A Prescription For Exercise: Researchers Seek Right Dose For Healthy Hearts And Minds

GAINESVILLE, Fla.---For high blood pressure or thyroid conditions, physicians generally know how many pills to prescribe and how often they should be taken. But when the prescription is for exercise rather than a chemical compound, the proper dosage is much less clear.

How intense and how frequent must physical activity be to keep the heart healthy and the mind psychologically fit? With a $2 million grant from the National Institutes of Health, University of Florida researchers will try to find the answer. At the same time, they will tackle the substantial problem of helping people continue an exercise regimen once they have started.

Michael Perri, professor in the College of Health Professions' clinical and health psychology department, will direct the four-year study, set to begin this fall.

The project was conceived by the late Michael Pollock, a world-renowned expert on exercise who led UF's Center for Exercise Science. Dr. Pollock, who died in June, had recruited researchers campuswide to contribute to the study. The team includes faculty from the colleges of Medicine, Health Professions, Health and Human Performance, and Liberal Arts and Sciences.

"In 1992, the American Heart Association said a lack of physical activity is a major risk factor for coronary heart disease," Perri said. "Since then, there has been a lot of talk about how much is necessary. Does it have to be high intensity or can it be low intensity? Do you have to show up every day or just a few days a week to make a real effect on cardiovascular disease and health? We really don't know the fine line on intensity and frequency."

Perri and his colleagues will randomly assign 500 research participants ages 30 to 65 to one of several different exercise regimens. While the main activity will consist of walking, the groups will differ in how often they don their sneakers and how quickly they move.

A high-intensity, high-frequency group will walk for 30 minutes five to seven days each week fast enough to get their hearts beating rapidly. Another group will walk just as often, but at a more leisurely pace. A third group will walk quickly, but fewer days per week. And a fourth group will have the most leisurely of the assignments: three or four days of walking at a moderate pace. The exercising participants will be compared to a group of people who receive physician advice about changing their activity level.

Meanwhile, researchers will track how exercise affects the volunteers physically and emotionally. Participants will be examined for changes in weight, aerobic fitness, blood pressure, cholesterol, bone density and muscle mass. Additionally, researchers will determine whether participants' self-esteem has risen and whether their overall levels of depression, stress and anxiety have dropped.

"One of the major strengths of this study is that we are looking at long-term effects of exercise," Perri said. "Most studies have been short-term, following people for six months or less. That's problematic, because it takes awhile for health to improve with exercise and because most people tend to abandon their workout programs.

"With this project, we will follow volunteers for at least two years and provide them with intensive assistance and counseling to help them continue. If there are barriers in their lives that get in the way of exercising, we will try to help the participants overcome them."

People often cite a lack of time as the reason for quitting an exercise program.

"We're going to give them a lot of flexibility in choosing where and when to do their walking," Perri said. "They can walk 30 minutes at a time, or break it up into 10-minute segments throughout the day. And in the end, we hope to be able to say how intensely and how often people really need to exercise."

Other scientists involved in the project include: Dr. Marian Limacher, professor of medicine and chief of cardiology at the Gainesville Veterans Affairs Medical Center; Daniel Martin, associate professor of