Daily Walking in Older Adults: Day-to-Day Variability and Criterion-Referenced Validity of Total Daily Step Counts

OBJECTIVE: To determine the day-to-day variability of older adults' physical activity, and to evaluate the accuracy of the 10,000-step goal for classifying whether older adults obtain 30 minutes of MVPA. METHODS: Ninety-one adults of age over 60 years of age wore a Yamax pedometer and Actigraph accelerometer for 7 days. Interday reliability was estimated via two-way ANOVA ICCs, and classification accuracy was evaluated via sensitivity, specificity, and ROC curve analysis. RESULTS: Interday reliability was high; 4 of 5 outcome measures had a reliability of > or = .80 with only 2 days of data. The 10,000-step cut point had high accuracy for identifying days with less than 30 minutes of MVPA, but poor accuracy for identifying days with more than 30 minutes of MVPA. CONCLUSIONS: Day-to-day variability in physical activity is lower in older adults than other age groups. The 10,000-step goal is inadequate for determining whether daily physical activity includes 30 minutes of MVPA in this population.