Healthy people who want to prevent heart attacks also find support at the Y. Motivated, often, by the illness or sudden death of a close friend or relative, they sign up for rigorous stress testing and blood tests to determine the health of their hearts and arteries and the risk of future trouble. Those who pass the tests with flying colors are sent on their way, says Bronz. 'Whatever you're doing, we tell them, keep it up!' Those with a medium to high risk of heart disease - about 10 per cent of the people tested - are invited to join the programme. Like the cardiac patients, they receive individually designed exercise schedules, advice from the nutritionist, stress counseling from the social worker and encouragement from the nurse.

'That's why the programme works so well - it doesn't just come at prevention from one aspect,' says nutritionist Gail Levely. 'It's comprehensive.' Participants, she adds, seem uncommonly receptive to nutritional advice. 'Some come to see me periodically for counseling on weight loss or to see if their diets are OK. I encourage a low-fat, high-carbohydrate diet, .lots of whole grains and fresh fruit and vegetables, less beef and more chicken and fish. They are really open to change.' Barbara Eisenstein, whose years as a coronary care unit nurse have taught her the need for programmes like Downstate's, is particularly enthusiastic. 'Once someone gets into the physical aspect of the programme, it becomes a way of life,' she says. 'It gives him or her a wholly different outlook, and it's all to the good.' That, in effect, is the fundamental idea of the Downstate programme - to start both patients and non-patients on the path to a healthier, more vigorous lifestyle. 'All we try to do is form a lifetime habit of exercise,' says Charles Bronz. 'We encourage people to be on their own.' More than a few of his patients have, in fact, become 'enthusiastic exercise addicts', Dr Stein says. But what about risks? Everyone has heard tales of stress tests interrupted by fatalities, and of apparently healthy middle-aged men found dead on the side of the running track.

One study that Dr Stein likes to cite shows the likelihood of death or serious complications in the course of a stress test to be 1 in 200,000. In a good, modem centre, he speculates, the risk may be even less. 'We do very careful screening before exercise testing, we always have a doctor and a nurse trained in ECG and cardiopulmonary resuscitation, and there's always a full set of cardiac-arrest equipment. With better monitoring devices, we can pick up early warning signs of when to stop a test.' Exercise itself, Dr Stein grants, does involve some increased risk for a heart patient. 'We minimize it by bringing your heart rate higher, when we test you on the treadmill, than it will be when you train. And overall, we lower the daily risk of the individual by putting him in a training programme.

If you exercise enough to train, in other words, then running for the bus on a windy day will involve less physical stress than it would otherwise.' In the years since the programme began, he adds, 'we've found out that people's hearts and bodies are much sturdier after a heart attack than we had thought. We're comfortable prescribing' more exercise than we used to - we seem to do it safely.' Similarly, he says, much of the anxiety about running for healthy people is - exaggerated. For a vigorous, active person under 40, without symptoms or significant risk factors (such as overweight or smoking), 'a stress test may be an unnecessary precaution. If you're in your late 40s, though, a stress test would be appropriate every three or four years.' And the 'competitive nut' who pushes himself the extra two mile$, or who ignores the heat of summer, may be moving into a high risk zone, Dr Stein adds. 'And if you feel an irregularity in your heartbeat or you start to have chest pains you've never had before, be prudent and see your doctor.'