Exercise and Arterial Stiffness in Systemic Lupus Erythematosus

12-weeks aerobic exercise intervention based on the physical activity guidelines from the American College of Sports Medicine (≥150 min/week of moderate to vigorous \[40-85% of the individual's heart rate reserve\] exercise). Participants will perform the exercise on treadmills at the hospital. The volume and intensity of the exercise will progressively increase throughout the 12 weeks.