title: Is there a sex difference in accelerometer counts during walking in older adults?
abstract: BACKGROUND
  Accelerometers have emerged as a useful tool for measuring free-living physical activity in epidemiological studies. Validity of activity estimates depends on the assumption that measurements are equivalent for males and females while performing activities of the same intensity. The primary purpose of this study was to compare accelerometer count values in males and females undergoing a standardized 6-minute walk test.
  
  
  METHODS
  The study population was older adults (78.6 ± 4.1 years) from the AGES-Reykjavik Study (N = 319). Participants performed a 6-minute walk test at a self-selected fast pace while wearing an ActiGraph GT3X at the hip. Vertical axis counts · s(-1) was the primary outcome. Covariates included walking speed, height, weight, BMI, waist circumference, femur length, and step length.
  
  
  RESULTS
  On average, males walked 7.2% faster than females (1.31 vs. 1.22 m · s(-1), P < .001) and had 32.3% greater vertical axis counts · s(-1) (54.6 vs. 39.4 counts · s(-1), P < .001). Accounting for walking speed reduced the sex difference to 19.2% and accounting for step length further reduced the difference to 13.4% (P < .001).
  
  
  CONCLUSIONS
  Vertical axis counts · s(-1) were disproportionally greater in males even after adjustment for walking speed. This difference could confound free-living activity estimates.
authors: Dept of Biostatistics and Bioinformatics, Rollins School of Public Health, Emory University, Atlanta, GA.
authors: Dane R
authors: DR
authors: Van Domelen
authors: Paolo
authors: P
authors: Caserotti
authors: Robert J
authors: RJ
authors: Brychta
authors: Tamara B
authors: TB
authors: Harris
authors: Kushang V
authors: KV
authors: Patel
authors: Kong Y
authors: KY
authors: Chen
authors: Nanna Ýr
authors: NÝ
authors: Arnardóttir
authors: Gudny
authors: G
authors: Eirikdottir
authors: Lenore J
authors: LJ
authors: Launer
authors: Vilmundur
authors: V
authors: Gudnason
authors: Thórarinn
authors: T
authors: Sveinsson
authors: Erlingur
authors: E
authors: Jóhannsson
authors: Annemarie
authors: A
authors: Koster
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D001835:Body Weight; D005080:Exercise Test; D005260:Female; D006801:Humans; D008297:Male; D018670:Monitoring, Ambulatory / Q000379:methods*; D009043:Motor Activity; D012737:Sex Factors; D012959:Socioeconomic Factors; D011795:Surveys and Questionnaires; D013997:Time Factors; D016138:Walking