10,000 steps In summary, at least in terms of normative data, it appears that healthy adults can take anywhere between approximately 4,000 and 18,000 steps/day, and that 10,000 steps/day is a reasonable target for healthy adults, although there are notable "low active populations," including the U.S. populace [3, 23].
An early review of 32 studies published between 1980 and 2000 [15] indicated that healthy younger adults (approximately 20-50 years of age) take 7,000-13,000 steps/day. Many more studies of step-defined physical activity measured using pedometers and accelerometers are published today, including a more recent review article of adult normative data. Specifically, Bohannon [16] used a meta-analytic approach to summarize and present steps/day taken by healthy adults (18+ years of age). Forty-two studies published between 1983 and 2004 were identified. Reported values for adults under 65 years of age ranged from approximately 5,400 steps/day (in a U.S. sample of multiethnic women mean age 54.2 years [17]) to 18,000 steps/day (in a sample of Amish men mean age 34 years [18]). Excluding the Amish sample, overall mean steps/day was 9,448 (95% CI = 8,899-9,996). The NHANES accelerometer data were adjusted to facilitate interpretation on a pedometer-based scale, since accelerometers typically detect more steps than pedometers [19, 20]. The findings indicate that, on average, U.S. adults take approximately 6,500 steps/day [3], not too different from two other U.S. estimates based on pedometer data: Colorado (≅6,800 steps/day) [21] and South Carolina (≅5,900 steps/day) [22]. A more recent article reported that U.S. adults average approximately 5,100 steps/day when measured by a pedometer [23]. In contrast, other representative samples indicate that Japanese people aged 15+ years take an average of approximately 7,200 steps/day [24], Western Australians aged 18+ years take approximately 9,600 steps/day [25], Belgian adults aged 25-75 years take approximately 9,600 steps/day [26], and Swiss adults aged 25-74 years of age take approximately 8,900 steps/day (women) and 10,400 steps/day (men) [27]. Despite differences in instrumentation used, the ability to compare results across studies that have used research-quality pedometers is reasonably good [28].
In 2004 Tudor-Locke and Bassett [11] introduced the concept of a graduated step index for healthy adults: 1) < 5,000 steps/day ('sedentary'); 2) 5,000-7,499 steps/day ('low active'); 3) 7,500-9,999 steps/day ('somewhat active'); 4) ≥10,000-12,499 steps/day ('active'); and 5) ≥12,500 steps/day ('highly active'). This index was revisited and given additional support in 2008 as part of an updated review of "How many steps/day are enough?" [12] and in 2009 the original 'sedentary' level (i.e., < 5,000 steps/day) was further split into two additional graduations: < 2,500 steps/day ('basal activity') and 2,500-4,999 steps/day ('limited activity') [3]. The utility of this graduated step index has been assessed in terms of discriminating individuals by body mass index (BMI) [29] and reflecting increased cardiometabolic risk [30] (reviewed in more detail below). Thus, step-based estimates of U.S. adults' habitual physical activity would classify the population as 'low active' according to this existing step-defined physical activity scale [11, 12].
Sixteen free-living healthy adult studies (Table 2) were identified that reported the percentage of their samples achieving specified step-defined cut points, including applying cut points associated with the graduated step index described above. Five used 10,000 steps/day as an exclusive cut point (no other cut point was considered). Eight reported using the graduated step index originally proposed by Tudor-Locke and Bassett [11]. Two studies of South African samples that also made use of the graduated step index were excluded from Table 1 because their lower age limits extended into adolescence [31, 32], beyond the scope of this specific review. Apparent patterns from Table 1 include: younger adults are more likely to achieve 10,000 steps/day, U.S. samples are more likely to take < 5,000 steps/day compared to Australian samples, and those with lower incomes are also more likely to take < 5,000 steps/day than high income earners. The studies that have reported data using versions of the graduated step index provide more robust (i.e., more levels) data for comparison and tracking purposes than those that have only reported relative attainment of any single value of steps/day.
Table 2 Studies of free-living behaviour reporting percent of participants meeting select step-defined cut points in adults Full size table
Interventions
Three different meta-analytic reviews of controlled and/or quasi-experimental studies have summarized the effects of pedometer-based physical activity interventions in adults, published in 2007 [33], 2008 [34], and 2009 [35], respectively. In addition, a selective review [36] has re-examined the studies published in the two earlier reviews [33, 34] to gain insight into why pedometers are effective behaviour change instruments. We therefore only offer a brief summary of these findings here. The use of pedometers in behaviour modification programs increases physical activity by approximately 2,000 [35] to 2,500 steps/day [33, 34]. This level of increase is associated with modest weight loss [33, 34] and improvements in blood pressure [33]. Studies employing a step goal [33], and in particular a 10,000 steps/day goal [35], appear to have had the greatest impact on increasing physical activity. As previously noted, however [36], few studies have evaluated alternative goals to 10,000 steps/day, and no study to date has systematically evaluated dose-response effects of different steps/day goals. Therefore it may be premature to make firm conclusions about the efficacy, effectiveness, or appropriateness of any specific step-based goal in terms of behaviour change. It is possible that working towards any goal that represents an increase over baseline values is likely to be much more important, from a behavioural perspective at least, than the value of the exact target number [36]. It is important to acknowledge that the nature of a goal (i.e., an objective that defines intention at the level of the individual) differs from, but may overlap, the concept of step-based recommendations consistent with public health physical activity guidelines pursued herein. It is also clear that other cognitive and behavioural strategies are important to incorporate into successful intervention programs [37].
Controlled studies
Eight controlled studies (Table 3) have been conducted using treadmills [38–43], tracks [40], or hallways [44] to determine exact step-based conversions of timed continuous ambulation. Sufficient data were reported in all these studies to summarize cadence (steps/minute values), speed (reported in either miles/hr or km/hr, otherwise converted here), and METs as reported, imputed, or otherwise inferred from Compendium of Physical Activity [45] values and summarized in Table 4. Each of these strategies is indicated in the table notes. The correlation between the mean values for steps/minute and speed (miles/hr or km/hr) is presented in Table 4 is r = 0.97 (strong). The correlation between steps/minute and MET level is also strong (r = 0.94). Cadence is known to be the primary strategy for increasing free-living walking speed [46] and although stride lengthening becomes relatively more important in running, cadence still increases with running speed [47]. The five studies that directly measured the number of steps and verified absolutely-defined moderate intensity activity [38–40, 43, 44] came to similar conclusions: despite inter-individual variation, 100 steps/minute represents a reasonable heuristic (i.e., guiding) value for absolutely-defined moderate intensity walking.
Table 3 Controlled study designs that have informed "how many steps/day are enough?" in adults Full size table
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Table 4 Speed, MET levels, and cadence from track, treadmill, and hallway walking/running studies of adults Full size table
Computed step count translations for physical activity guidelines
As noted above, five separate studies can be used to support the assertion that 3,000 steps in 30 minutes is approximately equivalent to at least moderate intensity walking in adults, based on a cadence of 100 steps/minute [38–40, 43, 44]. To be considered a true translation of public health guidelines' focus on time in MVPA, however, these steps should be of at least moderate intensity (i.e., be ≥100 steps/minute), accumulated in at least 10 minute bouts, and should be taken over and above some baseline level of steps/day indicative of sedentarism. Since a value of ≤5,000 steps/day had been proposed as a 'sedentary lifestyle index' [11, 12, 48], summing this value and the supplemental steps/day considered minimally representative of recommended amounts of time in MVPA produces a floor value of approximately 8,000 steps/day. Some physical activity guidelines recommend up to 60 minutes of activity that is of at least moderate intensity [6, 9]. Multiplying 60 minutes by 100 steps/minute results in 6,000 steps, that when added to a 'sedentary' level of 5,000 steps/day produces a total value of 11,000 steps/day. Therefore, a simple arithmetical translation of free-living physical activity that also includes recommended amounts of time in MVPA is 8,000 to 11,000 steps/day for adults, applied with the caveats listed above, and if expressed as a daily recommendation.
It is important to emphasize that these calculations consider only activities that generate steps. There are, of course, a wide range of human activities that may or may not generate steps, for example, those that may include upper body movement. However, bipedal locomotor activity is a fundamental aspect of human movement. Additionally, it has been shown that wrist-worn accelerometers add little extra information to those worn at the waist (and therefore are also most sensitive to ambulatory activity detected while on the wrist) [49]. The calculation above focused on adding recommended amounts of MVPA to baseline physical activity levels and therefore presumes 30 minutes of MVPA in a day. Some public health guidelines now clearly promote 150 minutes/week as the minimal amount of health-related moderate intensity [1, 7]. A computed translation of this expression is 15,000 steps/week, again based on the 100 steps/minute heuristic value described above. Considering 7 days at a baseline level of 5,000 steps/day (or 35,000 steps/week), adding these extra 15,000 steps/week (for a total of 50,000 steps/week), and averaging over 7 days, produces an average of approximately 7,100 steps/day. Adding an extra 30,000 steps/week (i.e., up to 300 minutes/week [1, 7]), produces an overall estimate of approximately 9,300 steps/day averaged over a week.
In summary, a computed translation of daily free-living ambulatory physical activity for adults that includes allowance for recommended amounts of time in MVPA is 8,000 to 11,000 steps/day. Allowing for a more flexible accumulation pattern that may include some "off" days, and averaged across a week, the estimate is 7,100 to 9,300 step/day. Together these estimates span 7,100 to 11,000 steps/day. In both cases, it remains important to emphasize that at least a portion of these steps (3,000 for the daily accumulation and 15,000 of the weekly total accumulation) are minimally taken at an intensity of at least 100 steps/minute (i.e., moderate intensity, absolutely defined), and in bouts of at least 10 minutes.
Direct studies of step equivalents of physical activity guidelines
Six studies (Table 5) were identified that have attempted to provide steps/day translations of recommended amounts of either time spent in MVPA or energy expended (kcal) in healthy adults. Tudor-Locke et al. [48] reported that people who averaged 30 minutes/day of accelerometer-determined MVPA also accumulated 8,000 pedometer-determined steps/day when the two instruments were worn concurrently. Miller and Brown [50] reported that working adults who self-reported accumulating at least 150 minutes of MVPA in a week averaged 9,547 steps/day. Behrens et al. [51] reported that college students who accumulated at least 30 minutes of moderate intensity activity (vigorous intensity not considered) averaged 11,822 steps/day. In the latter two studies, mean values of the sample can be influenced by skewed data, and the process does not effectively capture a threshold value necessarily associated with achieving public health guidelines.
Table 5 Studies that have attempted to set steps/day cut points in adults relative to time spent in MVPA or energy expended Full size table
Jordan et al. [52] described total steps/day associated with attaining prescribed and verified exercise equivalent to 120-150 minutes/week or 8 kcal/kg/week of energy expenditure in a sample of post-menopausal women participating in an intervention study. They found that 3-4 days of 10,000 steps/day met energy expenditure guidelines for the week, and when considered along with data collected beyond the formal exercise setting, that is, in the course of daily living outside of exercise sessions and on non-exercise days, was equivalent to approximately 7,300 steps/day (imputed from data reported in the original article). MacFarlane et al. [53] selected the 25th percentile of steps/day distribution in 49 Hong Kong Chinese people aged 15-55 years, examined sensitivity/specificity of achieving 30 minutes MVPA measured by various instruments across quartiles of steps/day distribution, and reported that the 25th percentile value of 8,000 steps/day provided the best overall accuracy, sensitivity and specificity compared with higher quartile splits.
Finally, Tudor-Locke et al. [54] adjusted the 2005-2006 NHANES accelerometer data to more closely represent pedometer-based scaling and considered concurrently detected minute-by-minute step and activity count data from over 3,500 individuals with at least one valid day of wear time defined as 10/24 hours/day. Considering any minute spent in MVPA, they reported that 30 minutes/day was associated with approximately 8,000 steps/day for both men and women. A focused analysis on a subsample of participants with 7 valid days indicated that 150 minutes/week of MVPA was associated with approximately 7,000 steps/day (or 49,000 steps/week). The authors concluded that 7,000 to 8,000 steps/day, acknowledging that more is better, is a reasonably simple message that is also congruent with public health recommendations focused on minimal amounts of MVPA. A caveat is that these data considered any minute above MVPA, and therefore do not reflect an exact translation of public health guidelines that include a directive for minimal bout lengths. However, the chasm between these guidelines that have been traditionally based on self-reported activity and objectively monitored activity has been pointed out previously by users of these NHANES data [55].
In summary, directly studied estimates of free-living behaviour suggest that a total daily volume of ambulatory physical activity associated with meeting minimal amounts of MVPA is at least 7,000-8,000 steps/day. This range is similar to the threshold produced from the assumption-based computations above (i.e., 7,100 steps/day). Collectively, the results suggest that the designation of 'active' originally reserved for achieving at least 10,000 steps/day [11, 12], actually encompasses a range that begins as low as 7,000 steps/day if 'active' is intended to indicate likelihood of achieving recommended amounts of weekly MVPA. Spread out over a week, more modest increases of ≅ 2,800 steps on three days/week, in line with just 50% of public health guidelines, and relative to a sedentary baseline (i.e., ≅ 4,700 steps/day) have produced important improvements in a number of health outcomes [52, 56–58]. This is in keeping with the recent physical activity guidelines [1] that acknowledge that, especially for inactive adults, "some physical activity is better than none."
Steps/day associated with various health outcomes
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Although this section does not deal directly with a step-based translation of existing physical activity guidelines, five cross-sectional studies were identified that have attempted to set steps/day cut points relative to any health-related outcome, and these fit under the general purpose of this review to consider "how many steps/day are enough?" McKercher et al. [59] reported that women who achieved ≥ 7,500 steps/day had a 50% lower prevalence of depression than women taking < 5,000 steps/day. No additional benefit for depression was observed from attaining higher step-defined physical activity levels. Men who achieved ≥ 12,500 steps/day also had a 50% reduction in prevalence of depression compared with those taking < 5,000 steps/day. Only the women's results were statistically significant.
Krumm et al. [29] examined the relationship between pedometer-determined steps/day and body composition variables in 93 post-menopausal women. In relation to BMI, a linear relationship was observed such that women who took 5,000-7,500 steps/day had a significantly lower BMI than those who took < 5,000 steps/day. Further, women who took 7,500-9,999 steps/day had a significantly lower BMI than those who took 5,000-7,500 steps/day. There was no significant difference in BMI between women who took 7,500-9,999 steps/day and those who took > 10,000 steps/day.
Although Dwyer et al. [60] did not expressly set any specific steps/day cut point, they did document an inverse cross-sectional relationship between steps/day and markers of obesity in a population-based adult sample. Further, the logarithmic nature of the relationship was such that greater relative differences in waist circumference and BMI were observed for those taking habitually lower steps/day. Specifically, an extra 2,000 steps/day for someone habitually taking only 2,000 steps/day was associated with a 2.8 cm lower waist circumference in men compared with 0.7 cm lower for men already walking 10,000 steps/day. The corresponding values for potential reductions in waist circumference for women were 2.2 and 0.6 cm, respectively, for a 2,000 step addition to the two habitual walking level examples. Not surprisingly, there were larger differences in both waist circumference and BMI between those reporting 2,000 steps/day and those reporting higher counts of 10,000, 15,000 or 20,000 steps/day, but the relative benefits of small differences at lower habitual levels were still notable.
Tudor-Locke et al. [61] applied a contrasting groups method to identify optimal steps/day related to BMI- defined normal weight vs. overweight/obese in an amalgamated data base featuring pedometer and BMI data that were independently collected but using similar protocols and the same type of pedometer from Australia, Canada, France, Sweden, and the USA. Despite data limitations (e.g., fewer data available for men than women), the researchers suggested that a total number of steps/day related to a normal BMI in adults would range from 11,000 to 12,000 in men and from 8,000 to 12,000 in women, and that values were consistently lower in older age groups than in younger age groups. Spring-levered pedometers are known to undercount steps related to obesity, so the values in this data base reflect that potential threat to validity [62]. However, their use does not completely misrepresent the general findings that steps/day differ significantly across BMI-defined obesity categories, even when measured by more sensitive accelerometers [63]. Once again, however, since pedometers are more likely to be used in clinical and public health applications, the presentation of pedometer-determined steps/day as detected in free-living populations, that include obese individuals, is relevant and therefore defensible.
It is important to consider whether we are asking the wrong question (at least for some health parameters): "How many steps/day are enough?" The question itself promotes a single-minded pursuit of threshold values, a presumed phenomenon that may not accurately characterize the true shape of a specific dose-response curve. Further, if such a threshold exists, it might only be readily achieved by a small and possibly already active subsample of any population. Recently, there has been growing interest in the study of sedentary behaviour and its potentially deleterious effects on health [64, 65]. Considering this, it may be that the more appropriate question to ask in terms of pedometer-determined physical activity cut points is "How many steps/day are too few?" In support of this notion, many of the studies herein could be re-interpreted to conclude what levels of step-defined physical activity were associated with compromised health outcomes. For example, Schmidt et al. [30] reported that individuals taking < 5,000 steps/day had a substantially higher prevalence of a number of adverse cardiometabolic risk factors than those taking higher steps/day. From a public health practice point of view it is both rational and appealing to focus on motivating behaviour change in the larger portions of the population with low to very low physical activity levels rather than to focus solely on tailoring messages that may very well only appeal to subsamples that are already comparatively active. The adoption and use of a fully expanded steps/day scale that incorporates step-based translations of recommended amounts of MVPA would facilitate efforts designed to communicate both "How many steps/day are enough?" and also "How many steps/day are too few?"
In summary, it may be that specific thresholds of step-defined physical activity are associated in different ways with specific health outcomes. For example, relatively greater benefits in body composition parameters may be realized with small increments (e.g., adding 2,000 steps/day) over low levels of habitual activity in individuals who already have excess body fat, but "normalization" (with no further needed improvements) may require optimally higher physical activity levels (e.g., 11,000 to 12,000 steps/day in men, 8,000 to 12,000 step/day in women) and be relatively more difficult to achieve. Other health parameters may exhibit a more classic threshold effect, for example, positive effects on depression at ≥ 7,500 steps/day [59]. The concept of distinctly different dose-response curves related to physical activity is in keeping with the findings presented at the historic dose-response symposium in 2001 [66].
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