Global caffeine consumption is estimated at 120,000 tonnes each year (1).  This makes caffeine the most widely consumed psycho-active substance (aka drug) on earth.  Some say coffee helps them concentrate, others swear it reduces fatigue.  It has also been shown to enhance endurance performance.  But, does caffeine deserve a place in fit, healthy lives?

What happens to my body when I drink caffeine?

Caffeine is absorbed through the digestive system and reaches maximum concentration in the bloodstream in close to one hour.  From there, it is gradually metabolized (processed) by the liver, and has a half-life (time it takes for half the dose to be processed) of around three hours, though it depends on the person.  Once in the body, caffeine:

  • Mobilises free fatty acids (FFAs) which can be used as a fuel in endurance sport.  This means less glycogen is used so precious muscle and liver glycogen stores will last longer and can be saved for later in the event when we need them most.

  • Enhances motoneural excitability (makes it easier for the nerves to tell the muscles to work so we can recruit more fibres mor easily and therefore work harder).

  • Stimulates β-endorphin release which, among other things, produces an analgesic (pain killing) effect on the central nervous system and improves morale.

  • Stimulates release of adrenalin which makes us feel more alert.


Do these effects of caffeine really improve my performance?

In a word, yes!  The International Society of Sports Nutrition released a position stand on caffeine and performance (2).  Among other things, it states that caffeine is effective when taken in low to moderate doses (3-6mg/kg) though does not give further improvements when taken in high doses (>9mg/kg).  It states that caffeine can enhance vigilance during extended exercise and sleep deprivation, and that caffeine is also highly effective in enhancing sustained maximum effort.  One literature review of 21 different studies (3) found that time trial performance improved by an average of 3.2 +/- 4.3% following caffeine ingestion.

I’ve heard of having a ‘crash’ when the caffeine runs out.  Should I be worried about this?

If you are doing a short event (3-6 hours), you’ll probably finish the race before the caffeine wears out.  But it is a consideration for expedition or multi day races.

During normal waking hours, when brain neurons are firing, they produce a substance called adenosine as a by-product.  Your body monitors the amount of adenosine and when enough of it builds up, you feel tired and want to sleep.  However, when you drink caffeine, the caffeine molecules bind to the same ‘receptors’ that adenosine molecules normally bind to.  The result is that your body doesn’t realise how tired it is (imagine the receptors as a keyhole which have been plugged with blue-tac (caffeine) so the key (adenosine) can’t fit in to turn the lock (make you feel tired).

However, when the caffeine runs out and the receptors become ‘free’ again, all the adenosine is still in your body from before, plus more which has built up during the last you hours you were under the effects of the caffeine.  So you will likely feel very tired when the caffeine wears off.

Caffeine withdrawal symptoms can also include headache, fatigue, anxiety, irritability, depressed mood, difficulty concentrating.   If you have been drinking caffeine regularly over a longer period, the start of withdrawal symptoms is 12-24 hours after you stop taking caffeine, with the peak intensity 20-51 hours after.  Adventure racing is hard enough already – you don’t want to experience any of these symptoms in a race!

What about my health?

While caffeine fits the definition of a drug, it does not have the same serious consequences of long term use as some ‘harder’ drugs.   In the short term, excess caffeine can increase cardiac arrhythmia (abnormal heart rhythms) by increasing stress hormones and increasing blood pressure.  It can also increase the risk of stroke, increase urination and worsen anxiety disorders.  If you are at risk or concerned about any of these, check with your doctor.

In the long term, a review of studies on the effects of caffeine on health (4) concluded moderate intakes of less than 400mg per day are unlikely to adversely affect health.  However, excessive consumption (more than 400mg or roughly 4 store bought coffess/day) on a long term basis may affect calcium balance and should also be minimised during pregnancy.  On the upside, caffeine consumption has even been associated with reduced likelihood of developing type 2 diabetes (5).  Though, if you have already developed diabetes, caffeine may reduce insulin sensitivity further and make it more difficult to control the diabetes (5).

What does all this mean for me, my training and my racing?

Used in the right way, caffeine can help our performance in adventure racing. However, we need to be careful about the amount and the timing so we don’t experience the negative effects of withdrawal.  Here are some points to remember:

  • For maximum effect on race day, it is ideal not to have caffeine for a week prior to the target event (not easy to do for us coffee lovers!).

  • For ‘sprint’ races up to 6hrs, caffeine enhances performance.  3-6mg/kg is the standard dose (2).  For a 70kg person, this is 210 – 420mg.  A regular cup of coffee contains 100mg of caffeine, tea around 30mg per cup. A can of Coke or Pepsi has about 40mg.  ‘No Doze’ caffeine tablets contain 100mg per tablet.  Caffeine takes around one hour to reach maximum concentration in the bloodstream so there’s no performance benefit taking it near the end of the race.

  • For expeditions and multi day races, you need to take care.  If you have less than your usual daily caffeine intake during the race you will feel withdrawal symptoms (so try not to have caffeine in the week before the race).  Also, if you start taking caffeine in the race and then stop you will probably feel worse than if you hadn’t taken it at all.  My suggestion is to avoid caffeine in the race as long as possible to keep it for emergencies.  If you desperately need some (e.g. if it’s a downhill mountain bike and you’re having microsleeps, take a No Doze instead of ending arse over tits).  Then in the final day or two, you could take caffeine until the finish because you won’t get the ‘crash’ while you’re racing.

All in all, the use of caffeine in adventure racing is very individual.  I know teams who use it heavily and other world-beating teams who never touch it.  Individual responses and physiology varies, along with how much you like it.  According to the science, it helps endurance performance physically and mentally, but we need to be careful of the timing and amount.  Should you use it in your next race?  It depends why you race and for how long, but I probably will.  And with that, I’m off to enjoy a cup of coffee…

References:
1) Gilbert RM.  Caffeine Consumption.  Progress in Clinical and Biological Research. 1984 Jan;158:185-213.
2) Goldstein ER, Ziegenfuss T, Kalman D, Kreider R, Campbell B, Wilborn C, Taylor L, Willoughby D, Stout J, Graves S, Wildman R, Ivy JL, Spano M, Smith AE, Antonio J.  International society of sports nutrition position stand: caffeine and performance.  Journal of the International Society of Sports Nutrition. 2010, 7:5 (27 January 2010).
3) Ganio MS, Klau JF, Casa DJ, Armstrong LE, Maresh CM.  Effect of caffeine on sport-specific endurance performance: a systematic review.  Journal of Strength and Conditioning Research. 2009 Jan;23(1):315-24.
4) Nawrot P, Jordan S, Eastwood J, Rotstein J, Hugenholtz A, Feeley M.  Effects of caffeine on human health.  Food Additives and Contaminants. 2003 Jan;20(1):1-30.
5) Van Dam RM, Hu FB.  Coffee Consumption and Risk of Type 2 Diabetes: A Systematic Review. JAMA. 2005;294(1):97-104.