Too Much Sitting Is Not the Same as Too Little
Physical Activity
Travis Saunders MSc CSEP-CEP PhD (c)
R
egardless of age, gender or body weight, living
an active lifestyle is associated with a higher
quality of life and reduced risk of disease and
death. Although it is well-established that physical
activity is important for good health, recent evidence
suggests that physical activity is only part of the
story. It is increasingly clear that the amount of sedentary behaviour you engage in has a large impact on
health, regardless of your level of physical activity.
Sitting Too Much Is Not the Same
as Exercising Too Little
Sedentary behaviour is characterized as any behaviour with extremely low energy expenditure (1).
Activity-related energy expenditure is quantified
using metabolic equivalents (METs). One MET is
equivalent to 3.5 mL of oxygen consumption per
kilogram of body weight, and represents the resting metabolic rate while sitting at rest. Sedentary
behaviour is defined as any behaviour with an
energy expenditure of 1.5 METs or less (1). This
means that anytime you are sitting or lying down,
you are engaging in sedentary behaviour. There are
few exceptions when an individual can be sitting
or lying down but still have a high level of energy
expenditure (e.g. riding a stationary bike).
This definition of sedentary behaviour is different from its traditional usage. In the past, referring
to someone as sedentary meant they did not meet
physical activity guidelines. In this new context, a
sedentary lifestyle is one that is characterized by
high levels of sedentary behaviour, irrespective of
an individual’s level of moderate or vigorous physical activity. This definition recognizes that sedentary behaviour is a risk factor for chronic disease
and that it is possible for an individual to accumulate high levels of both physical activity and sedentary behaviour. As sedentary behaviour researcher
Marc Hamilton has argued sitting too much is not
the same as exercising too little (2).
Health Risks Associated with
Sedentary Lifestyles
Recent epidemiologic findings suggest that sedentary
behaviour is an independent risk factor for both
morbidity and mortality. A cohort of 17 000
Canadian adults was examined and found that individuals who spent the majority of their day sitting
were roughly 50% more likely to die during the
follow-up period than individuals who sat less than
a quarter of the day, even after controlling for age,
smoking and physical activity levels (3). A similar
longitudinal study from Australia found that each
hour of daily television viewing (a proxy of sedentary time) was associated with an 11% increase in
the risk of all-cause mortality, regardless of age, sex,
waist circumference and physical activity level (4).
Other studies have also linked sedentary behaviour to increased risk of chronic diseases, including obesity, diabetes and cardiovascular disease.
During a 6-year longitudinal study of nearly
70 000 women in the Nurses Health Study, Hu
and colleagues report that each 2-hour increase in
daily TV time was independently associated with
a 23% increased risk of developing obesity and a
14% increased risk of developing type 2 diabetes
(5). These results are supported by a similar study
in men (6), as well as recent findings suggesting
that sedentary time is also associated with prospective risk of cardiovascular events (7).
The studies described above have examined the
health impact of chronic sedentary behaviour, but
there is evidence that even short episodes of sedentary behaviour may negatively impact metabolic
health. For example, Stephens and colleagues at the
University of Massachusetts found that 1 full day
of sitting reduced insulin action by 39% in a group
of 14 healthy adults (8). Similarly, Hamburg and
colleagues reported that 5 days of bed rest resulted
in a 50% increase in insulin resistance and a 35%
increase in plasma triglyceride levels in 20 adults
(9). These findings are supported by work in animal models, which suggest that just 4 to 6 hours
of sedentary behaviour may result in dramatic
metabolic adaptations in skeletal muscle, resulting in reduced uptake of triglycerides and glucose
(10,11). These results suggest that even short bouts
of sedentary behaviour have a measurable impact
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on metabolic health, and help to explain the consistent associations between sedentary behaviour
and disease risk observed at the population level.
Living a Less Sedentary Lifestyle
It likely comes as no surprise that current lifestyles promote extremely high levels of sedentary
behaviour. We drive to and from work, and accumulate large amounts of uninterrupted sedentary
behaviour during the workday. After driving home
we may relax in front of the television. Canadian
adults average nearly 10 hours per day of sedentary
behaviour—well over half their waking hours. The
situation is no better for Canadian children, who
are sedentary for more than 70% of their school
day (12), and spend an average of 6 hours per day
using screen-based entertainment devices (13).
While sedentary behaviour is ubiquitous in
Canadian society, it is also a behaviour that lends
itself to simple and inexpensive interventions.
Commuting actively (e.g. travelling by foot, bike
or transit) whenever possible is a simple way to
reduce sedentary behaviour. Setting daily limits
for television and computer use (including smart
phones and other screen-based devices) can also
reduce sedentary behaviour during discretionary
time. A recent randomized trial suggests that this
approach may not only reduce sedentary behaviour, but may also help to reduce body weight
(14). The Canadian Society for Exercise Physiology
recently released the world’s first evidence-based
sedentary behaviour guidelines for children and
youth (15), which suggest that children should
accumulate less than 2 hours of screen time per
day, although lower levels of screen time are associated with additional health benefits. While sedentary behaviour guidelines have yet to be released
for other age groups, it is safe to conclude that
limiting screen time is likely to be associated with
health benefits in all populations.
Although modern office-based work is largely
sedentary, it does not have to be. For example, simple activities like talking on the phone or holding
small meetings can be done just as well while standing. With a proper workplace setup, even traditionally sedentary activities such using a computer don’t
have to include sitting. Most of this review was
written standing up, using a standing workstation.
When workplace sedentary behaviour cannot
be avoided, it is worth exploring ways in which
it can at least be broken up. It has been reported
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that for a given amount of total daily sedentary
time and physical activity, individuals who take
more frequent breaks (e.g. standing, or walking
down the hall at a leisurely pace) have lower body
weight, waist circumference, triglycerides and
higher oral glucose tolerance (16). This suggests
that simply breaking up sedentary time may help
mitigate the health risks when sedentary behaviour is unavoidable.
Assessing Sedentary Behaviour
in the Clinical Setting
Currently there is no objective tool for assessing sedentary behaviour in the clinical setting.
Accelerometers are the preferred tool for research,
but can cost $500 per unit. While pedometers
offer an inexpensive means of quantifying physical activity, they give no information related to
sedentary time. At present the best ways for
assessing sedentary time in the clinical setting are
questionnaire-based approaches. Regardless of
the questionnaire used, it is important to quantify
the amount of sedentary behaviour throughout
the day (morning, afternoon and evening, both
weekdays and weekends), and the modality of
sedentary behaviour (driving, watching television,
using a computer, playing videogames and reading). Once the amount of daily sedentary behaviour and its distribution across modalities has been
assessed, appropriate targets and action plans can
be developed.
Clinicians should discuss the importance of
limiting sedentary behaviour with their clients as
part of any lifestyle intervention. Most individuals are not aware that sedentary behaviour influences health, independent of physical activity
levels. Thus, simply educating clients on the health
impact of sedentary behaviour may be an important step in reducing their chronic disease risk.
Conclusions
Rapidly increasing evidence suggests that sedentary behaviour is associated with increased risk
of both morbidity and mortality independent of
physical activity levels. Interventions aimed at
reducing sedentary behaviour are simple and cost
little to implement. Until more cost-effective tools
allow for objectively assessing sedentary behaviour
in the clinical setting, practitioners should ask
patients about the quality and quantity of sedentary behaviour they accumulate on a regular basis.
Once this has been done, clinicians should work
with patients to reduce levels of sedentary behaviour, as they would with other risk factors.
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References
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Hamilton MT, Healy GN, Dunstan DW, et al. Too little exercise and too much sitting: inactivity physiology and the
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Katzmarzyk PT, Church TS, Craig CL, Bouchard C. Sitting time
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Dunstan DW, Barr ELM, Healy GN, et al. Television viewing
time and mortality: the Australian Diabetes, Obesity and
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Hu FB, Li TY, Colditz GA, et al. Television watching and other
sedentary behaviors in relation to risk of obesity and type 2
diabetes mellitus in women. JAMA. 2003;289:1785-1791.
Hu FB, Leitzmann MF, Stampfer MJ, et al. Physical activity and
television watching in relation to risk for type 2 diabetes mellitus in men. Arch Intern Med. 2001;161:1542-1548.
Stamatakis E, Hamer M, Dunstan DW. Screen-based entertainment time, all-cause mortality, and cardiovascular events:
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Benefits of Yoga…continued from page 8
in their studies. Table 1 gives the recommended
asanas from 3 sources. There is much agreement
regarding which asanas to include, but salabhasana
(locus posture) is the exception—one source recommended it (6) and another indicated it worsens
diabetes control (4). Unfortunately, no detail was
given as to how this was documented or how it
was determined which asanas would be beneficial.
Multiple sources also recommend Pranayama
(4-6). Prana means breath, life, vitality, energy or
strength, and ayama means length, expansion or
stretch. Pranayama then refers to the extension of
breath and its control. Slow, rhythmic breathing
calms the mind, strengthens the respiratory system,
soothes the nervous system, and reduces cravings (6).
The reviews report positive effects of yoga on
short-term parameters of diabetes. It is unclear about
the long-term benefits due to the short duration of
the trials and the small number of participants. In
order to be conclusive about the effect of yoga on
managing diabetes, well-designed randomized con-
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Hamburg NM, McMackin CJ, Huang AL, et al. Physical inactivity rapidly induces insulin resistance and microvascular dysfunction in healthy volunteers. Arterioscler Thromb Vasc Biol.
2007;27:2650-2656.
Bey L. Suppression of skeletal muscle lipoprotein lipase activity during physical inactivity: a molecular reason to maintain
daily low-intensity activity. J Physiol. 2003;551:673-682.
Henriksen EJ, Rodnick KJ, Mondon CE, et al. Effect of denervation or unweighting on GLUT-4 protein in rat soleus muscle.
J Appl Physiol. 1991 May;70:2322-2327.
Nettlefold L, McKay HA, Warburton DER, et al. The challenge
of low physical activity during the school day: at recess, lunch
and in physical education. Br J Sports Med. In press.
Active Healthy Kids Canada. It’s time to unplug our kids:
Canada’s report card on physical activity for children and
youth 2008. http://www.activehealthykids.ca/ecms.ashx/
ArchivedReportCards /2008-AHKC-Long-Form-EN.pdf.
Accessed May 25, 2011
Epstein LH, Roemmich JN, Robinson JL, et al. A randomized
trial of the effects of reducing television viewing and computer use on body mass index in young children. Arch Pediatr
Adolesc Med. 2008;162:239-245.
Canadian Society for Exercise Physiology. Canadian sedentary behaviour guidelines. http://www.csep.ca/english/view.
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Healy GN, Dunstan DW, Salmon J, et al. Breaks in sedentary
time: beneficial associations with metabolic risk. Diabetes
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trol trials are needed. In the meantime I feel comfortable in encouraging my friend to continue his yoga
practice to help him manage his diabetes. Namaste.
References
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Aljasir B, Bryson M, Al-shehri B. Yoga practice for the management of type II diabetes mellitus in adults: a systemic review.
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Innes KE, Vincent HK. The influence of yoga-based programs
on risk profiles in adults with type 2 diabetes mellitus: a
systematic review. Evid Based Complement Alternat Med.
2007;4:469-486.
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Gordon LA, Morrison EY, McGrowder DA, et al. Effect of exercise therapy on lipid profile and oxidative stress indicators in
patients with type 2 diabetes. BMC Complement Altern Med.
2008;8:21.
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Sahay BK. Role of yoga in diabetes. J Assoc Physicians India.
2007;55:121-126.
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Kosuri M. Sridhar GR. Yoga practice in diabetes improves
physical and psychological outcomes. Metab Syndr Relat
Disord. 2009;7:515-517.
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Iyengar BKS. Light on yoga. London: Harper Collins Publishers.
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