Caffeine
Will It Enhance Your Performance?

caffiene sports performance

How Do We Know

Research about the effects of caffeine on sport performance is extensive. But it is also conflicting. What is caffeine's affect on endurance, strength, recovery, hydration? How does caffeine affect cognitive performance? How does it work in your body? Does it make a difference if you combine it with carbohydrates? How much caffeine should you consume? In what form? Does caffeine affect men and women differently?

To answer questions like these, KHF staff often turn to peer-reviewed, scientific journals—such as the Journal of the International Society of Sports Nutrition (JISSN). From time to time, the ISSN publishes "position papers." These are not statements of policy, but rather the highlights, and summaries, of the scientific literature.

Following is a summary of the ISSN's findings on caffeine and performance. [For the complete paper, go here.]

What We Know

  • Caffeine definitely improves sports performance. But how much depends upon your condition as well as the intensity, duration and type of activity you're involved in.
  • Caffeine's effect is stronger when you consume it in capsule/tablet or powder form compared to coffee. [See sidebar for kosher sources.]
  • Caffeine consumed 15-30 minutes prior to exercise seems to be as beneficial as 60 minutes prior.
  • Caffeine is most effective for enhancing performance when you consume low-to-moderate amounts—approximately 3-6mg/kg (of body weight). [For a 150 lb. person, approximately 200-400mg, or the caffeine in 3-5 cups of brewed coffee.] However, more is not necessarily better. There is no additional benefit from consuming 9 or more mg/kg.
  • During periods of sleep deprivation, as well as exhaustive exercise requiring sustained focus, caffeine can enhance alertness and vigilance.
  • Caffeine can enhance endurance performance, although this depends upon your specific conditioning. Caffeine is very effective for improving time trial performance.
  • During recovery, caffeine can help you rebuild your glycogen stores.
  • Contrary to popular belief, caffeine will not dehydrate you (diuretic)—it can be as hydrating as water. In fact, several studies show no significant change in sweat rate, total water loss, or negative change in fluid balance that would adversely affect performance, even under conditions of heat stress.
  • The jury is still out on whether or not caffeine enhance your strength and power training.

When, How and Where Does Caffeine Work?

Actually, we don't know. Or better, there's no simple answer.

Caffeine is absorbed by your gut, metabolized by your liver, and enters your bloodstream within 15-45 minutes of consumption. It peaks in about an hour, can hang around for 2-10 hours, and then is either absorbed by your body (tissues) or gets flushed out through your kidneys.

caffiene chemical structure

This is where things get fuzzy. Its not clear whether caffeine affects your muscles, nerves, or both during exercise. If its neural, it may work by suppressing adenosine, which promotes sleep and suppresses arousal. If muscular, it may affect muscle contraction. But because it crosses the blood brain barrier, its difficult to determine in exactly which system (nervous, skeletal, or muscular) caffeine has the greatest effect.

At least during endurance activities, caffeine may decrease your reliance on glycogen (glucose) and increase your ability to use fat for muscle energy. Caffeine may also increase endorphins in your body—decreasing your perception of pain and leading to the feeling known as "runner's high." One other effect of caffeine may be to increase how long it takes before you feel muscle fatigue—particularly in your legs.

Caffeine and Carbs

caffiene carbs

During endurance (90+ minutes) activities, most of us consume some form of glucose—whether in the form of gels, sports bars, or carbohydrate-containing drinks. But combine that with a moderate amount of caffeine (5mg/kg, or 225-320mg), and you may find your performance improving 5-10%, especially if you're doing a time trial. However, in this case, less is worse: lower doses of caffeine (3mg/kg) don't seem to have the same effect.

When it comes to rebuilding your glycogen stores after an intense workout, caffeine may also be helpful. In fact, it may improve your bodies ability to replenish glycogen by as much as 66%. However, as we mentioned above, it takes between 3 to 6 hours for caffeine to clear your bloodstream. So be careful that post-activity caffeine consumption doesn't interrupt your sleep regimen.

How Much Caffeine Do You Really Need

This really depends upon your level of training, regular caffeine consumption, and type of exercise. But if we had to pick a magic number, we'd guess around 200 - 400mg of caffeine. As we mentioned above, the positive performance effects of caffeine kick in around 3mg/kg (of body weight). But many studies peg the greatest benefits for endurance athletes and enthusiasts around 6mg/kg.

Use the Caffeine Calculator (sidebar) to approximate the optimal range for you.