Physical activity as the cure-all, is it always true?

The work environment is associated with some risk factors for health and especially for cardiovascular diseases (CVDs). Job strain, sedentary behaviour and a low physical activity level during work time have been proposed to play a major role in CVDs. The level of job strain has been proposed for a long time as a risk for diabetes and some CVDs, such as coronary heart disease (CHD), atrial fibrillation and stroke, but with no association with common cancers or chronic obstructive pulmonary disease. For about 100 years the industrial and technological revolutions have largely promoted the development of sedentary and physically inactive lifestyles in the workers. Physical inactivity (a daily physical activity level lower than the World Health Organization’s recommendations) must not be confused with sedentary behaviour (sitting and lying daily activities inducing a low energy expenditure 1.5 MET). Today, low physical activity level and sedentary behaviour are well proven as independent leading risk factors for noncommunicable diseases. It is recommended to combine regular and moderate physical activity practice and limitation of sedentary behaviour, which both reduce global and cardiovascular morbidity and mortality in the general population. With 8 h mean waking time spent on in the workplace during working days, it is clear that occupational tasks and environments play a major role in the individual’s daily physical activity and sedentary behaviour times. Thus, the World Health Organization and World Economic Forum have indicated that the workplace offers an arena to promote physical activity and reduce sedentary time. It has been recommended first to decrease global working sedentary time and to introduce regular short break periods during prolonged sitting periods and, second, to increase the daily physical activity level of workers. However, the objective measurements of times spent in sedentary behaviour and physical activity vary greatly among different occupations. Briefly, during working time white-collar workers have significantly longer sedentary behaviour times and lower light-intensity or moderate-to-vigorous physical activity levels than blue-collar workers during their work hours. Despite a trend towards a reduction of occupational physical activity (OPA) level over the past decades, many manual jobs still impose a marked physical constraint. Recently the possibility of a physical activity healthparadox has arisen because of the observation of an increased early death rate reported among men with high level OPA. Last, a debate concerning the cardiovascular protective effect of leisure-time physical activity (LTPA) in this population has begun. The aims of the epidemiologic study presented in this issue were to investigate the interplay between OPA and LTPA as well as job strain on CHD risk in a large population (N1⁄4 3310; 25–64 years old) of Northern Italian working men coming from three previous longitudinal (follow-up 13–16 years) pooled cohorts study. Results of this study have confirmed the major beneficial effect of LTPA on CHD risk in physically inactive male workers. Moreover, the combination of physical inactivity with high job strain work presents a multiplier effect on the risk for CHD and the recommended (intermediate American Heart Association level of physical activity) LTPA practice has a marked protective effect. Thus, LTPA practice must always be recommended in these populations. Moreover, in accordance with other studies, it must be associated with a decrease of sedentary time during working time. However, the study from Ferrario and colleagues showed also a lack of protective effect of LTPA practice in other OPA–job strain categories and its potentially (because of the low number of CHD events) harmful effect in the highest OPA group. Thus, it is possible that the classical LTPA recommendation may not be appropriate for this worker