Using three objective criteria to examine pedometer guidelines for free-living individuals.

The purpose was to examine in free-living individuals from a high-density city (1) the objectively determined physical activity levels across quartiles derived from pedometer step counts, (2) the pedometer steps day(-1) required to meet health-enhancing guidelines of accruing 30 min day(-1) of moderate physical activity and (3) the agreement between three objective criteria for the pedometer guidelines. Over 7 days 49 Hong Kong Chinese aged 15-55 years (n = 30 males) wore a polar heart rate monitor (HRM), an MTI and Tritrac accelerometer, plus a Yamax pedometer for >or=600 min day(-1). Participants averaged 9,839 +/- 3,088 steps day(-1), whilst accumulating 44.5 +/- 22.6, 43.1 +/- 21.7, and 24.7 +/- 19.3 min day(-1) of moderate physical activity by the Tritrac, MTI and HRM, respectively. Significant differences between quartiles of pedometer-determined activity were predominantly seen in the accelerometry data, especially during moderate and moderate-to-vigorous intensity activity (effect sizes >1.5 between upper and lower quartiles), but not seen in the HRM data. Using both criterion accelerometer datasets, a threshold of 8,000 steps day(-1) accurately categorized approximately 90% of those achieving, and approximately 80% of those not achieving, 30 min day(-1) of appropriate activity. They also produced a screening sensitivity of approximately 95% and a specificity of approximately 70%, which were considerably higher than those from the HRM data. Overall, the agreement between the three criterion measures suggests 8,000 steps day(-1) might be a valid screening tool as a proxy for classifying those meeting public health physical activity recommendations of 30 min day(-1) of moderate activity.