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‘Too Much Sitting’ and Metabolic Risk—Has Modern Technology Caught Up with Us?
Sedentary Behavior and Cardio-metabolic Health Figure 3: A Hypothetical Representation of the
In contrast to the decades of research pertaining to the cardio-
Physical Activity and Sedentary Patterns and Energy
Equivalent (METS) Over a 12-hour Day for Two
metabolic benefits of moderate to vigorous physical activity, the
Individuals, Both of Whom Participate in Equivalent
scientific interest in understanding the influence of prolonged sitting
Amounts of Health-enhancing Physical Activity*
on cardio-metabolic risk is in its relative infancy, with most of the
evidence being centered on epidemiological associations. In
particular, most of this work has focused on the associations between
7
a specific, yet very common, leisure-time sedentary behavior: TV
6
viewing time. In cross-sectional studies, prolonged TV viewing
time has been shown to be deleteriously associated with several
5
cardio-metabolic outcomes, including overweight/obesity, metabolic
4
syndrome, abnormal glucose metabolism, and other biomarkers of
METS
chronic disease risk.
7,8,14–18 3
2
In longitudinal studies, prolonged TV viewing time has been shown to
be associated with an increased incidence of type 2 diabetes, cancer,
1
and weight gain.
19–23
Importantly, many studies have reported such
0
associations with TV viewing time to be independent of leisure-time 9am 10 11 noon 1 2 3 4 5 6 7 8 9pm
physical activity. Indeed, there is evidence that even among adults
‘Active’ couch potato ‘Active’ non-couch potato
who are meeting the current public health guidelines on physical
activity, those who watch high amounts of TV have a less favorable
*>3 metabolic equivalents (METS) for the purpose of this figure. The key distinction between
these individuals is that the ‘active couch potato’ spends a considerable proportion of the
health profile than do those watching lesser amounts.
8,9
remainder of the day in activities that have low energy expenditure (1.0–1.8 METS—sedentary
time), whereas the ‘active non-couch potato’ spends the remainder of the day largely engaged
in light-intensity activity (1.8–3.0 METS), with little time spent being sedentary. Both of these
Accelerometers—Using Technology to
individuals would be seen as being physically active, yet the active couch potato clearly spends
More Accurately Capture Sedentary Time
a substantially greater amount of time being sedentary than the non-couch potato.
The development of objective physical activity measurement
Figure 4: Objectively Measured (Accelerometer) Time
technology has provided epidemiologists and other researchers with
Spent in Activities <100 Counts per Minute (Sedentary)
sophisticated tools to more accurately measure the entire range of and ≥100 Counts per Minute (Non-sedentary) in Two
activity, from sedentary through to very vigorous activities, in free-
Australian Adults Who Shared Identical Total Time Spent
living subjects over a number of days. One of the key objective
Being Sedentary During a 14-hour Day
measurement tools is the accelerometer. Accelerometers are small
electronic devices that are generally worn on the hip and that allow
Morning
detailed data to be recorded on not only the amount of active (or
sedentary) behavior an individual has undertaken, but also the
100
intensity, duration, frequency, and patterns of these behaviors.
24
Given 200
the inherent bias and difficulty associated with self-report measures,
300
the incorporation of accelerometers into population-based public Minutes
health research has been instrumental in advancing the field of
400
research on physical activity as well as on sedentary behaviors.
500
Recent cross-sectional studies in adults that have used
600
accelerometers show that objectively measured sedentary time is
700
deleteriously associated with a number of cardio-metabolic
Evening
Person 1 Person 2
biomarkers, including waist circumference, blood glucose, insulin, and Prolonger Breaker
triglycerides.
3,25–27
In general, these findings were independent of
Sedentary time <100 counts/min Non-sedentary time 100+ counts/min
objectively measured moderate- to vigorous-intensity activity.
3,27
Sedentary time (dark area) in person 1 is accumulated over prolonged periods throughout
the day (‘prolonger’), while person 2 has a high frequency of transitions from sedentary to
Furthermore, our recent work in Australian adults revealed that
non-sedentary time (light area) during the day (‘breaker’).
people who interrupted their sedentary time more frequently (for
example, they might go to get a drink, or simply stand up to answer These studies of objectively measured total sedentary time confirmed
the telephone) had a better metabolic profile than those whose sitting what was previously shown for self-reported TV viewing time: that is,
time was mostly uninterrupted.
28
The relationship for these ‘breakers’ sedentary time is a distinct risk behavior for cardio-metabolic health.
compared with ‘prolongers’ (see Figure 4) was independent of their These findings also reaffirm our earlier suggestion that public health
total sedentary time and their time spent in moderate- to vigorous- strategies for chronic disease prevention and management need to
intensity activity, further emphasizing the key message to ‘move concurrently address the two distinct, yet very common, behavioral
more, more often.’ entities of too much sitting and too little exercise.
29,30
US ENDOCRINOLOGY 31
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