Endogenously produced nitric oxide (NO) is detectable in the exhaled air of
resting humans, and the amount of exhaled NO increases during exercise. It
is believed that NO is likely to have an important role in the normal phys
iological response to exercise. Despite accumulating evidence of exhaled NO
during exercise, the effects and relevance of NO to exercise are not yet c
ompletely understood. Scientific debate surrounds the site of NO production
and the stimuli for production. Resolution of these controversial issues w
ill explain the significance of exhaled NO during exercise.