East Project
Effects of Caffeine on
Endurance Athletes
Estella Nelson & Amanda Taylor
April 25, 2007
Linking Consumers
Together with Caffeine
Facts
This study was done to recognize the
knowledge, beliefs, and behaviors of
physically active consumers in regards to
effects of caffeine during performance.
A table of Contents
An Overview of Caffeine
 Pharmacokinetics of Caffeine
 Pharmacodynamics of Caffeine
 Caffeine and Exercise Performance
 Survey Results
 Conclusion
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An Overview of Caffeine
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Caffeine is a CNS and metabolic stimulant
Ingested in many foods, beverages, supplements, and
medications
Considered the most widely consumed psychoactive
‘drug’
Most commonly used stimulant in sports
Major sources:
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Adults= coffee (60-75%) and tea (15-30%)
Children= caffeinated soft drinks and chocolate
May cause insomnia and nervousness
High doses may cause medullary stimulation and
convulsions
Caffeine=methylxanthine
Common Caffeinated Products
Caffeine Per Serving
(mg)
Product
Serving Size
Caffeine Tablets
1 Tablet
200
Excedrin Tablet
1Tablet
65
Coffee Brewed
240 mL (8fl oz)
135
Coffee Decaffeinated
240 mL (8fl oz)
5
Coffee Espresso
57 ML (2 fl oz)
100
Chocolate Dark (Hershey's Special)
1 bar (43 g 1.5 oz
31
Bawls Guarana
296 mL (10 fl oz)
67
Soft Drink Mountain Dew"dew Fuel"
355 mL (12 fl oz)
54.5
Soft Drink Coca-Cola Classic
355 mL (12 fl oz)
34
Tea, Green
240 mL (8 fl oz)
15
Tea, leaf or bag
240 Ml (8 fl oz)
50
Chocolate Milk (Hershey Bar)
1 bar (43 g 1.5 oz
10
Red Bull
250 Ml (8.2 fl oz)
80
Rockstar energy drink
473 mL (16 fl oz)
170
Jolt Cola
674 mL (23.5 fl oz)
150
Pharmacokinetics of Caffeine
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Absorbed after oral, rectal, parental
administration, and through the skin
Absorbed from G.I. Tract
Peak plasma levels occur in 45 minutes
to 2 hours resulting in high levels of
energy
Caffeine is then distributed in to body
water
The liver metabolizes caffeine to 3,7theobromine, 1,3-theophyllline, and 1,7paraxanthine
Caffeine is then excreted in urine, saliva,
semen, and breast milk
The half-life of caffeine in healthy adults
is 3.0 to 7.5 hours
Pharmacodynamics of Caffeine
Caffeine effects the CNS, kidney, and cardiac
and skeletal muscle as well as smooth muscle
 Acts as stimulant towards the central nervous
system
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Inhibits an enzyme, has an antagonistic effect at
central adenosine receptors
 Binds to surface cells of adenosine receptors
without activating them
 Reduces adenosine activity and increases the activity
of the neurotransmitter dopamine
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Pharmacodynamics of Caffeine
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Effects
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G.I. tract (stimulates secretion of both gastric acid
and digestive enzymes) kidneys (weak diuretic)
cardiac muscle (bronchodialation) skeletal muscle
(strengthens contractions) smooth muscle (reverses
fatigue of diaphragm in patients with chronic
obstructive lung diseases)
High doses results in: cardiovascular effects,
arrhythmias, sinus tachycardia and increased
cardiac output
Caffeine and Exercise Performance
Used as ergogenic aid-and is regulated by
officials
 Studies show an increase in performance in
prolonged, endurance exercise but not during
short term, high intensity activities
 When evaluating the effects, take in to
consideration caffeine naïve or caffeine tolerant
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Naïve subjects- caffeine increases epinephrine
output in proportion to dose
Caffeine and Exercise Performance
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Graham, Hibbert, and
Sathasivam (1998) recently
found that caffeine ingested
as capsules improved
treadmill running by 31%
compared to placebo
Berglund and Hemmingsson
(1982) studied cross-country
skiing and found that
performance increased as
altitude increased with
consumption of caffeine
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Another study (Spriet et al.
1992) of cyclists, single doses
of caffeine consumed 1 hour
prior to testing produced an
increase in cycling time in
recreational cyclists
Nancy Clark states,
“ Caffeine’s energy-enhancing
effect is more likely related to
its ability to make exercise
seem easier. Through its
stimulant effect upon the brain,
caffeine may reduce the fatigue
associated with long bouts of
exercise…”
Survey Results
Product
% of
participants
(some may
use multiple
products)
2+/day
users consume participants
prior exercise that knew
milligrams
of caffeine
Coffee
28%
7 participants 7 participants
Soda
Beverage
58%
7 participants 11
participants
Tea
34%
6 participants 4 participants
1 participant
Energy
Drink
20%
1 participant
7 participants
1 participant
Energy
Tablet
4%
1 participant
1 participant
1 participant
Additional Results
Male
Female
Not
Active
Active
Moderately
Active
Very
Active
46%
54%
0%
20%
44%
36%
Does
Does Not
Did Not
Answer
64%
14%
10%
20 females /
17 males
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2 females / 5
males
Enhances
Decreases
Neither
Did Not
Answer
52%
14%
30%
4%
4 females /1
male
Table 1 shows percent of male vs. female
Table 2 shows how active the clients are
Table 3 shows how the client’s perceive caffeine compared to exercise, and how
many females vs. males
Table 4 shows what the client’s view on caffeine is
Conclusion
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Caffeine is a commonly used stimulant in sports
Can be derived from many sources:
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Food, energy drinks, supplements, and medications
Methylxanthines effect the central nervous system,
cardiac and skeletal muscle as well as smooth muscle
Caffeine is metabolized by the liver in to 3 primary
metabolites
Studies show caffeine has a positive effect on exercise
endurance and performance.
Surveys conclude that the physical active consumer
References:
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