title: Using Activity Monitors to Measure Sit-to-Stand Transitions in Overweight/Obese Youth.
abstract: Reducing sedentary behavior has emerged as an important health intervention strategy. Although hip-worn, and more recently wrist-worn, accelerometers are commonly used for measuring physical activity and sedentary behavior, they may not provide accurate measures of postural changes. The current study examined the validity of commonly used hip- and wrist-worn accelerometer cut points and the thigh-worn activPAL activity monitor for measuring sit-to-stand transitions as compared with direct observation in youth with overweight and obesity.
  
  
  
  Nine children wore three activity monitors while being directly observed. The monitors included a hip- and wrist-worn ActiGraph and thigh-worn activPAL. The hip-worn ActiGraph was processed with the normal- and low-frequency filters and the inclinometer function. Cut points of ≤25 counts per 15-s epoch for the hip and ≤105 counts per 15-s epoch for the wrist were applied to the vertical axis to identify sit-to-stand transitions. Epoch-level absolute agreement, Bland-Altman plots, mixed-effects linear regression, and intraclass correlation coefficients (ICC) were investigated.
  
  
  
  The hip and wrist accelerometer cut points and the hip inclinometer function overestimated the number of hourly sit-to-stand transitions by approximately triple as compared with direct observation. ICC values between the ActiGraph methods and the direct observation were all <0.12. Sit-to-stand transitions assessed from activPAL were within 17% of direct observation; ICC was 0.26.
  
  
  
  Despite the common use of the 100-count hip-worn accelerometer cut point for assessing sedentary time, these processing decisions should be used with caution for assessing sit-to-stand transitions. Future research should investigate other processing methods for ActiGraph data, and studies investigating postural changes should consider including devices such as activPAL.
authors.affiliation: 1University of Kansas, Lawrence, KS; 2Children's Mercy Hospital, Kansas City, MO; 3University of California San Diego, La Jolla, CA; and 4University of Missouri Kansas City, Kansas City, MO.
authors.forename: Tarrah
authors.initials: T
authors.lastname: Mitchell
authors.forename: Kelsey
authors.initials: K
authors.lastname: Borner
authors.forename: Jonathan
authors.initials: J
authors.lastname: Finch
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Kerr
authors.forename: Jordan A
authors.initials: JA
authors.lastname: Carlson
mesh_terms: D061725:Accelerometry / Q000379:methods*; D002648:Child; D006615:Hip; D006801:Humans; D063766:Pediatric Obesity / Q000503:physiopathology*; D011187:Posture / Q000502:physiology*; D015203:Reproducibility of Results; D057185:Sedentary Behavior; D013848:Thigh; D014953:Wrist