Exercise
Expert Commentary: Exercise And Your Health, - Just Do It
August 18, 1997
The headlines are everywhere: "30 minutes of moderate exercise three or four times a week is as good as running marathons" ... "Forget the aerobics and start walking" ... "Forget the walking and just park farther from the door at the grocery store" ... New and ever-changing information, most of it conflicting, keeps emerging about exercise: How much? When? What type is best? In this five-part series on exercise, InteliHealth spoke with several leading experts on the latest research and recommendations regarding exercise and exactly what role it plays in disease prevention and treatment. one experts says all the research points to one conclusion.
Q: With so much research out there about exercise, is there any one take-home message?
A: Yes, there is. The take-home message is that the average Joe and Jane are not getting enough exercise. The epidemiologic evidence shows that those people who accumulate at least 30 minutes of physical activity per day - preferably every day or at least on most days of the week - experience less disease of all types and a reduced death rate from most diseases. The primary benefit seems to come in terms of heart disease, but other diseases and conditions also show a reduction with regular exercise.
Q: Is there a linear relationship between the amount of exercise someone does and the reduction of disease risk, so that the more exercise individuals do, the more they reduce their risk?
A: No. In studies that have looked at physical activity and death from all causes, the biggest effect is seen when someone goes from being essentially sedentary - that is, no exercise at all - to very moderate activity, such as brisk walking. With increasing amounts of activity a benefit is still seen, but it is not proportional to the intensity of exercise. It's very important here to distinguish between health benefits and fitness. In order to accrue health benefits, such as reduced disease risk, only relatively modest amounts and intensity of exercise are necessary. In order to become fit or to achieve other goals, greater intensity is required. The potential downside to greater exercise intensity is a greater risk of injury.
Q: So, if intense physical activity is not required to reduce disease risk, how much is enough?
A: The minimum is about 30 minutes of activity per day. Notice I didn't say exercise, and that's because we're trying to get people moving in a variety of ways, whether that's walking, bicycling, climbing steps or working in the garden. The other point that's important is that they can accumulate this much over the course of a day; they don't have to do it all at once.
Q: What specific health benefits can someone expect to see after adopting a program of moderate activity?
A: One thing people can usually expect is a reduction in blood pressure. We're looking at the effects of exercise on something called vascular reactivity, which is the ability of the blood vessels to contract and expand as needed. Smoking or high blood cholesterol result in a decreased ability of blood vessels to relax, while physical activity helps to improve the tone of blood vessels and restores their ability to relax as needed. When people start to move around, their blood cholesterol profile improves, and so does their insulin profile.
Q: What does the level of insulin in the blood have to do with fitness?
A: Type II diabetes, the type that usually affects older people and may not require insulin to treat it, is a condition of insulin resistance. That is, there is a lot of insulin in the blood, but the body does not react to it, and blood sugar levels may rise. Over time this high sugar level can produce all of the problems we associate with diabetes. Exercise helps to improve the body's ability to respond to insulin, and therefore use up the sugars in the blood.
Q: Doesn't exercise also increase the amount of muscle tissue in the body?
A: That's right. And increased muscle tissue or lean body mass has lots of benefits. Muscle tissue is the body's engine, where we burn fuel taken in as food. The greater the percentage of muscle, the more effectively we burn up calories in food and the more sensitive our bodies are to insulin. That's why any program of exercise should include a weight training or resistive component, such as machines provide. These help to develop and maintain muscle mass. A combination of both aerobic and resistive training is the most effective for improving exercise performance and reducing metabolic risk factors for cardiovascular disease.
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