HEALTH / Second Opinion

RESOLUTIONS about improving our health commonly include an intention to take more exercise, but we are uneasily aware that some heart attacks, in middle-aged men in particular, are brought on by physical exertion. Three activities notorious for their lethal potential are shovelling away an unexpected snowfall, jogging and sex (especially sex with someone other than a regular partner). Yet medical experts recommend exercise as a way of reducing the risk of heart disease. Does it protect or are the cynics correct when they say that the natural state of urban man is sedentary?

Two studies, one from Boston and one from Berlin, recently reported in the New England Journal of Medicine, have provided some reliable answers to those questions. More than 2,000 victims of heart attacks were questioned: 4.4 per cent of the Americans and 7 per cent of the Germans reported that they had undertaken heavy physical exertion within one hour before the onset of chest pain. Further questioning, however, came up with some striking data.

The risk of having a heart attack in the hour after vigorous physical activity was found to be critically dependent on how much exercise the individual habitually took. People who usually took no exercise at all ran a substantial risk if they went out and shovelled snow - their risk of an attack was increased by a factor of more than 100. People who took exercise twice a week cut this risk to 20 or so, while those who took exercise five times a week reduced their risk to only 2.4 times the risk at rest. In other words, people who take no exercise put their lives at risk if they attempt some really demanding physical task.

So should middle-aged slobs give up and stay unhealthy, not putting their hearts at risk? Well, no; they should balance the risks. Long-term studies have consistently shown that people who take regular exercise reduce their risk of dying not only from heart disease but also, for example, from falls in old age. Exercise helps in the treatment of disorders as various as diabetes and depression. The fact that a heart attack is more likely during exertion than at rest is entirely compatible with exercise protecting against heart attacks: exercise raises the short-term possibility but reduces the overall long-term risk, and the long-term effect is the important one when it comes to counting gravestones.

How much exercise, then? Again, the research findings are clear. Much so-called exercise is useless. A gentle round of golf provides relaxation and some fresh air but does nothing for the heart. What is needed is exercise vigorous enough to cause sweating and breathlessness: achieved by running, cycling, playing squash, or heavy digging, mixing concrete by hand, or some other vigorous non-sporting activities. The exertion needs to be regular and repeated: at least three sessions a week of 20 minutes each.

And it is never too late. More than 200 years ago William Heberden, the physician who first described the features of angina pectoris, reported a patient who 'set himself a task of sawing wood for half an hour each day and was nearly cured'. But take care: unaccustomed exercise may seriously endanger your health.