PURPOSE: Although prior work highlights an exercise dose-response relationship for glucose regulation, no study has assessed the exercise dose needed for reducing arterial stiffness. We tested the hypothesis that increased exercise dose would correlate with reduced arterial stiffness in obese adults with prediabetes. METHODS: In this prospective study, 14 subjects (Age: 61.2±2.5 y, BMI: 32.5±1.4 kg/m2) were screened for prediabetes using American Diabetes Association criteria (75g OGTT and/or HbA1c). Aerobic fitness (VO2peak) was measured on a cycle ergometer by indirect calorimetry, and subjects performed supervised continuous aerobic exercise at 70% of HRpeak for 60min/d over 2-weeks. Arterial stiffness (augmentation index; AI), mean arterial pressure (MAP), and glucose tolerance during a 75g OGTT were analyzed by total area under the curve (tAUC) before and after training. Exercise dose was assessed using VO2-heart rate derived linear regression equations. RESULTS: Mean energy expenditure was 312.5±12.0 kcal/session. Exercise training improved VO2peak by 4.8% (trend: p=0.10), with no change in body weight. Continuous training also reduced AI (p=0.03) and MAP (p=0.05) tAUC180min by 20.9% and 5.4%, respectively. This reduced arterial stiffness tended to correlate with increased exercise energy expenditure (r=-0.53, p=0.06). Improved VO2peak was also related to reduced AI tAUC180min (r=-0.63, p=0.02), whereas decreased fasting plasma glucose was significantly related to lower MAP tAUC180min (r=-0.70, p=0.005). CONCLUSION: Short-term exercise training reduces arterial stiffness in a dose-dependent manner. These findings suggest that increasing exercise energy expenditure may be important for enhancing vascular function in adults with prediabetes.