The American College of Sports Medicine (ACSM) and the American Heart Association (AHA), along with the U.S. Department of Health and Human Services (DHHS) have reviewed the relevant science and generally agree that physical activity leads to improved health and fitness.
All three entities agree in the general principle that a person should obtain at least 30 minutes of moderate physical activity, at least 5 days a week, to maintain a generally healthy level of physical fitness. It is believed that these modest amounts of physical activity will improve health and cardiovascular fitness of inactive persons. Additional health gains, such as, weight loss or weight maintenance, may require more than 30 minutes of moderate physical activity, most days of the week.
Does sitting kill you?
The term “sedentary behavior” is used to describe prolonged sitting, instead of the absence of physical activity. It is important to think of these as two separate activities, which are independent of one another. Sedentary behaviors usually have very low energy expenditure, typically less than 1.5 METs (i.e. sitting in a classroom).
There is a rapidly expanding body of evidence suggesting that time spent in sedentary behaviors is associated with adverse health risks, which may be independent of the protective contributions of physical activity. In other words, being physically active is beneficial to one’s health, but being sedentary stands alone and may be a strong negative detractor to one’s overall good health. Physical activity, even at the recommended levels, does not appear to cancel out the negatives of prolonged sitting.
The Centers for Disease Control and Prevention (CDC) reported in 2011, that diseases of the heart is the number one killer in the United States. Stroke is listed as the number 4 killer and Diabetes Mellitus is the number 7 killer.
A study conducted in 1953 examined occupational activities and observed higher rates of cardiovascular events in sedentary bus drivers and mail sorters, than in more active bus conductors and postal workers. More recent studies have led to a renewed interest in the health effects of prolonged sitting.These studies have demonstrated associations of sitting time with obesity, metabolic syndrome and Type 2 diabetes, markers of cardiovascular disease risk, and premature mortality.
Where Do People Spend Time Sitting?
According to previous surveys of working adults in the United States and other Western cultures, at least half of the time spent at work is done while sitting. This is in addition to time spent sitting in a vehicle commuting and time spent watching TV, using a computer, or playing games, while not at work. Add in time spent sleeping and there is not much time left in the day.
A study in 2009 found that people sitting more than 4 hours in leisure had almost double the risk of metabolic syndrome than those sitting less than 1 hour. However, for those that work in an occupation with a higher activity level, there was no association between occupational sitting and metabolic syndrome.
The end message appears to be that a body in motion tends to stay in motion. The body that sits still tends to become ill and reach permanent stillness (death) more quickly.
Who is killing you?
Science has not yet been able to fully explain why sitting for prolonged periods appears to be associated with the onset or worsening conditions of metabolic syndrome or Type 2 Diabetes. There does appear to be some biological plausibility of an association between sitting and the risk to ones health. It comes down to muscles not bearing any load for long periods of time in a day and the biological effect that then occurs. You know, like when you are sitting in classes or studying for the next exam in college.
If this is the case, then the simple solution is to avoid long, chronic bouts of sitting by simply standing (or walking) more frequently during the day. This, in combination with the basic levels of recommended physical activity, that being 30 minutes a day of moderate physical activity, at least 5 days a week, might be just what the doctor ordered.
American Heart Association
American College of Sports Medicine
National Institutes of Health