1. Centers for Disease Control and Prevention. Trends in leisure-time physical inactivity by age, sex, and race/ethnicity—United States, 1994–2004. MMWR Morb Mortal Wkly Rep. 2005; 54(39): 991–994.
2. US Department of Health and Human Services. Healthy People 2010. Washington, D.C: US Department of Health and Human Services; 2000.
3. Centers for Disease Control and Prevention. Prevalence of regular physical activity among adults—United States, 2001 and 2005. MMWR Morb Mortal Wkly Rep. 2007; 56: 1209–1212.
4. Barnes P. Physical activity among adults: United States, 2000 and 2005. Hyattsville: US Department of Health and Human Services, CDC; 2007. Available at http://www.cdc.gov/nchs/products/pubs/pubd/hestats/physicalactivity/physicalactivity.htm .
5. Crespo CJ, Smith E, Andersen RE, Carter-Pokras O, Ainsworth BE. Race/ethnicity, social class and their relation to physical inactivity during leisure time: Results from the Third National Health and Nutrition Examination Survey, 1988–1994. Am J Prev Med. 2000; 18: 46–53.