Rates of fluid ingestion alter pacing but not thermoregulatory responses during prolonged exercise in hot and humid conditions with appropriate convective cooling

  • J. P. Dugas
  • U. Oosthuizen
  • R. Tucker
  • T. D. Noakes
Original Article

Abstract

The aim of the study was to examine the effects of fluid replacement on thermoregulation and cycling performance in hot, humid conditions. Six male cyclists (PPO = 426 ± 39 W) performed six 80 km time trials. Subjects replaced 0% (0); 33% (33); 66% (66); or 100% (100) of the weight lost during an “ad libitum” trial (Ad Lib). In another condition (WET), subjects rinsed their mouths at 10 km intervals. There was no trial effect on any thermoregulatory variables or on performance. When WET, 0, 33 (“LO”) were compared to Ad Lib; 66, 100 (“HI”), power output was higher in HI (209 ± 22 vs. 193 ± 22 W, p < 0.05). Restricting fluid below ad libitum rates impaired performance (LO group). Rates greater than ad libitum did not result in further improvements. Ad libitum fluid ingestion is optimal as it prevents athletes from ingesting too little or too much fluid.

Keywords

Heat Rectal temperature Temperature Cycling Performance Exercise Time trial Dehydration Anticipatory regulation Fluid balance 

References

  1. Adams WC, Mack GW, Langhans GW, Nadel ER (1992) Effects of varied air velocity on sweating and evaporative rates during exercise. J Appl Physiol 73:2668–2674PubMedGoogle Scholar
  2. Armstrong LE, Costill DL, Fink WJ (1985) Influence of diuretic-induced dehydration on competitive running performance. Med Sci Sports Exerc 17:456–461PubMedCrossRefGoogle Scholar
  3. Armstrong LE, Costill DL, Grosso M, Barnett A, Orheim A, Fink W, Hermansen L (1981) Influence of diminished plasma-volume on running performance. Med Sci Sports Exerc 13:101–101Google Scholar
  4. Armstrong LE, Maresh CM, Gabaree CV, Hoffman JR, Kavouras SA, Kenefick RW, Castellani JW, Ahlquist LE (1997) Thermal and circulatory responses during exercise: effects of hypohydration, dehydration, and water intake. J Appl Physiol 82:2028–2035PubMedGoogle Scholar
  5. Baker LB, Munce TA, Kenney WL (2005) Sex differences in voluntary fluid intake by older adults during exercise. Med Sci Sports Exerc 37:789–796PubMedCrossRefGoogle Scholar
  6. Barr SI (1999) Effects of dehydration on exercise performance. Can J Appl Physiol 24:164–172PubMedGoogle Scholar
  7. Below PR, Mora-Rodriguez R, Gonzalez-Alonso J, Coyle EF (1995) Fluid and carbohydrate ingestion independently improve performance during 1 h of intense exercise. Med Sci Sports Exerc 27:200–210PubMedGoogle Scholar
  8. Carter JM, Jeukendrup AE, Jones DA (2004) The effect of carbohydrate mouth rinse on 1-h cycle time trial performance. Med Sci Sports Exerc 36:2107–2111PubMedCrossRefGoogle Scholar
  9. Casa DJ, Armstrong LE, Hillman SK, Montain SJ, Reiff RV, Rich BSE, Roberts WO, Stone JA (2000) National Athletic Trainers’ Association position statement: fluid replacement for athletes. J Athl Train 35:212–224PubMedGoogle Scholar
  10. Cheuvront SN, Carter RIII, Montain S, Stephenson LA, Sawka MN (2004) Influence of hydration and airflow on thermoregulatory control in the heat. J Thermal Biol 29:471–477CrossRefGoogle Scholar
  11. Convertino VA, Armstrong LE, Coyle EF, Mack GW, Sawka MN, Senay LC, Sherman WM (1996) American College of Sports Medicine position stand—exercise and fluid replacement. Med Sci Sports Exerc 28:R1–R7CrossRefGoogle Scholar
  12. Costill DL, Kammer WF, Fisher A (1970) Fluid ingestion during distance running. Arch Environ Health 21:520PubMedGoogle Scholar
  13. Coyle EF (2004) Fluid and fuel intake during exercise. J Sports Sci 22:39–55PubMedCrossRefGoogle Scholar
  14. du Bois DBS, du Bois EF (1916) A Formula to estimate the approximate surface area if height and weight be known. Arch Intern Med 17:963–971Google Scholar
  15. Eichner ER (1998) Treatment of suspected heat illness. Int J Sports Med 19(Suppl 2):S150–S153PubMedCrossRefGoogle Scholar
  16. Epstein Y, Armstrong LE (1999) Fluid-electrolyte balance during labor and exercise: concepts and misconceptions. Int J Sport Nutr 9:1–12PubMedGoogle Scholar
  17. Gagge AP, Stolwijk JAJ, Hardy JD (1967) Comfort and thermal sensations and associated physiological responses at various ambient temperatures. Environ Res 1:1–20PubMedCrossRefGoogle Scholar
  18. Gisolfi CV, Copping JR (1974) Thermal effects of prolonged treadmill exercise in heat. Med Sci Sports Exerc 6:108–113Google Scholar
  19. Gisolfi CV, Duchman SM (1992) Guidelines for optimal replacement beverages for different athletic events. Med Sci Sports Exerc 24:679–687PubMedGoogle Scholar
  20. Gonzalez-Alonso J (1998) Separate and combined influences of dehydration and hyperthermia on cardiovascular responses to exercise. Int J Sports Med 19(Suppl 2):S111–S114PubMedCrossRefGoogle Scholar
  21. Gonzalez-Alonso J, Teller C, Andersen SL, Jensen FB, Hyldig T, Nielsen B (1999) Influence of body temperature on the development of fatigue during prolonged exercise in the heat. J Appl Physiol 86:1032–1039PubMedGoogle Scholar
  22. Gonzalez-Alonso J, Mora-Rodriguez R, Coyle EF (2000) Stroke volume during exercise: interaction of environment and hydration. Am J Physiol Heart Circ Physiol 278:H321–H330PubMedGoogle Scholar
  23. Kay D, Marino FE (2003) Failure of fluid ingestion to improve self-paced exercise performance in moderate-to-warm humid environments. J Thermal Biol 28:29–34CrossRefGoogle Scholar
  24. Kyle CR (1988) How weight affects bicycle speed. Bicycling Mag 29:186–190Google Scholar
  25. Marino FE (2004) Anticipatory regulation and avoidance of catastrophe during exercise-induced hyperthermia. Comp Biochem Physiol B Biochem Mol Biol 139:561–569PubMedCrossRefGoogle Scholar
  26. Marino FE, Kay D, Cannon J (2003) Glycerol hyperhydration fails to improve endurance performance and thermoregulation in humans in a warm humid environment. Pflügers Arch Eur J Physiol 446:455–462CrossRefGoogle Scholar
  27. Marino FE, Lambert MI, Noakes TD (2004) Superior performance of African runners in warm humid but not in cool environmental conditions. J Appl Physiol 96:124–130PubMedCrossRefGoogle Scholar
  28. Maughan RJ (2003) Impact of mild dehydration on wellness and on exercise performance. Eur J Clin Nutr 57(Suppl 2):S19–S23PubMedCrossRefGoogle Scholar
  29. Millard-Stafford ML, Sparling PB, Rosskopf LB, Snow TK, DiCarlo LJ, Hinson BT (1995) Fluid intake in male and female runners during a 40-km field run in the heat. J Sports Sci 13:257–263PubMedCrossRefGoogle Scholar
  30. Mitchell JB, Schiller ER, Miller JR, Dugas JP (2001) The influence of different external cooling methods on thermoregulatory responses before and after intense intermittent exercise in the heat. J Strength Cond Res 15:247–254PubMedCrossRefGoogle Scholar
  31. Montain SJ, Coyle EF (1992) Influence of graded dehydration on hyperthermia and cardiovascular drift during exercise. J Appl Physiol 73:1340–1350PubMedGoogle Scholar
  32. Ramanathan NL (1964) A new weighting system for mean surface temperature of the human body. J Appl Physiol 19:531–533PubMedGoogle Scholar
  33. Saunders AG, Dugas JP, Tucker R, Lambert MI, Noakes TD (2005) The effects of different air velocities on heat storage and body temperature in humans cycling in a hot, humid environment. Acta Physiol Scand 183:241–255PubMedCrossRefGoogle Scholar
  34. Tatterson AJ, Hahn AG, Martin DT, Febbraio MA (2000) Effects of heat stress on physiological responses and exercise performance in elite cyclists. J Sci Med Sport 3:186–193PubMedCrossRefGoogle Scholar
  35. Tucker R, Rauch L, Harley YX, Noakes TD (2004) Impaired exercise performance in the heat is associated with an anticipatory reduction in skeletal muscle recruitment. Pflügers Archiv 448:422–430PubMedCrossRefGoogle Scholar
  36. Tucker R, Marle T, Lambert EV, Noakes TD (2006) The rate of heat storage mediates an anticipatory reduction in exercise intensity during cycling at a fixed rating of perceived exertion. J Physiol 574:905–915PubMedCrossRefGoogle Scholar
  37. Walsh RM, Noakes TD, Hawley JA, Dennis SC (1994) Impaired high-intensity cycling performance time at low-levels of dehydration. Int J Sports Med 15:392–398PubMedCrossRefGoogle Scholar

Copyright information

© Springer-Verlag 2008

Authors and Affiliations

  • J. P. Dugas
    • 1
    • 2
  • U. Oosthuizen
    • 1
  • R. Tucker
    • 1
  • T. D. Noakes
    • 1
  1. 1.UCT/MRC Research Unit for Exercise Science and Sports Medicine, Department of Human BiologyUniversity of Cape Town, Sports Science InstituteCape TownSouth Africa
  2. 2.ChicagoUSA

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