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Aviation Physiology
Published in Monica Martinussen, David R. Hunter, Aviation Psychology and Human Factors, 2017
Monica Martinussen, David R. Hunter
Caffeine is considered a moderately effective stimulant that acts as an adenosine receptor antagonist. Adenosine promotes sleepiness, and caffeine blocks the adenosine receptor to prevent feeling sleepy. It works best when taken on an intermittent basis. Because the body builds up a tolerance for caffeine, habitual consumers must take larger doses in order to achieve the same alerting effects. A typical dose of caffeine is in the range of 50–200 mg. Although there is a large range of caffeine content dependent upon the method of brewing, a cup (8 oz) of brewed coffee typically contains about 100 mg of caffeine while a cup of black tea contains about 55 mg. Some beverages marketed as “high energy” drinks contain 150–180 mg of caffeine (Fredholm et al. 1999). In addition to beverages (and some foods such as chocolate), caffeine is also available in a powdered form. Ingesting caffeine in this form can be hazardous, since a lethal amount of caffeine is contained in less than a tablespoon (15 mL). The LD50 (the amount of caffeine that is fatal to 50% of the population) for caffeine is about 150–200 mg/kg of body weight (Peters 1967). Therefore, ingesting 12.25 grams (0.43 oz) of powdered caffeine would be fatal about half the time for an adult weighing 70 kg (150 lb). That amount of caffeine is contained in about 75–100 cups of coffee, so it is unlikely that an adult would consume enough to be potentially lethal by drinking coffee. However, even sublethal doses of caffeine can cause cardiac arrhythmia, particularly in individuals with some preexisting cardiac condition. So, do not overdo it.
Incorporating methods and findings from neuroscience to better understand placebo and nocebo effects in sport
Published in European Journal of Sport Science, 2020
Christopher Beedie, Fabrizio Benedetti, Diletta Barbiani, Eleanora Camerone, Jacob Lindheimer, Bart Roelands
Caffeine reduces fatigue in sport (Grgic et al., 2019). On this basis, caffeine has been widely studied by sport scientists, with 21 meta-analyses published to date (Grgic et al., 2019). The effects of caffeine are consistent with a neural as well as a metabolic explanation (Meeusen, Roelands, & Spriet, 2013). Caffeine is an adenosine receptor antagonist. Adenosine, a product of the breakdown of adenosine triphosphate, in turn has an antagonistic interaction with dopamine (Wisor, 2018). Therefore caffeine enhances dopamine signalling by antagonising adenosine receptors (Volkow et al., 2015).