[1]. http://www.who.int/topics/physical_activity/en/
[2]. Haskell, W.L., Lee, I.M., Pate, R.R., Powell, K.E., Blair, S.N., Franklin, B.A., Macera, C.A., Heath, G.W., Thompson, P.D. and Bauman, A., 2007. Physical activity and public health: updated recommendation for adults from the American College of Sports Medicine and the American Heart Association. Circulation, 116(9), 2007, 1081.
[3]. Blair, Steven N. Physical inactivity: the biggest public health problem of the 21st century, British journal of sports medicine , 43(1), 2009: 1-2.
[4]. Dumith, Samuel C., Pedro C. Hallal, Rodrigo S. Reis, and Harold W. Kohl, Worldwide prevalence of physical inactivity and its association with human development index in 76 countries,Preventive medicine 53(1),2011,24-28.
[5]. Johnson, Cheryl A., Sheila A. Corrigan, Patricia M. Dubbert, and Sandra E. Gramling,Perceived barriers to excercise and weight control practices in community women, Women & Health 16 (3-4), 1990, 177-191.