Validation of the Actical Activity Monitor in Middle-Aged and Older Adults

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 (>= 3 METs) 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.