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What is it? Caffeine acts as a central nervous system stimulant and is one of the most widely consumed psychoactive drugs. It can be obtained from various sources with the most common source being coffee, an average cup of coffee contains around 90mg and a double expresso will contain around 125mg. Other natural sources of caffeine include tea and dark chocolate, it’s important to note thatcaffeine content can vary considerably between brands, for sports performance it would be beneficial to consume a pre-measured form i.e., gum, tablet, or powder form.

How does it work? ATP is broken down in the body to produce energy, adenosine is a product of this process and as adenosine levels increase, some of the adenosine exits the cells where it can attach to adenosine receptors A1 (found on neurons which keep the brain awake, making them less active) and A2 (found on neurons which are sleep-promoting, making them more active). The structure of caffeine and adenosine are very similar therefore caffeine binds to adenosine receptors, acting as an adenosine receptor antagonist. If you ingest caffeine daily, your caffeine tolerance (more coffee for same effect) may be higher than someone who doesn’t. This is due to the synthesis of more adenosine receptors to compensate for the receptors blocked by caffeine. Therefore, you require more caffeine to offset the increase in receptors.

How much should I have? Health organisations suggest 300mg of caffeine daily is safe and pregnant women should consume no more than 200mg however the dose response is known to vary a lot between individuals. Studies which have investigated the effect of dosage on performance have found that 2-4mg of caffeine per kilogram of body mass his sufficient to elicit positive effects on performance. Doses above had no further effect on performance.

When should I have it? Caffeine is readily absorbed with peak blood levels occurring approximately 45-60min after ingestion i.e. consume 1 hour prior to you wanting to experience the greatest benefit. However, forms of caffeine which are absorbed through the buccal mucosa in the mouth (gum) can reach peak levels much faster (15-20mins) compared with capsule delivery and absorption in the gut. It’s important to note that caffeine has a 6hr half-life i.e., if you consume 200mg at 4pm you still have 100mg in your system at 10pm. Therefore, your caffeine strategy should consider the possible implications on sleep.

Side effects? Caffeine has a number of possible side effects which are most likely to be experienced by those who don’t normally consume caffeine or when chronic users stop consuming caffeine (may last for a week until adenosine receptors return to normal), these side effects may include:

  • GI distress

  • - Insomnia (known to have a half-life between 2-10 hours)

  • - Irritability

  • - Tremor

  • - Increased blood pressure Note: start low and build up dosage until you find a suitable dose for yourself and any implementation should be tested outside of competition.

Matthew Hooks|SENr


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