Coffee before exercise won't kill you

The study showed a small decrease in blood flow in participants, but it was not significant enough to recommend healthy exercisers stop drinking their cup of coffee before a workout.

Healthy individuals will have adequate 'flow reserve' of blood, experts say. People with no heart problems would have adequate capacity to increase blood flow to keep up with the demands of exercise.

Eighteen young, healthy people who were regular coffee drinkers took part in the study. They did not have coffee for 36 hours before the testing.

The participants were split into two groups, with everyone swallowing a tablet containing 200 milligrams of caffeine - the equivalent of two cups of coffee - 50 minutes before riding a stationary bicycle.

In the first group, measurements of the blood flow to the hearts of 10 participants were taken before and immediately after riding a stationary bicycle. The test was repeated on the second group of eight people, who were put in a chamber simulating an altitude of 15,000 feet. This test was to mimic how coronary heart disease deprives the heart of oxygen.

After taking the caffeine, the ratio of exercise blood flow to resting blood flow was 22 percent lower in the group at normal air pressure and 39 percent lower in the group in the high-altitude test.

The results show that "if someone has normal myocardial blood flow and doesn't have significant heart disease, if they want to have a cup of coffee after exercise, that's fine," said an associate professor in the department of health and human performance. "In an absolute worst-case scenario, and if someone had significant cardiac disease, and had a pot of coffee, it may sort of be an issue."

The study does not measure blood flow during exercise, which is research that those medicine men would like to see.

If you need your caffeine before that early morning workout, it is suggested waiting for half an hour before exercise. It also recommended waiting 30 minutes after exercising before having a caffeinated drink. Or you can swap your coffee with water, and black or green teas that contain healthy phytochemicals.

While a cup or two of coffee isn't bad, many people don't limit it to that.

"In general, if you can work out and get enough sleep and hydrate yourself and eat nutritiously, you shouldn't be relying on caffeine to give you pep or energy," that is what doctors said.