For years, researchers and exercise professionals have been proclaiming the health benefits of regular cardiovascular exercise. There is strong scientific evidence that moderate- to vigorous-intensity exercise plays a significant role in preventing cardiovascular disease, type 2 diabetes, obesity and some cancers (ACSM 2006).
Presently, the science of sedentary behavior, also called inactivity physiology, is an emerging field of research in health, fitness and medicine. This new field involves the study of sitting for extended periods of time and the biological ramifications associated with too much of this kind of behavior. Being sedentary is a distinctive form of human behavior and should not be regarded simply as the endpoint of the physical activity continuum (Katzmarzyk et al. 2009). In the United States, adults and children spend the majority of their nonexercising waking day in various forms of sedentary behavior, such as riding in
a car, working at a desk, eating a meal at a table, playing video games, working on
a computer and watching television (Owen, Bauman & Brown 2009; Katzmarzyk et al. 2009). This article reviews some of the current findings and detrimental health effects of a sedentary lifestyle.
The Deleterious Effects of Too Much Sitting
The word sedentary comes from the Latin word sedere, meaning “to sit” (Owen, Bauman & Brown 2009). Most individuals can sit for many hours at a time, day after day. In fact, as noted in the example in Figure 1, of the 16 hours of waking time in a day (24 hours minus 8 hours of sleep), more than 90% may be spent in sitting behaviors, even for the physically active person illustrated here.
Initial findings on the hazardous effects of sitting behavior came to light in the 1950s, when researchers showed that, compared with their inactive counterparts, men in physically active jobs had less coronary artery disease during middle age, and what disease they had was less severe. In addition, disease developed later in life among the physically active men (Morris & Crawford 1958).
Leaping forward half a century, a recent large investigation into mortality rates, over 12 years, among the 7,278 men and 9,735 women enrolled in the Canadian Physical Activity Longitudinal Study found 759 deaths from cardiovascular disease, 547 deaths from cancer and 526 deaths from other causes (e.g., respiratory diseases, injuries, violence, mental disease, nervous system illnesses and digestive system disorders) (Katzmarzyk et al. 2009). Participants were 18–90 years of age, with a mean age of 42 years. After adjusting the data for potential confounders (e.g., age, sex, smoking status, alcohol consumption, leisure time and physical activity), the authors pointed out that even among physically active individuals, there was a strong association between sitting and mortality risk from “all causes” and from cardiovascular disease (CVD). Thus, an important finding from the Katzmarzyk study is that physical activity does not cancel out the ill effects of too much sitting. This is true even for people who meet the current minimum physical activity guidelines of 30 minutes of moderate-intensity exercise per day, most days of the week (ACSM 2006). The highest mortality subpopulation group is obese men and women who spend most of their waking time sitting.
Physiological Mechanisms to Sedentary Behavior
Although the preponderance of investigations comparing the physiology of sedentary behavior with that of light physical activity and moderate- to vigorous-intensity exercise have focused on animals, new insights into this unique behavior are surfacing. Hamilton et al. (2008) explain that when rats are not allowed to stand, there is a very dramatic drop in lipoprotein lipase, the enzyme in the leg muscles that captures fat (triglyceride) out of the blood to be used by the body as fuel. Thus, with consistent sitting, blood triglyceride levels start to soar, elevating the risk for CVD. Scientists hypothesize that this same physiological phenomenon occurs in humans.
Also, Hamilton and colleagues note that a clinically relevant decrease in HDL (“good”) cholesterol is also observed with long periods of sitting (on a daily basis). Therefore, according to this early research, sedentary behavior appears to have a significant effect on some of the main factors that contribute to CVD. Hamilton and associates explain that their preliminary research supports the specificity of training principle, stating that the body will adapt specifically and uniquely to the demands (or lack of physical demands) placed on it. Katzmarzyk and colleagues (2009) underscore that evidence indicates the physiological mechanisms associated with extensive sitting are different from the physiological benefits associated with consistent cardiovascular exercise.
A New Approach for Fitness Professionals
For decades, exercise professionals have been emphasizing the need for structured exercise as the guiding tenet of physical activity and exercise program design. It is now clear that too much sitting is hazardous to one’s health, regardless of whether one meets the minimal daily exercise guidelines or not. Hamilton et al. (2008) suggest that fitness and health professionals need to consider recommending, in addition to existing program design guidelines, innovative approaches to reducing sedentary behavior. Following is an example of how to create a metabolic profile (Step 1), with a case study (Step 2) on how to implement a plan to reduce sedentary behavior in a client.
Step 1. Create a Waking-Day Metabolic Profile. One way for exercise professionals to approach Hamilton and colleagues’ recommendation is to develop a waking-day metabolic-profile timeline (or energy expenditure profile) for each client or student, as seen in Figure 1. This waking-day timeline serves as an awareness index to help the client realize how much sitting is occurring on a daily basis. The next step is to find ways to sit less and stand more throughout the day, particularly during sustained periods of sitting. This leads to the concept of incorporating frequent episodes of spontaneous physical activity throughout sustained sitting times. The most notable spontaneous physical activity research has been pioneered by James Levine, MD, PhD, who calls this type of energy expenditure non-exercise activity thermogenesis (NEAT) (see “A NEAT ‘New’ Strategy for Weight Control,” by Len Kravitz, PhD, April 2006 IDEA Fitness Journal). Levine encourages all individuals to add activity to their daily life wherever and whenever possible. So, once an exercise professional has a clear metabolic profile for a client, working together to incorporate bouts of spontaneous physical activity during sustained periods of sitting is the next objective.
Step 2. Case Study: How to Implement a Plan to Reduce Sedentary Behavior. Let’s do a case study of a client whose metabolic profile shows that person sitting at a desktop computer workstation 5 days a week for 4 hours in the morning and 4 hours in the afternoon, then watching TV and reading for 2 hours each night.
Spontaneous physical activity options to break up the sustained sitting periods during work hours might include (but would not be limited to) the following:
- Stand up and walk around the office every 30 minutes.
- Stand up and get some water.
- Walk to the farthest bathroom in the worksite facility (if multiple bathrooms are an option).
- Always stand and/or walk around the room while talking on the telephone.
- Consider getting a standing workstation for the computer (most of these work desks can be raised and lowered to enable a user who becomes fatigued to lower the station and sit on a physioball instead of standing).
- Take a 5-minute walk break with every coffee break.
- Don’t e-mail office colleagues; walk to their desks instead.
For the 2-hour time frame spent watching TV and reading, some of these options might work:
- Get up and move during every commercial.
- Take a 5-minute walk break every 30 minutes.
- Set a stationary piece of cardiovascular exercise equipment near the TV, and use it for several minutes every half-hour.
- Stand up and do some easy (not strenuous) lunges or squats at least once every half-hour.
- Stand up and do some alternating leg balance exercises at least once every half-hour.
- Stand up and move for the opening segment of each TV show.
- Get up and walk around the room or house after reading a preset number of pages in a book.
Sit Less and Move More!
The information and research presented above suggests that sedentary behavior can be very harmful to one’s health. Fitness professionals need to address this issue with creative and novel strategies to help clients stand up and move during sustained sitting periods of the day. We can do it!
American College of Sports Medicine (ACSM). 2006. ACSM’s Guidelines for Exercise Testing and Prescription (7th ed.). Philadelphia: Lippincott Williams & Wilkins.
Hamilton, M.T., et al. 2008. Too little exercise and too much sitting: Inactivity physiology and the need for new recommendations on sedentary behavior. Current Cardiovascular Risk Reports, 2, 292–98.
Katzmarzyk, P.T., et al. 2009. Sitting time and mortality from all causes, cardiovascular disease, and cancer. Medicine & Science in Sports & Exercise, 41 (5), 998–1005.
Morris, J.N., & Crawford, M.D. 1958. Coronary heart disease and physical activity of work: Evidence of a national necropsy survey. British Medical Journal, 2, 1486–96.
Owen, N., Bauman, A., & Brown, W. 2009. Too much sitting: A novel and important predictor of chronic disease risk? British Journal of Sports Medicine, 43 (2), 81–83.
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