Exercise Dose and Metformin for Vascular Health in Metabolic Syndrome

Oral metformin 2000 mg/d for 16 weeks. Metformin dosage will follow 500 mg/d ramp up progression: Week 1 = 500 mg/d; Week 2 = 1,000 mg/d; Week 3 = 1500 mg/d; Week 4-16 = 2000 mg/d.

Oral placebo for 16 weeks. Placebo tablets will follow a four-stage progression: Week 1 = 1 tablet; Week 2 = 2 tablets; Week 3 = 3 tablets; Week 4-16 = 4 tablets.

Low intensity exercise will consist of 16 weeks of walking at \~55% of each participant's predetermined VO2max and monitored via heart rate. Supervised exercised will occur on a treadmill 3d/wk and the duration will be determined based on individual fitness levels to expand 400 kcals. Supervised exercise training will follow a three-phase progression: Weeks 1-2 = 3 supervised sessions at 75% duration; Week 3-4 = 3 supervised sessions at 87% duration; Weeks 5-16 = 3 supervised sessions at 100% duration. Unsupervised exercised will be 2d/wk and the duration will half the time of the supervised training sessions.

High intensity exercise will consist of 16 weeks of walking at \~85% of each participant's predetermined VO2max and monitored via heart rate. Supervised exercised will occur on a treadmill 3d/wk and the duration will be determined based on individual fitness levels to expand 400 kcals. Supervised exercise training will follow a three-phase progression: Weeks 1-2 = 3 supervised sessions at 75% duration; Week 3-4 = 3 supervised sessions at 87% duration; Weeks 5-16 = 3 supervised sessions at 100% duration. Unsupervised exercised will be 2d/wk and the duration will half the time of the supervised training sessions.