Recommendations for physical activity within the general population: is this all what we need to keep us healthy?

Abstract

In the natural habitat of our ancestors, physical activity was not a preventive intervention but a matter of survival. From our genetic pool genes were selected which were very effective in regulating food intake and utilization. This was a clear survival advantage in periods of food deprivation, because they could rely on larger previously generated energy stores. Unfortunately, our selected gene pool has not changed dramatically since then, but we are no longer faced with long periods of food deprivation, and we are no longer forced to run several miles to chase our food. In addition to this ‘old’ genotype, physical inactivity is one important risk factor for the development of several diseases. Several landmark studies around 1990 clearly documented that physical inactivity is a modifiable risk factor for cardiovascular disease and several other chronic diseases, including diabetes mellitus, cancer, obesity, hypertension, bone and joint diseases, and depression. Immediately it became evident that increasing physical activity and exercise would be a powerful tool to reduce the overall incidence of cardiovascular and even all-cause mortality. Over the years many studies in more than 100,000 individuals have clearly documented that the higher the level of physical fitness, the less likely an individual will suffer premature cardiovascular death. The importance of fitness for the risk of overall death becomes very clear in one of the landmark studies of Jonathan Myers and colleagues in 2002. In this trial the authors studied a total of 6213 consecutive men referred for treadmill exercise testing. Among these individuals 3679 individuals had an abnormal exercise test result or a history of cardiovascular events. The rest were classified as healthy. Comparing the relative risk of a healthy but unfit individual with a fit subject but having signs for cardiovascular disease, the risk to die from any cause was much higher for the unfit healthy individual. This clearly shows that being unfit is even worse than being overweight, having diabetes or other risk factors for premature death. Therefore, improving fitness warrants at least as much attention as other risk factors, such as body mass index (BMI), smoking, diabetes or hypertension. Moreover, improving physical activity reduces these common risk factors and therefore may potentiate its beneficial effects. One challenging question of the present time is how much we have to exercise, how often and what kind of exercise is beneficial in influencing the relative risk of cardiovascular death. To answer this question maybe we should look back again to our ancestors to see what they did in their daily life. They walked longer distances and hunted for the food they needed. So one can imagine that if we were able to increase these forms of exercise, we may reach our goal. In 1995 the Centers for Disease Control and Prevention (CDC) and the American College of Sports Medicine (ACSM) published a recommendation stating that ‘Every US adult should accumulate 30 minutes or more of moderateintensity physical activity on most, preferably all, days of the week’. The purpose of these recommendations was to provide a clear and easy to understand guidance for the general population to engage in physical activity. This recommendation was updated in 2007 and specifically extended to adults aged 65 and over. In comparison with the recommendations of 1995, several important points were adjusted: (1) the frequency was fixed to 5 days per week, (2) vigorous-intensity physical activity was incorporated into what is complementary to moderate-intensity, (3) the recommended aerobic activity is in addition to routine daily activity, (4) musclestrengthening activities besides aerobic activities are recommended. In addition to all of the recommendations on physical activity for adults, the Canadian Society for Exercise Physiology (CSEP) recently published physical activity guidelines for children aged 0 to 4 years. In their recommendations they state that: