Sedentary Activities

Sedentary Activities: Can You Outwork Sitting?

Can you really undo the effects of a sedentary life? Sitting is not benign. It causes immediate changes in our oxygen levels, circulation, and muscle activity, and in high doses, it causes whole-body changes that read like the opposite of what we try to accomplish under the bar or when we exercise for health.

Sedentary Activities: Can You Outwork Sitting?

Refrigerators are marvelous devices. The Second Law of Thermodynamics states that entropy always increases with time, a constant change that is observed in the transfer of heat: heat will not transfer naturally from a cold object to a hot one. Yet, within most modern households, there is a little box of defiance within which a constant cycle of liquid expansion and contraction reduces entropy, dumping heat into the surrounding area so that we can enjoy leftovers as the universe marches inexorably toward its ultimate heat death.

Physical decline as we age is as certain as entropy increasing, but like the refrigerator, we can find ways to impose our will and slow the spoil of our youth. We can make ourselves healthier, stronger, and more durable, but that takes work.

And we are working against our species’ version of entropy: human apathy for physical work increases with time and technology. Many of us exercise to undo the forced sedentariness of a job, to adjust to the work-from-home migration, or to set an example for kids whose lives are more automated every day. Sedentary behaviors take up more of our days now than any other time in history, and the days aren’t getting any longer.

But can you really undo the effects of a sedentary life? Sitting is not benign. It causes immediate changes in our oxygen levels, circulation, and muscle activity, and in high doses, it causes whole-body changes that read like the opposite of what we try to accomplish under the bar or when we exercise for health.

Sedentary Activities

Active people tend to ignore discussions of sedentariness. That’s not our fault. The most common definition of sedentary comes from the exercise science literature, which has not distinguished between sedentary activities and a general lack of exercise. Sedentary control groups are usually people who do not meet some minimum threshold for moderate or vigorous exercise, making it impossible for a person to be both sedentary and active in the same 24-hour period. People who lift weights and exercise cannot also be sedentary because they lift weights and exercise—at least in this common view.

Yet many dedicated lifters may spend six or more hours a day sitting—at a desk, on a commute, or in front of a television. According to a lot of exercise literature, that’s okay, as long as they meet the minimum threshold for being not sedentary. That common belief has been challenged in the last decade by a connection between sedentary activities and poor health outcomes that appear to be independent of how much a person exercises. Paying attention only to our healthful activities may be like eating a healthy, balanced meal every day but spending most of our time snacking on whatever is at hand.

A better approach is to look at our days as a tableau of physical activities: (1) moderate- to high-intensity exercise, (2) sleep, (3) non-exercise or light-exercise, and (4) sedentary activities. While not all training, sleep, or physical activities are equally valuable, health outcomes tend to reflect the balance of these activities rather than the quality of a single one. (In comparison, performance outcomes depend more heavily on the quality of your training, recovery, and nutrition.)

We are learning more about this balance from changes in how researchers monitor and quantify daily activities. Traditionally, studies have relied on self-reported surveys. People who reported more exercise tended to be in better health, giving us “[r]obust evidence on the health benefits of optimal patterns of sleep and moderate-to-vigorous physical activity” and “specific, time-based public health guidelines for both of these activities in adults.”[1] Unfortunately, survey data is limited in its usefulness. It depends on the questions asked, and participant’s responses come filtered through memory and self-perception. As a result, “much of the data published… deals with the relationship of specific health outcomes to time spent in only one activity during a daily 24-h cycle,” as opposed to the complete picture of physical activities that might make up a person’s day.[2]

Relatively new measurement devices, such as accelerometers, measure behaviors continuously and can be worn for days or weeks. With more comprehensive data, we can better study whether time spent in one kind of physical activity affects health outcomes related to other activities. In this tableau, sedentary behaviors are the negative space in our day, highlighting the positive things we do for health, but given too much of our time, sedentary activities threaten to wash out our best efforts in the gym or in other healthful pursuits.

Defining Sedentary

Most often, sedentary behavior is measured in MET units, which stands for the metabolic equivalent of task. METs are numerical representations of how much energy you use when doing different tasks, not in actual caloric expenditures but in comparison to a baseline activity, 1.0 METs. One MET is roughly equal to the energy spent while sitting quietly (about one kilocalorie per kilogram of body weight per hour). MET units are useful because, while the actual energy expenditure between two people for different activities will vary, the difference between those activities—say sitting (1.0 MET) and walking (2.0 MET)—will be about the same for everyone.

In an attempt to standardize sedentary as a technical term, a group of professors and professionals have proposed the following definition:

We suggest that journals formally define sedentary behavior as any waking behavior characterized by an energy expenditure ≤1.5 METs while in a sitting or reclining posture. In contrast, we suggest that authors use the term “inactive” to describe those who are performing insufficient amounts of MVPA (i.e., not meeting specified physical activity guidelines).[3]

One attempt to quantify the connection between MET measurements and cardiovascular disease and diabetes suggested that an at-risk person could improve their chances by increasing their physical activity by 11.25 MET-hours per week. To get that, a person would need to add about five and a half hours of walking during the week.

The problem is that not all energy expenditure is equal, and recommendations from the research differ depending on the particular focus of the study. Studies looking at the benefits of exercise tend to view sedentary behaviors as the absence of a daily threshold of energy expenditure: people are sedentary when they do not meet the minimum activity requirements. The letter quoted above suggests that a better term for people who do not meet exercise guidelines is “inactive.” The sedentary literature treats activities as sedentary, causing physical changes that are independent of the person’s other activities. The difference is that sedentary studies view sitting for prolonged periods as having a net negative effect. So, a person’s 2.0 METs from walking for one hour are much more healthful than 2.0 MET-hours’ worth of sitting. In the world of sedentary studies, everything we do either moves us closer to health or to disease—there is no middle ground.

That’s a bit extreme, but it highlights the point that a person can be both active and sedentary in the same 24-hour period.[4] The idea that sedentary activities may cause their own negative health effects has led the American Heart Association and others to take up the idea that, as James Hamblin writes, “you can’t undo sitting.”

Is Sitting Really that Bad?

We sit—a lot. The numbers vary depending on the study methods, but one study’s participants, who wore activity monitors 24 hours a day, spent nearly 55% of their monitored time sedentary, averaging to about 7.7 hours per day.[5] The text Sedentary Behavior Epidemiology, which breaks up our awake time into three types of physical activities (sedentary behavior, light-intensity, and moderate- to vigorous-intensity), says that “on average, sedentary and light-intensity activities comprise a much larger proportion of total waking time (~95%) compared to moderate-to-vigorous intensity physical activity (~5%).”[6] That makes sense since, by definition, you cannot engage in high-intensity exercise for several hours every day of the week.

Plenty of people have deep indents in their couches and still manage to live active, healthy lifestyles. Plenty of people train hard, exercise well, and eat right but have serious health problems that may be related to sitting. The latter is more concerning because we tend to excuse sedentary activities by dedicated exercise. The weekend warrior who works a desk job cannot outwork six to eight hours a day behind a computer during the weekend.

The obvious problem is that when you sit, you aren’t burning very many calories, but too much sitting is distinct from too little exercise. “[W]hile contractile activity of skeletal muscles is important for common activities involved in being upright (i.e., standing and ambulation), this muscle activity largely ‘flatlines” during sitting postures—as demonstrates by an unloading of the major locomotor muscle groups in studies measuring muscle electromyographic (EMG) activity.”[7] Most people sit in a slouched or awkward posture, compressing their chest cavity and decreasing their overall oxidation.[8] Many workstations are poorly set up for ergonomics, exacerbating muscle weakness and back pain. Longer-term, prolonged habitual sitting may increase risks of cardiovascular disease and insulin resistance, contribute to chronic low-grade inflammation, and increase incidences of all-cause mortality. “[T]hese associations appear to be largely additional to the risks associated with lack of moderate- to vigorous-intensity physical activity during leisure time.”[9] Sitting and poor circulation also increases the risk for deep vein thrombosis, a potentially life-threatening condition. Psychologically, when people exercise more, they tend to engage in less hedonic or self-rewarding behaviors (like sweet treats), an inhibition that is not present in people who are relatively sedentary throughout the day.

Can You Undo Sitting?

Yes and no. The AHA and other policy-driven bodies are notorious for aiming low: the easiest answers will be adopted by the most people and, therefore, create the biggest change. So one of the mantras that has come from sedentary studies is to “sit less, move more.” Writer James Hamblin of The Atlantic notes that this advice is only mildly aspirational: “by ‘move,’ they mean almost anything that is not sitting or reclining—anything that increases your metabolism to 1.5 times that of being absolutely still. Which is a very low bar. ‘Leisurely walking’ is close to 2.5, while gardening or throwing a baseball with a kid gets you closer to four.”[10]

You cannot undo sitting, especially when accumulated in long, unbroken bouts. The negative effects seem to run independently of everything else you might do in your day. However, sitting also isn’t poison. Its effects on the body are intertwined with your other (read: healthier) activities. Notice that most negative effects from sitting are the opposite of the positive effects of exercise and strength training: increased risks of cardiovascular disease and diabetes, muscular atrophy, sarcopenia, back pain, and a net-positive energy balance.

Sitting is potent, but so is exercise. While sitting less is a good thing, you may be able to outwork prolonged sedentary behaviors if you have no other choice. [11]

But you cannot excuse sitting by your other activities. If you have to sit for six to eight hours a day, it behooves you to consider that time as a negative stressor on your body and something that is working against your health goals. The best interventions for copious sedentary behaviors are quantity- over quality-based. While you should already be including high-quality strength and conditioning training into your week, high-quantity, low-impact activities can help mitigate negative health effects from prolonged sitting. Interrupt your sitting frequently (every 30 to 45 minutes) with at least moderate-intensity movement—just standing up doesn’t seem to do much. And include longer bouts of lighter-intensity exercise in your day—walking and low-impact cardio is vastly underrated for this purpose.

While you cannot undo the effects of prolonged sitting, and you certainly cannot excuse sitting with punctuated workouts—you may be able to outwork sitting (if you have to).


Notes

[1] Mary E. Rosenberger, Janet E. Fulton, Matthew P. Buman, Richard P. Troiano, Michael A. Grandner, David M. Buchner, William L. Haskell, “The 24-Hour Activity Cycle: A New Paradigm for Physical Activity,” Medicine & Science in Sports & Exercise. Vol. 51:3 (March 2019): 454-64, https://doi.org/10.1249/MSS.0000000000001811.

[2] Id.

[3] Sedentary Behaviour Research Network. Letter to the editor: standardized use of the terms“sedentary” and “sedentary behaviours.” Appl Physiol Nutr Metab. 37(3) (2012): 540–2.

[4] Id.

[5] Charles E. Matthews, Kong Y. Chen, Patty S. Freedson, Maciej S. Buchowski, Bettina M. Beech, Russell R. Pate, and Richard P. Troiano, “Amount of time spent in sedentary behaviors in the United States,” Am J Epidemiol. 167:875-81 (2008): 877–78, DOI: 10.1093/aje/kwm390.

[6] Paddy C. Dempsey and John P. Thyfault, “Physiological Responses to Sedentary Behaviour,” Sedentary Behaviour Epidemiology. Ch. 5 (2018): Fig. 5.1, Page 110.

[7] Id. At 116.

[8] Fang Lin, Sriranjani Parthasarathy, Susan J. Taylor, Deborah Pucci, Ronald W. Hendrix, Mohsen Makhsous, “Effect of Different Sitting Postures on Lung Capacity, Expiratory Flow, and Lumbar Lordosis,” Archives of Physical Medicine and Rehabilitation. Vol. 87, Isssue 4 (April 2006): 504–09 https://doi.org/10.1016/j.apmr.2005.11.031.

[9] Epidemiology, supra, p. 120

[10] James Hamblin, “The Futility of the Workout-Sit Cycle,” The Atlantic. (August 12, 2016): available at https://www.theatlantic.com/health/archive/2016/08/the-new-exercise-mantra/495908/.

[11] Ulf Ekelund, Jostein Steene-Johannessen, Wendy J Brown, Morten Wang Fagerland, Neville Owen, Kenneth E Powell, Adrian Bauman, I-Min Lee, “Does physical activity attenuate, or even eliminate, the detrimental association of sitting time with mortality? A harmonised meta-analysis of data from more than 1 million men and womenm” Lancet. 388 (July 2016): 1302–10, http://dx.doi.org/10.1016/S0140-6736(16)30370-1. (“High levels of moderate intensity physical activity (ie, about 60–75 min per day) seem to eliminate the increased risk  of  death  associated  with  high  sitting  time.  However,  this  high  activity  level  attenuates,  but  does  not  eliminate  the  increased  risk  associated  with  high  TV-viewing  time.  These  results  provide  further  evidence  on  the  benefits of physical activity, particularly in societies where increasing numbers of people have to sit for long hours for work and may also inform future public health recommendations.”)

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