This month’s theme on HMMR Media is around the personalization and individualization of performance. Typically, this focuses on the physical side, but at the start of this month I wrote about how a focus on differences in stress tolerance—a largely psychological aspect—might guide individualized training a bit more. But there is another area where we can turn our attention; that of ergogenic aids such as caffeine. Towards the end of last year I co-authored a paper with John Kiely on factors that might impact the individual response to caffeine intake in athletes. In this article, I want to expand on that topic, and discuss how athletes and coaches might use this information in a real-world setting.
The state of caffeine research
The first point I’d like to make is that caffeine has been reliably shown to enhance performance across a number of domains. For example, caffeine certainly improves all aspects of endurance performance—most likely due to a large part on its impact on pain—including strength endurance. There is some evidence that caffeine can improve motor firing rates, which may allow it to enhance strength and power, although further research likely is needed.
One area where its performance enhancing effects are slightly controversial is that of one-off, short-duration, high-intensity exercise, such as a 100m sprint. That said, caffeine exerts its performance enhancing effects through a wide variety of potential mechanisms, such that, even if it didn’t have a direct effect on sprint performance, it likely has a positive impact on both mood and motivation, which is turn should indirectly enhance performance. Given caffeine’s well-established and well-replicated positive effect on performance, I strongly believe that all athletes should at least consider using caffeine to enhance both competition and training performance.
Genetic factors impacting caffeine dosing
The typical recommendation is to consume 3-6mg/kg of caffeine around 60 minutes prior to activity, but in practice finding the right does is not that simple. If we put the recommendation into practice we immediately see that this dose of caffeine appears not to improve performance in some individuals. This is perhaps best illustrated by a study published earlier this year, which put over 100 male athletes through a 10-km cycle time trial having consumed either no, 2mg/kg, or 4mg/kg of caffeine beforehand. Overall, the higher caffeine dose enhanced performance by around 3%. However, for a subsection of people, this dose of caffeine led to a performance decrement, increasing the time trial duration by almost 14% when compared to placebo.
When we look closer we start to see the role of genetics appear. All the people who saw their performance worsen has the CC version of a gene called CYP1A2. This gene encodes for cytochrome P450 1A2, which is responsible for around 95% of all caffeine metabolization in the body; those with the CC genotype produce less of this enzyme, and hence metabolize caffeine slower. As a result, the normally recommended amount of caffeine (3-6mg/kg), consumed at the normally recommended time (~60 minutes pre-exercise) not only failed to improve peformance, but actually saw them perform worse.
The good news is that less than 10% of people have this version of CYP1A2, but almost half of us—myself included—have the AC version which, in this study, lead to no real improvement in time-trial performance at either dose of caffeine tested. Of course, this doesn’t mean that caffeine cannot improve performance for CC or AC genotypes, just that it likely doesn’t at the level of the current guidelines. My own hypothesis is that AC and CC genotypes should consume caffeine a greater amount of time pre-exercise—such as 90-120 minutes—but this has yet to be experimentally tested.
Other genes also no doubt play a role. One with some promise is ADORA2A, which encodes for a specific type of adenosine receptor (caffeine is a competitive adenosine antagonist, meaning that it competes with adenosine for its receptors). A common variant in this gene has the potential to impact regular caffeine consumption—which may in turn alter the ergogenic effects of caffeine (more on this in a minute)—as well as sleep disturbances and anxiety following caffeine ingestion. Clearly, then, genotype is an important factor in understanding the individual response to caffeine, and a key area for future research on understanding how best to individualize caffeine use in sport.
Other factors impacting caffeine and performance
Other factors also impact how you respond to a given dose of caffeine in terms of performance enhancement. All of these also need to be considered when using caffeine pre-competition. One of these is the belief of the athlete as to whether caffeine enhances performance; if you believe it does, and you believe you’ve consumed caffeine, you tend to see the greatest performance benefits. Age is also a factor, with some early research suggesting that muscles in older individuals are less sensitive than their younger counterparts. There is even some evidence that caffeine has a greater effect on trained compared to untrained individuals.
Another factor of particular interest to me is the effect of habitual caffeine use. Surprisingly, this isn’t all that well researched. As a very brief overview, some studies suggest that regular caffeine use reduces the performance enhancing effects of pre-exercise caffeine ingestion, such that, if we want to get the maximum benefits from caffeine, we should limit our exposure to it. Conversely, some studies report the opposite finding; that regular caffeine use has no impact on its ergogenic effects.
I have an hypothesis—which again is untested—that the regular caffeine dose is what is important; I wrote about it last year on HMMRMedia, and I have a paper coming out on it soon. My belief is that the pre-competition dose has to be somewhat larger than the regular caffeine dose in order to harness all of caffeine’s performance enhancing potential. So, if you regularly consume 3mg/kg of caffeine across a day, you might need 5-6mg/kg pre-competition. The implications of this are that, the more regularly you use caffeine, the more caffeine you need to get the same effects, meaning that, if you’re more sensitive to caffeine for whatever reason (genotype, etc.), you run the risk of experiencing some of the negative side effects of caffeine ingestion (such as anxiety, sleep disturbances, etc.). Conversely, if you are highly sensitive to caffeine and can’t tolerate it pre-competition, regular exposure to caffeine may actually reduce some of those negative side effects, because you build up some level of tolerance.
Clearly, it’s a complicated, nuanced area, with no real, firm answers. Even more frustratingly, it’s difficult to understand how much caffeine you regularly consume, as the caffeine content of drinks (the most common method of caffeine ingestion) varies both between different brands, but also within the same drink at different times.
Defining your routine
It’s clear that there are many factors which can affect caffeine use for both competition and training. Some of these will be readily apparent, while others will be harder to quantify. Additionally, there are unknown unknowns; things we don’t even know affect caffeine use in athletes. As such, it’s easy to get bogged down in the details, so we need a practical, pragmatic approach to discovering the optimal caffeine strategy for a given athlete at a given time. Ultimately, this is evidence-guided trial and error. Thankfully we know which variables can be modified to find what works best for each athlete: dosage amount, the source of caffeine, and timing.
As I mentioned above, most guidelines recommend a dose of 3-6mg/kg of caffeine, approximately an hour prior to the exercise bout that you’re taking caffeine for (as a side note, if you’re taking caffeine for training, use the time the main aspect of the session starts, not the warm-up). It’s a good idea to start with these broadly recommended guidelines; consume 3mg/kg, 60 minutes before, and note how you feel and how you performed. Then adjust the dose up and down for some self-experimental trials, and again, note how you feel. You can then adjust the timing of caffeine intake; perhaps experiment with consuming it 45 minutes before, or 90 minutes before. If you know your CYP1A2 genotype, you could test my hypothesis by extending the time between caffeine intake and performance to 90-120 minutes. Then you can experiment with different sources of caffeine—tablets, energy drinks, gels/bars, and gum.
Dealing with complexities
Hopefully, it should go without saying that you should practice this in training, not in competition. But it’s also worth pointing out that, in my opinion (and I have no research aside from practical experience to back this up), the caffeine strategy you use in training won’t necessarily be optimal for competition. When it comes to the competition day, it’s likely—especially if it’s a big competition—that you will be feeling more anxious than usual. Caffeine has the potential to increase these feelings of anxiety, and also increase the physiological symptoms of anxiety, such as an increased heart rate. For some people, therefore, they might require a lower caffeine dose pre-competition than they do in training, although this becomes further complicated by the fact that, in my opinion (and I’ve just had a paper accepted exploring this), it is important that the pre-competition dose is greater than the habitual caffeine dose. In this case, there might be some logic for this athlete to limit their exposure to caffeine during the competition period, in order to “re-sensitize” themselves to caffeine’s ergogenic effects at a lower dose (although again, I should add, this recommendation would likely be considered controversial and there isn’t much evidence to support this at all).
Finally, for some people, caffeine disturbs their sleep, both increasing the time taken to fall asleep, and decreasing the depth of sleep achieved. For evening competitions, this means that athletes may not sleep well afterwards. For one-off competitions, this is less of an issue, but for multiple-day competitions, it becomes something that must be considered, as an athlete consuming caffeine for a race on day 1 (say, a quarter-final) may impact their recovery for the subsequent days competition (which could be a semi-final and final). Of course, we again need to be pragmatic; if the athlete likely needs caffeine to progress through the first race, they should take it, but, conversely, if I were advising Usain Bolt, I’d tell him to save the higher doses of caffeine for the second day of competition.
My own trials and errors
If you’ve gotten to this point, you’ll have realized that, outside of the broad recommendations regarding caffeine use, it’s difficult to give specific advice that is highly accurate—essentially, it comes down to a trial and error process.
In my career, I started off using caffeine as a caffeine-naïve seventeen year old, where I would consume a can of energy drink (~80mg of caffeine, so around 1mg/kg) 60-minutes pre-race. When I moved into the senior ranks, I found training much more fatiguing, and so I got to the point of having two cans of energy drink 60-minutes pre-training (2mg/kg) on a daily basis. At this point, I experimented with my pre-competition caffeine intake a bit more, trying out caffeine tablets for a total of 200mg (~2.5mg/kg) 60-mins pre-race. In training, this was fine, but in competition I felt hyper-stimulated and anxious, so I had to move away from that and back to the energy drinks. In 2010, I began adding caffeine in the form of caffeinated bars and gels pre-race, and also moved to a split dose. Here, I’d consume a caffeinated bar 90 minutes pre-race, a caffeinated energy drink at 75 minutes pre-race, a caffeinated gel 60 minutes pre-race, and a caffeinated energy drink again at 45 minutes pre-race, for a total of 200mg (~2.5mg/kg) of caffeine. Note that this is below the widely accepted optimal intake of 3-6mg/kg; when I experimented with >3mg/kg pre-race, I didn’t like it.
The take-home, therefore, is to play around with a variety of different options—dose, timing, delivery method—until you find what works for you, and then continue to refine the process on an on-going basis.