The investigators will recruit 42 untrained, healthy males and females aged 18-35 yrs. Half of the group will be placed on an exercise program for 15 weeks. The other half will serve as untrained control subjects. In addition to basic anthropometric measures, the investigators will measure concentrations of inflammatory and anti-inflammatory cytokines (ELISA) and cell surface expression of MC1R, MC3R, and MC5R on monocytes (flow cytometry).