Cardiovascular drift in euhydrated prepubertal boys.
"Classic" cardiovascular drift is characterized by findings of decreasing stroke volume and mean arterial pressure, rising heart rate, and stable cardiac output during sustained constant-load exercise. Recent studies in adults indicate that when dehydration is prevented by fluid intake, this pattern is altered, with no change in stroke volume and progressive rise in cardiac output. This study was designed to examine this influence of hydration in prepubertal subjects and assess the relationship between cardiovascular drift and aerobic drift (changes in VO2). Eight boys (Tanner stage 1, mean age 11.7 +/- 0.4 y) cycled at an average of 62.9% +/- 3.9% VO2 peak to exhaustion (41.38 +/- 6.30 min) in a thermoneutral environment. Rectal temperature rose from 37.6 +/- 0.1 degrees C at rest to 38.1 +/- 0.2 degrees C at end exercise. Between 5 min and end exercise, average heart rate rose by 13.2% and cardiac output rose by 14.9%, systemic vascular resistance fell by 10.5%, and stroke volume remained stable. Increases in cardiac output paralleled those of VO2, with no change in arterial venous oxygen difference. These findings are consistent with the conclusion that cardiovascular drift is a reflection of aerobic drift, a relationship obscured by the superimposed physiological effects of dehydration during sustained constant load. This study also suggests that such patterns are no different in prepubertal boys and young adult men.
Rowland
Thomas
T
Department of Pediatrics, Baystate Medical Center, Springfield, MA 01199, USA. thomas.rowland@bhs.org
Pober
David
D
Garrison
Anne
A
D001794:Blood Pressure / Q000502:physiology; D001833:Body Temperature Regulation; D002302:Cardiac Output / Q000502:physiology*; D002648:Child; D003681:Dehydration / Q000517:prevention & control; D005080:Exercise Test / Q000706:statistics & numerical data*; D017079:Exercise Tolerance; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D010807:Physical Endurance / Q000502:physiology*; D005082:Physical Exertion; D011627:Puberty / Q000502:physiology*; D013318:Stroke Volume / Q000502:physiology; D013997:Time Factors; D014655:Vascular Resistance / Q000502:physiology*