Sedentary behavior is not the same as physical inactivity: sedentary behavior is defined as "any waking behavior characterized by an energy expenditure less than or equal to 1.5 metabolic equivalents, while in a sitting, reclining or lying posture". Spending most waking hours sitting does not necessarily mean that an individual is sedentary, though sitting and laying most frequently are sedentary behaviors.
Health effects
Effects of a sedentary work life or lifestyle can be either direct or indirect. One of the most prominent direct effect of a sedentary lifestyle is an increased BMI leading to obesity. A lack of physical activity is one of the leading causes of preventable death worldwide. At least 300,000 premature deaths, and $90 billion in direct healthcare costs are caused by obesity and sedentary lifestyle per year in the US alone. The risk is higher among those that sit still more than per day. It is shown to be a risk factor on its own independent of hard exercise and BMI. People that sit still more than per day have a higher risk than those that sit fewer than per day. However, those that exercise at least per week are as healthy as those that sit fewer than per day. Indirectly, an increased BMI due to a sedentary lifestyle can lead to decreased productivity and increased absenteeism from necessary activities like work. Missing work and not being productive results in obvious short term and long term effects like less income and job security. A sedentary lifestyle and lack of physical activity can contribute to or be a risk factor for:
Adults and children spend long amounts of time sitting in the workplace and at school, which is why interventions have been focused in these two areas.
In the workplace
Some workplaces have implemented exercise classes at lunch, walking challenges among coworkers, or allowing employees to stand rather than sit at their desks during work. Workplace interventions such as alternative activity workstations, sit-stand desks, and promotion of stair use are among measures implemented to counter the harms of a sedentary workplace. A 2018 Cochrane review concluded that "at present there is very low quality evidence that sit-stand desks can reduce sitting at work at the short term. There is no evidence for other types of interventions." There is no high-quality evidence that such interventions provide long-term health benefits.
In education
The majority of time children are in a classroom, they are seated. Children who regularly engage in physical activity are more likely to become healthy adults; children benefit both physically and mentally when they replace sedentary behavior with active behavior. Despite this knowledge and due in part to an increase in sedentary behaviors, children have lost an average of 8 hours of free play each week over the last 20 years. Several studies have examined the effects of adding height-adjustable standing desks to classrooms, which have reduced the time spent sitting. However, associating the reduction in sitting with health effects is challenging. In one study conducted on Australian school children, known as the Transform-Us! study, interventions reduced the amount of time children spent sitting in the classroom, which was associated with lower body mass index and waist circumference. The interventions used in the study included stand-up desks and easels, the use of timers, and sport and circus equipment in the classroom. Teachers also made lessons more active, and added breaks to lessons to promote active time. In the US, another intervention for children is promoting the use of active transportation to and from school, such as through the Safe Routes to School program.
History
Over the last hundred years, there has been a large shift from manual labor jobs to office jobs which is due to many contributing factors including globalization, outsourcing of jobs and technological advances. In 1960, there was a decline of jobs requiring moderate physical activity from 50% to 20%, and one in two Americans had a physically demanding job, while in 2011 this ratio was one in five. From 1990 to 2016, there was a decrease of about one third in manual labor jobs/employment. In 2008, the United States American National Health Interview Survey found that 36% of adults were inactive, and 59% of adult respondents never participated in vigorous physical activity lasting more than 10 minutes per week. According to a 2018 study, office based workers typically spend 70-85% sitting. In the US population, prevalence of sitting watching television or videos at least 2 h/d was high in 2015-2016 ; the estimated prevalence of computer use outside school or work for at least 1 h/d increased from 2001 to 2016 ; and estimated total sitting time increased from 2007 to 2016.
