title: Comparison of physical activity assessed using hip- and wrist-worn accelerometers.
abstract: OBJECTIVE
  It is unclear how physical activity estimates differ when assessed using hip- vs wrist-worn accelerometers. The objective of this study was to compare physical activity assessed by hip- and wrist-worn accelerometers in free-living older women.
  
  
  METHODS
  A cross-sectional study collecting data in free-living environment.
  
  
  METHODS
  Participants were from the Women's Health Study, in which an ancillary study is objectively measuring physical activity using accelerometers (ActiGraph GT3X+). We analyzed data from 94 women (mean (SD) age=71.9 (6.0) years) who wore a hip-worn and wrist-worn accelerometers simultaneously for 7 days.
  
  
  RESULTS
  Using triaxial data (vector magnitude, VM), total activity volume (counts per day) between the two locations was moderately correlated (Spearman's r=0.73). Hip and wrist monitors wear locations identically classified 71% individuals who were at the highest 40% or lowest 40% of their respective distributions. Similar patterns and slightly stronger agreements were observed when examining steps instead of VM counts.
  
  
  CONCLUSIONS
  Accelerometer-assessed physical activity using hip- vs wrist-worn devices was moderately correlated in older, free-living women. However, further research needs to be conducted to examine comparisons of specific activities or physical activity intensity levels.
authors.affiliation: Division of Preventive Medicine, Brigham and Women's Hospital, Harvard Medical School, 900 Commonwealth Ave East, Boston, MA 02215, USA; Department of Health Promotion and Exercise, National Institute of Health and Nutrition, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8636 Japan. Electronic address: kamada@gakushikai.jp.
authors.forename: Masamitsu
authors.initials: M
authors.lastname: Kamada
authors.affiliation: Division of Preventive Medicine, Brigham and Women's Hospital, Harvard Medical School, 900 Commonwealth Ave East, Boston, MA 02215, USA; National Institute on Aging, National Institutes of Health, 31 Center Drive, MSC 2292, Bethesda, MD 20892, USA.
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Shiroma
authors.affiliation: National Institute on Aging, National Institutes of Health, 31 Center Drive, MSC 2292, Bethesda, MD 20892, USA.
authors.forename: Tamara B
authors.initials: TB
authors.lastname: Harris
authors.affiliation: Division of Preventive Medicine, Brigham and Women's Hospital, Harvard Medical School, 900 Commonwealth Ave East, Boston, MA 02215, USA; Department of Epidemiology, Harvard T.H. Chan School of Public Health, 677 Huntington Ave, Boston, MA 02115, USA.
authors.forename: I-Min
authors.initials: IM
authors.lastname: Lee
mesh_terms: D061725:Accelerometry / Q000295:instrumentation*; D000368:Aged; D003430:Cross-Sectional Studies; D005260:Female; D006615:Hip; D006801:Humans; D009043:Motor Activity; D014953:Wrist
keywords: Epidemiology; Exercise; Measurement; Objective monitoring; Step counts