A step-defined sedentary lifestyle index: <5000 steps/day
Publication: Applied Physiology, Nutrition, and Metabolism
8 November 2012
Abstract
Step counting (using pedometers or accelerometers) is widely accepted by researchers, practitioners, and the general public. Given the mounting evidence of the link between low steps/day and time spent in sedentary behaviours, how few steps/day some populations actually perform, and the growing interest in the potentially deleterious effects of excessive sedentary behaviours on health, an emerging question is “How many steps/day are too few?” This review examines the utility, appropriateness, and limitations of using a reoccurring candidate for a step-defined sedentary lifestyle index: <5000 steps/day. Adults taking <5000 steps/day are more likely to have a lower household income and be female, older, of African-American vs. European-American heritage, a current vs. never smoker, and (or) living with chronic disease and (or) disability. Little is known about how contextual factors (e.g., built environment) foster such low levels of step-defined physical activity. Unfavorable indicators of body composition and cardiometabolic risk have been consistently associated with taking <5000 steps/day. The acute transition (3–14 days) of healthy active young people from higher (>10 000) to lower (<5000 or as low as 1500) daily step counts induces reduced insulin sensitivity and glycemic control, increased adiposity, and other negative changes in health parameters. Although few alternative values have been considered, the continued use of <5000 steps/day as a step-defined sedentary lifestyle index for adults is appropriate for researchers and practitioners and for communicating with the general public. There is little evidence to advocate any specific value indicative of a step-defined sedentary lifestyle index in children and adolescents.
Résumé
Le comptage du nombre de foulées au moyen de podomètre ou d'accéléromètre est une approche largement répandue auprès des chercheurs, des praticiens et du public en général. La documentation disponible révèle de plus en plus un lien entre le faible nombre de foulées effectuées par jour et le temps consacré à des comportements sédentaires et entre le peu de foulées réalisées par jour par certaines populations et le souci grandissant des effets nuisibles des comportements sédentaires excessifs sur la santé; on peut donc se poser la question suivante: « Quel est le minimum de foulées à effectuer dans une journée pour le qualifier de trop peu? » Cette analyse documentaire se penche sur l'utilité, l'à-propos et les limites d'une norme refaisant surface et définissant un mode de vie sédentaire par le nombre de foulées, soit <5000 foulées par jour. Les adultes effectuant <5000 foulées par jour ont vraisemblablement un plus faible revenu familial, sont des femmes, d'un âge avancé, appartenant au groupe ethnique afro-américain (comparativement au groupe euraméricain), aux habitudes de tabac (comparativement à des personnes n'ayant jamais fumé) et/ou présentant une maladie chronique et/ou une incapacité. On sait peu de choses au sujet des facteurs contextuels (p. ex., environnement construit) conditionnant un niveau si faible de pratique de l'activité physique. La composition corporelle et le risque cardiométabolique font partie des facteurs défavorables associés à la réalisation de <5000 foulées par jour. Le passage rapide (3–14 jours) des jeunes personnes actives et en bonne santé de >10 000 foulées par jour à <5000 foulées et même 1500 foulées cause la diminution de la sensibilité à l'insuline et du contrôle glycémique, l'augmentation de l'adiposité et entraîne des modifications nuisibles sur le plan de la santé. Même s'il y a eu quelques autres valeurs suggérées par le passé, l'utilisation de <5000 foulées par jour comme norme pour définir le seuil du comportement sédentaire chez des adultes s'avère justifiée pour les chercheurs, les praticiens et l'information du public en général. Il y a peu de données probantes pour définir en termes de foulées un seuil de comportement sédentaire chez des enfants et des adolescents.
Introduction
Step counting (using pedometers or accelerometers) is widely accepted by researchers, practitioners, and the general public alike for assessing, tracking, and communicating physical activity doses. For example, researchers recently reported 5-year changes in body mass index (BMI), waist-to-hip-ratio, and insulin sensitivity related to 1000-step incremental changes in step-defined physical activity (Dwyer et al. 2011); a practice-based journal published a unique collection of articles largely focused on step-counting applications in a variety of special populations (Bassett and John 2010; Bradley et al. 2010; Gardner et al. 2010; Jakicic et al. 2010; Lutes and Steinbaugh 2010; Motl and Sandroff 2010; Richardson 2010; Rogers 2010; Shephard and Aoyagi 2010; Temple 2010; Tully and Tudor-Locke 2010); and government–agency–professional organizations from around the world have published different step-based recommendations (Tudor-Locke et al. 2011h). This widespread adoption and practice of step counting provides a unique opportunity for bridging research to clinical practice and ultimately to real-world application because it allows a range of users to communicate using the same metric that captures an objective measure of ambulatory activity accumulated throughout the day. To further facilitate this communication, the purpose of this review is to present the rationale, utility, appropriateness, and limitations of a “step-defined sedentary lifestyle index”. The content reflects our collective understanding of the ever-increasing scope and nature of the step-based literature; specific articles are cited to support arguments and offer examples.
Why ambulatory activity?
Although there are other types of movements in the human behavioural repertoire, it is logical to focus on assessing and promoting ambulatory activity. Relatively few (or no) steps are accumulated during sedentary behaviours (Tudor-Locke et al. 2009a; Wong et al. 2011), and relatively more steps/min are accumulated during increasingly intense ambulatory activity (Abel et al. 2011; Beets et al. 2010b; Marshall et al. 2009; Rowe et al. 2011; Tudor-Locke et al. 2005), with the highest rates of accumulation occurring during performance of moderate-to-vigorous physical activity (MVPA) (Abel et al. 2011; Beets et al. 2010b; Marshall et al. 2009; Rowe et al. 2011; Tudor-Locke et al. 2005). The relationship between accelerometer-determined activity counts/day and steps/day is strong (r2 = 0.87) (Tudor-Locke et al. 2011a). Steps/day explains approximately 62% (women) to 67% (men) of the daily variability in time spent in MVPA (Tudor-Locke et al. 2011a). Further, attaining approximately 7000–8000 steps/day is a reasonable approximation of also obtaining at least 30 min/day of MVPA (or at least 150 min/week) (Tudor-Locke et al. 2011d). Attainment of at least 7000 steps/day is listed among the most recent evidence-based exercise recommendations issued by the American College of Sport Medicine (Garber et al. 2011).
Can steps/day be used to indirectly estimate sedentary time?
Low step counts also imply that individuals have spent more time in sedentary behaviour. This approach to estimating time spent in sedentary behaviour from a relative lack of movement is the same concept used in accelerometry; a relatively low accelerometer activity count/min (e.g., <100) is typically used to define time spent in sedentary behaviours (Matthews et al. 2008). On a daily basis, participants who took <5000 steps/day in the accelerometer-monitoring component of the 2005–2006 National Health and Nutrition Examination Survey (NHANES) averaged 522 to 577 min/day in sedentary behaviours, compared with 348 to 412 min/day in those who took ≥10 000 steps/day, translating to a 2.75 to 2.9 h/day difference in sedentary behaviours associated with these different categories of step-defined physical activity (Tudor-Locke et al. 2011a). Twenty-five percent of the variability in time (i.e., minutes) spent in daily sedentary behaviours as collected in these NHANES data is explained by a simple count of steps/day (Tudor-Locke et al. 2011a). Although this explanatory power may appear to be low when compared with the stark differences in time estimates presented previously, it is important to clarify that a single minute of “sedentary activity” (defined by Wong et al. (2011) as a minute in which zero steps are taken, which they considered the “criterion measure” of this classification) is a missed opportunity to accumulate any number of steps taken between 1 and ≥120 steps/min (Tudor-Locke et al. 2011e).
It may be more meaningful to look beyond cross-sectional associations and examine the effects of changes in steps/day on time spent in sedentary behaviours. Gilson et al. (2009) did not show changes in self-reported sitting time at work with pedometer-enabled walking strategies; however, the intervention was confined to working hours only (which may have had limited success), and the method of assessing time was likely not sensitive to potential real changes in behaviour. De Cocker et al. (2008) evaluated changes in self-reported sitting time by participants engaged in a pedometer-based community intervention focused on increasing steps/day. In 254 participants who increased their steps/day, an increase of 2840 steps/day was associated with a self-reported decrease of 18 min/day in sitting time (both changes were statistically significant). De Greef et al. (2010) documented an increase of 2502 steps/day in 20 individuals with type 2 diabetes with a pedometer-based intervention that also produced a >1 h decrease in accelerometer-determined sedentary behaviour (again, both changes were statistically significant). In another pedometer-based intervention study, of 92 individuals with type 2 diabetes, De Greef et al. (2011) reported a significant increase of 2744 steps/day and a decrease in accelerometer-determined sedentary behaviour of 23 min/day. Finally, Mikus et al. (2012) recruited young adult volunteers who habitually took >10 000 steps/day and instructed them to temporarily reduce their activity to <5000 steps/day based on self-monitored pedometer feedback. Concurrent accelerometer monitoring during this transition captured an average 2.5 h increase in sitting time (from 593 min/day to 745 min/day). Although the difference was not statistically significant (the sample size of 12 participants was not powered to evaluate this specific outcome), few would suggest that a 2.5 h/day increase in sitting time is an unremarkable change. Combining the results from the studies using objective monitoring, one would expect an increase of 2500 steps/day to be associated with a 37–45 min/day reduction in sedentary behaviour.
How many steps/day are too few?
Recently, a series of papers have explored the question, “How many steps are enough?” in terms of a step-based translation of current public health physical activity guidelines (Tudor-Locke et al. 2011f, 2011g, 2011h), which have focused historically on engagement in activities that are of at least moderate intensity. Although recent public health guidelines in the United States continue to emphasize the benefits of time spent in MVPA, they also acknowledge that some activity is better than none (regardless of any intensity criterion), even while encouraging that more is better (Physical Activity Guidelines Advisory Committee 2008). The Canadian Physical Activity Guidelines produced by the Canadian Society of Exercise Physiology (CSEP) (Tremblay et al. 2011b) focus on the health benefits of MVPA; however, they also state that for adults and older adults “who are physically inactive, doing amounts below the recommended levels can provide some health benefits”. At the same time, interest continues to grow in the independent and potentially deleterious health effects of excessive time spent in sedentary behaviours (Katzmarzyk 2010; Katzmarzyk et al. 2009). CSEP's recent Sedentary Behaviour Guidelines for children and adolescents advocate sitting less (Tremblay et al. 2011a, 2012). The accompanying CSEP-endorsed press release clearly interpreted this as an opportunity to move more: “the majority of sedentary time can be replaced with light intensity activity and this can be done in a variety of ways” (CSEP 2011). Given that steps/day explain a large part of time spent in light- and moderate-intensity activities (Tudor-Locke et al. 2011a) and that there is an inverse relationship between accumulation of daily steps and time spent in sedentary behaviours, it has been suggested that asking, “How many steps are too few?” may be a more relevant public health question, especially given the mounting evidence of just how little physical activity some populations actually perform (Tudor-Locke et al. 2011h).
Tudor-Locke and colleagues (2001) first suggested that taking <5000 steps/day might be a useful metric indicative of a “sedentary lifestyle index”. In that study, they examined the distribution of BMI-defined weight status categories across step-defined physical activity in approximately 100 adults. They observed that individuals taking <5000 steps/day were more frequently classified as obese compared with all other BMI-defined weight status categories. Subsequently, Tudor-Locke and Bassett (2004) used 5000 steps/day as the anchor for their proposed graduated step index, which included <5000 (labelled “sedentary”), 5000–7499 (“low active”), 7500–9999 (“somewhat active”), 10 000–12 499 (“active”), and ≥12 500 (“highly active”) steps/day. The researchers used <5000 steps/day as a “sedentary lifestyle” indicator again in 2008 (Tudor-Locke et al. 2008b). In 2009, Tudor-Locke et al. (2009a) suggested additional subcategories below this very broad category capped by 5000 steps/day and labelled them “basal activity” (<2500 steps/day) and “limited activity” (2500–4999 steps/day).
Terminology
When the term “sedentary lifestyle index” was first proposed (Tudor-Locke et al. 2001), it was appropriate, given the state of knowledge at that time. The sedentary behaviour research field has grown substantially and rapidly since then, and the explosion of work focusing on this low end of the movement spectrum has inevitably led to debate regarding terminology. Specifically, recent calls for standardized use of the terms “sedentary” and “sedentary behaviours” (Sedentary Behaviour Research Network 2012) have made more complex the idea of using any number of steps/day to define a “sedentary lifestyle index”. What follows is the case to retain the original terminology applied to a step-based index.
Caspersen et al. (1985) first clarified the terms “physical activity” (“any bodily movement produced by the skeletal muscles that results in energy expenditure”) and “exercise” (“a subset of physical activity that is planned, structured, and repetitive and has as a final or intermediate objective the improvement or maintenance of physical fitness”). In 2000, Owen et al. (2000) called for a shift in traditional approaches to studying exercise and sport and introduced the concept of studying sedentary behaviour as distinct from physical activity. They defined sedentary behaviours in terms of “low levels of energy expenditure”, specifically those activities that expend energy at 1.0–1.5 metabolic equivalent units (METs), one MET being the energy cost of resting quietly, or 3.5 mL of oxygen uptake per kilogram of body weight per minute. Pate et al. (2008) echoed this MET-based definition of sedentary behaviour in 2008. Hamilton et al. (2007) emphasized that the study of “acute and chronic physiological effects of sedentary behaviors” should include the study of “nonexercise activity deficiency”. Thus, these pioneering researchers recognized that the effects of sedentary behaviour might extend beyond its impact on energy expenditure only and included in their definition a focus on relative lack of movement (which they termed “nonexercise activity” or, elsewhere in the manuscript, “nonexercise physical activity”).
Tremblay et al. (2010) assembled terms they believed important to describing and measuring sedentary behaviour in their 2010 publication. They defined “sedentary” as “characterized by little physical movement and low energy expenditure”. Further, “sedentarism” was defined as “extended engagement in behaviours characterized by minimal movement, low energy expenditure, and rest”. To be clear, both definitions recognized the relative lack of physical movement associated with sedentary behaviours. In contrast with the broader definition of “physical activity” advocated by Caspersen et al. (1985), Tremblay et al. (2010) specifically defined “physical activity” as “activities of at least moderate intensity”. In addition, these authors defined “physically active” as “meeting established guidelines for physical activity (usually reflected in achieving a threshold number of minutes of moderate to vigorous physical activity per day)”. They also clarified “physical inactivity” as “the absence of physical activity: usually reflected as the amount or proportion of time not engaged in physical activity of some predetermined intensity”. Because they had defined “physically active” in terms of MVPA attainment, it followed that the subsequently listed definition of “physical inactivity” also referred to this specific intensity. The authors specifically argued against using the term “sedentary” to indicate “the absence of MVPA”. Owen et al. (2010) also stated that “it is our contention that sedentary behaviour is not simply the absence of moderate-to-vigorous physical activity”. They also summarized objectively assessed sedentary behaviour from the AusDiab findings (Healy et al. 2007; Healy et al. 2008) and concluded
As logically would be expected, sedentary time and light-intensity activity time were highly negatively correlated (r = –0.96): more time spent in light-intensity activity is associated with less time spent sedentary. This suggests that it may be a feasible approach to promote light intensity activities as a way of ameliorating the deleterious health 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 light-intensity activity has an inverse linear relationship with a number of cardio-metabolic biomarkers.
Although the term “sedentary time” has been used interchangeably with “sitting” (Healy et al. 2011), examples of postures that expend <1.5 METs include lying down–reclining, standing still (e.g., standing quietly, standing in line, Compendium Code 07040), and sitting behaviours (Ainsworth et al. 2011). A number of original references catalogued in the 2011 Compendium on-line resources (located at https://sites.google.com/site/compendiumofphysicalactivities/) report that standing behaviours expend <1.5 METs; 2 recent examples include Levine et al. (2000) (average, 1.1 METs) and Crouter et al. (2006) (average, 1.19 METs). More recently, however, Owen et al. (2011) explicitly defined sedentary behaviours as “sitting without being otherwise active”. Researchers expressly interested in sitting behaviours are able to more precisely assess such postures using inclinometers (Kozey-Keadle et al. 2011).
Sedentary behaviour has also been defined by a relatively low accumulation of accelerometer-determined activity counts/min. Specifically, Matthews et al. (2008) wrote about defining sedentary behaviour in their well-known, descriptive epidemiology paper based on data from the United States: “Activity counts recorded while sitting and working at a desk are very low (≤50 counts/min), and counts recorded while driving an automobile are typically below 100 counts/min (unpublished observations)”. Since that time, 100 counts/min has been used routinely to define sedentary behaviours from accelerometer data (Tudor-Locke et al. 2012). Crouter et al. (2006) reported that standing averaged 13.4 activity counts/min and filing averaged 59.8 activity counts/min, so it is apparent that these types of activities would also be classified as “sedentary behaviours” by this activity count/min definition. Regardless, the use of the terms “sedentary behaviours” and “sedentary time” attempt to capture time allocation to specific types of behaviours (at any particular point in time or accumulated over a specified period of time) and are defined by relatively low rates of energy expenditure, posture, or relatively low accumulated activity counts/min.
Because time spent in such behaviours appears to be ubiquitously high in population-level data (Matthews et al. 2008), an index is needed to help classify what is potentially excessive in terms of habitual daily behaviour (i.e., an index of lifestyle in contrast to a measured behaviour captured at any particular point in time or accumulated duration of time). For example, a joint report of the Food and Agriculture Organization of the United Nations (FAO), the World Health Organization (WHO), and the United Nations University (UNU) (FAO/WHO/UNU 2001) uses the ratio of total energy expenditure to basal metabolic rate to estimate “physical activity level” or PAL, and then defines “sedentary or light activity lifestyle” as a PAL of 1.40–1.69 (the lower end of the range implies a sedentary lifestyle and the upper end implies a light-activity lifestyle). Because direct measures of energy expenditure are less accessible to many practitioners and the general public, it is rational to attempt to provide a reasonable sedentary lifestyle index using more available instrumentation (e.g., step-counting devices). Specifically, objectively determined PAL (using multisensory armband accelerometer technology) is the strongest individual-level predictor of all-cause mortality in patients with chronic obstructive pulmonary disease (COPD) (Waschki et al. 2011), and <4580 steps/day has been identified as the best cut-point for predicting a “sedentary” PAL of <1.40 in this population (DePew et al. 2012 ). Just as METs are to PAL (i.e., metabolic cost of behaviours captured at any particular point in time vs. lifestyle indicators of energy expenditure), steps/min are to steps/day. A cadence of 100 steps/min has been associated consistently with an absolute definition of moderate intensity (i.e., 3 METs) (Abel et al. 2011; Beets et al. 2010b; Marshall et al. 2009; Rowe et al. 2011; Tudor-Locke et al. 2005), and zero steps/min is considered to be the “criterion measure” of “sedentary activity” (Wong et al. 2011). A low level of PAL is indicative of a sedentary lifestyle (FAO, WHO, and UNU 2001), and a low level of steps/day should likewise be interpreted as a sedentary lifestyle if some degree of consistency is to be maintained. Although we considered alternative terminology, the continued use of “sedentary lifestyle index” applied to a low-level step-defined threshold is harmonious with the use of the term “sedentary lifestyle” defined by relatively low levels of daily energy expenditure as previously established by the FAO, WHO, and UNU. Further, as presented in the following sections, it has already been applied consistently in a growing number of studies, and to relabel it now would only add to the confusion.
To ease communication, we offer a simple schematic (Fig. 1) to graphically present the combined application of these various definitions in defense of a “step-defined sedentary lifestyle index”. Because we have demonstrated that NHANES participants who accumulate 7000 to 8000 steps/day meet MVPA guidelines (Tudor-Locke et al. 2011d), we have set the “physically active lifestyle” threshold at 7500 steps/day. This is also congruent with an international review of steps/day values associated with attainment of public health recommendations of time in MVPA (Tudor-Locke et al. 2011h). Because the FAO, WHO, and UNU (2001) consider a “light activity lifestyle” to be relatively more active than a “sedentary lifestyle”, and others have persuasively argued that the term “inactive” should be reserved specifically for nonattainment of MVPA recommendations (Owen et al. 2010; Tremblay et al. 2010) (indeed, a letter has been written urging journal editors and reviewers to oversee this appropriate use (Sedentary Behaviour Research Network 2012)), we consider “physical inactivity” to refer to the spectrum of behaviour below the MVPA recommendation and have assigned the term “low active lifestyle” (terminology selected in keeping with previous recommendations (Tudor-Locke and Bassett 2004; Tudor-Locke et al. 2008b)) to fall immediately below this MVPA-associated threshold (i.e., 5000 to 7499 steps/day) but above the “sedentary lifestyle” (i.e., <5000 steps/day). Finally, because previous esteemed researchers have (i) recognized that the study of sedentary behaviours includes “nonexercise activity deficiency” (Hamilton et al. 2007), (ii) acknowledged that more time in “light-intensity activity” is strongly associated with less time in sedentary behaviours (Healy et al. 2007, 2008; Owen et al. 2010), and (iii) characterized “sedentarism” (Tremblay et al. 2010) as minimal movement and low energy expenditure, we remain resolute in identifying a steps/day value that could be used as a “sedentary lifestyle index”. An “index” is considered to be a guide, an indicator, a sign, or a pointer, and we wish to emphasize that this is a “step-defined sedentary lifestyle index”. In much the same way, others have offered a “PAL-defined sedentary lifestyle index” (FAO/WHO/UNU 2001). In the future, still others may offer a “posture-defined sedentary lifestyle index”, and so on. Finally, we believe that the use of “sedentary lifestyle” does not detract from the continued use of “sedentary behaviour” to define behaviours captured at any particular point in time (or the accumulation of time spent in such behaviours) and defined by a relative lack of energy expenditure, a seated posture, or relatively low accumulated activity counts/min.
Fig. 1.
Utility, appropriateness, and limitations of <5000 steps/day
Semantics aside, the purpose of this review is not only to present the rationale, but also to examine and update the utility, appropriateness, and limitations of using the originally proposed cut-point of <5000 steps/day as a step-defined sedentary lifestyle index. The need for this selective focus is evident from the simple fact that there are few other contenders at this time, as is presented in more detail later. The remainder of the article is organized into the following sections, categorized according to emergent themes identified in the step-based literature: (i) studies reporting sample proportions taking <5000 steps/day, (ii) characteristics of people taking <5000 steps/day, (iii) contextual factors that can limit accumulation of step-defined physical activity to values of <5000 steps/day, (iv) health risks associated with taking <5000 steps/day, (v) health effects of increasing physical activity levels from <5000 steps/day to >5000 steps/day, (vi) health effects of reducing physical activity levels to <5000 steps/day, (vii) alternative step-based definitions for a sedentary lifestyle index, (viii) relevance to children and adolescents, and (ix) limitations to this approach. Throughout, we distinguish the terminology used in original research studies by using quotation marks (e.g., “sedentary”).
Prevalence of taking <5000 steps/day
The descriptive epidemiology of various steps/day cut-points has been compiled previously (Tudor-Locke et al. 2011h) but is reassembled, updated, and extended here to focus on 25 studies that included a specific report of the proportion of the study sample taking <5000 steps/day (Table 1). Only one (with the largest, most inclusive sample reported) of the related Cook and colleagues' papers (Cook et al. 2010a, 2010b, 2011) of rural black South Africans taking <5000 steps/day is presented in the table. Proportions classified by this step-defined sedentary lifestyle index ranged from 2% in a small sample of male university students in the United States (Mestek et al. 2008) and <5% in a male South African sample (Cook et al. 2010b) and also in a Czech Republic sample (Sigmundova et al. 2011) to 56% in an American sample of multiethnic, low-income housing residents 18 to ≥70 years of age (Bennett et al. 2006), 71% in a small sample of African-American Medicaid recipients aged 31–63 years (Panton et al. 2007), and 76% in overweight–obese individuals recruited to a physical activity intervention to promote weight maintenance following a behavioural and weight-loss program (Villanova et al. 2006). Because at least 8 analyses of the 2005–2006 NHANES accelerometer step data (adjusted to become more in line with a pedometer scaling) have also focused on <5000 steps/day as at least one studied step-based cut-point (Sisson et al. 2010, 2012; Tudor-Locke et al. 2009a, 2010b, 2011a, 2011b, 2011d; Yang et al. 2011), the table includes only the study with the most inclusive (i.e., largest) sample from the original data source that also specifically reported the weighted proportion classified as taking <5000 steps/day (Sisson et al. 2012). Accordingly, this nationally representative adult sample indicated that 36.1% of adults in the United States took <5000 steps/day. In a separate analysis of these NHANES data, it appears that approximately 17% of the American population takes <2500 steps/day (considered indicative of “basal activity”) (Tudor-Locke et al. 2009a).
Table 1.
Note: CDAHS, Childhood Determinants of Health Study; TOACS, Tasmanian Older Adult Cohort study.
∗
Inconsistencies in presentation of instrument brand–model details reflect underlying reporting inconsistencies in original articles.
Not included in this table are 2 studies that reported number of days of <5000 steps/day in monitored samples. Analyses performed on 8197 person-days of data collected over a year-long study of 23 participants from 2 universities in the southern United States (Tudor-Locke et al. 2004c) indicated that 15.9% of all person-days were <5000 steps/day, whereas the sample mean was 10 082 ± 3319 steps/day. Only a single individual's values from this small and ostensibly healthy sample averaged <5000 steps/day over the course of the year. Finally, Barreira et al. (2012b) collected 93 person-days of pedometer-determined data from 23 overweight–obese individuals. The sample average was 8025 ± 3967 steps/day, and 25% of all person-days were <5000 steps/day.
Characteristics of people taking <5000 steps/day
Sisson et al. (2012) reported that adults in the United States taking <5000 steps/day were more likely to have a relatively lower household income and be female, older, of African-American vs. European-American heritage, and a current vs. never smoker. Hornbuckle et al. (2005) also reported significant age differences between those taking <5000 steps/day (relatively older) and those taking ≥7500 steps/day (relatively younger). The lowest reported mean pedometer-determined physical activity reported in a review of expected values for older adults was 2015 steps/day in a sample of ≥85-year-olds (Croteau and Richeson 2005). More recently, a value of 12 727 ± 9387 steps/week (translating to 1818 steps/day) was reported for a sample of older African-American women (73.3 ± 9.6 years) engaged in a faith-based intervention (Duru et al. 2010). A review of cross-sectional studies of individuals living with heart and vascular diseases, COPD, dialysis, arthritis, joint replacement, fibromyalgia, and physical disability indicates that all average <5000 steps/day (Tudor-Locke et al. 2009b). Recent additions to this body of research indicate that patients with COPD average 3826 (DePew et al. 2012) to 5680 steps/day (Moy et al. 2012), those with diabetes (without mobility limitations) average 6429 steps/day (van Sloten et al. 2011), and those undergoing total joint arthroplasty average 6721 steps/day (Naal and Impellizzeri 2010). Even in these samples showing average values somewhat greater than 5000 steps/day, lower values were associated with compromised health-related outcomes (Moy et al. 2012; van Sloten et al. 2011).
In a recent review of pedometer-based physical activity interventions for older adults (aged ≥65 years) (Tudor-Locke et al. 2011g), 10 of 12 studies identified reported baseline values of <5000 steps/day, and only 3 of those studies with samples averaging <5000 steps/day at baseline were able to elicit a level of increase that put the average over 5000 steps/day after intervention. Pedometer-based intervention studies conducted in special populations were included in the same review (Tudor-Locke et al. 2011g). Baseline values were <5000 steps/day for 2 of 9 cancer–cancer survivor studies identified, one of 3 COPD studies, zero of 2 coronary heart disease and related disorder studies, 4 of 15 diabetes and related disorder studies, and 3 of 3 joint and muscle disorder studies. It appears that not all these interventions were focused on recruiting sedentary individuals, at least as defined by taking <5000 steps/day at baseline.
Finally, morbidly obese individuals have been shown to take, on average, <5000 steps/day (Damschroder et al. 2010; Duru et al. 2010; Maraki et al. 2011). For instance, Vanhecke et al. (2008) reported that 10 morbidly obese (BMI = 53.6 ± 11.7) individuals averaged 3763 ± 2223 steps/day.
Contextual factors related to <5000 steps/day
Contextual factors that shape sedentary behaviour and physical inactivity include social, natural, or built environments and organizational or situational factors (Spence and Lee 2003). The built environment is associated with sedentary behaviour in both children (Timperio et al. 2012) and adults (Kozo et al. 2012; Sugiyama et al. 2007). Lower steps/day are also associated with inaccessible and (or) a lack of destinations in children (McCormack et al. 2011a), adults (Kondo et al. 2009), and older adults (King et al. 2003). A negative perception of neighbourhood environment is associated with lower steps/day in older adults (Oka and Shibata 2012). Further, mode of transport influences steps/day: Wener and Evans (2007) reported that car commuters took 30% fewer steps/day than did those who commuted by train. Van Dyck et al. (2009) showed that residents of low-walkable neighbourhoods took fewer steps/day and also walked less frequently for transportation in their neighbourhood. As well, Bennett et al. (2007) reported that steps/day were positively associated with perceived night-time safety; thus, those with the greatest safety concerns also took the fewest steps/day. Despite these accumulating reports, few studies have directly examined the effects of these contextual factors on taking <5000 steps/day. Perhaps most illuminating, however, is a study examining the differences in pedometer-determined physical activity of an unconfined submarine crew stationed on land vs. deployed to sea and engaged in structured tasks conducted in a confined and crowded space; 109 crew members from 2 submarines averaged approximately 7000 steps/day while stationed on land, and this was reduced to approximately 2000 steps/day when deployed (Choi et al. 2010).
The weather (e.g., ambient temperature, rainfall) is another contextual factor related to pedometer-determined physical activity (Chan et al. 2006; Duncan et al. 2008). Specifically, Dasgupta et al. (2010) demonstrated that average step-defined physical activity dips to <5000 steps/day in fall–winter in individuals with type 2 diabetes living in Montreal, Canada. Similarly, daily steps in a sample of older adults (aged 75–83 years) decreased to below 5000 steps/day during the winter months of December and January in Japan (Yasunaga et al. 2008). In another study, male office workers in rural Japan walked fewer steps/day in the winter compared with in the summer, and this dropped to below 5000 steps/day on nonworking days (Mitsui et al. 2010).
Health risks associated with taking <5000 steps/day
As indicated previously, Tudor-Locke and colleagues (2001) first reported that individuals in the United States taking fewer than approximately 5000 steps/day (representing the 25th percentile for distribution of steps/day in that particular sample) had a significantly higher BMI than did those categorized into 2 higher step-defined physical activity categories (between the 25th and 75th percentiles and above the 75th percentile). Cook et al. (2008) also reported the increased risk of BMI-defined obesity for South-African individuals taking <5000 steps/day compared with all other levels of step-defined physical activity. Higher BMIs in those taking <5000 steps/day have also been reported by Mitsui et al. (2008) studying a Japanese sample, Wyatt et al. (2005) in a Colorado-based sample, Hornbuckle et al. (2005) in African-American women, and Krumm et al. (2006) in a postmenopausal sample. Similarly, the odds of experiencing excessive gestational weight gain were higher in pregnant Chinese women taking <5000 steps/day (defined as “sedentary”) than in “active” women (>10 000 steps/day) in the second trimester and “somewhat active” women (7500–10 000 steps/day) in the third trimester (Jiang et al. 2012). Similar findings have been reported for percentage of body fat (Hornbuckle et al. 2005; Tudor-Locke et al. 2001) and waist circumference (Dwyer et al. 2007; Hornbuckle et al. 2005).
Schmidt et al. (2009) reported that, with the exception of younger men, individuals taking <5000 steps/day had a substantially higher prevalence of cardiometabolic risk factors (including metabolic syndrome and ≥3 elevated risk factors such as waist circumference, systolic blood pressure, and fasting glucose, triglyceride, and HDL cholesterol values) than those taking more steps/day. Sisson et al. (2010) also showed that each higher category of step-defined physical activity showed lower odds of having metabolic syndrome compared with the category defined by taking <5000 steps/day. For example, the odds were 40% lower for individuals taking 5000–9999 steps/day and 72% lower for those taking ≥10 000 steps/day compared with those taking <5000 steps/day. Recently, Jennersjo et al. (2012) reported that individuals with type 2 diabetes who took <5000 steps/day had higher BMI, waist circumference, C-reactive protein, interleukin–6, and pulse-wave velocity than did those who took ≥10 000 steps/day. Finally, McKercher et al. (2009) reported a 50% higher prevalence of depression associated with taking <5000 steps/day compared with taking ≥7500 steps/day in women, and taking ≥12 500 steps/day in men.
Effects of increasing from <5000 steps/day to >5000 steps/day
Interventions designed to move people from taking <5000 steps/day to relatively higher values have demonstrated positive health outcomes. Swartz et al. (2003) reported improved glucose tolerance with an 8-week pedometer-based walking program in 18 postmenopausal women who averaged 4491 ± 2269 steps/day at baseline and ended up averaging 9213 ± 362 steps/day. Participants in a 12-week worksite pedometer program who increased their daily steps from 4244 ± 899 to 9889 ± 1609 experienced significant decreases in body weight, BMI, and resting heart rate relative to a no-change comparison group (Musto et al. 2010). A nonsignificant increase from 4471 ± 2315 steps/day to 5257 ± 2355 steps/day among 14 obese middle-aged veterans was associated with a significant weight loss (–3.8 ± 3.6 kg) in a lifestyle-coaching intervention that included nutritional goals; therefore, the relative contribution of the change in steps/day to the weight change is unknown (Damschroder et al. 2010). Villanova et al. (2006) reported that 76% of 200 overweight–obese participants in a 9-month behaviour program took <5000 steps/day at baseline, and only 16% were below this value at the end of the program; the probability of an increased amount of weight loss was enhanced with increased steps/day. As far as we are aware, no other interventions have expressly recruited participants who took <5000 steps/day at baseline and studied the effects of attaining at least this cut-point or beyond.
Bell and colleagues (2010) compared the effectiveness of a walking program with a fitness training group and control group among “sedentary” (<5500 steps/day) individuals ranging in age from 20 to 65 years. At the end of a 6-month period, the walking group had achieved 9221 ± 1429 steps/day with the ultimate goal of averaging 10 000 steps/day. Though changes were observed in several health-related variables for all groups (even the control group) at the end of the intervention, the authors concluded the greatest reductions in body weight, waist circumference, and waist-to-hip ratio occurred in the 2 activity groups.
Finally, achieving a steps/day value of >5000 steps/day may not be completely necessary to reap at least some health benefits in those who take <2500 steps/day (considered indicative of “basal activity”(Tudor-Locke et al. 2009a)). Duru et al. (2010) studied obese African-American women who increased their physical activity by 1411 steps/day from a baseline value of 1818 steps/day as a result of a multicomponent faith-based intervention (a pedometer was used for measurement and as part of weekly pedometer competitions during the intervention, but pedometer readings were never revealed to participants). This modest improvement over seemingly very low initial baseline values was associated with a significant decrease in systolic blood pressure but no changes in body weight or diastolic blood pressure compared with a control group.
Effects of reducing to <5000 steps/day
Thyfault and Krogh-Madsen (2011) reviewed a number of recent studies that examined the health effects of recruiting relatively healthy and active subjects and temporarily transitioning them to very low values of steps/day. These studies, and a few recent additions, are described briefly here.
Seminal animal studies from Dr. Frank Booth's laboratory showed that transitioning rodents from naturally high daily activity (access to running wheels) to low activity (locking running wheels) induced fast and dramatic changes in body composition, insulin sensitivity, and tissue metabolism, suggesting that the conversion to inactivity brought about by an abrupt removal of opportunity for activity triggers potentially harmful metabolic changes in a short period of time (Kump and Booth 2005a, 2005b; Kump et al. 2006; Laye et al. 2007). These rodent studies prompted another group led by Dr. Bente Pedersen to determine if transitioning young, active, but nonexercising men to a lower daily ambulatory activity would have similar results. In the first study, Olsen et al. (2008) examined metabolic responses in 8 young men whose step-defined physical activity was reduced from a mean value of 6203 steps/day to 1394 steps/day for 22 days. Plasma insulin area under the curve (AUC), assessed by an oral glucose tolerance test, increased significantly from 757 pmol·L−1·3 h−1 to 1352 pmol·L−1·3 h−1 after 3 weeks of reduced step activity. Olsen et al. (2008) also reported a second study, conducted in 10 healthy young men transitioned from a mean activity level of 10 501 ± 808 steps/day to 1344 ± 33 steps/day for 2 weeks. Plasma insulin AUC increased significantly from 599 pmol·L−1·3 h−1 to 942 pmol·L−1·3 h−1. In addition, plasma C-peptide AUC increased significantly from 4310 pmol·L−1·3 h−1 to 5795 pmol·L−1·3 h−1. These results suggested that it took a greater insulin response to dispose of blood glucose during postprandial conditions because of reduced insulin sensitivity in skeletal muscle. The 2-week intervention was also associated with a 7% increase in intra-abdominal fat mass with no change in total fat mass, and a decrease in both total fat-free mass and BMI. Krogh-Madsen et al. (2010) analyzed additional data collected from this same sample of 10 men and confirmed that there was indeed reduced insulin sensitivity in skeletal muscle (17% reduction in the glucose infusion rate during a hyperinsulinemic-euglycemic clamp) and reduced activation of insulin signalling in biopsied skeletal muscle samples. Moreover, they reported a 7% decline in maximal oxygen consumption and a 0.5-kg decrease in leg lean mass after a 2-week decrease of about 9000–10 000 steps/day. Although <1500 steps/day is much lower than 5000 steps/day, this study shows that reducing daily ambulatory activity to such very low levels causes dramatic changes in health indices known to powerfully influence the risk of morbidity and mortality.
The same research group has performed follow-up studies to determine if reducing daily steps from >10 000 to <1500 combined with a higher calorie diet (>50% kcal) would induce greater changes in insulin sensitivity and body composition (Knudsen et al. 2012). They also performed oral glucose tolerance tests and measured body fat, visceral adiposity, and body weight at baseline and 3, 7, and 14 days after the transition to reduced steps/day to determine if a change in insulin sensitivity occurred before or after significant changes in adiposity and body weight. Insulin sensitivity, derived from an index of the glucose and insulin responses to the OGTT, was significantly reduced by 37% after only 3 days of inactivity and occurred prior to significant increases in body weight and adiposity (both whole body and visceral) that trended up at days 3 and 7 but were not significantly greater than baseline until day 14, at which time visceral adiposity had increased by 49% above baseline. Importantly, this study confirmed earlier findings that an acute transition to very low daily steps induces significant changes in insulin sensitivity and adiposity. Another interesting outcome of this study was that measures were again collected 16 days after the 2 weeks of inactivity to determine if a return to the subject's normal daily step count returned measured variables to baseline levels. Interestingly, despite insulin sensitivity returning to normal, both body weight and body fat were still elevated (visceral adiposity was not assessed), suggesting that acute periods of inactivity may lead to an incremental increase in adiposity and body weight over time.
Reduced skeletal muscle insulin sensitivity plays a fundamental role in impaired postprandial glycemic control. An increased postprandial glucose response is both a risk factor for the development of type 2 diabetes and an independent risk factor for cardiovascular disease in people with and without type 2 diabetes. A study conducted by Mikus et al. (2012) transitioned healthy, active individuals who were achieving >10 000 steps/day to <5000 steps/day for only 3 days to determine if this abrupt and temporary change in daily physical activity would modify postprandial and overall glycemic control as measured by continuous glucose monitors, devices that measure blood glucose minute-by-minute during free-living conditions. The study found that only 3 days of reduced activity led to significant increases in average glucose excursions following meals. Moreover, daily measures of glucose control, including maximal and minimal glucose levels, and the duration of time above a high threshold of euglycemia were also altered significantly. In summary, these findings suggest that making even temporary transitions to <5000 steps/day dramatically alters glycemic control and may play a fundamental role in the increased risk of diabetes and other metabolic diseases in people who chronically take <5000 steps/day.
Another research group has recently examined the combined effects of inactivity and overeating on body composition and mental health. Ernersson et al. (2010a, 2010b, 2010c) reported that young healthy individuals who adopted obesity-provoking behaviours for 4 weeks that included doubled energy intake (primarily from fast food) and taking <5000 steps/day increased their body weight (Ernersson et al. 2010a, 2010c), increased both fat-free mass and fat mass (Ernersson et al. 2010a), decreased their health-related quality of life (Ernersson et al. 2010c), and reported developing a lack of energy (related to emotional life, relations, and life habits) (Ernersson et al. 2010b). One year after this brief intervention, the body weight increase remained higher relative to a control group (Ernersson et al. 2010a). In addition, fat-free mass was unchanged relative to baseline, but the increase in fat mass remained (Ernersson et al. 2010a). This study again suggests that acute periods of inactivity and dietary excess may lead to an incremental increase in body weight that is then sustained over time. The relative contribution of the decreases in step-defined physical activity compared with the energy intake hyperalimentation was not determined.
Alternative definitions
Thompson et al. (2004) defined “inactive” as <6000 steps/day in a study of middle-aged American women. Others have also used this cut-point (Graff et al. 2012; Lara et al. 2010), with Lara and colleagues (2010) labelling it “sedentary”. Tudor-Locke et al. (2008a) defined <7500 steps/day as “inactive” in an Australian sample with a relatively high mean steps/day. This same steps/day cut-point has been labelled “sedentary” (Barbat-Artigas et al. 2012) and also “sedentary to low active” (Inoue et al. 2011b). In an intervention study conducted in a Canadian sample with type 2 diabetes, Tudor-Locke et al. (2004a) defined “insufficiently active” as <8800 steps/day for recruitment purposes based on a previous cross-sectional study of individuals with type 2 diabetes in which this level approximated the 75th percentile of distribution (Tudor-Locke et al. 2002). Oka et al. (2012) defined “insufficiently active” as <6700 steps/day (men) and <5900 steps/day (women) based on not attaining a Japanese national physical activity objective applied specifically to adults ≥70 years of age. Finally, a number of other Japanese researchers have defined “sedentary” as <4000 steps/day (Inoue et al. 2011a; Ishikawa-Takata et al. 2010; Park et al. 2007). Differences in exact steps/day values used and associated terminology reflect earlier thinking and (or) a need to accommodate study-specific and unique-sample distribution parameters. The variation in terminology between original research studies and review articles relating to what relatively low daily step values mean reinforces why the present review is so important.
There are weaknesses in using <5000 steps/day as a step-defined sedentary lifestyle index. First and foremost, the evidence supporting its use has been derived largely as a result of a “self-fulfilling prophecy”. For example, the demographic results reported by Sisson et al. (2012) likely would not have changed if alternative cut-points of 4000 or 6000 steps/day had been considered. Further, the detrimental effects of taking even fewer steps/day (e.g., <1500 steps/day) are becoming known (Knudsen et al. 2012; Krogh-Madsen et al. 2010; Olsen et al. 2008). Because <5000 steps/day has been the most common candidate for a step-defined sedentary lifestyle index presented to date, however, it gets reinforced simply by repetition. Widespread use and repetition are not evidence of veracity. Alternative thresholds might be more valid but have not been used extensively and are therefore lacking confirmation. A creative analysis would attempt to identify a specific steps/day value associated with select disease conditions or specific health parameters. This is a challenging pursuit, however, because, hypothetically, relatively (and incrementally) lower values will always be associated with increasingly negative results and relatively (and incrementally) higher values will be associated with increasingly positive results. Moreover, related changes in some health parameters may mediate or modify changes in other health parameters (i.e., waist circumference, insulin sensitivity, or blood lipids). Where the line is drawn becomes somewhat subjective against this indistinct background; there are likely to be samples with even lower steps/day values than any identified cut-point. On the other hand, the usefulness of any index is compromised if it is too low; if it is so low that few people are affected by it, then its public health relevance is limited. For example, data from the United States suggest that only approximately 17% of the population take <2500 steps/day (Tudor-Locke et al. 2009a), and we could only assume this percentage would be much lower in other, more active populations. Ultimately, validation with longitudinal data with various health outcome measures is warranted. Although it may continue to be debated, and despite its simplistic origins, the consistent use of a standardized definition of a sedentary lifestyle index as <5000 steps/day would facilitate comparisons among studies and population groups.
Relevance to children and adolescents
NHANES accelerometer data indicate that, during the monitored day, American children and adolescents (6–19 years of age) spend, on average, approximately 4 h at zero steps/min (nonmovement), 8.9 h between 1–59 steps/min, 22 min/day at 60–79 steps/min, 13 min/day at 80–99 steps/min, 9 min/day at 100–119 steps/min, and 3 min/day at cadences ≥120 steps/min (Barreira et al. 2012a). However, unlike the growing evidence to support an adult step-defined sedentary lifestyle index, there are relatively few pertinent studies to make decisions regarding a similar index for children and (or) adolescents. Though the step-based pediatric literature is quite consistent with regard to (i) boys accruing more steps/day than girls (Craig et al. 2010; Tudor-Locke et al. 2009c), (ii) steps/day declining from childhood to adolescence (Beets et al. 2010a; Craig et al. 2010), and (iii) the inverse relationship between steps/day and body composition (Duncan et al. 2010; McCormack et al. 2011b; Tudor-Locke et al. 2011c; Tudor-Locke et al. 2004b) and between steps/day and aerobic fitness in children and adolescents (Le Masurier and Corbin 2006; Lubans et al. 2008), the majority of the general pediatric physical activity literature focuses on the assessment of compliance with intensity-based guidelines or meeting specific physical activity targets other than any number of steps/day. However, the focus on “how many steps/day are enough?” in children and adolescents (Tudor-Locke et al. 2011f) has recently driven the pursuit of a steps/day translation of accumulating at least 60 min of daily MVPA, an accepted time-and-intensity-based public health recommendation (Janssen and Leblanc 2010).
Using accelerometer data from the Canadian Health Measures Survey, Colley et al. (2012) recently proposed that 12 000 steps/day be used as this target for children and adolescents. Because the Sedentary Behaviour Research Network (2012) has recommended that journal editors and reviewers require that “authors use the term “inactive” to describe those who are performing insufficient amounts of MVPA (i.e., not meeting specified physical activity guidelines)”, the implication of the research conducted by Colley et al. (2012) is that children and adolescents who take <12 000 steps/day are physically inactive. This is only a single example, and whether or not it was these authors' intent, we believe it is more prudent to move beyond a simple dichotomous classification of active vs. inactive. We suggest instead that there is a lower value (similar to that presented in Fig. 1 but more relevant to a child–adolescent population), perhaps based on a low-level percentile of distribution, or tied to a deleterious health parameter, or a combination of these, that would be more useful for identifying those who are most likely to be putting their health at risk as a result of their behaviour.
Emerging research on the population distribution of steps/day among children and adolescents could inform a percentile-based definition of the index. Without question, the largest population study is the ongoing nationally representative Canadian Physical Activity Levels among Children and Youth study (CANPLAY) (Craig et al. 2010, 2013), which has been collecting pedometer data on about 6000 children annually since 2005–2006. Based on the criterion of a steps/day cut-point at the lowest 15th percentile of the distribution (equivalent to a mean value minus one standard deviation) derived from 17 314 boys and 16 913 girls (Craig et al. 2013), “taking too few steps” may be defined as taking <8448 steps/day among boys 5–13 years, <6336 steps/day among boys 14–19 years, <7761 steps/day among girls 5–13 years, and <5867 steps/day among girls 14–19 years. Applying this distribution-based criterion to published data from a smaller national study in the United States (Tudor-Locke et al. 2010a), the associated pedometer-equivalent step-based values are <6040 and <3695 steps/day among boys 6–13 and 14–19 years, respectively, and <4855 and <2850 steps/day among girls 6–13 and 14–19 years, respectively. Such distribution-based cut-points derived from population-level data reflect the current physical activity patterns of the specified population, which may also be associated with lower than ideal health measures within that population. For example, we know that the physical fitness of children and youth has declined over time in Canada (Craig et al. 2012) while obesity levels have increased (Janssen et al. 2011, 2012). A step-defined sedentary lifestyle index derived from normative distributions of other populations engaging in more traditional lifestyles reflective of lower rates of obesity (such as the North American Amish (Bassett, Jr. et al. 2007)) would provide substantially different values. Both the American and Canadian distribution-based cut-points listed above are more in line with cut-points for outliers (mean minus 3 standard deviations) in the Amish population (<6385 and <5450 steps/day for boys aged 6–12 and 13–18 years, respectively, and <7250 and <3155 steps/day for girls aged 6–12 and 13–18 years, respectively), whereas an equivalent distribution-based criterion (mean minus 1 standard deviation) for establishing an Amish step-defined sedentary lifestyle index (<13 410 and <13 770 steps/day for boys aged 12 and 13–18 years, respectively, and <11 840 and <9165 steps/day for girls aged 6–12 and 13–18 years, respectively) exceeds the average daily steps of North American children. The variation among populations illuminates the problem with distribution-based thresholds and underscores the need to define a standardized index based on health-related outcomes.
An early suggestion (Tudor-Locke et al. 2008b) that values of <10 000 and <7000 steps/day be used to identify a sedentary lifestyle for school-aged boys and girls (6–12 years), respectively, was loosely based on BMI-referenced anchors (Tudor-Locke et al. 2004b) and modeled after a proposed adult graduated step index (Tudor-Locke and Bassett 2004). This is consistent with a more recent finding from CANPLAY that the odds of obesity decreased for every 3000-step increase in steps/day so that boys (5–13 years) taking roughly 10 000 steps/day and girls taking about 8000 steps/day were 19% more likely to be obese than the average boy (mean = 12 813 steps/day for 5–9-year-olds and 12 845 steps/day for 10–13-year-olds) and girl (mean = 11 738 steps/day for 5–9-year-olds and 11 265 for 10–13-year-olds), controlling for television viewing time (Tudor-Locke et al. 2011c).
Applying these sex-specific cut-points (i.e., <10 000 and <7000 for boys and girls, respectively) to 2610 children's and adolescents' data collected as part of NHANES accelerometer monitoring, Tudor-Locke et al. (2010a) reported that as many as 42% of boys and almost 21% of girls in the United States may be considered “sedentary” when the accelerometer data were adjusted to be more in line with expected step values from pedometry. The appropriateness of a sex-specific definition is debatable. When both boys and girls were evaluated relative to a standard cut-point of 7000 steps/day in the Canadian CANPLAY pedometer surveillance data of 19 789 children and adolescents, Craig et al. (2010) reported that approximately 25% of boys and 33% of girls were considered “low active” and 6% of both boys and girls took <5000 steps/day and were considered “sedentary”. Although not specifically looking to examine the usefulness of these potential markers of a physically inactive lifestyle, Kambas et al. (2012) did demonstrate that preschool-aged children who accumulated approximately <7000 steps/day (discerned from a figure) were also categorized within the lowest quartile of motor proficiency. Although <7000 steps/day has been repeated more frequently in the pediatric literature at this time as a potential low-end candidate, unlike the adult data, the paucity of the additional evidence on this topic does not allow us to conclusively identify a minimum value of steps/day to inform a clear, evidence-based child- and adolescent-specific step-defined sedentary lifestyle index at this time. We anticipate that this will improve as this gap is recognized and the research process inevitably unfolds.
Limitations
The approach of using a step-based definition as a sedentary lifestyle index has a number of limitations that must be acknowledged. First, a variety of step-counting devices is available for use among researchers, practitioners, and the general public. Each one of these user groups has different but overlapping needs, and it would be best if any unit of measurement could be simply translated at all levels. However, it has become increasingly apparent that there are differences in how these various objective monitors detect and present a “step” (Crouter et al. 2003; Feito et al. 2012; Le Masurier and Tudor-Locke 2003; Le Masurier et al. 2004). This is not limited just to step counting; estimates of time spent in sedentary behaviours and at any intensity of physical activity are also variable among different types of instrumentation that attempt to capture such data (Tudor-Locke 2010). Perhaps even more concerning, evidence suggests that different generations of instrumentation are inconsistently sensitive (Rothney et al. 2008). As with all measures, a trade-off exists between sensitivity and specificity; increasing sensitivity to capture very low force movements in an attempt to be maximally inclusive leads to increased capture of “erroneous steps” (Le Masurier and Tudor-Locke 2003), and vice versa.
To be clear, the original graduated step index was presented in an article whose title was “Preliminary pedometer indices for public health” (Tudor-Locke and Bassett 2004). That article included the proposed values for (what was known at the time as) a “sedentary lifestyle index”, which itself was originally formulated based on pedometer measures (Tudor-Locke et al. 2001). Most of the research (23 out of 25 studies) presented in Table 1 has been collected with pedometers. Further, 1 of the 2 remaining studies represented in the table that used accelerometers to collect the step data actually adjusted the output to be more translatable in terms of what might be expected using pedometry before applying the pedometer-based index to the data (Sisson et al. 2012). Because pedometers are less expensive, and therefore more accessible and feasible for use in practical applications, including widespread adoption by the general public, it is reasonable to provide index values to guide their use at this level. Physical activity recommendations expressed in terms of steps/day produced by various governmental and health organizations around the world (Tudor-Locke et al. 2011h) are ultimately intended for public consumption, and therefore have been logically designed for users of such low-cost and accessible technologies. Producing cut-points and other indices that are only to be used by other researchers with access to enhanced technological precision may be necessary to address specific research questions, but may ultimately have little application to the real-world condition outside the laboratory.
Although many accelerometers have evolved to include step-based outputs in addition to their more traditional activity count outputs, we acknowledge that these similarly named outputs are not likely to be on the exact same scale as that captured by lower-technology pedometers. Therefore, researchers should cautiously compare and interpret any steps/day value and be careful when they apply any index to data collected using different types of instrumentation. This specifically means it may be just as debatable to cast an accelerometer-generated steps/day estimate as an unadjusted index for pedometer users as it is to interpret accelerometer-determined steps/day using an index originally intended to interpret pedometer data. For example, one of the studies listed in Table 1 used an ankle-worn StepWatch Activity Monitor to monitor steps/day in an older adult sample (mean age, approximately 80 years) (Cavanaugh et al. 2010). This instrument is known to be highly sensitive to low-force accelerations and detects 11%–15% more daily steps in free living than do commonly used pedometers (Karabulut et al. 2005). Perhaps unaware of the implications of this difference in instrument sensitivity, Cavanaugh et al. (2010) applied the pedometer-based graduated step index (Tudor-Locke and Bassett 2004) to interpret their data without any form of adjustment. As a result, they concluded that only 26% of this aged sample took <5000 steps/day, and at least 29% were “highly active” (i.e., accumulating >10 000 steps/day). Directly (and inappropriately) compared with national estimates from the United States (where average values were closer to 6500 steps/day and comparable categories were 36% and 16%, respectively) collected with an accelerometer but adjusted to be more in line with a pedometer-based scale (Sisson et al. 2012), this smaller sample could be described as uniquely active for their age. However, it is more likely that the differences in instrumentation explain the remarkable finding.
It is worth repeating that step-counting devices are now widely available in a number of different commercially available formats, including those worn at the waist, on the arm, at the wrist, on the ankle, in a pocket, as a piece of jewelry, as an ear piece, in cell phones, and so forth. Their measurement mechanisms are patent protected, they change and become obsolete, and it has become clear that similarly named outputs do not necessarily capture the same behaviour among instruments (Tudor-Locke 2010). Industry standards have helped to make ambulatory monitoring more uniform in Japan (Crouter et al. 2003); however, this is not the case elsewhere. Although it is lamentable, it may be that instrument-specific index values will be necessary. This is already known to be the case for the application of accelerometer activity count cut-points. Methods of adjustment are sorely needed to aid in the translation and comparison among instruments. Despite these inconvenient truths, we must be careful not to “throw the baby out with the bathwater”. Still, any value offered as a generic step-defined sedentary lifestyle index must be treated as a “heuristic” (i.e., guiding) value that must also be thoughtfully applied and communicated, keeping in mind the end user.
Another limitation also related to instrumentation and measurement is the concern about optimal amounts of wearing time. Instruments with time-stamping technology (typically accelerometer-type devices) provide researchers with additional information that can be processed and used to determine wear time and limit data queries to the best-quality data using user-defined criteria. However, a number of researchers (Choi et al. 2011; Masse et al. 2005; Tudor-Locke et al. 2011b) have shown that it is the estimate of time spent in sedentary behaviour that is most affected by the premature removal of accelerometers; the impact on detected movement (e.g., steps/day) is less profound (Schmidt et al. 2007; Tudor-Locke et al. 2011b). Nevertheless, researchers remain very cognizant of this potential threat to validity, and addressing it is often a foremost consideration. From the practitioner's point of view, however, and especially from that of the general public, the potential impact of wear time on an estimate of steps/day is not likely to be as much of a concern; Schmidt et al. (2007) have demonstrated that adjustments for wear time did not alter correlations between pedometer steps/day and cardiovascular risk factors. Further, a wealth of health-related step data has been accumulated to date primarily using pedometers that have not had time-stamping technology, and the consistency and robustness of the findings have been clear (Tudor-Locke et al. 2011f, 2011g, 2011h). Perhaps most compelling, meta-analyses (Bravata et al. 2007; Kang et al. 2009; Richardson et al. 2008) of pedometer-based behaviour interventions demonstrate statistically consistent and clinically significant changes (i.e., approximately 2000–2500 steps/day) in ambulatory activity and related improvement in health outcomes using this simple technology, without any consideration of wearing time.
Finally, and as mentioned earlier, not all human movement is represented by a measure of daily steps taken. Step-counting devices do not characterize nonambulatory activities well (e.g., weight training, bicycling, swimming, skateboarding, roller blading, hockey, kite surfing) (Miller et al. 2006). However, it is clear that ambulatory behaviours, and specifically walking, are fundamental to basic human mobility across all domains of daily life, including exercise, recreation, work, chores, shopping, social interactions, and cultural exchanges (Ainsworth et al. 2011; Tudor-Locke and Ham 2008). Further, although steps/day explains 61%–67% of the variability in MVPA (Tudor-Locke et al. 2011a), and taking 5000 steps/day is associated with approximately 10 min (not necessarily consecutive) of MVPA (Tudor-Locke et al. 2011a), a measure of total steps taken in a day is not a direct indication of physical activity intensity, a dominant precept of public health guidelines (Physical Activity Guidelines Advisory Committee 2008; Tremblay et al. 2011b). Nonetheless, step-counting devices, especially those accessible to the general public, are important health-behaviour tools (Tudor-Locke and Lutes 2009). Their utility is limited, however, without the provision of evidence-based, applicable, and reasonable index values to help guide and interpret their output.
Conclusions
A growing number of studies have used the <5000 steps/day cut-point since it was first proposed to categorize individuals as “sedentary”(McKercher et al. 2009; Schmidt et al. 2009) or “inactive”(Cavanaugh et al. 2010; Hirvensalo et al. 2011; Tudor-Locke et al. 2001) and have subsequently included it in a more fully expanded graduated step index (Tudor-Locke and Bassett 2004; Tudor-Locke et al. 2008b). The profile of individuals more likely to be taking <5000 steps/day includes having a relatively lower household income and being female, older, of African-American vs. European-American heritage, a current vs. never smoker, and (or) living with chronic disease and (or) disability (including morbid obesity). Although the fall–winter season in the Northern hemisphere appears to discourage taking >5000 steps/day, little else is known about how other contextual factors foster such low levels of step-defined physical activity. Adverse measures of body composition have been consistently associated with taking <5000 steps/day in a range of population samples. Indicators of cardiometabolic risk, and specifically metabolic syndrome, have also been associated with taking <5000 steps/day. Using <5000 steps/day to identify and recruit physically inactive and (or) sedentary individuals to interventions focused on increasing physical activity and (or) reducing sedentary behaviours seems to be a prudent approach to maximizing the potential for effect in a population most at need, but this approach has not yet been adopted systematically. Interventions have typically focused on attaining a singular and lofty goal (e.g., 10 000 steps/day) (Bravata et al. 2007) and not necessarily on shifting individuals who take relatively few steps/day onto the next immediately higher categories (e.g., “low active”, defined as 5000–7500 steps/day, or “somewhat active”, defined as 7500–9999 steps/day (Tudor-Locke and Bassett 2004; Tudor-Locke et al. 2008b)). Short-term interventions to reduce step-defined physical activity to values <5000 steps/day conducted with small samples of young, healthy, and active individuals have shown dramatic adverse effects on a number of health parameters. Consistent implementation of a standardized steps/day definition for a sedentary lifestyle index would facilitate comparisons among studies and groups; however, unique sample distributions (i.e., generally active, or generally low active) may require tolerance for a degree of flexibility, including segmenting the <5000 steps/day category into “basal activity” (<2500 steps/day) and “limited activity” (2500–4999 steps/day) (Tudor-Locke et al. 2009a). A standardized definition would be useful for screening, recruiting, and tracking purposes. Although additional research is needed to further illuminate the appropriateness of using <5000 steps/day as a step-defined sedentary lifestyle index, especially its application across different types of objective monitoring technologies, it clearly demonstrates multiform utility for researchers and practitioners and, perhaps most importantly, for communicating with the general public at this time. There is currently little evidence to advocate any specific value indicative of a step-defined sedentary lifestyle index in children or adolescents.
Acknowledgements
We acknowledge our colleagues who supported our initial ideas and the reviewers who helped shape the final product.
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Published In
Applied Physiology, Nutrition, and Metabolism
Volume 38 • Number 2 • February 2013
Pages: 100 - 114
History
Received: 20 June 2012
Accepted: 5 September 2012
Accepted manuscript online: 8 November 2012
Version of record online: 8 November 2012
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© 2013.
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Tudor-LockeCatrine, CraigCora L., ThyfaultJohn P., and SpenceJohn C.. 2013. A step-defined sedentary lifestyle index: <5000 steps/day. Applied Physiology, Nutrition, and Metabolism. 38(2): 100-114. https://doi.org/10.1139/apnm-2012-0235