Age alters regional distribution of blood flow during moderate
intensity exercise.
Kenney, W. Larry, and Cheng-Wen Ho.
Noll Physiological Research Center, Penn State University,
University Park, PA 16802-6900
APStracts 2:0205A, 1995.
During dynamic exercise in warm environments, requisite increases in
skin and active muscle blood flows are supported by increasing
cardiac output (Qc) and redistributing flow away from splanchnic and
renal circulations. To examine the effect of age on these responses,
6 young (Y; 26+/-2 yrs) and 6 older (O; 64+/-2 yrs) men performed
upright cycle exercise at 35% and 60% VO2peak in 22 C and 36 C
environments. To further isolate age, the two age groups were closely
matched for VO2peak, weight, surface area, and body composition.
Measurements included heart rate (HR), Qc (CO2 rebreathing), skin
blood flow (from increases in forearm blood flow, FBF; venous
occlusion plethysmography), splanchnic blood flow (SBF; indocyanine
green dilution), renal blood flow (RBF, p-aminohippurate clearance),
and plasma norepinephrine (NE) concentration. There were no
significant age differences in Qc; however, in both environments O
maintained Qc at a higher stroke volume and lower HR . At 60%
VO2peak, FBF was significantly lower in the O in each environment.
SBF fell (by 12-14% in both groups) at the lower intensity, then
decreased to a greater extent at 60% VO2peak in the Y than in the O
(e.g., -45+/-2% vs -33+/-3% for the hot environment; p<0.01). RBF
was lower at rest in the O, remained relatively constant at 35%
VO2peak, then decreased by 20-25% in both groups at 60% VO2peak. At
60% VO2peak, Y redistributed 27% and 37% more total blood flow away
from these two circulations than their older counterparts at 22 C and
36 C, respectively. It was concluded that the greater increase in
skin blood flow in young exercising subjects (compared to O) is
partially supported by a greater redistribution of blood flow away
from splanchnic and renal vascular beds.
Received 27 February 1995; accepted in final form 11 May 1995.
APS Manuscript Number A224-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 May 1995.