The swimming training will be performed at two swimming pools on the campus of The University of Texas at Austin (University Aquatic Center or Gregory Gym pool). In the first 2-3 weeks a swimming instructor will provide personalized skill feedback to the subjects in the swim training group. Subjects will swim 15-20 minutes/day at a relatively low intensity of exercise while they receive swimming skill instructions. As their overall level of fitness and exercise skill improve, the intensity and duration of exercise will increase to 40-45 minutes/day at a moderate intensity of 70-75% of maximal heart rate. Exercise training will be performed three days per week.

The cycling training will be conducted in the newly-constructed Exercise Training Intervention Core-Laboratory in the Department of Kinesiology and Health Education on the University of Texas campus. In the first 2-3 weeks a cycling instructor will provide personalized skill feedback to the subjects in the cycle training group. Subjects will cycle 15-20 minutes/day at a relatively low intensity of exercise while they receive cycling skill instructions. As their overall level of fitness and exercise skill improve, the intensity and duration of exercise will increase to 40-45 minutes/day at a moderate intensity of 70-75% of maximal heart rate. Exercise training will be performed three days per week.

Central Arterial Compliance: Common carotid artery diameter will be measured from the images derived from an ultrasound machine (Philips HDI-5000, Bothel, WA) equipped with a high-resolution linear-array transducer as previously described. A longitudinal image of the cephalic portion of the common carotid artery will be acquired 1-2 cm proximal to the carotid bulb with the transducer placed at 90 degrees to the vessel. The images will be analyzed with Vascular Tools 5 image analyses software. Similarly, intima-media thickness will be measured at end diastole as previously described. The combination of ultrasound imaging of a common carotid artery with simultaneous tonometric-obtained arterial pressure waveforms from the contralateral artery permits noninvasive determination of carotid artery compliance. Arterial compliance is a function of the increase in arterial pressure and a corresponding increase in cross-sectional area.

Fasted state, venous blood samples will be obtained to assess biological markers of inflammation. Serum C-reactive protein (CRP) will be assayed using ELISA (Alpha Diagnostics; San Antonio, TX). Inflammatory cytokines including Interleukin-6 (IL-6), TNF-α, and soluble receptor 1 (sTNFR1) will be analyzed from serum samples using a multiplex assay system (Bioplex, BioRad; Hercules, CA)

Flow-Mediated Dilatation is a non-invasive method to assess vascular endothelial function as previously described. Brachial artery diameters and blood flow velocity will be measured from images derived from a Doppler ultrasound machine equipped with a high-resolution linear array transducer. A longitudinal image of the brachial artery will be acquired 5-10 cm proximal to the antecubital fossa. A blood pressure cuff will be placed on the forearm 3-5 cm distal to the antecubital fossa. The cuff will be inflated to 100 mmHg above resting systolic blood pressure for 5 minutes. After cuff deflation, ultrasound-derived measurements of the brachial artery diameters and blood velocity will be taken for 3 minutes. FMD will be calculated as a percent increase in brachial artery diameter at the post-blood flow occlusion compared with the pre-blood flow occlusion.

Six-minute walk distance will be used for a measure of mobility and functional status. Participants will be instructed to walk as far as possible on a flat, indoor surface.