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 x 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 x min(-1) (multiple regression); 101 step x min(-1) (mixed modeling); and 102 step x min(-1) (ROC curve). For women, step counts per minute associated with walking at 3 METs were 91 step x min(-1) (multiple regression); 111 step x min(-1) (mixed modeling); and 115 step x 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 x min(-1). However, step counts per minute is a poor proxy for METs, and so 100 step x 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.