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Caffeine and Endurance Performance
By Matt Hanson, EdD
The use of caffeine has become common practice among endurance athletes. It’s well accepted that caffeine can not only improve performance, but it can also reduce the perceived exertion during an endurance event as well as possibly masking some of the pain involved with strenuous exercise. However, one thing that does not seem to be fully clear among endurance athletes is the dosage of caffeine which is necessary to give us the desired outcome.
We endurance athletes tend to take a “more is better” approach to supplements, fueling, hydration, and the like – often for very good reasons. But is that the case for caffeine? Let’s take a look at some available literature and decide.
Caffeine works in the body in multiple ways that are beneficial to performance. Upstairs, caffeine can work in the brain to prevent adenosine from binding to receptors, helping an athlete feel more alertness and less fatigue – effects that people around the world take advantage of daily with coffee, tea, energy drinks, etc.
For athletes specifically, caffeine’s mental effects can include less pain while training, and it can also stimulate calcium release within muscles throughout the body, which can allow a greater force production from the working muscle.
Narrowing the focus further to endurance athletes, caffeine has been shown to mobilize fat cells for easier use during endurance exercise, which can lead to lower glucose burn, reduced lactate production, and glycogen preservation – all of which are especially valuable during the long hours of endurance training.
All of these things are very positive. However, caffeine in excess can lead to elevated heart rate, increased skin temperature, and difficulty cooling the body down. Given those negative returns, it’s clear that some level of balance needs to be struck. (It’s also worth mentioning that a small portion of individuals’ genetic coding might make any level of caffeine intake ineffective or even detrimental to performance, but I won’t dwell on that here.)
Too much is… too much
In my opinion, most gels and caffeinated sports drinks really gear towards the “more is better” approach. I don’t believe there is evidence in the literature to justify taking a gel with 100mg caffeine every 45 minutes.
Call me conservative, but 800-1000mg of caffeine during an 8 hour race just seems a bit excessive – in fact, it can be detrimental. The pitfalls of elevated heart rate are obvious, so I’d like to focus on increased skin temperature and decreased cooling efficiency.
While exercising, we produce a great deal of heat regardless of environmental conditions. We try to get rid of this heat through bringing blood to the surface of the body – which also brings excess heat to the surface – and then sweating to cool our skin and the surface-circulating blood via evaporation.
There are two critical impacts here: Blood going to the surface of the skin isn’t being used to bring oxygen to working muscles, and the fluids lost through sweat lead to dehydration. Both of these factors result in decreased performance, and both are exacerbated by increased skin temperature.
I previously mentioned that caffeine can increase skin temperature, especially in high doses. This is why my personal preference is to aim closer to the minimal effective dose rather than push the upper limits. I just don’t want to add additional heat stress to a system that is already struggling to keep up.
Dialing the dose
Despite those concerns, so many caffeinated gels, chews, and drinks seem to think 100mg+ of caffeine per serving is necessary. With such high doses, you either significantly overdose on caffeine with each gel or you are left having to take a large shot of caffeine, then go to a few non-caff gels, and then back to another large shot.
While helping First Endurance develop the new caffeinated Liquid Shot, I reviewed a number of studies that have tried to find the optimal dose of caffeine to maximize endurance performance. Unfortunately for endurance athletes (especially long-course triathletes), most of these studies are done on events lasting fewer than 2 hours.
Considering the limits of reliable studies and the variability in personal responses, universal recommendations in mg/kg body weight aren’t particularly helpful for events that are long enough that your body metabolizes the caffeine ingested during the event. Despite that, we can learn a thing or two from these studies in order to broadly benefit endurance athletes.
Many of the studies use 6mg/kg body weight as a starting point, equating to roughly 400mg caffeine for a 150lb individual. However, many other studies showed no additional benefit to consuming more than 3mg/kg body weight. Some have even demonstrated that 2mg/kg body weight shows the same performance benefits as 6mg/kg, so that 3.0 range describes a sweet spot between performance benefits and potential impediments.
My caffeine routine
This is why I was very happy to see First Endurance keep the caffeine dose to 25mg for the Kona Mocha Liquid Shot. At this level, I’m able to take a caffeinated gel every time I need one to supplement the carbs in EFS/EFS-PRO (roughly every 45 minutes) while maintaining a steady – but not overwhelming – intake of caffeine throughout the event. To illustrate this point, here’s how I’ve incorporated the caffeinated Liquid Shot into my long-course race days to chase that 3mg/kg of body weight goal.
I have one cup of coffee when I wake up (roughly 100mg of caffeine), take a caffeinated Liquid Shot right before the swim, and take another as soon as I get on the bike. By the time I’m on the bike, I’m already at a 2.25mg/kg of caffeine on the day.
The half-life of caffeine in the body is about 5 hours, so if I continue to take 25mg every 45-60 minutes during the race, I’ll hit roughly 3.0mg/kg of caffeine about 90 minutes into the bike, which is typically about 4 hours since my first cup of coffee. Continuing on with 25mg caffeine every 45-60 minutes throughout the race keeps me right in that sweet spot.
For a cooler 70.3, I might aim to get into that 3.0 range a little sooner by having a second cup of coffee in the morning, but I still want to stick with the steady stream of 25mg every 45-60 minutes throughout the rest of the race.
If I were doing a 40k TT, a sprint tri, or running a 5k or 10k, then sure: I’d load up with caffeine – that’s what the FE PreRace is for! However, for longer duration events (anything longer than 2 hours), heat management becomes a crucial part of performance, and overdosing on caffeine can negatively impact that aspect of exercise.
By maintaining consistent levels of caffeine on the lower end of the suggested range (2-3mg/kg body weight), you can minimize your heat load while still getting the benefits that caffeine use has to offer. The steady, relatively low supply of 25mg in Kona Mocha Liquid Shot helps maintain that sweet spot of caffeination while still allowing you to carb fuel appropriately throughout a several-hour event.