I get asked this one a lot and it frequently comes up on forums and message boards.
Caffeine has been shown to decrease oxygen demand and improve running economy.
It’s also been shown to improve time trial ability for running and biking, as well as other measured performances for ball-sport athletes. I’ve seen improvements in performance from 0.5% to 4% depending on the studies you look at.
Yes, caffeine works. This I think I can say without equivocation.
The critical and logical questions then become:
- How does it work?
- How much is needed for it to work? And,
- How much is too much?
How we (used to) think caffeine works in performance
One common explanation that I see repeatedly online and even in some training books is that caffeine spares the use of muscle and liver glycogen during a race and this is one way that it can boost performance since muscle and liver glycogen depletion potentially creates the onset of fatigue. It’s coupled with the idea that caffeine mobilizes fat into the blood stream and therefore this increases fat utilization.
Research so far has shown that this isn’t true. While studies have shown that caffeine does mobilize free fatty acids, what hasn’t been shown is that fat metabolism increases or changes any. In fact fat and carbohydrate metabolism remain the same.
So as far as research showing that caffeine has a glycogen-sparing effect — that doesn’t seem to be supported. Most of the glycogen/metabolic studies focus on diabetics and some haven’t found differences in post exercise blood glucose and insulin levels with the use of caffeine versus placebo — and few if any have noted any real changes. But it would be difficult to extrapolate anything from diabetics into the realm of endurance athletics though. It could be having an effect but I’m not aware of studies that show that caffeine has any metabolic effect.
In another article from a usually well-researched group of bloggers they mention a research article that says combining caffeine with carbohydrate improved storage of glycogen, and the researchers of this study say that this was indeed “the first evidence” of this sort. But later studies show differently stating that as long as you consume a certain amount of carbohydrate following a workout the amount of glycogen storage isn’t appreciably more with caffeine use. So take the metabolic effects of caffeine with a grain of salt (as it were).
In fact a review articles done in 2008 looking at caffeine’s role in changing metabolism of substrates states that “There is very little evidence to support the hypothesis that caffeine has ergogenic effects as a result of enhanced fat oxidation.”
There’s a lot of evidence that caffeine will boost performance in the absence of any effect on glycogen sparing — a 2013 study in Medicine and Science in Sports and Exercise found that caffeine ingestion increased 60min TT effort among 12 endurance trained triathletes even in a manipulated glycogen-depleted state. This makes it clear that it doesn’t need to effect glycogen in order to give your performance a boost.
How does caffeine actually work?
Frankly we don’t know with 100% certainty. A number of theories have been proposed:
Enhanced Calcium mobilization and/or enhanced Na+/K+ (sodium and potassium pump) transport. But neither of these have been shown to be the case in research studies.
As one review of literature in 2009 seems to be that caffeine stimulates the CNS directly. It has a hypoalgesic effect — meaning it helps you to feel less pain — so it decreases the level of perceived exertion at a given workload, increases arousal and alertness, and has “effects on negating decreased firing rates (ed. notice the double negative there) of motor units and possibly produce a more sustainable and forceful muscle contraction.”
The $.02 version? It gets you amped up.
Simple and effective.
How much caffeine should you take?
Most of the research points to about 1.5mg/lb (~3 mg/kg) of body weight per hour. Most caffeine supplements come in 200 mg tablets (you can find 100s too) so for a 150 pound athlete taking one of those tablets per hour will get you pretty close.
Dosages at 6mg/kg per hour didn’t show any improvement over the recommended 3mg dosage. Consuming 9 mg/kg per hour seemed to have a negative effect.
What about coffee?
Coffee has a bit of a checkered track record with sports performance. Some studies show it to be inferior to caffeine pill supplementation, while others still show good effect.
One thing that stands out with coffee is understanding what you’re getting. When different brands of coffee and even different coffee shops were tested they showed a huge disparity in the number of milligrams of caffeine in a standard cup. In fact, in an informal review of a number of different Starbucks and tested each of their Breakfast Blends and found a 6-fold variation in the number of milligrams! So get one amount at one Starbucks and potentially at the store down the street get the same coffee with six times as much caffeine. Yikes!
I’ve found that individual variation is huge, so test what works best for you. Just use what seems to be a therapeutic dose for you — it may end up being less than the recommended, which is okay. I think you can only benefit by sticking to the minimal effective dose given your metabolism.
He lives with his wife and two kids and runs multiple businesses in Grand Junction, Colorado.