Researchers at Harding University in Searcy, Ark., say their study is the first to investigate the effects of caffeine on both cardiovascular and metabolic responses to exercise in healthy boys and girls. Although the physical effects of caffeine have been studied for years, the effect of caffeine on children is still a new field of research.

In the study, 52 7- to 9-year old boys and girls each randomly received a placebo or a caffeinated drink twice each on four separate days. An hour later, after taking resting measures, each child rode a stationary bicycle while blood pressure, heart rate and oxygen consumption were measured.

The results of the study demonstrated caffeine acutely elevates both resting and exercise blood pressure, but acutely reduces heart rate in boys and girls given a moderate to high dose of caffeine an hour before exercise.

The scientists said the caffeine did not affect metabolism, nor were there significant differences found between boys and girls.

The study appears in the March issue of Medicine & Science in Sports & Exercise.