![]() Kinetics at Rest was measured first (R): the subjects remained at rest for 8 h after.The world’s most commonly used stimulant- caffeine is omnipresent in the daily life of many. The effect of moderate exercise on the kinetics of caffeine in 12 healthy volunteers-6 heavy coffee drinkers (HD) and 6 light coffee drinkers (LD) has been studied. Sources: PubMed Effects of moderate exercise on the pharmacokinetics of caffeine - PubMed There isn’t a whole lot of research in this area though so we don’t have much to work with. Also, their version of “exercise” was 30% VO2 max which is better than nothing, but we’re more interested in something like 70% VO2 max efforts. Subsequent studies didn’t show a significant difference between exercise or non exercise. All of which can affect caffeine metabolism. That 1991 paper wasn’t the best because they didn’t control for cigarette smokers, menstruation cycle amongst other things. With rest, it was around 4 hours ,’with excerise it was around 2.5 hours. There were some study, 60 min rest or 60 min excersice was compared. Different drugs lead to desensitization at different rates. If this happens acutely during a race or more chronically, I’m not sure. ![]() Since caffeine must act at extracellular receptors, my assumption without looking into more research, is that the receptors will become desensitized overtime and a larger intake will be needed. If there is enzyme mediated breakdown of caffeine, it could be a multitude of possibilities based on the rate limiting component. (You’d have increased rate of circulation through the kidneys and also increased pressure at the glomerulus). If freely filtered in the kidneys, the elevated HR and systolic BP would lead to elevated GFR and quicker losses. This would depend on the kinetics and mechanism of caffeine excretion. One patient, a 35-year-old man who had.įinally does the physiological impact of racing mean the caffeine gets cleared faster from the body than when just sitting at a desk typing at a computer so the racer would have less than 102mg? The mean serum caffeine half-life for the healthy subjects was 5.7 hours. Results are presented describing serum caffeine half-lives for three healthy subjects and two patients having alcoholic hepatic disease. So, does having 102mg of caffeine in the system mean the racer’s body will experience the same effect of that caffeine as when they took most of that in back earlier in the day? Or does this latent caffeine that’s been in the body for many hours end up losing its effect? Or, finally does the physiological impact of racing mean the caffeine gets cleared faster from the body than when just sitting at a desk typing at a computer so the racer would have less than 102mg? PubMed Serum caffeine half-lives. Then if they take a gel with 20mg of caffeine every hour after the start of the race for a 5 hour race, they will end up with 102mg of caffeine in their system at the end of the race. If that race starts at 9am, they will still have 78mg of caffeine in their system when the gun goes off. Let’s assume a racer has a cup of coffee (100mg) at 7am before a race. So by my math (degree in physics so I’m pretty sure I got this right) that means there is a k value of 0.1216 for caffeine when using hours and we can do some interesting calculations. I saw a paper that suggested that caffeine has an approximate half-life in the body of 5.7hrs. After seeing the post this morning “How much caffeine on 100mi gravel” I went down a rabbit hole and have a question that I think merits its own topic.
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