Caffeine Power Enhancement
Caffeine is often referred to as the most widely used drug in the world. Over, forty double-blind studies have proven that cycling power output is increased an average over 12%[Doherty and Smith 2004].
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Caffeine is a stimulant increasing dopamine levels.
Mechanism of action: Caffeine blocks Adenosine in cells.
Specifically, Caffeine has a similar molecule structure to Adenosine, and it binds to the cells blocking Adenosine. The net result is the adrenal gland produce more adrenaline which increases alertness, cell metabolism, dopamine production and constrict blood vessels[Nehlig and Debry 1992]. The US FDA classifies caffeine as a drug if the content is over 0.02% (for reference, the concentration of espresso is 0.004%).
Interesting Facts
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Caffeine content [Full Caffeine Database]:
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A cup of drip coffee ~ 95mg
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Each shot (1 fluid oz) of espresso ~ 64mg
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A can of Coke-Cola ~ 34mg
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A can of diet Coke ~ 46mg
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A can of Pepsi/ diet Pepsi ~ 64 mg
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A cup of green / black tea ~ 30-50mg
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A bar (162grams) of chocolate ~ 70mg
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A cup of hot chocolate ~ 5mg
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Optimal dose for performance enhancement: 3-6mg/kg of body weight… about 200-500 mg[Doherty et al. 2004].
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Increasing amount of caffeine beyond this dose does not further increase performance[Doherty et al. 2004].
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Abstaining from caffeine for at least 7 days before use will increase the magnitude of this effect[Ganio et al. 2009].
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Areas of Concerns
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Caffeine is not recommended for adolescents as it effects developing brain chemistry (it is a drug increasing dopamine levels), sleep and nutrition[Adamson et al. 2014].
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Caffeine increases blood pressure[Hartley et al. 2000].
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Not everyone has a similar stimulus effect… there is a genetic component to the caffeine response[Guest et al. 2018].