The Effects of Caffeine on Ventilation and Pulmonary Function During Exercise - Caffeine: Chemistry, Analysis, Function and Effects - page 347

significantly alter the rate in which caffeine is cleared from the body. Generally
caffeine absorption is complete within about 1 hour after ingestion and the
plasma concentration peaks after about 90 min. For doses lower than 10 mg
kg 21 , the half-life of caffeine in the plasma is about 2.5-4.5 hours in healthy
adults. Partly due to these individual differences in caffeine clearance, caffeine
was removed from the banned list and is currently considered part of a
''Monitoring Program'' by the World Anti-Doping Agency, with no upper
limit for a positive test outcome.

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18.6 Summary
In light of caffeine's universal accessibility and increasing social acceptance as
an ergogenic aid for exercise and sport, it is important to have an
understanding of the ventilatory and pulmonary function effects of caffeine,
independent of metabolic, neural, and hormonal responses. While coffee and
colas have been the traditional modes of caffeine ingestion, caffeine infused
''energy drinks'' have dramatically increased in popularity, particularly among
younger individuals. For the clinician, coach, and scientist, this increase in
caffeine use and acceptance may result in a) an increased reporting of dyspnea
during exercise by patients and athletes, secondary to central and possibly
peripheral chemoreceptor stimulation increasing ventilatory drive, and b)
possible changes in the outcomes of pulmonary function testing.
From an ergogenic standpoint, the significant increase in exercise ventilation
seen with high dose (.7mgkg 21 ) caffeine ingestion resulted in a rise in end
tidal PO 2 and SaO 2 in a) athletes with exercise induced hypoxemia, and b)
athletes exercising submaximally at a simulated altitude. Additionally, caffeine
has been shown to significantly mitigate the fall in FEV 1 post-exercise in
patients with EIB. Therefore, the effect of caffeine specifically on ventilation
and pulmonary function may be ergogenic under these circumstances, but this
hypothesis has not been examined directly in performance-based testing.
Additionally, it is also important to consider that an increase in the work of
breathing with a caffeine-mediated increase in VE and a potential metaboreflex
effect, diverting blood flow away from the locomotor muscles to the
ventilatory muscles, may combine to negate any potential ergogenic advantage
from an increase in alveolar oxygenation. These observations on caffeine's
effects on ventilation and pulmonary function are separate from the well
documented effects of caffeine on metabolism, substrate utilization, catecho-
lamine release, central nervous system function, and exercise performance in
general.

Summary Points

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This chapter focuses on the effects of caffeine on exercise ventilation and
pulmonary function.