A model analysis of the asymmetrical response of pulmonary o2
uptake during incremental and decremental ramp exercise.
Niizeki, Kyuichi, Tatsuhisa Takahashi, and Yoshimi Miyamoto.
Laboratory of Biological Cybernetics, Department of Electrical and
Information Engineering, Yamagata University, Yonezawa 992, Japan
APStracts 2:0348A, 1995.
The responses of gas exchange and ventilatory variables exhibit
obvious asymmetry between the incremental and decremental phases of
trapezoidal ramp exercise (29). Computer simulation was performed to
explore the possible mechanisms producing this asymmetry of pulmonary
oxygen uptake (Vo2) dynamics. The model consisted of three
compartments (the lungs, the exercising muscles, and the other organs
and tissues), which were perfused by respective regional
circulations. Exercise was simulated by increasing the pulmonary
blood flow (Q) and the muscle Vo2 in proportion to work rate. The
dynamic responses of Q and the muscle Vo2 were assumed to obey first
-order linear kinetics. The ratio of blood flow in the muscle
compartment to total cardiac output was assumed to increase linearly
with work rate. Our simulation demonstrated that the muscle blood
flow and mixed venous O2 content exhibited significant asymmetry
between the incremental and decremental phases of exercise. The model
suggested that the asymmetry of Vo2 between incremental and
decremental ramp exercise was dependent on the redistribution ratio
of blood flow to the working muscles. The validity of the model was
then evaluated by comparing the simulated results with experimental
data obtained.
Received 29 November 1993; accepted in final form 28 June 1995.
APS Manuscript Number A1137-3.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 14 August 1995.