Regarding the effect of the combination of both aerobic
exercise and smoking on mucociliary clearance, the STT
was also shorter compared with the resting condition. The
combined stimuli were expected to lead to a more en-
hanced mucociliary response. However, no significant dif-
ferences were found among the different stimuli. None-
theless, despite the lack of statistical significance, aerobic
exercise alone led to greater mucociliary clearance com-
pared with the combined stimuli. One hypothesis for this
response is the fact that smoking occurred immediately
following exercise, which may have reduced the effect of
exercise. Thus, as mucociliary clearance was evaluated
only after smoking in the P1 protocol, the stress caused by
exercise, such as hyperventilation and sympathetic stimu-
lation, may have been attenuated after the subjects sat
down and began smoking. The different mechanisms by
which exercise and smoking modify mucociliary clearance
may have exerted an influence on this response.