The role of activity for cardiovascular disease protection is well recognized. And a graded negative association of activity levels or exercise intensity with cardiovascular morbidity or mortality has been known for over 2 decades. However, excessive sedentary behaviour as defined by activities involving prolonged sitting may be linked to a poor cardiovascular profile as well. The question remains whether it is amount of sedentary time or exercise volumes that are better predictor of cardiovascular health.
Most of studies using sedentary time as a risk factor used self-reported data, and have shown an increased risk of overall mortality and cardiovascular disease incidence. These results are independent of participation in moderate or vigorous physical activity. In general terms, sedentary time is usually considered as time spent for TV viewing. However, this time is also associated with other behavioral risk factors, such as consuming high-energy snack foods and/or influence of TV advertisements. Therefore, a relationship between TV viewing time with adverse cardio-metabolic profile may be not truly because of sedentary behaviour but because of unhealthy (drinking/eating etc.) lifestyle.
An objective measurement of sedentary time, such as by use of accelerometers, could give a better explanation for the association of cardio-metabolic risk and being remain idle. A recent study while comparing both self-reported and objectively measured sedentary time with risk of cardio-metabolic factors has shown worse profile including high BMI, high waist circumference, high total cholesterol and being hypertensive with self-reported measures. However, objectively measured sedentary time was only associated with increased total cholesterol. (http://www.ncbi.nlm.nih.gov/pubmed?term=Sedentary%20time%20in%20relation%20to%20cardio-metabolic%20risk%20factors%3A%20differential%20associations%20for%20self-report%20vs%20accelerometry%20in%20working%20age%20adults)
Benefits of physical activity outweigh the luxury and comfort of being a couch-potato. TV viewing or sedentary time should be monitored while still being engaged in exercise activities.