K. Fox, A. Stathi, J. Mckenna, and M. Davis, Physical activity and mental well-being in older people participating in the Better Ageing Project, European Journal of Applied Physiology, vol.330, issue.5, pp.591-602, 2007.
DOI : 10.1007/s00421-007-0392-0

K. Patrick, G. Norman, K. Calfas, J. Sallis, M. Zabinski et al., Diet, Physical Activity, and Sedentary Behaviors as Risk Factors for Overweight in Adolescence, Archives of Pediatrics & Adolescent Medicine, vol.158, issue.4, pp.385-90, 2004.
DOI : 10.1001/archpedi.158.4.385

J. Toschke, R. Von-kries, E. Rosenfeld, and A. Toschke, Reliability of physical activity measures from accelerometry among preschoolers in free-living conditions, Clinical Nutrition, vol.26, issue.4, pp.416-436, 2007.
DOI : 10.1016/j.clnu.2007.03.009

K. Chen and D. Bassett, The Technology of Accelerometry-Based Activity Monitors: Current and Future, Medicine & Science in Sports & Exercise, vol.37, issue.Supplement, pp.490-500, 2005.
DOI : 10.1249/01.mss.0000185571.49104.82

L. Moreno, M. González-gross, M. Kersting, D. Molnár, S. De-henauw et al., Assessing, understanding and modifying nutritional status, eating habits and physical activity in European adolescents. The HELENA Study, Public Health Nutr, vol.11, pp.288-299, 2008.

T. Cole, M. Bellizzi, K. Flegal, and W. Dietz, Establishing a standard definition for child overweight and obesity worldwide: international survey, BMJ, vol.320, issue.7244, pp.1240-1243, 2000.
DOI : 10.1136/bmj.320.7244.1240

J. Tanner, 1 Normal growth and techniques of growth assessment, Clinics in Endocrinology and Metabolism, vol.15, issue.3, pp.411-51, 1986.
DOI : 10.1016/S0300-595X(86)80005-6

L. Béghin, M. Castera, Y. Manios, C. Gilbert, M. Kersting et al., Quality assurance of ethical issues and regulatory aspects relating to good clinical practices in the HELENA Cross-Sectional Study, International Journal of Obesity, vol.14, pp.12-20, 2008.
DOI : 10.1207/s15327019eb1403_3

S. Powell, D. Jones, and A. Rowlands, Technical Variability of the RT3 Accelerometer, Medicine & Science in Sports & Exercise, vol.35, issue.10, pp.1773-1781, 2003.
DOI : 10.1249/01.MSS.0000089341.68754.BA

J. Vanhelst, L. Béghin, P. Rasoamanana, D. Theunynck, T. Meskini et al., Calibration of the RT3 accelerometer for various patterns of physical activity in children and adolescents, Journal of Sports Sciences, vol.36, issue.4, pp.381-388, 2010.
DOI : 10.1038/sj.ijo.0800810

J. Krasnoff, M. Kohn, F. Choy, J. Doyle, K. Johansen et al., Interunit and Intraunit Reliability of the RT3 Triaxial Accelerometer, Journal of Physical Activity and Health, vol.5, issue.4, pp.527-565, 2008.
DOI : 10.1123/jpah.5.4.527

M. Reneman and M. Helmus, Interinstrument reliability of the RT3 accelerometer, International Journal of Rehabilitation Research, vol.33, issue.2, pp.178-187, 2010.
DOI : 10.1097/MRR.0b013e32832c1e73

J. Vanhelst, D. Theunynck, F. Gottrand, and L. Béghin, Reliability of the RT3 accelerometer for measurement of physical activity in adolescents, Journal of Sports Sciences, vol.36, issue.4, pp.375-384, 2010.
DOI : 10.1249/MSS.0b013e31818ff636

J. Vanhelst, L. Béghin, D. Turck, and F. Gottrand, New validated thresholds for various intensities of physical activity in adolescents using the Actigraph accelerometer, International Journal of Rehabilitation Research, vol.34, issue.2, pp.175-77, 2011.
DOI : 10.1097/MRR.0b013e328340129e

D. Esliger and M. Tremblay, Technical Reliability Assessment of Three Accelerometer Models in a Mechanical Setup, Medicine & Science in Sports & Exercise, vol.38, issue.12, pp.2173-81, 2006.
DOI : 10.1249/01.mss.0000239394.55461.08

J. Fleiss, Design and analysis of clinical experiments, 1986.
DOI : 10.1002/9781118032923

J. Bland and D. Altman, Statistical methods for assessing agreement between two methods of clinical measurement, International Journal of Nursing Studies, vol.47, issue.8, pp.307-310, 1986.
DOI : 10.1016/j.ijnurstu.2009.10.001

R. Eston, A. Rowlands, and D. Ingledew, Validity of heart rate, pedometry, and accelerometry for predicting the energy cost of children's activities, J Appl Physiol, vol.84, pp.362-71, 1998.

G. Plasqui, A. Joosen, A. Kester, A. Goris, and K. Westerterp, Measuring Free-Living Energy Expenditure and Physical Activity with Triaxial Accelerometry, Obesity Research, vol.79, issue.suppl, pp.1363-1372, 2005.
DOI : 10.1038/oby.2005.165

K. Westerterp, Assessment of physical activity level in relation to obesity: current evidence and research issues, Medicine & Science in Sports & Exercise, vol.31, issue.Supplement 1, pp.522-527, 1999.
DOI : 10.1097/00005768-199911001-00006

C. Howe, J. Staudenmayer, and P. Freedson, Accelerometer Prediction of Energy Expenditure, Medicine & Science in Sports & Exercise, vol.41, issue.12, pp.2199-206, 2009.
DOI : 10.1249/MSS.0b013e3181aa3a0e

D. Macfarlane, C. Lee, E. Ho, K. Chan, and D. Chan, Convergent validity of six methods to assess physical activity in daily life, Journal of Applied Physiology, vol.101, issue.5, pp.1328-1362, 2006.
DOI : 10.1152/japplphysiol.00336.2006

D. Paul, M. Kramer, A. Moshfegh, D. Baer, and W. Rumpler, Comparison of two different physical activity monitors, BMC Medical Research Methodology, vol.38, issue.8476, p.26, 2007.
DOI : 10.2307/2683247

M. Rothney, E. Schaefer, M. Neumann, L. Choi, and K. Chen, Validity of Physical Activity Intensity Predictions by ActiGraph, Actical, and RT3 Accelerometers, Obesity, vol.99, issue.Suppl 9, pp.1946-52, 2008.
DOI : 10.1038/oby.2008.279

N. Leenders, W. Sherman, and H. Nagaraja, Energy Expenditure Estimated by Accelerometry and Doubly Labeled Water, Medicine & Science in Sports & Exercise, vol.38, issue.12, pp.2165-72, 2006.
DOI : 10.1249/01.mss.0000235883.94357.95

G. Baquet, G. Stratton, E. Van-praagh, and S. Berthoin, Improving physical activity assessment in prepubertal children with high-frequency accelerometry monitoring: A methodological issue, Preventive Medicine, vol.44, issue.2, pp.143-150, 2007.
DOI : 10.1016/j.ypmed.2006.10.004

M. Treuth, K. Schmitz, D. Catellier, R. Mcmurray, D. Murray et al., Defining accelerometer thresholds for activity intensities in adolescent girls, Med Sci Sports Exerc, vol.36, pp.1259-66, 2004.

M. Puyau, A. Adolph, F. Vohra, and N. Butte, Validation and Calibration of Physical Activity Monitors in Children, Obesity Research, vol.11, issue.Suppl, pp.150-157, 2002.
DOI : 10.1038/oby.2002.24

U. Ekelund, L. Sardinha, S. Anderssen, M. Harro, P. Franks et al., Associations between objectively assessed physical activity and indicators of body fatness in 9 to 10-year-old European children: a population-based study from 4 distinct regions in Europe (the European Youth Heart Study), Am J Clin Nutr, vol.80, pp.584-590, 2004.