Cycling and coffee (II)

That's the finding of a study published in the Journal of American College of Cardiology this month. Two cups of java reduced the body's ability to increase blood flow to the heart during exercise.

Caffeine is not a physical stimulant, the researchers maintain, but it could cause problems to people with coronary artery disease, especially if they're cycling at high elevations, reports an article about the study in News-Medical.Net.

That sounds counter to everything I've heard. Coffee was supposed to give you that extra zip on a ride. Cycling Performance Tips recommend coffee because it speeds up metabolism of free fatty acids, decreasing the use of muscle glycogen and staving off fatigue. 

Now along come the researchers who took 18 healthy, young adult coffee drinkers, kept them off coffee for 36 hours, then dosed them with 200 milligrams of caffeine (the equivalent of two cups), and put them on a stationary bicycle, reports News-Medical.Net.

One group was tested at sea level, the other in a chamber representing 15,000 feet of elevation in order to duplicate the way coronary heart disease deprives heart muscles of oxygen.

“The ratio of exercise blood flow to resting blood flow, called the myocardial flow reserve, was 22 percent lower in the group at normal air pressure after ingesting caffeine and 39 percent lower in the group in the high-altitude chamber.”

One researcher said caffeine may interfere with signals for the blood vessels to dilate. They wrote:

“Although these findings seem not to have a clinical importance in healthy volunteers, they may raise safety questions in patients with reduced coronary flow reserve, as seen in coronary artery disease, particularly before physical exercise and at high-altitude exposure.”

A cardiologist not connected with the study said the issue raises the need for further research.