Introduction Individuals with type 2 diabetes have a risk of heart failure 2-5 times greater than age matched controls, and the risk is greater for women compared to men. Prior to the onset of heart failure, individuals with type 2 diabetes exhibit structural and functional abnormalities of the myocardium. Although exercise training improves myocardial function in animal models of type 2 diabetes, data is in humans is limited. This study aimed to investigate the effect of moderate intensity exercise training upon cardiac function in overweight and obese postmenopausal women with type 2 diabetes (T2) compared to BMI matched, healthy controls (ND). Methods Seven T2 and 8 ND women (BMI > 25 kg/m2) volunteered for the study; all were postmenopausal (mean age 57 ± 4.9 years). Prior to and following 6 months of moderate intensity exercise training (55-75% heart rate reserve), participants completed a modified Bruce cardiopulmonary exercise test to assess VO 2peak. Cardiac function (resting and peak cardiac power output; pkCPO, and cardiac reserve; C-res) were calculated from cardiac output, determined by non -invasive inert gas re-breathing, and mean arterial pressure (MAP) determined by manual sphygmomanometry. Anthropometry (body mass, height, waist and hip circumferences) and a fasting venous blood sample (for insulin, glucose, HbA1c) were also assessed. One-way mixed mode ANOVA assessed group differences at baseline. Two-way mixed mode ANOVA with repeated measures tested the interaction between time (0 Vs 6 months) and group (T2 Vs ND). Results At baseline ND and T2 groups were similar for VO2 peak, pkCPO, C-res and anthropometry (P>0.05). T2 women had greater insulin resistance (P<0.05 for glucose, insulin, HbA1c , HOMA). Following training changes in body mass (-3.3 ±3.5 kg, ND; -1.9 ±2.4 kg, T2) and BMI (-1.2 ± 1.4 kg/m2, ND; -0.9 ± 0.8 kg/m2, T2) were similar for both groups (P>0.05). Change in VO2 peak was not significantly different between the groups although ND women showed a trend for greater increases (+349.8 ± 308.6 ml.min-1, ND; +143.3 ± 157.4 ml.min-1, T2). T2 women improved waist (-4 ±2 cm, P=0.03) and hip circumferences (-3.5 ±2 cm, P=0.05) whereas ND women did not. The exercise training significantly improved PkCPO and C-res in the ND but not in the T2 women (P<0.05; Figure 1). Peak cardiac output increased in the ND (+3 ± 1.7 L.min-1) but not in the T2 women (-0.63 ±2.3 L.min-1; P<0.05) and peak MAP (+2.4 ± 9.9mmHg ND; -0.9 ± 12.3mmHg, T2) was no different between the groups. Conclusion Compared to ND women, the cardiac function of T2 women in response to moderate intensity exercise training is impaired. This appears to be a function of a lack of plasticity of the flow generating capacity of the heart.