Influence of simulated microgravity on cardiac output and blood
flow distribution during exercise.
Woodman, Christopher R., L. A. Sebastian, and Charles M. Tipton.
Department of Exercise and Sport Sciences, Ina E. Gittings
Building, University of Arizona, Tucson, AZ 85721
APStracts 2:0354A, 1995.
Rats exposed to simulated conditions of microgravity by the use of
head down suspension (HDS) exhibit reductions in aerobic capacity.
This may be due to an impaired ability to augment cardiac output and
to redistribute blood flow during exercise. The purpose of this
investigation was to measure cardiac output and blood flow
distribution in rats that were exposed to 14 days of HDS or cage
control (CC) conditions. Measurements were obtained at rest, and
during light (15 m/min) and heavy (25 m/min; 10% grade) intensity
treadmill exercise. Cardiac output was similar in HDS and CC rats at
rest and light intensity exercise, but was significantly lower in HDS
rats (-33%) during heavy exercise. Soleus muscle blood flow (ml/min)
was lower at rest and during exercise in HDS rats; however, when
expressed relative to muscle mass (ml/min/100g), soleus blood flow
was lower only during light exercise. Plantaris muscle blood flow was
lower in HDS rats during heavy exercise. Blood flow to the ankle
flexor, knee extensor, and knee flexor muscles was not altered by
HDS. Blood flow to the spleen and kidney was significantly higher in
HDS rats. It was concluded that the reduction in aerobic capacity
associated with HDS is due, in part, to an impaired ability to
augment cardiac output during exercise.
Received 27 January 1995; accepted in final form 27 June 1995.
APS Manuscript Number A104-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 14 August 1995.