Caffeine: The Evidence

1,3,7-trimethylxanthine the world's most used psychoactive and pharmacological substance.

Ergogenic aid?

I love good coffee and also use caffeine to help with my racing. Back in my university days I was a guinea pig in a number of studies involving caffeine, substrate metabolism and endurance performance. My knowledge was current then, but there has been a lot of research since . Time to check in on where things are up to with caffeine and race performance.

A recent review (Caffeine Use In Sports: Considerations For The Athlete) provided an good starting point. The review added a fair amount of speculation and personal interpretation on the data so it was essential to look at the original research presented.

Here I present my own summary of caffeine and it's effect on sports performance. I skip the theories on mechanisms and pharmacology and stick with the practicalities.


  • Improves time to exhaustion and work output in endurance exercise that lasts between 5 minutes and 2 hours.
  • Improves peak power output, speed and strength in lasting less than 15 seconds.
  • Improves sprint or power output in repeated sprints if they each repeat last for 6 seconds or less.

  • No benefit or even a detriment to performance lasting between 15 seconds to 3 minutes.
  • Decreased performance for repeated bouts of exercise that last greater than 15 seconds each.

  • Improves cognitive performance, arousal and mood.
  • Lowers respiratory exchange ratio (RER).
  • Reduces sensation of peripheral fatigue.
  • Improves fat oxidation during endurance exercise.

  • Doses of 3-13mg/kg have all shown ergogenic benefits.
  • Negative side effects are more likely when dosing exceeds 9mg/kg.
  • There does not appear to be any increase in performance beyond 9mg/kg even without the negative side effects.

  • Tolerance due to habitual use appears to affect the dosage required for ergogenic gains plus limit the magnitude of effect.
  • Non-users will likely have the highest ergogenic effect within the range of 2-6mg/kg.
  • Moderate users (3mg/kg/day or less) will have a slightly blunted effect and require doses between 3-7mg/kg
  • Heavy users (6mg/kg/day or more) will have a further reduced effect and are likely to require doses between 6-10mg/kg.

Withdrawal symptoms from caffeine (lowered mood, tiredness, headaches, lowered pain tolerance) peak between 28-48 hours following caffeine cessation. It takes 4-7 days for these symptoms to resolve. Exercise performance is significantly impaired at 2-4 days following cessation of caffeine.

Acute caffeine intake reverses withdrawal symptoms. A period of abstinence from caffeine may reduce tolerance and therefore increase the ergogenic gains when taken for performance. However, this would appear to require 7 days of withdrawal. This area requires further research.


  • Capsule form has been shown to consistently work.
  • The research is limited on other forms, but there is some evidence that taken in the form of coffee, caffeine may be ineffective as an ergogenic aid.


  • Onset of effects is typically quoted as 5-10 minutes, however, we all seem to experience an almost immediate effect with that first sip of coffee.
  • Peak plasma levels are reached in 30-75 minutes.
  • Half-life is 4-5 hours. After 6-7 hours 75% has been cleared.
  • Therefore it is recommended that an acute dose is taken approximately 60 minutes prior to exercise performance. Redosing during the event does not appear to offer any benefit unless exercise lass longer than 6 hours.

What I Do?

I love coffee consuming 2-6 strong espressos per day. For most races I don't alter my coffee intake, but for a big event I will limit myself to 2 coffees/day for a week prior.

Race morning I will also have my morning coffee with breakfast.

Pre-race I'll take caffeine in capsule form (NoDoze) about 50-60min prior to race start. The dosing I take will usually be 300mg (4mg/kg) for minor races. For the bigger events I'll take 400mg (6mg/kg). These appears to consistently work for me.


Sokmen B, Armstrong LE, Kraemer WJ, Casa DJ, Dias JC, Judelson DA, Maresh CM. Caffeine Use In Sports: Considerations For The Athlete. J Str & Cond Res. 2008:22(3);978-986


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