1. Statistics. Running USA. Available at: http://www.runningusa.org/statistics. Accessed December 1, 2013.
2. Global Recommendations on Physical Activity for Health. World Health Organization. Available at: http://www.who.int/dietphysicalactivity/factsheet_recommendations/en/. Accessed December 1, 2013.
3. Physical Activity Guidelines for Americans. U.S. Department of Health and Human Services. Available at: http://health.gov/paguidelines. Accessed December 1, 2013.
4. Physical Activity Guidelines Advisory Committee Report. U.S. Department of Health and Human Services. Available at: http://health.gov/paguidelines/Report. Accessed December 1, 2013.
5. Surrogate measures of physical activity and physical fitness. Evidence for sedentary traits of resting tachycardia, obesity, and low vital capacity;Blair;Am J Epidemiol,1989