695
  4. Van Rosendal SP, Osborne MA, Fassett RG, Lancashire B, Coombes JS: Intravenous versus oral rehydration in athletes. Sports Med 2010;40:327-346
  5. Kenefick RW, Maresh CM, Armstrong LE, Riebe D, Echegaray ME, Castellani JW: Rehydration with fluid of varying tonicities: effects on fluid regulatory hormones and exercise performance in the heat. J Appl Physiol 2007;102:1899-1905
  6. Deschamps A, Levy RD, Cosio MG, Marliss EB, Magder S: Effect of saline infusion on body temperature and endurance during heavy exercise. J Appl Physiol 1989;66:2799-2804
  7. Fortney SM, Vroman NB, Beckett WS, Permutt S, LaFrance ND: Effect of exercise hemoconcentration and hyperosmolality on exercise responses. J Appl Physiol 1988;65:519-524
  8. Nose H, Mack GW, Shi XR, Morimoto K, Nadel ER: Effect of saline infusion during exercise on thermal and circulatory regulations. J Appl Physiol 1990;69:609-616
  9. Harrison MH, Edwards RJ, Fennessy PA: Intravascular volume and tonicity as factors in the regulation of body temperature. J Appl Physiol 1978;44:69-75
  10. Sanders B, Noakes TD, Dennis SC: Water and electrolyte shifts with partial fluid replacement during exercise. Eur J Appl Physiol Occup Physiol 1999;80:318-323
  11. Sanders B, Noakes TD, Dennis SC: Sodium replacement and fluid shifts during prolonged exercise in humans. Eur J Appl Physiol 2001;84:419-425
  12. Greenleaf JE, Looft-Wilson R, Wisherd JL, et al: Hypervolemia in men from fluid ingestion at rest and during exercise. Aviat Space Environ Med 1998;69:374-386
  13. Greenleaf JE, Looft-Wilson R, Wisherd JL, McKenzie MA, Jensen CD, Whittam JH: Pre-exercise hypervolemia and cycle ergometer endurance in men. Biol Sport 1997;14:103-114
  14. Coles MG, Luetkemeier MJ: Sodium-facilitated hypervolemia, endurance performance, and thermoregulation. Int J Sports Med 2005;26:182-187
  15. Sims ST, Rehrer NJ, Bell ML, Cotter JD: Pre-exercise sodium loading aids fluid balance and endurance for women exercising in the heat. J Appl Physiol 2007;103:534-541
  16. Sims ST, van Vliet L, Cotter JD, Rehrer NJ: Sodium loading aids fluid balance and reduces physiological strain of trained men exercising in the heat. Med Sci Sports Exerc 2007;39:123-130
  17. Nelson MD, Stuart-Hill LA, Sleivert GG: Hypervolemia and blood alkalinity: effect on physiological strain in a warm environment. Int J Sports Physiol Perform 2008;3:501-515
  18. Green HJ, Sutton JR, Coates G, Ali M, Jones S: Response of red cell and plasma volume to prolonged training in humans. J Appl Physiol 1991;70:1810-1815
  19. Coyle EF, Hopper MK, Coggan AR: Maximal oxygen uptake relative to plasma volume expansion. Int J Sports Med 1990;11:116-119
  20. Jeukendrup A, Saris WHM, Brouns F, et al: A new validated endurance performance test. Med Sci Sports Exerc 1996;28:266-270

Pay-per-View Options
Direct payment This item at the regular price: USD 33.00
Payment from account With a Karger Pay-per-View account (down payment USD 150) you profit from a special rate for this and other single items.
This item at the discounted price: USD 23.00