[By the sweat of your brow shall you eat bread: a blessing or a curse?].
Physical activity is crucial for maintaining normal structure and function of metabolic processes and body organs, such as the heart and muscles. Lack of regular activity leads to the deterioration of these organs, thereby increasing levels of morbidity and mortality. Physical activity is associated with lower incidence of total mortality and mortality from heart diseases. It also inhibits high blood pressure, diabetes mellitus, colon cancer and probably breast cancer, osteoporosis, mental depression, and improves quality of life. While the favorable outcomes are usually related to activity level in a dose-response pattern, the greatest benefit is observed in the transition from sedentary to moderately active lifestyle. Despite possible direct and indirect adverse effects of physical activity, the benefits markedly outweigh the risk. In order to benefit from physical activity, people should perform activities that involve large muscle mass, at moderate intensity, during most of the week, or at least 3 days/week, for about 30 minutes a day. It is desirable to add strength and flexibility exercises. The need for medical screening prior to initiation of activity is questionable, and there are no solid recommendations. In the opinion of the authors, at all ages people should be aware of whether they possess one or more risk factors for cardiovascular disease. Young healthy people free of risk factors may start activity, gradually, without special preparations or screening. However, men and women above the age of 45 or 50 years, respectively, or younger, if a risk factor is present, should consult their family physician or a specialist in order to perform relevant screening and obtain instructions on the desired nature of recommended physical activity, its length and intensity.