I am frequently asked by athletes if drinking coffee is beneficial to their performance, and if so, how much is needed and how best to time its intake. There is a wealth of published research on this subject. Unfortunately, it is not in complete agreement.
We might start with the disagreement between the World Anti-Doping Association (WADA) and the International Olympic Committee (IOC) on the subject of caffeine as a banned substance. According to WADA’s 2008 listing, caffeine is not a banned substance although it is being monitored. On the other hand, the IOC as of 2008 considers a urine concentration of greater than 12mg per liter to be a doping offense. It would take on the order of 7 to 8 cups of strong coffee in a short period of time for a 150-pound athlete to reach this IOC-banned level. Interestingly, the research that finds a benefit from taking in caffeine in the form of coffee requires far less than this amount.
The research that has shown an ergogenic effect from caffeine [ 2,6,7,10,11,12,14,15] found that an intake of 3 to 9mg per kg of body weight. (about x-x cups of strong coffee) was sufficient. The following are a few examples of body weight intake at this level and a table of common beverages with their caffeine content.
Caffeine Intake by Body Weight for Ergogenic Benefit Based on Select Studies
Body Weight in Pounds (kg) 3mg/kg 9mg/kg
120 (54.5) 163.5 490.5
140 (63.6) 190.8 572.4
160 (72.7) 218.1 654.3
180 (81.8) 245.4 736.2
200 (90.9) 272.7 818.1
Caffeine Content of Common Beverages
Beverage (6oz/180ml) Caffeine Content (mg)
Espresso coffee 300
Drip coffee 180
Instant coffee 165
Percolated coffee 149
Brewed tea 60
Red Bull 59
Mountain Dew 28
Pepsi One 28
Chocolate syrup 24
Coca-Cola (regular or diet) 23
Pepsi Cola (regular or diet) 19
Instant decaf coffee 2
SOURCES: National Soft Drink Association, US Food and Drug Administration
To determine your intake level to possibly experience an ergogenic benefit find your weight in the top table which shows the intake required at 3 to 6mg per kg. Then look in the lower table to find your preferred drink and how much would be required. For example, if you weigh 160 pounds the range of intake for you would be 218 to 654mg. If your preferred drink is drip coffee you would need to drink 1.2 to 3.6, 6-ounce cups (about 7-22 ounces) to perhaps get a performance-enhancing effect.
I put the qualifiers “possible” and “perhaps” in the above paragraph because, as mentioned, the research is not in complete agreement on the ergogenic qualities of caffeine, especially in drinks such as coffee. Several studies have found no benefit for endurance athletes when using caffeine at the rates suggested above [1,8,16,21]. This may have to do the type of caffeinated products that were used in the studies  and the unique characteristics of the subjects such as their habituation to caffeine.
What causes the benefit, if there is one, is not well understood. For years it was believed that caffeine caused the release of free fatty acid stores into the blood thus reducing the reliance on limited glycogen stores to produce energy. But some studies [11,14,15,20,21,23] have not found such an effect. The cause may well be neuromuscular.
In most of the research in which a benefit was found the caffeinated product was consumed about one hour prior to exercise[2,9,11,12,13,14,19], although other studies found a benefit when it was taken in immediately on starting  and even during exercise [6,15]. There appears to be no differences in the effects on men or women . Non-users of caffeinated drinks may experience a benefit greater than habitual users  but the research is not in agreement on this .
For years it was believed that coffee was a diuretic, probably because of the common urge to urinate after drinking it. There is considerable research showing that it does not cause the loss of water or dehydration [3,9,11,17,18]. Of course, the reason you need to visit the toilet is that you don’t drink coffee to satisfy thirst but rather for the taste and physical effects. So, essentially, once your water reserves reach a normal level the excess fluid must be removed.
This article is not meant to be an endorsement ergogenic aids such as caffeine. Whether or not you use a caffeinated drink before exercise is an individual decision. Some athletes consider the use of any performance-enhancing supplements to be a violation of the spirit of sport. If you are not a regular user of coffee or other such drinks realize that it may cause an upset stomach and over-stimulate the nervous system. It can also be habit-forming.
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