Coffee Before Exercise May Restrict Blood Flow to Heart

The good news about coffee before exercise is twofold: it appears to delay or prevent post-exercise tiredness by up
to 60 percent, and to help the body burn fat faster. The bad news is that it can restrict blood flow to the heart. PreventDisease.com reports on a survey conducted at the University Hospital Zurich and Center for Integrative
Human Physiology that looked at blood flow to the hearts of 18 healthy young people before and after theyrode a stationary bike. Ten of them exercised in normal conditions, and eight were in a chamber that simulated an altitude of 15,000 feet. The story reports that both groups repeated the test after ingesting 200 milligrams of caffeine — the amount contained in two cups of coffee. Researchers found that the caffeine did not affect heart blood flow when the participants were inactive, but did so for those who had exercised. Heart blood flow was 22 percent lower in those who exercised in normal air pressure and 39 percent lower in those who exercised in the high-altitude chamber.
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