Journal of Applied Physiology, Vol 71, Issue 3 871-877, Copyright © 1991 by American Physiological Society

ARTICLES

Fluid replacement and glucose infusion during exercise prevent cardiovascular drift

M. T. Hamilton, J. Gonzalez-Alonso, S. J. Montain and E. F. Coyle
Department of Kinesiology and Health Education, University of Texas, Austin 78712.

This study examined the influence of both hydration and blood glucose concentration on cardiovascular drift during exercise. We first determined if the prevention of dehydration during exercise by full fluid replacement prevents the decline in stroke volume (SV) and cardiac output (CO) during prolonged exercise. On two occasions, 10 endurance-trained subjects cycled an ergometer in a 22 degrees C room for 2 h, beginning at 70 +/- 1% maximal O2 uptake (VO2max) and in a euhydrated state. During one trial, no fluid (NF) replacement was provided and the subject's body weight declined 2.09 +/- 0.19 kg or 2.9%. During the fluid replacement trial (FR), water was ingested at a rate that prevented body weight from declining after 2 h of exercise (i.e., 2.34 +/- 0.17 1/2 h). SV declined 15% and CO declined 7% during the 20- to 120-min period of the NF trial while heart rate (HR) increased 10% and O2 uptake (VO2) increased 6% (all P less than 0.05). In contrast, SV was maintained during the 20- to 120-min period of FR while HR increased 5% and thus CO actually increased 7% (all P less than 0.05). Rectal temperature, SV, and HR were similar during the 1st h of exercise during NF and FR. However, after 2 h of exercise, rectal temperature was 0.6 degree C higher (P less than 0.05) and SV and CO were 11-16% lower (P less than 0.05) during NF compared with FR.(ABSTRACT TRUNCATED AT 250 WORDS)

This article has been cited by other articles:

				E. A. Ashley, A. Kardos, E. S. Jack, W. Habenbacher, M. Wheeler, Y. M. Kim, J. Froning, J. Myers, G. Whyte, V. Froelicher, et al. Angiotensin-Converting Enzyme Genotype Predicts Cardiac and Autonomic Responses to Prolonged Exercise J. Am. Coll. Cardiol., August 1, 2006; 48(3): 523 - 531. [Abstract] [Full Text] [PDF]

				J. M. Goodman, P. P. Liu, and H. J. Green Left ventricular adaptations following short-term endurance training J Appl Physiol, February 1, 2005; 98(2): 454 - 460. [Abstract] [Full Text] [PDF]

				G Neumayr, R Pfister, G Mitterbauer, A Maurer, and H Hoertnagl Effect of ultramarathon cycling on the heart rate in elite cyclists Br. J. Sports Med., February 1, 2004; 38(1): 55 - 59. [Abstract] [Full Text] [PDF]

				S. Padilla, I. Mujika, F. Angulo, and J. J. Goiriena Scientific approach to the 1-h cycling world record: a case study J Appl Physiol, October 1, 2000; 89(4): 1522 - 1527. [Abstract] [Full Text] [PDF]

				A. Lucia, J. Hoyos, and J. L Chicharro The slow component of {V}O2 in professional cyclists Br. J. Sports Med., October 1, 2000; 34(5): 367 - 374. [Abstract] [Full Text] [PDF]

				R. G. Fritzsche, T. W. Switzer, B. J. Hodgkinson, S.-H. Lee, J. C. Martin, and E. F. Coyle Water and carbohydrate ingestion during prolonged exercise increase maximal neuromuscular power J Appl Physiol, February 1, 2000; 88(2): 730 - 737. [Abstract] [Full Text] [PDF]

				J. W. Castellani, C. M. Maresh, L. E. Armstrong, R. W. Kenefick, D. Riebe, M. Echegaray, D. Casa, and V. D. Castracane Intravenous vs. oral rehydration: effects on subsequent exercise-heat stress J Appl Physiol, March 1, 1997; 82(3): 799 - 806. [Abstract] [Full Text] [PDF]