title: Validation of the actical activity monitor in middle-aged and older adults.
abstract: OBJECTIVE
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Prevention Research Center, University of South Carolina, Columbia, SC, USA.
authors.forename: Steven P
authors.initials: SP
authors.lastname: Hooker
authors.forename: Anna
authors.initials: A
authors.lastname: Feeney
authors.forename: Brent
authors.initials: B
authors.lastname: Hutto
authors.forename: Karin A
authors.initials: KA
authors.lastname: Pfeiffer
authors.forename: Kerry
authors.initials: K
authors.lastname: McIver
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Heil
authors.forename: John E
authors.initials: JE
authors.lastname: Vena
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Lamonte
authors.forename: Steven N
authors.initials: SN
authors.lastname: Blair
mesh_terms: D000203:Activities of Daily Living; D000367:Age Factors; D015444:Exercise; D005260:Female; D006801:Humans; D008297:Male; D055686:Metabolic Equivalent; D008875:Middle Aged; D018670:Monitoring, Ambulatory / Q000295:instrumentation*; D012737:Sex Factors