Aerobic exercise - the most widely recommended health behavior - is recognized to reduce the risk of coronary heart disease, so much so that consensus panels routinely include it as part of a cardioprotective regimen for healthy people, but the physiological or mechanistic basis of this protection is uncertain. Understanding the mechanisms has considerable public health significance because it will allow development and testing of targeted interventions to produce comparable cardioprotective effects more directly or in cases where aerobic exercise is not possible. This application proposes to test the hypothesis that aerobic training leads to attenuation of the inflammatory response to LPS stimulation and to examine the role played by exercise-induced increases in vagal activity, improvements in mood, and decreased expression of Toll Receptor 4 (TLR4), the cognate receptor for endotoxin expressed by monocytes.