As health care practitioners, we are well aware of the health benefits associated with daily moderate to vigorous physical activity (MVPA) and the importance of meeting the American College of Sports Medicine’s physical activity guidelines (Table 1). However, did you know that even those who acquire 30 minutes of MVPA most days of the week may still be at risk for death and disease if they engage in excessive amounts of sedentary behavior for the remainder of the day? In fact, prolonged sedentary behavior also may contribute to chronic conditions such as cardiovascular disease (CVD) and type 2 diabetes mellitus (T2DM). Assuming 8 hours of sleep, current physical activity recommendations make up a small portion of our day, approximately 3% of waking hours. So what are people doing the other 15 to 16+ hours they are awake? And what about the nearly 50% of Americans who do not participate in 150 minutes or more of aerobic physical activity per week?
Current trends have not only highlighted a dramatic increase in sedentary behavior during the last 40 years but also have determined the significant health risk associated with too much sitting. In this article, we will discuss changes in our work/school day, transportation, surrounding environment, and leisure time activities that have contributed to this spike in sedentary behavior. We will discuss the negative impact on overall health, differentiate between physical inactivity and sedentary behavior, and highlight the benefits of adding in spurts of light physical activity to break up prolonged sedentary activities.
DEFINITION AND TRENDS
The unfortunate truth is that a substantial number of Americans are spending an inordinate amount of time engaging in sedentary behaviors, defined by the Sedentary Behaviour Research Network as “any waking activity characterized by an energy expenditure ≤1.5 metabolic equivalents and a sitting or reclining posture” (13). Total sedentary behavior refers to the total accumulated time spent sedentary per day, whereas prolonged sedentary behavior refers to a continuous bout of a specific activity such as sitting/reclining while watching television and/or working on the computer. A recent study found that, in the United States, children and adults accumulate more than 7.5 hours per day of total sedentary time, typically consisting of prolonged bouts of sedentary behavior (12). Even more alarming are the trends in time spent sedentary across the age span such that, as one ages, total sedentary time increases (12).
Historic trends reveal that we spend far more time engaging in sedentary behaviors now than 60 years ago, largely as a result of changes in transportation, built environment, technology, and the workforce/school day. Trends in transportation, for example, have shifted such that automobiles are no longer considered a luxury, and, instead, have become essential for travel. Furthermore, not only does owning a car reduce the likelihood of walking or biking to a destination but also we spend significantly more time sitting in traffic compared with 30 years ago, contributing to an even greater amount of time being stationary in our vehicles (1). Likewise, changes to our surrounding environment, known as built environment, further promotes sedentary lifestyles. This includes lack of sidewalks or bike paths and access to parks/recreation centers in some neighborhoods, making it exceedingly difficult for many to engage in active transportation or physical activity. Safety also is of paramount importance, and lack of safe parks and recreation centers at which to play forces people to participate in more home-based sedentary activities during leisure time (i.e., watching television or playing video games) and, subsequently, contribute to increased time spent viewing television and movies, playing video games, and “surfing the net.” Currently, we watch at least twice as much television as we did in the 1950s, with the average U.S. household increasing television viewing by 36 minutes every 10 years (1).
In addition, during the last 60 years, there has been an increase in jobs requiring little or no physical activity and a reduction in highly active occupations, including agricultural employment, which has fallen dramatically since 1950 (1). Our schoolchildren spend a large portion of their day sedentary as well potentially because of the decrease in time allocated for recess and physical education. It may be possible that physical activity is reduced further in the transition from elementary to high school and high school to college/workforce as people spend more time studying/working, subsequently contributing to increased sedentary time with aging. In fact, stability of sedentary behavior has been identified from adolescence into adulthood (5). It may be that, as young individuals become accustomed to a sedentary society, they may recognize it as a way of life and maintain those habits throughout adulthood.
SEDENTARY BEHAVIOR AND HEALTH IMPLICATIONS
Whereas we strive to remind our clients of the countless benefits associated with habitual exercise, it may be even more beneficial to educate them on the negative consequences of prolonged and total sedentary behavior. During the last decade or so, researchers have focused on examining the impact of sedentary time on health (8,11,14). Many are aware that these activities require little muscle movement, equating to low levels of energy expenditure and, subsequently, very few calories burned. Therefore, the risks of overweight and obesity are a concern for those accumulating large amounts of sedentary behavior. Yet, the risks go far beyond weight gain; in large epidemiologic studies, researchers have found that sedentary behavior is associated with increased death from all causes, CVD, and metabolic risk variables, including (7,9,11):
Men and women:
- ↑ waist circumference
- ↑ blood pressure
- ↑ plasma glucose
- ↑ body mass index
- ↑ fasting glucose
- ↑ triglycerides
- ↓ high-density lipoproteins
Furthermore, several studies have shown a dose-response relationship such that greater amounts of total time spent sitting resulted in increased risk of disease. For instance, a large cohort of women demonstrated that, for each 2-hour per day increase in time spent watching television, there was a 23% increase in risk for obesity and a 14% increase in the risk for T2DM (9). This is particularly alarming because our current daily habits and activities are conducive to prolonged sedentary behavior, rather than short bursts, contributing more so to the overall total time being sedentary.
SEDENTARY VERSUS PHYSICAL INACTIVITY
As most health care professionals strive to improve the health-related physical fitness of their clients by improving cardiovascular fitness, muscular strength and endurance, flexibility, and body composition, MVPA often is prescribed in the form of structured exercise, such as walking or running at a specific intensity, time, and frequency per week. In general, we want to assist our clients in achieving healthy lifestyles. In addition to MVPA, it is important to discuss, identify, and define other behaviors that can benefit overall health (Table 2). As stated previously, sedentary behaviors, including sitting, lying, or reclining quietly, require very little or no muscle movement and may impact blood lipid profiles and glucose metabolism negatively, contributing to increased risk for chronic diseases such as CVD and T2DM (7,11,14). Therefore, it is of paramount importance to educate clients on the awareness of these activities when trying to reach a health-related physical fitness goal.
Although the terms often are used interchangeably, sedentary and physically inactive are distinctly different. Contrary to sedentary behavior, physical inactivity refers to light movement or the lack of achieving physical activity recommendations (14). Evidence suggests that sedentary and light-intensity activities have opposing effects on health (8,9). In fact, greater amounts of time spent standing are related to decreased mortality rates from all causes and CVD (10). Simply moving from sitting at a desk to a standing position, for example, not only reduces time spent in prolonged sedentary behavior but also incorporates muscle movement, initiating a cascade of physiology that may contribute to improved health (14). Hence, it is essential to distinguish between sedentary and light activities when offering clients and patients tips on how to be more active and less sedentary (Table 2). Furthermore, it is important to remind clients that even light-intensity activity is better for overall health than remaining sedentary.
“ACTIVE COUCH POTATO”
Even those accumulating recommended amounts of MVPA are at risk for disease if they also engage in prolonged sedentary activities. This concept has been referred to affectionately as the Active Couch Potato phenomenon (7). Although some do participate in daily MVPA, they also may be spending copious amounts of time engaging in sedentary behavior. The detrimental impact of prolonged sedentary behavior to blood pressure, weight, and glucose metabolism was not only evident in those who did not attain sufficient physical activity but also in subjects accumulating 150 minutes or more of MVPA per week (7). It has been found that time spent watching television was not associated with time spent participating in MVPA, further highlighting the independent risk factors of sedentary behavior and physical inactivity. Even those participating in 1 hour of daily MVPA could not negate the effects of inactivity on glucose metabolism and cholesterol if they were sedentary for the remainder of the day (3). The risk of disease, therefore, seems to be more a result of prolonged sedentary behavior rather than too little time spent with physical activity (3,7,8). In fact, some findings suggest that excessive sedentary time may play a larger role in contributing to some metabolic risk variables than the accumulation of recommended time with MVPA (8). Although MVPA does play a significant role in contributing to improved health, it may be imperative that we identify methods for individuals to incorporate various short bursts of movement into their daily routine in addition to current MVPA. For those not accumulating recommended amounts of MVPA, this becomes increasingly important.
Replacing prolonged sedentary time with multiple short breaks has contributed to improvements in blood pressure, waist circumference, triglycerides, and glucose metabolism, even when the activities are of light intensity (3,6,7). In fact, one study identified a 12% decrease in the risk of T2DM for each 2-hour per day increase in time spent standing or walking around at home (9). Another study found that replacing prolonged sitting with light walking or standing throughout the day was more effective in improving insulin and lipid levels than adding 1 hour of MVPA (3). Although these physical activity breaks are not specifically designed to increase physical fitness significantly, they will decrease sedentary time and, ultimately, aid in the reduction of risk factors for many chronic diseases.
SEDENTARY BEHAVIOR RECOMMENDATIONS
Presently, there are no specific guidelines in the United States to reduce total sedentary behavior for adults. To ward off the negative health impact of sedentary behaviors across a lifetime, the American Academy of Pediatrics has developed the following recommendations for the reduction of sedentary behavior in youth:
- Limit screen time to less than 1 to 2 hours per day
- Discourage screen media exposure for children younger than 2 years
- Keep the TV set and Internet-connected electronic devices out of the child’s bedroom
- Model active parenting by establishing a family home use plan for all media
- ○ As part of the plan, enforce a mealtime and bedtime “curfew” for media devices, including cell phones. Establish reasonable but firm rules about cell phones (2).
The most recent ACSM Position Stand, “Quantity and Quality of Exercise for Developing and Maintaining Cardiorespiratory, Musculoskeletal, and Neuromotor Fitness in Apparently Healthy Adults: Guidance for Prescribing Exercise,” does recognize that sedentary behavior is a health risk, and that achieving physical activity recommendations does not negate sedentary behavior. Furthermore, the updated recommendations urge the reduction of prolonged time spent in sedentary behavior by suggesting the addition of short frequent bouts of standing or participating in other physical activity between periods of sedentary behavior (4).
It may, therefore, be appropriate to add the following recommendation to the current physical activity guidelines:
Reduce prolonged sedentary behavior to no more than 60 minutes at a time and break it up with bouts of any intensity activity.
Rather than prescribe a specific duration for the breaks in sedentary behavior, health practitioners should focus more on encouraging greater frequency of movement throughout the day to avoid prolonged sitting. In addition, suggestions should be offered for modes of incorporating various intensities of physical activity into traditionally longer bouts of sedentary behaviors. See figure for some examples by which traditional sedentary behaviors can be broken up with physical activity.
Assessing sedentary behavior should be a component of the initial consultation between health care providers and their clients. When obtaining health history information, including current and/or previous involvement with physical activity, it also may be beneficial to identify current specific sedentary activities in which your client participates and how long he or she spends with those activities at one time. To determine this behavior, clients can complete a sedentary behavior diary or log; they can be provided with a physical activity-tracking device, such as a pedometer or accelerometer; or clients can be shown how to use a variety of phone applications (“apps”) with which they can log their behaviors as well as receive reminders to be active throughout the day. Once the magnitude of the behavior is identified, clients can record daily reductions in sedentary behavior through increased steps and challenge themselves or a friend to decrease sedentary behavior each week with increased step counts. Having clients set a daily goal for steps may be the best approach for short-term goal setting. However, even without means to measure activity objectively, health care providers can work with their clients to focus on identifying one specific sedentary behavior in which they currently engage and add in frequent small breaks as often as possible.
Oftentimes, for those currently accumulating significant amounts of sedentary behavior, prescribing traditional exercise or prohibiting participation in sedentary activities may not be a realistic solution. Although the current physical activity recommendations should be the ultimate goal for currently sedentary clients, it may be particularly daunting and overwhelming for them to initially aim for 150 minutes per week of MVPA. Rather than discourage them by setting a potentially unrealistic goal, many will still benefit from making small changes in their current routine. Shifting from traditionally sedentary behavior to light activity may be a great jumping-off point and may aid in the introduction of MVPA into their daily routine. Likewise, it is important that we remind our physically active clients that they are not completely exempt from the poor health effects associated with sedentary behavior. Helping clients achieve MVPA recommendations combined with a concurrent reduction in sedentary time should be our end goal. In fact, almost everyone can benefit from reducing sedentary behavior by incorporating physical activity breaks and remembering to break it up!
BRIDGING THE GAP
Continuous bouts of sedentary behavior are associated with increased risk of diseases, even in individuals achieving recommended amounts of daily physical activity. Therefore, it is beneficial to break up sedentary activities with short spurts of movement including light or moderate activity, such as standing up, dancing, or taking a 1- to 3-minute walk.
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Keywords:© 2015 American College of Sports Medicine.
Breaks; Cardiovascular Health; Light Activity; Physical Activity; Sedentary