Background: Coexisting type 2 diabetes mellitus (T2DM) and coronary artery disease (CAD) substantially increase cardiovascular risk. While exercise is beneficial, long-term randomized controlled trials (RCTs) in this high-risk population are limited.

Methods: In this single-center RCT, 158 patients with T2DM and stable CAD post-PCI were randomized (1:1) to a 12-month individualized aerobic-resistance exercise program or a usual-care control. Prescriptions were based on ACSM guidelines and CPET-derived VO₂ peak. The intervention group trained three times per week (~150 min/week) using moderate-to-high intensity protocols, monitored using Polar heart rate devices. Primary outcomes were changes in HbA1c and VO₂ peak; secondary outcomes included ventilatory threshold (VT) and time to exhaustion (TTE). Both ITT and PP analyses were conducted. Subgroup analysis was based on prior myocardial infarction (AMI) and the presence of diabetic microvascular complications.

Results: A total of 124 patients completed follow-up (intervention: n=52; control: n=72). The intervention group showed significantly greater improvements in HbA1c (−0.28 ± 0.47% vs. −0.05 ± 0.50%, p=0.024) and VO₂ peak (+1.27 ± 2.15 vs. +0.11 ± 1.92 mL·kg⁻¹·min⁻¹, p=0.037). VT (+2.39 ± 3.52 vs. +0.09 ± 3.14, p=0.046), and TTE (+55 ± 98 vs. +10 ± 85 sec, p=0.034) also improved significantly. Subgroup analysis revealed stronger effects in patients without prior AMI or microvascular complications (HbA1c: p=0.012; VO₂peak: p=0.018), while benefits were attenuated in those with such conditions. A negative correlation was found between changes in HbA1c and VO₂ peak (r = −0.30, p = 0.024). Greater improvements were observed in participants with lower baseline VO₂ peak (p for trend = 0.038).

Conclusion: A 12-month individualized combined exercise intervention significantly improved glycemic control and physical capacity in T2DM patients with stable CAD, especially in those with lower vascular burden and baseline fitness.