Why Caffeine isn’t a Sure-Fire Way to Improve Your Athletic Performance


Contributor: Katherine Patton, MEd, RD, CSSD, LD

Caffeine’s role in improving athletic performance has been studied and promoted for close to 100 years. After conducting hundreds of studies, researchers concluded that caffeine has a positive effect on runners‘ and cyclists‘ performance in a laboratory setting.

Do these results apply to routine training or race-day performance? The answer is: maybe.

Little research

Few researchers have studied the effects of caffeine on race performance outside the lab. In addition, laboratory subjects typically took caffeine in the form of a pill. In the real world, athletes generally consume caffeine in the form of coffee, soda, tea and energy drinks.

Some of the data are conflicting. This is in part due to how the experimental studies were designed and what methods were used.

For example, one theory says that caffeine causes the body to rely more on fat as an energy source during endurance event like marathons or triathlons. This prevents the body from using up stored glucose (a more accessible energy source) too quickly, which prevents the early onset of fatigue.

However, some research negates that claim because it showed that caffeine has the potential to improve performance in shorter events, where fat is not used for energy.

The role of caffeine as an athletic performance-enhancing substance is still controversial.

How much caffeine might make an impact?

Research suggests that the amount of caffeine needed to potentially improve exercise performance is 2 mg to 5 mg per kilogram of body weight, taken one hour before exercise. In other words, an average cup of drip coffee contains 85 milligrams of caffeine, and so a 130-pound athlete would need 118 milligrams to 295 milligram of caffeine or 11 ounces to 27 ounces of coffee to see any potential benefit in performance.

The potential positive effects of caffeine on the central nervous system include increased alertness and decreased fatigue, making it easier to exercise at a given pace.

The negative effects of caffeine include anxiety, restlessness, insomnia, nausea, gastrointestinal distress, headaches and dehydration.

When you should avoid caffeine

A study published in 2006 by the American College of Cardiology noted that consuming 200 milligrams of caffeine before exercise may decrease blood flow to the heart. Blood flow normally increases in response to exercise.

The study indicates that caffeine reduces the body’s ability to boost blood flow to the muscle of the heart on demand.

The researchers theorize that caffeine may block certain receptors in the walls of blood vessels. This interferes with the normal process by which a compound in the blood signals blood vessels to dilate in response to the demands of physical activity.

This limits the availability of oxygen to the heart during exercise. So athletes with cardiovascular disease should limit their caffeine consumption before exercise to prevent an adverse cardiac event.

To sum up: the benefits of caffeine vary, and while it is a stimulant, it is not guaranteed to improve your athletic performance.