Why People Do Less Exercise the More They Sit Literature Reviews

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Exerc Sport Sci Rev. Author manuscript; bachelor in PMC 2012 Jul 25.

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As well Much Sitting: The Population-Health Science of Sedentary Behavior

Neville Owen

^oneCancer Prevention Inquiry Centre, Schoolhouse of Population Health, The University of Queensland, Queensland, Australia

Geneviève N Healy

¹Cancer Prevention Enquiry Centre, School of Population Wellness, The Academy of Queensland, Queensland, Australia

^twoBakery IDI Heart and Diabetes Constitute, Victoria, Australia

Charles E. Matthews

³Nutritional Epidemiology Branch, Segmentation of Cancer Epidemiology and Genetics, National Cancer Plant, Rockville, MD

David West. Dunstan

^twoBakery IDI Middle and Diabetes Institute, Victoria, Australia

Abstract

Even when adults meet concrete activeness guidelines, sitting for prolonged periods can compromise metabolic health. Television set time and objective-measurement studies show deleterious associations, and breaking up sedentary time is beneficial. Sitting time, Goggle box time, and time sitting in automobiles increase premature mortality risk. Further prove from prospective studies, intervention trials, and population-based behavioral studies is required.

Keywords: environmental and social change, TV fourth dimension, breaks in sedentary time, accelerometer measurement, blood glucose, triglycerides, metabolic health

INTRODUCTION

The physical, economic and social environments in which modern humans sit down or move within the contexts of their daily lives accept been changing chop-chop, and particularly so since the center of the concluding century. These changes — in transportation, communications, workplace and domestic-entertainment technologies — have been associated with significantly-reduced demands for physical action. However, these reductions in the ecology demands for being physically active are associated with some other course of wellness-related behaviors.

Sedentary behaviors (typically in the contexts of Tv set viewing, computer and game-console use, workplace sitting, and fourth dimension spent in automobiles) accept emerged as a new focus for inquiry on physical activity and wellness (xviii, 27, 31-33). Put only, the perspective that we propose is that too much sitting is distinct from as well little practice. Research findings on sedentary beliefs and health have proliferated in the ten years following publication of our first Exercise and Sport Sciences Reviews paper on this topic (32). As we will demonstrate, initial findings on the metabolic correlates of prolonged TV viewing time (TV time) have since been confirmed past contempo objective-measurement studies, which also show that breaking upwardly sedentary fourth dimension can be beneficial. Furthermore, nosotros describe recent studies from Canada, Australia, and the United States, which show prospective relationships of sedentary behaviors with premature mortality. Importantly, adults tin can meet public-health guidelines on physical activity, merely if they sit down for prolonged periods of fourth dimension, their metabolic wellness is compromised. This is a new and challenging area for exercise scientific discipline, behavioral science, and population-wellness research. However, many scientific questions remain to be answered before it can be concluded with a high degree of certainty that these adverse health consequences are uniquely due to besides much sitting, or if what has been observed so far can be accounted for by also petty light, moderate, and/or vigorous activeness.

The updated recommendation for adults on Physical Activity and Public Health from the American College of Sports Medicine and the American Heart Clan (ACSM/AHA) "conspicuously states that the recommended amount of aerobic activeness (whether of moderate- or vigorous-intensity) is in addition to routine activities of daily living which are of light intensity, such as self care, coincidental walking or grocery shopping, or less than ten min of elapsing such as walking to the parking lot or taking out the trash" ((20) p. 1426). Logically, doing such daily activities differently could involve reductions in sitting time, just sitting per se is not addressed specifically in the recommendations. In this context, the key question to be asked most the strength of the prove on sedentary beliefs and health that nosotros present in this paper is: Would one expect to encounter a statement on reducing sitting fourth dimension included in future concrete activity recommendations?

Sedentary Beliefs

Sedentary behaviors (from the Latin sedere, "to sit") include sitting during commuting, in the workplace and the domestic surround, and during leisure fourth dimension. Sedentary behaviors such TV viewing, computer apply, or sitting in an automobile typically are in the energy-expenditure range of 1.0 to 1.5 METs (multiples of the basal metabolic rate)(1). Thus, sedentary behaviors are those that involve sitting and low levels of energy expenditure. In contrast, moderate-to-vigorous concrete activity such as bicycling, swimming, walking, or running may be washed in a variety of body positions, simply require an free energy expenditure of 3 to 8 METs (1). In this perspective, light intensity action behaviors are those done while continuing, only that requires expenditure of no more than than 2.9 METS.

Addressing research on the wellness consequences of sedentary behavior requires some initial clarification of terminology. We refer to sedentary behaviors (dissimilar activities, for different purposes in different contexts; see higher up). We refer also to sitting time, a generic descriptor covering what these sedentary behaviors primarily involve. As we demonstrate beneath, adults spend the majority of their waking hours either sitting, or in light intensity activity (predominantly standing with some gentle airing).

Time in sedentary behaviors is significant, if only because it displaces time spent in higher intensity physical activity — contributing to a reduction in overall physical action energy expenditure. For example, displacement of ii hours per day of lite intensity activity (2.v METS) by sedentary behaviors (1.five METS) would exist predicted to reduce concrete activity energy expenditure by nearly two MET-hrs/d, or approximately the level of expenditure associated with walking for thirty min per day (0.5 hrs * iii.5 METs = 1.75 MET-hrs).

Research on physical activity and health has concentrated largely on quantifying the amount of time spent in activities involving levels of energy expenditure of 3 METs or more than, characterizing those with no participation at this level as "sedentary" (33). Still, this definition neglects the substantial contribution that lite intensity (1.9 to 2.9 METs) activities make to overall daily energy expenditure (eight), and likewise the potential health benefits of participating in these low-cal-intensity activities, rather than sitting. Furthermore, although individuals can be both sedentary and physically inactive, there is also the potential for high sedentary fourth dimension and beingness physically active to co-be (the Agile Couch Potato phenomenon, which we explain below). An case would be an office worker who jogs or bikes to and from work, but who then sits all day at a desk and spends several hours watching Idiot box in the evening.

Common behaviors in which humans now spend and so much time — TV viewing, computer utilise and electronic games, sitting in automobiles — involve prolonged periods of these low levels of metabolic free energy expenditure. It is our contention that sedentary behavior is not but the absence of moderate-to-vigorous physical activity, simply rather is a unique set of behaviors, with unique environmental determinants and a range of potentially-unique wellness consequences (43). Our population-health inquiry perspective is on the distinct part of sedentary beliefs, as it may influence obesity and other metabolic precursors of major chronic diseases (type two diabetes, cardiovascular illness, and breast and colon cancer).

Sedentary Behavior and Wellness: A Unique Underlying Biology?

Physiologically, singled-out effects are observed between prolonged sedentary fourth dimension and too petty physical action (17). At that place are broad consistencies betwixt the patterns of findings from epidemiologic studies on the cardio-metabolic correlates of prolonged sitting that we will draw, and recent evidence on biological mechanisms — "inactivity physiology" — identified in animal models. It seems probable that in that location is a unique physiology of sedentary fourth dimension, within which biological processes that are distinct from traditionally-understood practise physiology are operating. The groundbreaking piece of work of Hamilton and colleagues (3, xvi) provides a compelling body of evidence that the chronic, unbroken periods of muscular unloading associated with prolonged sedentary time may take deleterious biological consequences. Physiologically, information technology has been suggested that the loss of local contractile stimulation induced through sitting leads to both the suppression of skeletal muscle lipoprotein lipase (LPL) activity (which is necessary for triglyceride uptake and HDL-cholesterol production) and reduced glucose uptake (3, xvi). A detailed account of findings and implications from Hamilton'south studies has been provided in contempo reviews (17, xviii).

Hamilton'south findings suggest that standing, which involves isometric contraction of the anti-gravity (postural) muscles and only low levels of free energy expenditure, elicits EMG and skeletal muscle LPL changes. Yet, in the by, this form of continuing would be construed as a "sedentary behaviour" because of the limited corporeality of bodily motility and energy expenditure entailed. This highlights the demand for an evolution of the definitions used for sedentary behavior research. Within this perspective, continuing would not exist a sedentary action and our approach (subject to revision as farther findings accumulate) is to equate "sedentary" with "sitting."

THE METABOLIC Wellness CONSEQUENCES OF As well MUCH SITTING

TV Viewing Time: The AusDiab Studies

AusDiab (the Australian Diabetes, Obesity and Lifestyle study) conducted initially in 1999/2000, of a common leisure-time sedentary behavior — Television set viewing fourth dimension — with biomarkers of cardio-metabolic run a risk. AusDiab recruited a large, population-based sample of some 11,000 adults from all Australian states and the Northern Territory. Some of our first AusDiab findings were that among adults without known diabetes, self-reported Television viewing time was positively associated with undiagnosed abnormal glucose metabolism (12) and the metabolic syndrome (eleven). The strongest relationships were observed in the highest Television receiver fourth dimension category (four hours or more per day). When Telly fourth dimension was considered every bit a continuous measure (ten), a detrimental, dose-response association was observed in women between Television viewing time and two-h plasma glucose and fasting insulin. Importantly, all of these associations persisted later on adjustment for sustained moderate-to-vigorous intensity leisure time physical activity and waist circumference. Some of these cross sectional relationships have been replicated recently in prospective analyses: increases in Television set viewing over five-years predicted significant agin changes in waist circumference for men and women and in diastolic blood pressure and a clustered cardio-metabolic risk score for women. These associations were independent of baseline telly viewing time, baseline physical activity and physical activity change, and other potential confounders (48).

Beingness Sedentary and Meeting Physical Activity Guidelines: The Agile Couch Spud

We further examined relationships of Goggle box time with continuous metabolic risk in men and women who reported at least 150 min a week of moderate-to-vigorous intensity physical activeness — the mostly-accustomed public health guidelines for health-enhancing physical activeness (xx). Among these healthy, physically-active adults, pregnant detrimental dose-response associations of TV time were observed with waist circumference, systolic claret pressure level, and ii-h plasma glucose in both men and women, as well as fasting plasma glucose, triglycerides, and HDL-cholesterol in women only (23). This observation — the Agile Couch Potato miracle — is important. The item metabolic consequences of time spent watching Tv set are agin, even among those considered to be sufficiently physically active to reduce their chronic disease take chances. This finding reinforces the potential importance of the deleterious wellness consequences of prolonged sitting time, which may be independent of the protective effect of regular moderate-intensity physical activity.

Goggle box Viewing Time: Associations with Biomarkers for Men and for Women

I of the striking findings in the AusDiab TV-fourth dimension studies was that the associations with cardio-metabolic biomarkers were stronger for women than for men (x-12, 23). We afterward examined the associations of both TV fourth dimension and self-reported overall sitting time with these biomarkers in the 2004/2005 AusDiab sample (42). The Telly time relationships for women were replicated, but for self-reported overall sitting time (which is inclusive of the TV time component), the associations were similar for men and women. And so, the question remains every bit to whether there is a detail relationship of Tv time with metabolic wellness for women. There are some testable hypotheses that can exist put forrard in this context: Are there dietary or Television receiver time-related snacking differences between men and women? Are women (who have a lower average skeletal muscle mass and a higher average fat mass than men) metabolically more susceptible to the agin influences of prolonged sitting, post-obit the typically-large evening meal?

Although some of our nigh striking initial findings on the adverse wellness consequences of sedentary behavior accept been for TV time, there should be circumspection in treating this common leisure-time sedentary behavior as a marking for overall sedentary time. We have modest prove (39) that for women, TV time is positively correlated with other leisure time sedentary behaviors and with being less likely to meet physical activeness and wellness guidelines. However, these findings need to be replicated in other populations and with other measures. Furthermore, Television viewing is associated with other health-related behaviors (51) and those in the highest Television set time categories are more likely to eat in front of the Boob tube set (26). It is thus plausible that TV fourth dimension will influence energy balance in two chief ways. Most people sit down to sentinel TV and it has a lower free energy cost than the alternative activities that it replaces. Likewise, high levels of TV time are probable to increase energy intake because of prompts from frequent commercials about food and beverages, and unlike for many other activities, the hands are free to eat during Tv set time (51). It is thus a reasonable hypothesis that this latter factor may partially explain why college levels of Goggle box time are associated with higher waist circumferences and with adverse blood-glucose and lipid profiles.

We must emphasize that Tv set time is one of a number of sedentary behaviors that characterise how adults go about their daily lives, and there is potential measurement mistake associated with using the self-written report measures that are common to near TV-time studies. However, based on our recent systematic review (six), we take some confidence that the TV-time measures that nosotros have used are reasonably reliable and valid.

OBJECTIVE Cess OF SEDENTARY Time: NEW FINDINGS

Advances in the Objective Measurement of Sedentary Behavior

These Australian studies summarised above accept all relied on self-reported Telly time or overall sitting time. Withal, advances in measurement technology now provide significantly-enhanced scientific traction, which is helping to deal with the methodological limitation of measurement fault related to the use of cocky-written report items. Prior to summarising findings from our objective-measurement studies with AusDiab study participants, it is helpful to consider the new perspectives that sally when accelerometer data on sedentary time and physical activity are examined. Accelerometers (every bit distinct from pedometers which count and display number of steps taken) are small electronic devices worn on the hip, which provide an objective record of the volume, intensity, and frequency of activity betwixt and within days, which may be downloaded to calculator databases and used to derive scientifically-meaningful action variables. Accelerometers have been employed as part of the National Health and Nutrition Test Survey (NHANES), gathering data from large population-based samples of developed residents of the United States. Findings reported to date suggest that, compared to what has been assumed to be the case from self-report surveys, levels of participation in moderate-to-vigorous concrete activity are extremely low (44), and that some 60% or more of these adults' waking hours are spent sedentary (29).

Sedentary Behavior during Adults' Waking Hours

To illustrate the overall patterns of action in adults' daily lives, Effigy one shows a cluster heat map (49). This is a graphical representation from Genevieve Healy, showing accelerometer data for i individual over 1 week, in the fashion originally presented by Jane Kent-Braun'south group (15). The values taken by the accelerometer counts within each minute are represented equally colors in the two-dimensional map. The dark blue shading shows accelerometer counts that are below the currently used only nevertheless debated cut-off of 100 counts per infinitesimal for sedentary time, and which are taken to be indicative predominantly of sitting (a caveat, however, is that some of the minutes shown sedentary volition include standing quite nevertheless). The pale-blue through to yellow colorings indicate lite-intensity through to moderate-intensity concrete activities. The xanthous through to red indicate moderate-to-vigorous concrete activeness. From an free energy-expenditure perspective, the night bluish translates to very low levels of free energy expenditure, with the carmine reflecting high energy expenditure levels. What is striking in Figure 1 is the extent to which this person spends his or her time either in light-intensity activities (pale blue through to white) and beingness sedentary (dark blue). While we would not contend that this is a totally precise and unambiguous representation of sitting time, light intensity, and moderate-vigorous activity, it however is an informative perspective.

Beingness physically active, just also highly sedentary: 1 week of accelerometer-count data showing, on boilerplate, 31 mins/day moderate-to-vigorous activity time (> 1951 counts/min) and 71% of waking hours sedentary (< 100 counts/min).

Effigy 1 illustrates one of our cardinal letters almost the office of sedentary time in the concrete activity and health equation: it is possible to accomplish a level of activity consistent with the public-health guidelines for health-related concrete activeness (xxx min of moderate intensity physical activity on almost days of the week) but to spend the vast majority of waking hours involved in sedentary behaviors. In this case, nosotros encounter that the accumulated moderate-to-vigorous physical activeness fourth dimension is 31 min; all the same, this person spends 71% of their waking hours in sedentary time. Thus, it is possible for individuals to be physically active, yet highly sedentary — the Active Couch Potato phenomenon identified in the AusDiab TV-fourth dimension studies (24).

The principal scientific caveat for this perspective is that these data testify "activity," which we infer is reflective of "behavior." However, there are scientific devils in the detail of these objective-movement information: argue remains about what are the near appropriate activity-count cut points to identify sedentary and low-cal intensity time; also, different cut points may be appropriate for adults of different ages, race/ethnicity, and adiposity status.

Considerately-Assessed Sedentary Fourth dimension: Key Studies

Likewise as demonstrating remarkably-depression levels of physical activeness and high levels of sedentary time within contemporary homo environments (29, 44), objective measures have also demonstrated the agin bear on of prolonged sedentary time on cardio-metabolic biomarkers of risk. At least three studies in Europe and Australia accept examined the associations of objectively-measured sedentary fourth dimension with continuous cardio-metabolic biomarkers: the ProActive trial conducted in the United Kingdom (UK), the European RISC study, and the AusDiab study (2, 13, 14, 23, 25). For those in the UK ProActive trial (258 participants aged thirty-fifty twelvemonth with a family history of type two diabetes), sedentary fourth dimension was detrimentally associated with insulin in the cross-sectional assay (fourteen), just was of borderline statistical significance (p=0.07) in the i-yr prospective analysis (13). Detrimental cross-exclusive associations of sedentary time with insulin were likewise observed in participants of the European RISC written report (801 participants aged xxx-lx yr, salubrious adults), though the associations were attenuated post-obit adjustment for total activeness (2). In the AusDiab accelerometer-study sample (169 participants aged 30-87 yr, general population), we observed detrimental associations of sedentary time with waist circumference, triglycerides, and 2-hr plasma glucose (22, 24). It is important to betoken out that the participants in all of these studies were primarily White adults of European descent (2, 13, 14, 22, 24). A cardinal next step for this research is to examine whether the associations are consistent across different racial/ethnic groups, which is becoming feasible with the public availability of large, multi-ethnic population-based datasets, peculiarly NHANES (29, 44).

Objectively-Assessed Sedentary Behavior: AusDiab Findings

We used accelerometers to assess sedentary fourth dimension in a sub-sample of the AusDiab report participants. Sedentary time was defined every bit accelerometer counts below 100 per minute (encounter above), and was associated with a larger waist circumference, and more-agin 2-h plasma glucose and triglyceride profiles every bit well as a amassed metabolic risk score (22, 24). The associations of sedentary time with these biomarkers (with the exception of triglycerides) remained significant, following adjustment for time spent in moderate-to-vigorous intensity physical action (22, 24).

Every bit logically would be expected, sedentary fourth dimension and light-intensity activity time were highly negatively correlated (r = -0.96): more time spent in low-cal-intensity activeness is associated with less time spent sedentary. This suggests that it may be a feasible arroyo to promote light intensity activities as a manner of ameliorating the deleterious wellness consequences of sedentary time. Our evidence suggests that having a positive light intensity/sedentary time balance (that is; spending more time in light-intensity than sedentary time) is desirable, since lite-intensity activity has an inverse linear relationship with a number of cardio-metabolic biomarkers (22, 24).

Breaks in Sedentary Time: AusDiab Findings

One of the intriguing findings from our accelerometer-measurement studies is that breaks in sedentary time (every bit distinct from the overall volume of time spent being sedentary) were shown to take beneficial associations with metabolic biomarkers (21). Sedentary time was considered to exist interrupted if accelerometer counts rose up to or above 100 counts per minute (21). This can include behaviors that result in a transition from sitting to a standing position or from standing nonetheless to beginning to walk. Figure 2 is based on data from two of our AusDiab accelerometer-written report participants, showing a simple contrast between adults who have the same total book of sedentary fourth dimension, but who break up that time in contrasting patterns. The person whose data is shown in the right-mitt panel of Figure 2 (the "Breaker") interrupts their sedentary time far more than frequently than the person whose data are shown on the left panel (the "Prolonger").

Breaks in sedentary time: same corporeality of sedentary fourth dimension, but unlike ways of aggregating. CPM = counts per minute. (Reprinted from Dunstan DW, Healy GM, Sugiyama T, Owen N. 'Too Much Sitting' and Metabolic Risk – has modern technology caught up with usa? The states Endocrinology. 2009;5(one), 29-33. Copyright © 2009 Touch on Briefings. Used with permission.)

Independent of total sedentary time, moderate-to-vigorous intensity activity time and mean intensity of activity, nosotros constitute that having a higher number of breaks in sedentary time was beneficially associated with waist circumference, body mass index, triglycerides, and ii-h plasma glucose (21). Figure 3 shows considerately-measured waist circumference across quartiles of breaks in sedentary fourth dimension. Those in the bottom quarter of the "breaks" distribution had, on average, a 6cm larger waist circumference than did those in the meridian quarter of that distribution (21).

Associations of breaks in sedentary time with waist circumference (based on data from Healy et al. (21)).

These findings on breaks in sedentary time provide intriguing preliminary bear witness on the likely metabolic-health benefits of regular interruptions to sitting fourth dimension, which we would argue are boosted to the benefits that ought to accrue from reducing overall sedentary time. Interestingly, in a recent study (five), patterns of sedentary time aggregating (simply not total sedentary fourth dimension) were shown to differ among iv groups of adults with various activeness patterns (healthy grouping with active occupation; healthy group with sedentary occupation; group with chronic back pain; grouping with chronic fatigue syndrome). As nosotros will continue to suggest, while we believe that these are strongly-indicative findings, there is the demand to determine whether these associations can exist confirmed in experimental manipulations of sitting fourth dimension in the laboratory, and in intervention studies where sedentary time is reduced or broken up in naturalistic settings such as the domestic surround or the workplace.

Sedentary Behavior and Mortality

The significance of the prove on the adverse cardio-metabolic wellness consequences of prolonged sitting time is underscored by findings from a mortality follow-up of participants in the Canada Fitness Surveys. Canadians who reported spending the bulk of their day sitting had significantly poorer long-term bloodshed outcomes than did those who reported that they spent less time sitting. These relationships with mortality were consistent beyond all levels of a self-report measure of overall sitting time. Participants estimated the broad fractions of their waking hours that were spent sitting. Importantly, the sitting fourth dimension-mortality relationships were apparent even among those who were physically active, and were stronger among those who were overweight or obese (25). In a follow-upward of AusDiab report participants over 6.five year, loftier levels of TV time were significantly associated with increased all-cause and cardiovascular illness mortality (9). Each one hour increment in Idiot box time was plant to be associated with an 11% and an 18% increased run a risk of all-cause and cardiovascular disease mortality, respectively. Furthermore, relative to those watching less TV (< 2 hours/day), there was a 46% increased risk of all-cause and an 80% increased risk of cardiovascular illness mortality in those watching four or more than hours of TV per day, independent of traditional risk factors such as smoking, claret pressure, cholesterol and diet, as well every bit leisure-time physical activity and waist circumference. A recent study from the U.s.a. (47) examined sedentary behaviors in relation to cardiovascular mortality outcomes, based on 21 year of follow-upwards of 7744 men. Those who reported spending more than 10 h a calendar week sitting in automobiles (compared to less than four hours a week), and more than 23 h of combined television time and automobile time (compared to less than 11 hours a week) had an 82% and 64% greater risk of dying from cardiovascular disease, respectively. Television time lonely was not a meaning predictor (47).

Enquiry DIRECTIONS

Looking Back through a Sedentary Behavior Lens

Emerging findings on sedentary beliefs suggest a dissimilar perspective through which findings of earlier physical activity and health enquiry studies may be re-examined (we thank William L. Haskell for stimulating these observations). For example, physical action epidemiology studies that accept assessed physical activity comprehensively have often included measures of sitting time, which has been used mainly to derive overall daily energy expenditure estimates. Nosotros would predict (peradventure boldly) that if such studies were to be revisited, with farther analyses beingness conducted using sitting time as a distinct exposure variable, that stiff evidence would exist plant for deleterious outcome on subsequent wellness outcomes, independent of those related to physical inactivity.

Another potentially fruitful expanse in which the relevance of existing bear witness could exist re-examined, are the NASA goose egg-gravity studies. Comparing findings of those studies (that relate to the metabolic consequences of farthermost muscular unloading) with those of the recent findings from inactivity physiology (xvi, 17) may lead yield further insights relating to the underlying biological science of prolonged sedentary fourth dimension.

Research on physical activity and health had its roots in early occupational epidemiological studies that assessed workers in jobs that primarily involve sitting as the comparing groups, against which the protective benefits of physically-agile work were highlighted (four, 17, 18). In the perspective of the new evidence that we take highlighted, conducting further occupational epidemiology studies using new objective measurement capabilities, and examining a range of cardio-metabolic and inflammatory biomarkers as intermediate outcomes, could yield valuable insights.

Sedentary Beliefs Research Strategy

Our population-wellness research programme on sedentary beliefs is guided by the behavioral epidemiology framework (34, 36). Figure 4 shows half dozen inquiry phases. Every bit we demonstrate to a higher place, evidence inside the start phase (examining the relationships of sedentary behavior to cardio-metabolic biomarkers and health outcomes) has strengthened rapidly over the past ten yr.

Behavioral epidemiology framework: phases of testify for a population-health scientific discipline of sedentary behaviour.

Prolonged periods of sitting in people's lives need to be measured precisely (stage two). Their contextual determinants — that is, beliefs settings (32, 35) — need to exist identified in domestic, workplace, transportation and recreation contexts (stage iii). We have argued previously for a inquiry focus on the singled-out ecology determinants of sedentary behaviors, in contexts where they tin be amenable to intervention (31, 32, 37, 41). The feasibility and efficacy of such interventions demand to be tested rigorously (stage four). Importantly, public wellness policy responses need to be informed past evidence from all of these phases. Compared to the challenges for physical activity and public health, sedentary beliefs may be less of a "moving target" in this context, and may be shown to be a tractable public wellness objective (4).

The Population-Wellness Science of Sedentary Beliefs: Enquiry Opportunities

Dissimilar sedentary behaviors and their interactions with concrete activeness demand to exist examined in a range of contexts. For example, we have demonstrated leisure-fourth dimension Internet and computer employ is related to overweight and obesity in Australian adults (45), and that habitual active transport reduces the bear upon of Telly time on body mass index (40). Having identified these relationships, our programme is now broadening the evidence base through research with other populations. New studies include work with the large population-based dataset from the NHANES from the Usa, examining potential racial and ethnic differences in the relationships of full sedentary time and breaks in sedentary time with cardio-metabolic biomarkers. We have demonstrated significant associations of TV time with excess trunk weight among high school students in regional red china (52). In the context of the rapid economic development and increasing urbanisation amongst the populations of many developing countries, documenting the health consequences of reductions in physical activeness and increases sedentary time will be crucial for informing preventive-wellness measures.

Studies with high-adventure groups are as well required. For example, nosotros examined accelerometer-derived concrete activeness, sedentary time and obesity in chest cancer survivors, showing physical action to exist protective, but no deleterious relationship for sedentary time (28). Significant prospective relationships of TV fourth dimension with weight gain over 3 years were identified in a large, population-based cohort of Australian colorectal-cancer survivors (48). More such etiologic research is needed, to examine potential relationships between besides much sitting and the development of other diseases that have been linked to metabolic risk factors.

For the 2nd phase of the behavioral epidemiology framework (measurement; see Fig. 4), there is the need to identify the reliability and validity of self-report instruments (6). Population-based descriptive epidemiology studies using high-quality measures are needed. For example, we have shown that Australian adults with lower levels of educational attainment and living in rural areas our more likely to be in the highest TV time categories (7). We have also demonstrated that, for Australian women, being in the college categories of TV time can be associated with a broader pattern of leisure-time sedentary behavior and being less likely to come across physical activity recommendations (39). Using American Cancer Gild data from a big population-based written report, we identified clusters of adults in the iv hours or more category of Idiot box fourth dimension who are less-educated, obese, and snack while watching TV (26).

Studies have begun to place the environmental correlates of sedentary behavior, and initial findings appear puzzling. Among urban Australians, lower levels of objectively-assessed neighborhood walkability (poorly connected streets, low levels of residential density, and limited access to destinations) were found to be associated with higher Tv set fourth dimension in women (41). However, a recent report in the city of Ghent, Belgium showed college levels of walkability to be associated with higher amounts of accelerometer-assessed sedentary time (46). These plainly contradictory outcomes require farther research investigation. Such findings accept potential implications for the emerging area of research on built environment/obesity relationships, inside which sedentary behavior is probable to have a significant function (30).

Inquiry on sedentary behaviors also needs to be extended beyond the promising initial studies of Idiot box time, to understand the potential health consequences of other mutual sedentary behaviors. Evidence on the metabolic correlates of prolonged sitting in motor vehicles would be particularly informative, in the light of contempo evidence on relationships with premature mortality (47). The social and ecology attributes associated with high levels of fourth dimension spent sitting in automobiles also need to be identified.

The highest priority for the sedentary behavior inquiry calendar is to gather new evidence from prospective studies, human experimental work and intervention trials. There is the detail need to build on the promising findings on relationships of sedentary time — overall sitting time, Idiot box time and fourth dimension sitting in automobiles — with premature bloodshed (ix, 25, 47). Controlled experimental studies with humans should too exist peculiarly informative. For example, nosotros are currently conducting a laboratory written report experimentally manipulating different "sedentary break" weather condition, and examining associated changes in cardio-metabolic biomarkers (focusing on triglycerides, glucose and insulin).

Field studies are too needed on the feasibility and acceptability of reducing and breaking upwards occupational, transit and domestic sedentary time. For example, in a weight-command intervention trial for adults with type ii diabetes, we are testing the touch on of a sedentary behavior reduction intervention module and examining behavioral and biomarker changes associated with reducing and breaking upwards sedentary time. At that place are multiple enquiry opportunities that explored through integrating sedentary behavior modify intervention into physical activity trials. When accelerometer data are gathered from such studies, sedentary time measures tin be derived (21, 22, 24), and unique hypotheses may readily be tested. It is imperative that the field now moves to obtain such show through intervention trials, which will have the scientific discipline beyond the inherent logical limitations of cross-exclusive evidence.

Eleven Research Questions for a Science of Sedentary Behavior

1. Tin can further prospective studies examining incident disease outcomes ostend the initial sedentary behavior/mortality findings?

2. Tin can sedentary beliefs/disease relationships exist identified through re-analyses of established prospective epidemiological data sets, by treating sitting time as a singled-out exposure variable?

3. What are the most valid and reliable self-report and objective measures of sitting time for epidemiological, genetic, behavioural, and population-health studies?

4. Are the TV-time-biomarker relationships for women pointing to important biological and/or behavioral gender differences?

5. What amounts and intensities of action might be protective, in the context of prolonged sitting fourth dimension?

6. What genetic variations might underlie predispositions to sit, and greater susceptibility to the adverse metabolic correlates?

7. What is the feasibility of reducing and/or breaking up prolonged sitting fourth dimension, for dissimilar groups (older, younger) in different settings (workplace, domestic, transit)?

8. If intervention trials testify significant changes in sitting time, are there improvements in the relevant biomarkers?

9. What are the environmental determinants of prolonged sitting time in dissimilar contexts (neighborhood, workplace, at home)?

10. What tin exist learned from the sitting time and sedentary time indices in congenital-environment/physical action studies?

11. Can evidence on behavioral, adiposity, and other biomarker changes be gathered from "natural experiments" (for case, the introduction of height-adjustable workstations or new community transportation infrastructure)?

PRACTICAL AND POLICY IMPLICATIONS OF A Science OF SEDENTARY Beliefs

Practical and policy approaches to addressing besides much sitting as a population-health issue would involve innovations on multiple levels. For example, public data campaigns might emphasize reducing sitting time likewise as increasing physical action. There might be more than widespread use of innovative technologies that can provide more opportunities to reduce sitting fourth dimension (for example, summit-adjustable desks) or new regulations in workplaces to reduce or break-upward extended periods of job-related sitting. Agile ship modes could be promoted not merely as opportunities for walking, but also as alternatives to the prolonged periods of time that many people spend sitting in automobiles. Providing non-sitting alternatives at community entertainment venues or events might also be considered. If prove on the deleterious health touch of too much sitting continues to accrue every bit we predict, and if such innovations are implemented, there volition exist the demand for systematic evaluations, especially of approaches that accept the potential for broader dissemination.

Anecdotally, the recent experience in Commonwealth of australia has been that initiatives in the final phase of the behavioral epidemiology framework ("using the relevant evidence to inform public-wellness guidelines and policy") have already begun. This is happening largely on the basis of the first-stage show presented in Figure iv ("identifying relationships of sedentary behavior with health outcomes"). For example, the Australian National Preventative Health Task Force Report includes explicit recommendations to address prolonged sitting in the workplace in the context of reducing the burden of overweight and obesity, type 2 diabetes and cardiovascular affliction. The Western Australian state division of the Heart Foundation included reducing sitting time in a 2009 state-broad mass media campaigns for obesity prevention. In the state of Queensland, Health Promotion Queensland (a cross-departmental body) commissioned an show-based review in 2009 on health impacts and interventions to reduce workplace sitting, with view to time to come practical initiatives. Thus, in that location are growing expectations in Commonwealth of australia that likewise much sitting is a real and substantial risk to health. However, it remains to exist seen whether the science of sedentary behavior will deliver consistent new findings in all of the enquiry areas that are needed to inform such innovations (see Fig. iv).

Given the consistency of research findings reported thus far on sedentary behavior and health, we expect that in the near future there volition be a stronger trunk of confirmatory evidence from prospective studies and intervention trials. Furthermore, we predict that the next iteration of the Physical Activity and Public Health recommendations of ACSM/AHA will include a statement on the wellness benefits of reducing and breaking up prolonged sitting fourth dimension.

Acknowledgments

Funding Disclosure: Owen is supported by a Queensland Health Core Inquiry Infrastructure grant and by National Health and Medical Research Council Plan Grant funding (#301200; #569940). Healy is supported past a NHMRC (#569861)/National Middle Foundation of Commonwealth of australia (PH 08B 3905) Postdoctoral Fellowship. Dunstan is supported past a Victorian Health Promotion Foundation Public Health Inquiry Fellowship.

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Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3404815/

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