Being a coffee drinker, I feel somewhat out of sorts if by lunchtime I haven't had my daily hit. It works best for me mid- to late-morning - it gives me a wake-up charge and sustains my appetite through to lunchtime.
But as a runner, when best to have it? I've never really learned how to use caffeine to my advantage in training or racing.
The subject came up at a recent discussion night at The Body Mechanic physiotherapy clinic in Sydney, where a lot of endurance runners were keen for some tips on how to get the best from their bodies for the ultra and trail events season.
It seems I'm not alone in being confused about caffeine use; there was general consensus, learned the hard way in some cases, that it can play havoc with your stomach. It's one thing to have a coffee at your desk; it's another to have it before a race when bathrooms aren't easy to get to, or when the race is going to be long and you'll be needing to combine it with other energy sources as well.
How does it work?
Caffeine stimulates the central nervous system by blocking adenosine, a neurotransmitter that normally causes feelings of fatigue. A hit of caffeine alters your pain perception, allowing you to work harder with less perceived effort. It also mobilises fatty acids in your body.
"There's more energy in a gram of fat than there is in a gram of carbs and you carry almost infinite fat stores, certainly enough for a 100km race," says Body Mechanic physio and ultra runner Mark Green. "It's thought, therefore, that having caffeine will turn on your fat metabolism earlier."
Sports dietitian Peta Carige says it's important to practise with it before using it in a race. It's also available in many forms for runners – caffeinated marshmallows, seeds, nuts and gels, plus pills like No-Doz.
"I'm pro-caffeine and if your sport doesn't require accuracy, I definitely recommend trying it," says Carige.
"For shorter distances have it beforehand. During long runs, like marathons, I tell athletes to start taking it from half way to the back end of the race. The import thing is that the performance enhancement amount is different for everyone because some people have it daily, and others don't have it at all."
How much to take
Carige says the recommended amount of caffeine is 3.6mg per kg of body weight, so in the case of No-Doz, for example, you'd be taking two to three pills initially, depending on your weight.
"I say test with the true amount for performance enhancement, then scale back."
Caffeine stays in your system for up to four hours and takes about 30 minutes to kick in. After an initial dose, Carige says you should only take top-up amounts after that in the form of gels or cola. The idea is to keep enough caffeine in your system to do the job until the end of the race. The gels and cola have the added advantage of providing a sugar lift.
Carige says it's better to take caffeine later in a long race rather than taking it at the start and then not taking it again, because you will feel it when it's out of your system.
"Scientifically we think caffeine does affect our macro nutrient usage, but there's also stuff going on in the brain," Carige says. "There's a lot around performance enhancement and the brain that we don't actually understand."
For example, it's thought that putting something sweet in your mouth without even swallowing it triggers the cranial nerves from your mouth to your brain enough to give you a mental hit that allows you to overcome your exhaustion.
"If you're tired of drinking sports drink towards the end of a race, just swish it around in your mouth and spit it out," says Carige. "You'll still get a performance enhancement." Plus it can keep you going until your caffeine top-up has been absorbed.
Do you use caffeine when training or racing?