Caffeine
(Based on Aker Jeukendrup's article in 220 Triathlon issue - 220, May 2008)
Caffeine has been shown to improve endurance capacity at intensity levels similar to those used during triathlon events. For example one study found that at exercise intensities around 85% VO2 Max (similar to that seen during sprint and Olympic distance events) caffeine ingestion caused improvements in time to exhaustion of 10-20%. You can therefore speculate that you should be able to maintain a higher percentage of your VO2 Max for the duration of the race, although this has never been proven in studies.
Is it legal?
Yes. In January 2004 it was removed World Anti-Doping Agency's banned list and moved to the monitoring list. This means when an athlete is tested the level of caffeine in their sample is recorded.
Mechanism - How does caffeine improve performance?
Increase in plasma fatty acid concentrations following caffeine ingestion means that more fatty acids are available for use as a fuel source therefore sparing blood glucose and muscle/liver glycogen utilisation. Early studies believed this to be the case but subsequent studies have been unable to reproduce this effect.
Caffeine has also been shown to decrease the perceived level of exertion meaning that it was easier to produce the same level of effort.
Caffeine has also been shown to improve cognitive function (attention and memory) even in very low doses (2-3mg/kg) showing caffeine stimulates the central nervous system.
Caffeine assists in carbohydrate exhaustion. When co-ingested with glucose, oxidation of carbohydrate (broken down to carbon dioxide and in the process releasing energy) increased during exercise. This is most likely because caffeine stimulates the absorption process which results in a greater availability of glucose for the muscles.
How to use caffeine:
More work need to be done in this area but try an initial dose of 3-9mg/kg. So for a 70kg person this equals 210-630mg of caffeine or two to six strong cups of coffee.
It takes about 60 mins for ingested caffeine to reach peak levels in the blood. It has a half-life of 2-10 hours meaning that after 2-10 hours peak levels will have halved.
This means it is important not to leave taking caffeine supplements too late in the race to achieve maximum benefit.
Due to its long half life if you take an initial dose then only smaller doses are required to reach the previous peak. This is useful for endurance sports as the main loading can take place pre-event with smaller maintenance doses during the event.
Habitual users of caffeine (people who drink caffeinated drinks regularly) are less likely to experience potential side effects such as GI problems, headaches, increased heart rate, restlessness, irritability, tremors and rises in blood pressure. These are all caused by the effect of caffeine on the central nervous system.
There is no evidence for a reduce effect on performance for regular caffeine users.
Caffeine content of popular foods
Hot Drinks
Coffee, brewed (250ml) 102-200mgCoffee, instant (250ml) 270173mg
Tea (250ml) 40-120mg
Sports Drinks
Lucozade Sport with Caffeine Boost (500ml) 80mgHigh5 Energy Source Extreme (500ml) 150mg
Red Bull (250ml) 80mg
Energy Bars
Maxim Energy Bar with Cappuccino (55g) 60mgPowerBar Performance Bar, Coconut crisp (65g) 50mg
Cliff Bar, Strawberry (68g) 25mg
Soft Drinks
Pepsi (330ml) 38mgCoca Cola (330ml) 31mg
Diet Coke (330ml) 47mg