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Purpose:

This study was designed to validate the Actical activity monitor in middle-aged and older adults of varying body composition to develop accelerometer thresholds to distinguish between light and moderate intensity physical activity (PA).

Methods:

Nonobese 45 to 64 yr (N = 29), obese 45 to 64 yr (N = 21), and ≥65 yr (N = 23; varying body composition) participants completed laboratory-based sitting, household, and locomotive activities while wearing an Actical monitor and a portable metabolic measurement system. Nonlinear regression analysis was used to identify activity count (AC) cut-points to differentiate between light intensity (<3 METs) and moderate intensity (≥3METs) PA.

Results:

Using group-specific algorithms, AC cut points for 3 METs were 1634, 1107, and 431 for the obese 45 to 64 yr group, nonobese 45 to 64 yr group, and ≥65 yr group, respectively. However, sensitivity and specificity analysis revealed that an AC cut-point of 1065 yielded similar accuracy for detecting an activity as less than or greater than 3 METs, regardless of age and body composition.

Conclusion:

For the Actical activity monitor, an AC cut-point of 1065 can be used to determine light and moderate intensity PA in people ≥45 years of age.

Hooker, Feeney, and Hutto are with the Prevention Research Center, University of South Carolina, Columbia, SC. Pfeiffer is with the Dept of Kinesiology, Michigan State University, Lansing, MI. McIver and Blair are with the Dept of Exercise Science, University of South Carolina, Columbia, SC. Heil is with the Dept of Health and Human Development, Montana State University, Bozeman, MT. Vena is with the Dept of Epidemiology and Biostatistics, University of South Carolina, Columbia, SC. LaMonte is with the Dept of Social & Preventive Medicine, University at Buffalo, Buffalo, NY.