Effects of physical conditioning on endogenous nitric oxide output
during exercise.
Maroun, Martin J., Sanjay Mehta, Rene Turcotte, Manuel G. Cosio, and
Sabah N. A. Hussain.
Desmond N. Stoker Pulmonary Function Laboratories, Respiratory
Division, Royal Victoria Hospital and Department of Physical
Education, McGill University, Montreal, Quebec, Canada.
APStracts 2:0214A, 1995.
Nitric Oxide (NO) has been detected in the expiratory air of normal
animals and human subjects. Recent experiments revealed that
expiratory NO production rises during exercise and correlates well
with O2 consumption and heart rate. Whether or not physical
conditioning influences expiratory NO output production remains
unclear. In this study, NO concentration in expired gas was measured
in 18 healthy male volunteers subdivided into 3 groups (sedentary,
intermediate, athletes) based on their state of physical
conditioning. Measurements were taken at rest and during two steady
-state exercise bouts on a bicycle ergometer designed to elicit VO2 of
1 and 2 l/min with the athletes performing an additional bout at VO2
of 4 l/min. In the sedentary and intermediate groups, expired NO
concentrations declined significantly with increasing VO2. In
contrast, expired NO levels declined only slightly with increasing
VO2 in athletes. At a VO2 of 2 l/min, expired NO concentrations were
significantly higher in athletes compared with the other groups. When
correlated with VE, expired NO concentrations declined linearly with
the increase in VE in sedentary and intermediate groups but not in
the athletes. Only the athletes had a significant linear increase in
NO output (expired NO x VE) with increasing VO2 (p < 0.001). These
results support the notion that physical conditioning increases
expiratory NO output during exercise. We speculate that the rise in
expiratory NO output in athletes might be due to increased vascular
and/or epithelial production of NO. Enhanced vascular NO production
may be the result of increased shear stress and/or upregulation of
endothelial NO synthase gene expression.
Received 13 February 1994; accepted in final form 16 May 1995.
APS Manuscript Number A159-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 May 1995.