Research article
Translating Physical Activity Recommendations into a Pedometer-Based Step Goal: 3000 Steps in 30 Minutes

https://doi.org/10.1016/j.amepre.2009.01.021Get rights and content

Background

It is a public health recommendation to accumulate at least 150 minutes per week of moderate intensity physical activity. Although pedometers are widely used as a physical activity–monitoring tool, they are unable to measure activity intensity. Translating current physical activity recommendations into a pedometer-based guideline could increase the public health impact of physical activity interventions.

Methods

A community sample of 97 adults (60% women, with a mean age of 32.1 [±10.6] years and a mean BMI of 28.8 [±5.5]) completed four 6-minute incremental walking bouts on a level treadmill at 65, 80, 95, and 110 m·min–1. A calibrated metabolic cart was used to measure energy expenditure at each speed. Steps were measured using a Yamax SW-200 pedometer. Step-rate cut points associated with minimally moderate-intensity activity (defined as 3 METs) were determined using multiple regression, mixed modeling, and receiver operating characteristic (ROC) curves. All data were collected and analyzed in 2006.

Results

For men, step counts per minute associated with walking at 3 METs were 92 step·min–1 (multiple regression); 101 step·min–1 (mixed modeling); and 102 step·min–1 (ROC curve). For women, step counts per minute associated with walking at 3 METs were 91 step·min–1 (multiple regression); 111 step·min–1 (mixed modeling); and 115 step·min–1 (ROC curve). However, for each analysis there was substantial error in model fit.

Conclusions

Moderate-intensity walking appears approximately equal to at least 100 step·min–1. However, step counts per minute is a poor proxy for METs, and so 100 step·min–1 should be used only as a general physical activity promotion heuristic. To meet current guidelines, individuals are encouraged to walk a minimum of 3000 steps in 30 minutes on 5 days each week. Three bouts of 1000 steps in 10 minutes each day can also be used to meet the recommended goal.

Introduction

It is recommended that U.S. adults engage in moderate-intensity physical activity for a minimum of 150 minutes each week,1 equivalent to 30 minutes daily, 5 days per week. Health benefits can also be achieved when this 30-minute goal is accomplished as a series of shorter bouts (typically three bouts of 10 minutes) accumulated throughout the day. Although it is easy to measure the frequency and duration of physical activity, evidence suggests that many individuals are unable to gauge their activity intensity when reading or hearing a description about what it should feel like.2 This presents a challenge, because health benefits are dependent on the intensity of activity, yet there are few valid and reliable monitoring tools available to the public that are affordable and simple to use.

One objective activity-monitoring tool that is feasible for use in public health settings is the pedometer.3 A pedometer can be used to accurately track the volume of daily activity using the simple output of steps per day,4 and it may serve a motivational function because it instantly displays to the user the number of steps taken. A recent meta-analysis5 of 26 RCTs and observational studies reported that pedometer users increased their levels of physical activity by 27% over baseline levels. Significant decreases in BMI and blood pressure were also reported. Although the vast majority of commercially available pedometers do not measure activity intensity, pedometers are relatively inexpensive ($10–$25), which may explain why they have rapidly become a centerpiece of many local and national physical activity campaigns.6, 7 Moreover, individuals appear able to remember pedometer-based recommendations when targeted by public health campaigns8 and counseling.9 The most widely recognized step recommendation is to accumulate 10,000 steps per day.10 Although step goals do increase the effectiveness of pedometer use,5 the goal of 10,000 steps per day is based on limited evidence, may be unrealistic for many people,11 and does not incorporate activity intensity.

Researchers and practitioners have called for a directly measured index for the number of steps taken in 30 minutes of moderate-intensity walking.11 This would enable national recommendations to be translated easily for pedometer-based interventions and public health campaigns. Although accumulated evidence12, 13, 14, 15 suggests that 30 minutes of moderate-intensity walking translates to approximately 3000–4000 steps in healthy adults, the results are based on small samples, and activity intensity is often unmeasured, determined by self-report, or implied by walking speed. Only one study13 has used an objective measure of activity intensity to develop a step-based recommendation, but the findings lack generalizability because they are based on a sample of young healthy adults, and there was no control for data dependence in the analysis.16 The purposes of this study were (1) to evaluate the utility of using a commercially available pedometer to measure moderate-intensity walking in a community sample, (2) to determine the range of step counts per minute that define moderate-intensity walking for people of different weight status, and (3) to translate current recommendations for moderate-intensity physical activity into a pedometer-based step goal.

Section snippets

Participants

A community sample of 97 Latino adults (39 men, 58 women) with a mean age of 32.1 (±10.6) years, volunteered to participate in the study. The mean BMI for men was 27.5 (±3.7) kg·m2 and for women was 29.7 (±6.3) kg·m2. All participants were initially screened for age (18–55 years) and for cardiovascular abnormalities or symptoms using the Physical Activity Readiness Questionnaire.17 The study was approved by the IRB at San Diego State University, and all subjects provided informed consent before

Results

Means and SDs of measured variables at each treadmill speed by participant weight status are presented in Table 1. Although data analysis was conducted separately by gender, combined data are presented in the table because few gender differences emerged.

Discussion

The main finding of this study is that considerable error exists when using pedometer step counts to measure METs during treadmill walking in a community sample. Based on three different analytic models, the findings suggest that steps per minute explain 15%–41% of the variance in METs, and that only 50%–60% of individuals could be correctly classified as walking at moderate intensity using step rate alone.

Of the18 different step rates computed across subsamples and analytic methods, 11 (61%)

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