When I started running seven years ago, I could manage only about a quarter of a mile before I had to stop. Breathless and aching, I walked the next quarter of a mile, then I jogged the next quarter of a mile, alternating these two activities for a couple of miles. Within a few weeks I could jog half way round Hampstead Heath without stop-ping. Soon I started to run up the quarter-mile slope to the top of Parliament Hill, although I had to stop at the top to get my breath back. Eventually I found that I could even manage to get up the hill comfortably. I started to run because I felt desperately unfit. But the biggest pay-off for me was—and still is— the deep relaxation that I achieve by taking exercise. It tires me out but I find that it does calm me down. In those early days I saw few other runners. Now there are many more—and not just the macho sports freaks. Men and women of all ages have now taken up running. Some 25,000 runners aged five to 85 are attracted each year to the Sunday Times Fun Run in Hyde Park. In the last two years the London Marathon has become the biggest British sporting event— overtaking the boat race and the Derby in the number of spectators it attracts. When I started to jog I never dreamt of running in a marathon, but in 1982 I realized that if I trained for it, it was within my reach, and after a slow, six-month build-up I man-aged the 26.2 miles in just under four hours. A creditable performance for a first-timer and a far cry from those days when I had to stop for breath after a quarter of a mile. What about heart attacks?My story shows that an unfit 39-year-old, as I was when I started running, who had taken no serious exercise for 20 years, can do the marathon—and that this is a sport in which women can beat men. But is it crazy to do it? Does it make sense to run in the expectation of becoming healthier? What about the chances of injuring yourself or dying of a heart attack? I was personally convinced of the health benefits of running because I felt unfit, and I wasn't worried about the risk of a heart attack, because I was not a smoker and I was sticking to a fairly low animal-fat diet. But one person I knew well did die immediately after a jog and plenty of people told me I was mad to start running. Reassuring  evidence  now comes from doctors in Seattle, showing that vigorous exercise actually reduces the chances of heart attack. They found that people who had a sudden heart attack when they appeared to be completely fit had taken less exercise than those of similar age. According to their findings, published in the Journal of the American Medical Association (volume 248, p 3113) it is necessary to take 20 minutes of vigorous exercise at least two or three days a week to obtain some protection from heart attack. Apart from jogging, the exercise might be swimming, singles tennis or squash, digging or chopping wood. Whatever it is, the exercise should leave you out of breath. There is a small risk of unaccustomed stress causing a heart attack when a person is very unfit, but this can be reduced if exercise is always increased in easy stages. My advice is: if you are under 40, are healthy and feel well, you can begin as I did by jogging gently until you are out of breath, then walking, and alternating the two for about two miles. Build up the jogging in stages until you can do the whole distance comfortably. At first, two or three times a week will probably be enough. People over 40 who are in any doubt about their health should see their doctor before starting an exercise program. Over-40s should begin by making a vigorous walk of at least two miles part of the daily routine. When you can do this comfortably you can start the mixed jogging and walking routine and progress from there. You will have to expect soreness of muscles and joints to begin with. If soreness changes to pain, or if you find that you suffer from deep tiredness which you cannot shake off, then stop jogging for a while and just walk.