title: A community based study to test the reliability and validity of physical activity measurement techniques.
abstract: BACKGROUND
  Physical activity (PA) is protective against non-communicable diseases and it can reduce premature mortality. However, it is difficult to assess the frequency, duration, type and intensity of PA. The global physical activity questionnaire (GPAQ) has been developed by World Health Organization with the aim of having valid and reliable estimates of PA. The primary aim of this study is to assess the repeatability of the GPAQ instrument and the secondary aim is to validate it against International Physical Activity Questionnaire (IPAQ) and against an objective measure of PA (i.e., using pedometers) in both rural and peri-urban areas of North India.
  
  
  METHODS
  A total of 262 subjects were recruited by random selection from Ballabgarh Block of Haryana State in India. For test retest repeatability of GPAQ and IPAQ, the instruments were administered on two occasions separated by at least 3 days. For concurrent validity, both questionnaires were administered in random order and for criterion validity step counters were used. Spearman's correlation coefficient, intra-class correlation (ICC) and Cohen's kappa was used in the analysis.
  
  
  RESULTS
  For GPAQ validity, the spearman's Rho ranged from 0.40 to 0.59 and ICC ranged from 0.43 to 0.81 while for IPAQ validity, spearman correlation coefficient ranged from 0.42 to 0.43 and ICC ranged from 0.56 to 0.68. The observed concurrent validity coefficients suggested that both the questionnaires had reasonable agreement (Spearman Rho of >0.90; P < 0.0001; ICC: 0.76-0.91, P < 0.05).
  
  
  CONCLUSIONS
  GPAQ is similar to IPAQ in measuring PA and can be used for measurement of PA in community settings.
authors.affiliation: Centre for Community Medicine, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: Puneet
authors.initials: P
authors.lastname: Misra
authors.affiliation: Department of Community Medicine, Vardhman Mahavir Medical College and Safdarjung Hospital, New Delhi, India.
authors.forename: Ravi Prakash
authors.initials: RP
authors.lastname: Upadhyay
authors.affiliation: Centre for Community Medicine, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: Anand
authors.initials: A
authors.lastname: Krishnan
authors.affiliation: Department of Obstetrics and Gynecology, The Women's Health Center at Newark, USA.
authors.forename: Neelam
authors.initials: N
authors.lastname: Sharma
authors.affiliation: Department of Community Health, St. Stephen's Hospital, New Delhi, India.
authors.forename: Suresh K
authors.initials: SK
authors.lastname: Kapoor
keywords: Community setting; North India; global physical activity questionnaire; international physical activity questionnaire; pedometer; reliability; rural; validity