• Science Fueling Fitness

Caffeine: Sleep, Mood and Athletic Performance!

How does caffeine work?

Caffeine is one of the most commonly consumed substances in the world, due to its mood-enhancing and anti-fatiguing effects. Caffeine works by reducing our perceived level of fatigue! It does not provide energy per se, it simply reduces our feelings of fatigue and somewhat tricks the body into a state of arousal or readiness. It does this by competing with adenosine receptors in the brain and inhibiting the negative effects adenosine induces on arousal and pain perception. Adenosine is basically a sleep-regulating molecule and accumulates throughout the course of the day, making us feel more tired as the day goes on. Caffeine ‘intercepts’ the actions of adenosine by competing with it in the brain and blocking or restricting it from binding to certain receptors that promote sleepiness. This is how caffeine has an anti-fatiguing effect and why we feel more awake after a cup of coffee. Caffeine also promotes the release of dopamine – the feel-good hormone – which is why a cup of coffee also leaves us feeling better!

Caffeine peaks in the bloodstream within 60-90 minutes of consumption. It also has a half-life of anywhere from 6-9 hours, but this is very individual depending on how you metabolise it. Its lengthy half-life means that 6-9 hours later, half of your morning caffeine hit could still be in your body. This can then have major implications on sleep as caffeine is still inhibiting the role of adenosine (the sleep regulating molecule) so we find it difficult to feel sleepy when we have too much caffeine in our system!


How much and when?

We already know that caffeine has a direct effect on adenosine – the sleep regulating molecule. We also know that caffeine has a half-life of 6-9 hours (individual dependent) and so remains in the bloodstream for a relatively long time. So, in order to avoid the anti-sleep effects of caffeine and maintain a high quality of sleep, caffeine should ideally be cut-off 6-9 hours before we intend on sleeping. This makes sense, right? Why take an anti-fatiguing substance with effects lasting many hours, too late in the day?

Taking caffeine too late in the day can contribute to a vicious feed-forward loop of a late caffeine intake leading to lack of sleep, which in turn leads to increased feelings of fatigue the next day, meaning you require more caffeine to ‘get you through the day’ and the cycle repeats itself. In an ideal situation, caffeine is cut-off around 1-2pm, meaning that it will be out of our system by 10-11pm at the latest, thus not interfering with our sleep.

Of course, as with everything, there are pros and cons to limiting caffeine intake after mid-day. It is well known that caffeine can have performance-enhancing effects, and whether it be a gym session, a competitive game or a race, if that athletic event happens to take place in the evening then you may want to take caffeine beforehand to potentially improve performance - and just accept the anti-sleep effects that may come with that. It’s a trade-off between the potential benefits on performance vs the potential negative effects on sleep! In terms of enhancing performance, caffeine peaks in the blood around 60-90 minutes after consumption, so this should be accounted for when looking to improve performance. Taking a monster directly before a game, probably only benefits you towards the end of the game. Likewise, with a gym session, a coffee as you warm-up will likely not impact your session as much as it could do if you took it 60 minutes pre-gym.

Tolerance and Response

It is also worth mentioning that the more caffeine you consume, the more blunted your response to it becomes. Essentially your body gets used to it and its effects slightly decrease over time. With that in mind, it may be a good idea to ‘save’ or ‘plan’ your caffeine intake around big gym sessions (heavy strength or power focused sessions) and competitive games – as opposed to take it for every training session and becoming a little too familiarised with its effects. Saving a high caffeine intake for when you need it most is probably a smart idea in order to maximise your response to it. Likewise, it can be beneficial to cycle off caffeine in less busy or less stressful periods of work, study and life in general, so that you are potentially more receptive to it when you need to use it most!


Enhancing Athletic Performance

The effects of caffeine supplementation on performance are well documented. Studies show that caffeine improves endurance performance (both time to exhaustion and time-trial), speed endurance exercise (ranging from 60-180 seconds) and high-intensity intermittent exercise, in well-trained subjects. The studies assessing the impact of caffeine on athletic performance used well-trained subjects (and in some cases, professional cyclists) and had subjects perform testing in a variety of means - stationary bikes, cycling on road and running on a track, so the results are valid and relatable.

The majority of the research shows a benefit on anaerobic exercise such as resistance training, repeated sprints and repeated high-intensity efforts. Studies showing improvements in high-intensity exercise used short, intermittent-bouts of 4-6 seconds interspersed with longer active recovery periods to mimic the high-intensity, intermittent element of field sports such as Rugby, GAA, Soccer and Hockey.

One study used 6mg caffeine per kg of body mass on moderately trained men, which is 480mg of caffeine for an 80kg man – the equivalent of 4-5 standard cups of coffee or two and half cans of monster. This study showed an improvement in repeated sprint ability. Another similar study used 5mg/kg body mass and saw a 1.4% enhancement of repeated sprint ability. These may seem like trivial improvements but anyone competing at an elite level of sport who can gain an extra 1% from something as simple as proper caffeine consumption would be smart of avail of it!

The dose of caffeine used in these studies is worth noting. It may be much higher than most people expect and actually much higher than most peoples daily caffeine consumption. 5-6mg of caffeine per kg of body mass is the standard dose used in studies showing performance benefit, which can be difficult to consume in the hours before competition. Gastric issues aside, drinking 4-5 coffees or two and a half monster drinks is likely impractical for most athletes. One solution is to consume caffeine through stronger drinks such as an espresso or double espresso, with another practical option being caffeine chewing gum.


Caffeine Chewing Gum

The majority of research on the effects of caffeine on athletic performance use doses as high as 5mg-6mg/kg body mass. For reference, this equates to 400mg-480mg of caffeine for an 80kg athlete. One standard cup of coffee provides between 70mg-120mg of caffeine, with a standard monster drink providing between 180mg – 200mg. As you can see, a lot of coffee or a lot of monster needs to be consumed in order to get the required dose of caffeine needed for enhanced performance.

One way of getting around this may be the use of caffeine chewing gum. It is easy to use, does not involve the potential of gastric issues and has some good research supporting it. More importantly, lower doses of caffeine were used and needed in gum form, so it may be a much more practical option.

One study on competitive cyclists saw just over 5% improvement on performance in repeated sprint ability when using caffeinated gum with the equivalent of 240mg of caffeine (only 3mg/kg body mass for an 80kg athlete for example). The study showed that professional cyclists who used the chewing gum before performing, were able to maintain higher power outputs as the trial went on, as opposed to the placebo group whose power output dropped by 5%. A similar study also showed increased power outputs again in competitive cyclists.

A study conducted on university level rugby players used 200mg of caffeine chewing gum and seen performance enhancements in a number of different means. Subjects who used the chewing gum had a 14.5% improvement in yoyo test score, 3.6% improvement in CMJ (counter movement jump) and reduced levels of fatigue in repeated sprint tasks. All of this was after the subjects simply chewed the gum for 5 minutes pre performance – a really easy method of potentially enhancing performance!

Typical caffeine chewing gums provide 100mg of caffeine, so 2-3 pieces will likely result in a performance enhancement and is a much easier method than drinking 5mg-6mg caffeine before performance.


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