Now comes news that brisk walking can cut women's heart disease risk by as much as 40 percent, which is nothing to sneeze at.

This is the latest finding from the Nurses' Health Study, which began in 1976 and involves nearly 122,000 nurses who have provided some of the most significant findings to date about women's health. This phase of the study included 72,488 female nurses who were between 40 and 65 years of age -- the years when metabolism slows down, weight goes up and we suddenly start becoming experts on diets, exercise equipment, and the so-called lifestyle changes that will return us to the size 8 or 10 (I'm being realistic here) that we enjoyed in the Early Trim Epoch of our lives.

I have observed in previous columns that I get all the exercise I need from gardening and housework, which was true for many years. Astute readers may have noticed I haven't made such claims lately, which likely puts me in the same boat as many of them. We all have the same excuses: We don't have time to exercise; we're too tired by the time we finish work; we can't afford the equipment; or we can't afford to join a gym. But these are excuses of convenience, of laziness, and every time we make them, we get to hear our mother's voice whispering softly from deep within our past: "If you really wanted to do it, Sweetie, you would." This column is being edited by a colleague -- a woman -- who has been known to be at the gym at 6 a.m., so work or no work, if there's a will, there is a way. Furthermore, she doesn't brag about it, which I would do incessantly, in the unlikely event I should ever demonstrate such steely self-discipline.

I have, however, been walking, which started in two phases. I bought some walking shoes a year and a half ago, when I was in California. I actually used them a few times, but when I got back here in February, I stopped walking. I stopped going outdoors. The second phase of walking began a year ago when my sister invited me to join her in the 5K Race for the Cure in Greenville, S.C. That stroll is a little more than three miles. My sister has been getting up at 6:30 in the morning and taking brisk walks for years, so that's her usual workout. I'm not even awake at 6:30.

Moreover, we had walked in the countryside around the farm a few months after I finished chemotherapy, and I was gasping for breath as we went up one hill. I was so winded we had to stop. My sister did not forget this. Two months before the race, she telephoned me with this: "You'd better start walking and get yourself in training. I don't want to finish last." I got out my walking shoes and started walking again, and we did not finish last. Spurred on by that success, I investigated gym equipment and discovered that one of the largest sections in the classifieds is for "almost new" and "hardly ever used" exercise equipment. I did some soul-searching and realized that I could purchase one of these bargains, and within a few months, I, too, would be trying to sell a piece of exercise equipment in the classifieds.

This new study of walking has me revisiting the whole question of exercise. The study is the first to show the effect of walking on heart disease in women. As with men, heart disease is our biggest killer. Conducted by researchers at Harvard, the study found that women who walked at least three miles an hour or faster for three hours a week obtained the same reduction of heart disease risk as women who jogged, biked, did aerobics or other more-vigorous forms of exercise. One thing I have never, ever considered is doing aerobics in front of the TV with one of these skinny blond fitness princesses hollering encouragement at me from a California beach.

The study also showed that the more women walked, the more they cut their risk: five hours of brisk walking a week, cut their risk of heart disease in half, compared with women who did not exercise.

What we have is yet another piece of evidence that we can prevent disease by altering our habits, instead of waiting for something dire such as a heart attack or a cancer diagnosis to set us on the right course. Those are wake-up calls, no question about it. And I can attest to the fact that in the three years since I had a breast cancer diagnosis I have changed eating patterns to include a lot more fruits and vegetables, I'm taking vitamins and other dietary supplements, I've made a huge commitment to reducing stress in my life, and have succeeded better than my family gives me credit for.

Quitting smoking, which causes heart and lung disease, was the first lifestyle change to win a lot of us over to the merits of prevention. More recently, certain foods have been shown to be powerful antioxidants, which are believed to be helpful in preventing cancer.

Federal guidelines suggest that we do 30 minutes of moderate-intensity physical activity most days. But it is estimated that 60 percent of us don't do anything. Walkers say the best ways of getting into the habit is by walking with a buddy. Good walking shoes make a big difference. You can lay out a three-mile route using your car's odometer and then time yourself walking over that distance, or you can buy a pedometer at a sports store to tell you how much ground you've covered from the time you start until you finish.

"You don't have to make a science fair project out of it," says Bethesda cardiologist Sean Dwyer. "It's not a stroll. Walk to where you feel your pulse is accelerating. You are not drenched in sweat, but you feel you are expending energy rather than checking out your neighbor's flowers. It's common sense. If the walk is entirely enjoyable, you are not walking hard enough."

Many of us are past the Age of Invulnerability. Brisk walking is a low-cost way of achieving high maintenance for our hearts. It's something we can do to help avoid the enormous physical, financial and emotional costs of being diagnosed with serious illness. That should be worth a couple of hours a week of our time.