Berry JD, Willis B, Gupta S, et al. Lifetime Risks for Cardiovascular Disease Mortality by Cardiorespiratory Fitness Levels Measured at Ages 45, 55, and 65 Years in Men: The Cooper Center Longitudinal Study. J Am Coll Cardiol. 2011;57(15):1604-1610. doi:10.1016/j.jacc.2010.10.056.