Translating Physical Activity Recommendations into a Pedometer-Based Step Goal:

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.