Legend has it that an ancient Ethiopian goat herder first discovered coffee's stimulating effects when he noticed his animals becoming frisky after eating the wild plant. Centuries later, java is still giving people a buzz. Yet much about coffee's physiological effects remains poorly understood. For instance, the more often a person drinks a cup of joe, the less of an effect the substance seems to have. Now new research, published in the Journal of Applied Physiology, investigates this problem by looking at the impact of coffee consumption on exercise capacity in daily drinkers and non-drinkers.

Douglas Bell and Tom McLellan of Defense Research and Development Canada, in Toronto, gave 13 coffee drinkers and eight non-coffee drinkers either a caffeine solution or a placebo. One, three, or six hours after ingestion, the researchers instructed the subjects to exercise to exhaustion. The team found that caffeine increased the amount of time people in both groups could exercise, but non-coffee drinkers enjoyed the largest boost. Additionally, coffee continued to stimulate non-users up to six hours later, whereas by that time the habitual java drinkers had long since come off their high. So it seems that everyone gets a lift from coffee. But in order to get the most bang for your buck in today's gourmet coffee market, perhaps moderation is still the best policy.