The purpose of this study is twofold: (1) To establish a criterion-referenced cutoff score of daily step counts for middle-aged adults with respect to the ACSM/AHA recommendations for physical activity (PA) (≥ 150min/wk of moderate or 60min/wk of vigorous PA), and (2) To provide validity evidence to support the step-count cutoff score.
A total of 102 middle-aged adults (39 men), aged from 40 to 60 years old, wore an Omron pedometer (HJ-720) and an Actigraph GT1M accelerometer for 7 consecutive days. Participants were stratified into two groups based on their PA level: active vs. non-active group. Receiver operating characteristics (ROC) analysis was used to determine an optimal step-count cutoff score where the criterion was the minimum recommended PA level. Diagnostic accuracy was examined by the area under the curve (AUC). To validate the cutoff score, additional 25 participants (13 men) were recruited and asked to wear a pedometer for 7 consecutive days. They completed all measures of risk factors for metabolic syndrome (MetS). MetS status was determined by meeting three or more of the five indicators: blood glucose, HDL cholesterol, waist circumference, triglycerides, and blood pressure.
Gender-specific ROC analysis showed that optimal step-count cutoff scores for men and women were 5,055 steps/day (AUC=.74) and 6,575 steps/day (AUC=.89), respectively. There was a significant relationship between cutoff-determined PA group membership and MetS, x2(1)=6.25, p=.012, which supported the validity evidence.
The gender-specific cutoff scores can be used as a minimum level of daily PA to achieve substantive health benefits.
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