Research now shows that the benefits of exercise are even more abundant than first suspected. Backache, commonly associated with sedentary occupations, can be prevented with exercise; bones can be strengthened; the common cold and other infections possibly even be prevented because the number of white blood cells is increased by exercise, and it is these that are the front-line fighters against infection.
Exercise also increases the amount of another substance, pyrogen, in the body. Pyrogen produces a transient fever after exercise, which stimulates the immune system to resist infection.
The rewards of exercise were in fact first demonstrated dramatically more than 30 years ago by Professor Jermey Morris of the London School of Hygiene and Tropical Medicine. In a pioneering study he found that bus conductors who walked up and down stairs all day suffered fewer heart attacks and died less often from them than bus drivers. He also showed that postmen, walking several miles daily, had less heart disease than supervisors, clerks and telephonists who spent most of their working time sitting down.
But probably the largest and most comprehensive study has been one carried out with the alumni of America’s Harvard University, where Dr. Ralph Paffenbarger and colleagues at the School of Public Health have studied the exercise habits and incidence of heart disease and death among some 17,000 former students who attended Harvard between 1916 and 1950.
Paffenbarger found that the alumni who developed sedentary habits after they left college had the same high risk of heart disease and strokes as those who never took much exercise. Playing for the first team, in other words, offers no long-term protection unless a moderate level of exercise is maintained.
Conversely the study provides encouraging news for men and women who are late starters: those alumni who took no exercise at college but started afterwards were found to have a reduced risk of heart disease and stroke. ‘Men who are physically active in their youth do not have a lower risk of heart disease unless they maintain their vigorous activity throughout their life,’ says Paffenbarger. ‘Moreover, those physically inactive in adolescence or early adulthood are at decreased risk of coronary heart disease if their adult life acquires an adequate, sustained, physically active lifestyle.’
Family factors such as eating and exercise habits affect longevity. But though people whose parents suffer from heart disease or high blood pressure, for example, run an increased risk of suffering from these diseases themselves, the Harvard research holds out hope even in these cases. It shows that men and women can drastically reduce such ‘inherited’ risk.
But perhaps the most encouraging conclusion to emerge from the Harvard study is that it is not necessary to take up marathon running or long-distance swimming to reap the health benefits of exercise. Paffenbarger found that the risk of heart disease or stroke can be halved by physical activity that uses up only an extra 2,000 calories a week. As Paffenbarger says: ‘We are not talking about an amount of exercise which is overwhelming.’