Age, fitness, and regional blood flow during exercise in the heat

• Published in: Journal of applied physiology (1985) Vol. 82; no. 4; pp. 1126 - 1135
• Main Authors: Ho, C. W, Beard, J. L, Farrell, P. A, Minson, C. T, Kenney, W. L
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Am Physiological Soc 01-04-1997; American Physiological Society
• Subjects: Adult; Aged; Aging - physiology; Biological and medical sciences; Blood Pressure - physiology; Body Composition - physiology; Body Temperature - physiology; Cardiac Output - physiology; Cross-Sectional Studies; Exercise - physiology; Forearm - blood supply; Fundamental and applied biological sciences. Psychology; Heart Rate - physiology; Hot Temperature - adverse effects; Humans; Male; Middle Aged; Norepinephrine - blood; Oxygen Consumption; Physical Fitness - physiology; Regional Blood Flow - physiology; Space life sciences; Vertebrates: body movement. Posture. Locomotion. Flight. Swimming. Physical exercise. Rest. Sports; Physical exercise; Human; Regional blood flow; Temperature; Senescence; Bicycle ergometer; Environmental factor; Stress; Heart rate; Physical fitness; Heat; Hemodynamics; Hyperthermia; Age
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/jappl.1997.82.4.1126

C. W.
Ho,
J. L.
Beard,
P. A.
Farrell,
C. T.
Minson, and
W. L.
Kenney
Noll Physiological Research Center, Pennsylvania State
University, University Park, Pennsylvania 16802-6900
Received 23 May 1996; accepted in final form 2 December 1996.
Ho, C. W., J. L. Beard, P. A. Farrell, C. T. Minson, and W. L. Kenney. Age, fitness, and regional blood flow during exercise
in the heat. J. Appl. Physiol. 82(4):
1126-1135, 1997. During dynamic exercise in warm environments,
the requisite increase in skin blood flow (SkBF) is supported by an
increase in cardiac output ( c) and decreases in
splanchnic (SBF) and renal blood flows (RBF). To examine interactions
between age and fitness in determining this integrated response, 24 men, i.e., 6 younger fit (YF), 6 younger sedentary (YS), 6 older fit (OF), and 6 older sedentary (OS) rested for 50 min, then
exercised at 35 and 60% maximal
O 2 consumption
( O 2 max ) at
36°C ambient temperature. YF had a significantly higher
c and SkBF than any other group during exercise,
but fitness level had no significant effect on any measured variable in
the older men. At 60%
O 2 max , younger subjects had significantly greater decreases in SBF and RBF than the
older men, regardless of fitness level. Total flow redirected from
these two vascular beds ( SBF +  RBF) followed YF >> YS > OF > OS. A rigorous 4-wk endurance training program
increased exercise SkBF in OS, but SBF and RBF were unchanged.
Under these conditions, older men distribute c
differently to regional circulations, i.e., smaller increases in SkBF
and smaller decreases in SBF and RBF. In younger subjects, the higher
SkBF associated with a higher fitness level is a function of both a
higher c and a greater redistribution of flow from
splanchnic and renal circulations, but the attenuated splanchnic and
renal vasoconstriction in older men does not appear to change with
enhanced aerobic fitness.
skin blood flow; splanchnic blood flow; renal blood flow; cardiac
output; hyperthermia; heat stress; aging; regional circulation
0161-7567/97 $5.00
Copyright © 1997 the American Physiological Society