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

Abstract

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 ≥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 ∼90% of those achieving, and ∼80% of those not achieving, 30 min day -1 of appropriate activity. They also produced a screening sensitivity of ∼95% and a specificity of ∼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. © Springer-Verlag 2008.