Caffeine has been studied extensively for decades, and the evidence is very strong that it helps improve athletic performance. Heck, the International Olympic Committee had it on its banned substances list until 2004. So how does it work? How much do you need? And does everyone really benefit?
How does caffeine improve performance?
There are many different theories as to how caffeine helps performance, and unfortunately, nothing absolutely concrete stands out. The best theory out there right now is that caffeine intake can lower your perception of fatigue and make you able to push a bit harder than you otherwise would. This is a pretty intuitive answer: most regular caffeine users would have already agreed that caffeine makes you feel less tired and more willing to work!
How much caffeine and when?
In a lot of studies, athletes are given huge doses of caffeine before exercise – up to 9mg per kg or over 700mg for an 80-kg person – and exercise performance improves. Recent studies suggest that much smaller doses – around 1-3mg/kg or 80-240mg for an 80kg person – are just as effective. This is a good lesson for all of us: there’s no need to go overboard with caffeine intake (see the link at the end of the post).
After ingestion, it takes about 45 minutes for caffeine to build up in your body, and levels in the blood will stay elevated for several hours afterward. So if you’re looking for a boost in performance in a 5k or 10k, pre-exercise caffeine intake is recommended.
A recent study compared time trial performance after 2 hours of moderate exercise. In one trial, athletes took a large dose of caffeine an hour before exercise, and in the other, they took in 6 small doses (for the same total amount) throughout the 2 hour exercise period. On both occasions, performance in the time trial was increased compared to when athletes took in no caffeine at all. So for longer events such as a half- or full-marathon, taking in caffeine either before or during exercise should work equally well.
What about smaller amounts of caffeine late in exercise? Anyone who has done a marathon or other long distance event has probably gone through an aid station offering flat cola late in the race. But there’s only about 30mg of caffeine in one cup (~250mL) of cola. So does this really help? The same study mentioned above also examined the effects of cola intake late in exercise, compared with intake of a decaffeinated placebo drink. Surprisingly, performance was improved with the caffeine-containing cola drink. It appears that a fatigued athlete may be more sensitive to the effects of caffeine, and so can benefit from small amounts late in exercise.
Common caffeine sources: Where to get your fix
Caffeine is present in small amounts in common items such as chocolate, cola and tea, and in sports nutrition products like gels, chews and drinks. For many people, the go-to pre-exercise caffeine source is coffee. Tim Horton’s must be up to date on the research, because their coffee contains precisely 1-3mg/kg of caffeine for an 80kg person. An extra small (230 mL) contains 80mg, and an extra large (710 mL) contains 240 mg.
Caffeine may be a diuretic for those who don’t normally use it, but really, drinking 710mL of any fluid in a short period will probably make you want to pee. If you want a bit more bang for your buck, Starbucks has you covered: Their 230-mL “small” option packs 180mg of caffeine. Or if you want to eliminate the fluid altogether, just go straight to the source and pop a couple caffeine pills. Most will contain about 100mg. This is a good idea if you’re in unfamiliar coffee territory and don’t want to risk the possible side effects of a foreign brew.
Not everyone will benefit from caffeine intake
Unfortunately there is no cut and dry answer when it comes to “will this work for me?”. Some athletes find that having caffeine before a race makes them jittery and may cause problems with pacing or concentration. Some (but not all) regular caffeine users may not get as much of a boost from caffeine. Some (but not all) regular users may benefit from avoiding caffeine for a couple days before the race, or taking a larger-than-normal dose beforehand. A few researchers have suggested that the main benefit of pre-exercise caffeine intake for regular users is to avoid the negative effects of not having it!
People with pre-existing heart issues should consult a doctor before they consider using caffeine during exercise. Pregnant athletes hoping to establish a new PB should look elsewhere for an edge. And for all you kids out there thinking it might be a good idea to load up on energy drinks before your next race, think again: You don’t want to end up like this guy.
Armstrong LE et al. Fluid, electrolyte, and renal indices of hydration during 11 days of controlled caffeine consumption. Int J Sport Nutr Exerc Metab. 2005;15(3):252-65
Cox, GR et al. Effect of different protocols of caffeine intake on metabolism and endurance performance. J Appl Physiol. 2002;93,990–999.
Irwin C et al. Caffeine withdrawal and high intensity endurance cycling performance. Journal of Sports Sciences. 2011;29,509–515.
Van Soeren MH et al. Caffeine metabolism and epinephrine responses during exercise in users and nonusers. J Appl Physiol. 1993;75,805–812.