Stanford Wockets Activity Project (SWAP)

Sedentary Behavior – Too much sitting appears to be a major health risk  - or - get off your fatty acids

Understanding the health risks of sedentary behavior

The physical, economic, and social environments in which modern humans sit or move during their daily lives have been changing rapidly, particularly since the middle of the last century. Changes in transportation, communication, workplace, domestic and entertainment technologies have been associated with significantly reduced demands for physical activity. However, these reductions in the daily demands for being physically active are associated with another class of health related behavior – sitting around which is commonly referred to as sedentary behavior. Examples of sedentary behaviors include watching television, playing video games, using the computer, reading, driving or riding in a car/bus and sitting around talking, eating or drinking.

It appears that too much sitting is distinct from too little exercise. Research findings on sedentary behavior and health have proliferated since the early 2000s. Initial findings on the metabolic correlates of prolonged TV viewing time have since been confirmed by recent objective measurement studies, which also suggest that breaking up sedentary time (by standing instead of sitting) can be beneficial. Studies from Canada, Australia, and the United States have shown significant relationships between sedentary behavior and the increased likelihood of being obese or developing type 2 diabetes, high blood pressure or heart disease.

Risks of sedentary behavior appear independent of being physically active

Importantly, it seems that adults can meet public health physical activity guidelines, but if they sit for prolonged periods, their metabolic health is compromised. This is a new and challenging area for exercise science, behavioral science, and population health research. However, many scientific questions remain to be answered before it can be concluded with a high degree of certainty that these adverse health consequences are uniquely caused by too much sitting, or if what has been observed so far can be accounted for by too little light, moderate, and/or vigorous physical activity.

Physiology of sitting different than physiology of exercise

At the basic science level, it appears that there are unique physiological processes and pathways associated with sedentary behavior, particularly prolonged sitting There are some promising studies that point to what is likely to be a unique ‘sedentary physiology’, which is distinct from what is known about the physiological processes generated by moderate or vigorous intensity exercise.

In Australia Genevieve Healy, Ph.D. and David Dunstan, Ph.D. used accelerometers to measure sedentary behavior in order to confirm their studies showing harmful metabolic relationships with blood fats and blood glucose associated with large amounts of television viewing time. Healy's research has identified the importance of breaking up sitting time. People who stand up and simply move around more have healthier blood fat and blood glucose levels than those whose sitting time is not broken up by these transitions. Healy has also shown that even among active adults - those who participate in 30 minutes of moderate-to-vigorous physical activity on most days of the week, large amounts of television viewing time were still associated with poorer metabolic health. 

Research conducted at the University of Queensland and at the Pennington Research Institute in Louisiana is trying to understand the metabolic consequences of prolonged sitting, as well as the benefits of getting up from your chair more often throughout the day. The average amount of time spent in sedentary behaviors by adults in the U.S. is approximately eight hours per day.  The most sedentary population groups were older adolescents (16-19 years old) and adults aged 60 and older.  Both spent about 60 percent of their time during the day in sedentary behaviors.

Candidate biological mechanisms relating to the consequences of chronic ‘unloading’ of skeletal muscles suggest possible pathways through which deleterious effects on blood glucose and blood lipids can occur.  Studies of bed rest, and NASA-supported studies of the biological consequences of zero gravity environments, also provide important clues about mechanisms through which prolonged sitting may exert its deleterious health consequences.

It is well established that walking for 30 minutes a day expends a significant amount of energy and is associated with better health.  If a person reduced their sitting time by two hours per day and shifted this time to light intensity activities, they could expend about the same amount of energy as they would during a 30-minute walk.  We now need to find out if the health benefits start to add up along with less sitting and more moving about.

Need for the Stanford Wockets Activity Project (SWAP)

One of the major challenges in establishing the health risks of sedentary behavior and the possible health benefits of light intensity activity is obtaining accurate measurements 24/7 for weeks or months on representative samples of the population. The Wocket wireless sensor and mobile phone monitoring system is the first to provide such measurements of research quality at a relatively low cost and low subject burden. Click here to learn more about the Stanford Wocket Activity Project (SWAP).

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