1Caspersen CJ, Powell K, Christenson G. Physical activity, exercise, and physical fitness: definitions and distinctions for health-related research. Public Health Reports 1985; 100: 126–31.
2Kriska AM, Caspersen CJ. A collection of physical activity questionnaires for health-related research. Medicine and Science in Sports and Exercise 1997; 29: S5–9.
3Wareham NJ, Rennie K. The assessment of physical activity in individuals and populations: why try to be more precise about how physical activity is assessed?. International Journal of Obesity and Related Metabolic Disorders 1998; 22: S30–8.
4Craig CL, Marshall AL, Sjöström M, Bauman AE, Booth ML, Ainsworth BE, et al. International physical activity questionnaire: 12-country reliability and validity. Medicine and Science in Sports and Exercise 2003; 35: 1381–95.
5Pate RR, Pratt M, Blair S, Haskell WL, Macera CA, Bouchard C, et al. Physical activity and public health. A recommendation from the Centers for Disease Control and Prevention and the American College of Sports Medicine. Journal of the American Medical Association 1995; 273: 402–7.
6Tryon W, Williams R. Fully proportional actigraphy: a new instrument. Behavior Research Methods, Instruments, & Computers 1996; 28: 392–403.
7Brage S, Wedderkopp N, Franks PW, Andersen LB, Froberg K. Reexamination of validity and reliability of the CSA monitor in walking and running. Medicine and Science in Sports and Exercise 2003; 35: 1447–54.
8Freedson P, Melanson E, Sirard J. Calibration of the Computer Science and Applications, Inc. accelerometer. Medicine and Science in Sports and Exercise 1998; 30: 777–81.
9Hendelman D, Miller K, Baggett C, Debold E, Freedson P. Validity of accelerometry for the assessment of moderate intensity physical activity in the field. Medicine and Science in Sports and Exercise 2000; 32: S442–9.
10Trost S, Ward D, Moorehead S, Watson P, Riner W, Burke J. Validity of the Computer Science and Applications (CSA) activity monitor in children. Medicine and Science in Sports and Exercise 1998; 30: 629–33.
11Ekelund U, Tingström P, Kamwendo K, Krantz M, Nylander E, Sjöström M, et al. The validity of the Computer Science and Applications activity monitor for use in coronary artery disease patients during level walking. Clinical Physiology and Functional Imaging 2002; 22: 248–53.
12Ekelund U, Sjöström M, Yngve A, Poortvliet E, Nilsson A, Froberg K, et al. Physical activity assessed by activity monitor and doubly labeled water in children. Medicine and Science in Sports and Exercise 2001; 33: 275–81.
13Ekelund U, Åman J, Westerterp K. Is the ArteACC index a valid indicator of free-living physical activity in adolescents?. Obesity Research 2003; 11: 793–801.
14Leenders NY, Sherman WM, Nagaraja HN, Kien CL. Evaluation of methods to assess physical activity in free-living conditions. Medicine and Science in Sports and Exercise 2001; 33: 1233–40.
15Ekelund U, Yngve A, Sjöström M, Westerterp K. Field evaluation of the Computer Science and Application's Inc. activity monitor during running and skating training in adolescent athletes. International Journal of Sports Medicine 2000; 21: 586–92.
16Ekelund U, Aman J, Yngve A, Renman C, Westerterp K, Sjöstrom M. Physical activity but not energy expenditure is reduced in obese adolescents: a case–control study. American Journal of Clinical Nutrition 2002; 76: 935–41.
17Bland JM, Altman DG. Statistical methods for assessing agreement between two methods of clinical measurement. Lancet 1986; 1(8476): 307–10.
18Sundquist K, Qvist J, Johansson SE, Sundquist J. Increasing trends of obesity in Sweden between 1996/97 and 2000/01. International Journal of Obesity and Related Metabolic Disorders 2004; 28: 254–61.
19Wareham NJ, Jakes RW, Rennie KL, Mitchell J, Hennings S, Day NE. Validity and repeatability of the EPIC–Norfolk Physical Activity Questionnaire. International Journal of Epidemiology 2002; 31: 168–74.
20Jacobs DR Jr, Ainsworth BE, Hartman TJ, Leon AS. A simultaneous evaluation of 10 commonly used physical activity questionnaires. Medicine and Science in Sports and Exercise 1993; 25: 81–91.
21Chasan-Taber L, Erickson JB, Nasca PC, Chasan-Taber S, Freedson PS. Validity and reproducibility of a physical activity questionnaire in women. Medicine and Science in Sports and Exercise 2002; 34: 987–92.
22Aadahl M, Jorgensen T. Validation of a new self-report instrument for measuring physical activity. Medicine and Science in Sports and Exercise 2003; 35: 1196–202.
23Norman A, Bellocco R, Bergström A, Wolk A. Validity and reproducibility of self-reported total physical activity – differences by relative weight. International Journal of Obesity and Related Metabolic Disorders 2001; 25: 682–8.