Numerous studies have shown that by stimulating the central nervous system, pre-exercise caffeine can help combat fatigue during endurance activities such as swimming, cycling and running, making it an ideal sports supplement for endurance. The obvious question of course is how much caffeine should you take to gain maximum performance benefits?
You could just use a "sledgehammer approach" and take very high doses to make sure you're getting plenty to boost performance. The problem however is that caffeine is not without its side effects (e.g. rapid or irregular heartbeats, anxiety, insomnia, to name but a few) so using the minimum required dose, yet one that still boosts performance is a far better strategy!
Optimum caffeine dosage
In terms of research on optimum caffeine dose rates, a large number of studies have reported a wide range of results. These can be summarized as follows (all figures in milligrams of caffeine per kilo of bodyweight - mgs/kg):
In short, the recent balance of scientific opinion about the likely caffeine dose required to produce a performance effect can be summarised as follows
For events less than 30 minutes, 6mgs/kg
For events of 30-60 minutes, 3-6mgs/kg
For events over one hour, 3mgs/kg or less
There's also evidence that when it comes to caffeine dose, unless the event is very short, less may be more (and more could be less)5. When trained cyclists took either 3mgs or 6mgs of caffeine per kilo, their performance was significantly improved compared to no caffeine; however, it improved more (4.2% reduction in time) when taking the 3mg/kg dose compared to the 6mg/kg dose (2.9% reduction). When the scientists number crunched the data, they found that the increase in performance when taking caffeine was essentially the same regardless of the dose taken - i.e. the extra 1.3% performance increase measured by researchers when the cyclists took 3mgs was not statistically meaningful. In a larger study with more subjects, it might have been possible to show that a 6mgs/kg dose produced significantly worse performance than a 3mgs/kg dose. Regardless of this, these results definitely showed that taking 6mgs/kg gave absolutely no additional performance over a 3mgs/kg dose.
How much caffeine should we be taking?
If you're a regular caffeine user, how can you apply these findings to your own training? Here are some tips:
For races/training over an hour, stick to a caffeine dose of 3mgs/kg. Higher doses won't give additional performance gains and may even be detrimental.
Caffeine breaks down only slowly in the body; this means that there's no need to top up unless your event exceeds two hours and even then, just 1-2mgs/kg is likely to be ample.
Bear in mind that not everyone responds uniformly to caffeine so use these figures as a good starting point for further experimentation rather than gospel.
When to take?
Consuming 1-2 hours before your event or big workout is ideal. Having your morning coffee or tea with your breakfast works well.
For a long event like a half ironman or full ironman you would then look to consume 1-2mgs/kg near the end of the ride so your ready to run. For the half ironman that would most likely be it. You might add a little more during the run in the form of pills, energy drink, or the famous coke at aid stations, if that falls within your nutrition plan. During an Ironman, you would probable plan a dose midway through the bike and mid way through the run. The key being, all of this needs to be practice beforehand in training.
The key as stated above, less is more. A big load early in the race will most likely leave you feeling the “coming down” effects and negatively impact your performance.
1. J Appl Physiol 1995; 78:867-874
2. Int J Sports Med 1995; 16:225-230
3. J Appl Physiol 1998; 85:709-715
4. J Appl Physiol 2002a; 93:990-999
5. J Sports Sci. 2012;30(2):115-20
6. Andrew Hamilton