In the moderate-intensity aerobic exercise group, participants performed a self-paced 1-mile walk (3-5 METs) on an indoor track in the same exercise center as the high-intensity exercise group. Initial sessions lasted 20-30 minutes and were increased weekly to 45 minutes in parallel to the duration of the high-intensity exercise group.

In the high-intensity aerobic exercise group, exercise training was performed on a motorized treadmill with occasional substitution with the elliptical machine as needed for joint pain. Target heart rate was based on the baseline treadmill test and was calculated as percentage of the heart rate reserve (HRR=maximal HR-resting HR). Initially, participants trained for 20-30 minutes at 50-60% of HRR. Duration and intensity was increased by 10% weekly so that within 5-7 weeks the aerobic exercise sessions lasted 30-45 minutes at 70-85% of HRR and at the end of the 16 weeks lasted 40-45 minutes at 75-90% of HRR.

Participants attended center-based exercise sessions three times per week at the research exercise training facility located at the Baltimore VA Medical Center. All exercise training was performed under the supervision of research exercise physiologists. Heart rate (HR) was measured continuously during each session using a Polar HR watch and chest strap allowing for assessment and maintenance of treatment fidelity. Exercise logs included details on exercise type, duration, time in target heart rate zone, blood pressure and perceived intensity during each training session.

Cardiorespiratory Fitness measured by VO2peak

Distance walked at normal pace in 6 minutes

body composition measured as total and regional lean tissue and fat mass (DXA)

activity of enzymes in oxidative function from muscle biopsy