title: Effect of varying accelerometry criteria on physical activity: the look ahead study.
abstract: The importance of physical activity in weight management is widely documented. Although accelerometers offer an objective measure of activity that provide a valuable tool for intervention research, considerations for processing these data need further development.
  
  
  OBJECTIVE
  This study tests the effects of using different criteria for accelerometry data reduction.
  
  
  METHODS
  Data were obtained from 2,240 overweight and obese individuals with type 2 diabetes mellitus (T2DM) from the Look AHEAD study, with 2,177 baseline accelerometer files used for analysis. Number, duration, and intensity of moderate (≥ 3 metabolic equivalents (METS)) and vigorous (≥ 6 METS) activity bouts were compared using various data reduction criteria. Daily wear time was identified as 1,440 min/day minus non-wear time. Comparisons of physical activity patterns for non-wear time (using either 20, 30, or 60 min of continuous zeros), minimal daily wear time (8, 10, and 12 h), number of days with available data (4, 5, and 6 days), weekdays vs. weekends, and 1- or 2-min time interruptions in an activity bout were performed.
  
  
  RESULTS
  In this mostly obese population with T2DM (BMI = 36.4 kg/m(2) ; mean age = 59.0 years), there were minimal differences in physical activity patterns using the different methods of data reduction. Altering criteria led to differences in the number of available data (sample size) meeting specific criteria.
  
  
  CONCLUSIONS
  Although our results are likely directly applicable only to obese individuals with T2DM, an understudied population with regards to physical activity, the systematic analysis for data reduction employed can be more generalizable and provide guidance in this area in the absence of standard procedures.
authors.affiliation: Department of Health and Exercise Science, Wake Forest University, Winston-Salem, North Carolina, USA. millergd@wfu.edu
authors.forename: Gary D
authors.initials: GD
authors.lastname: Miller
authors.forename: John M
authors.initials: JM
authors.lastname: Jakicic
authors.forename: W Jack
authors.initials: WJ
authors.lastname: Rejeski
authors.forename: Melicia C
authors.initials: MC
authors.lastname: Whit-Glover
authors.forename: Wei
authors.initials: W
authors.lastname: Lang
authors.forename: Michael P
authors.initials: MP
authors.lastname: Walkup
authors.forename: Mimi L
authors.initials: ML
authors.lastname: Hodges
mesh_terms: D061725:Accelerometry / Q000379:methods*; D000368:Aged; D015992:Body Mass Index; D003924:Diabetes Mellitus, Type 2 / Q000150:complications; D015444:Exercise; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018670:Monitoring, Ambulatory; D009043:Motor Activity; D009765:Obesity / Q000150:complications / Q000503:physiopathology*; D050177:Overweight; D005082:Physical Exertion