Purpose: Impaired cardiorespiratory fitness (CRF) is a predictor of mortality in patients with type 2 diabetes mellitus (T2DM). It is still not known how the exercise hemodynamic response correlates with CRF. The purpose was to assess the correlation between hemodynamic changes and CRF in middle-aged patients with T2DM.Methods: After 1:1 matching by age and sex, 139 T2DM patients and 139 non-T2DM controls who completed the exercise treadmill test were included. Maximal aerobic capacity (VO2max), exercise-induced changes in heart rate (ΔHR), systolic blood pressure (ΔSBP), diastolic blood pressure (ΔDBP), and rate-pressure product (ΔRPP) were measured. HRR1 was calculated as the maximum heart rate minus the heart rate after 1 min of rest.Results: Compared to the control population, T2DM patients had decreased ΔHR (87 (77, 97) v 93 (84, 104) bpm, p < 0.05), ΔRPP (3833.64 ± 1670.34 v 4381.16 ± 1587.78 bpm∙mmHg, p < 0.05), HRR1 (21 (14, 27) v 21 (17, 27) bpm, p < 0.05), and VO2max (32.76 ± 5.63 v 34.68 ± 5.70 ml/kg/min, p < 0.05). Multiple linear regression analysis showed that ΔHR and HRR1, yielded a positive correlation with VO2max in T2DM patients (β = 0.325, P < 0.001; β = 0.173, P = 0.01).Conclusion: The presence of impaired hemodynamic response and VO2max in middle-aged T2DM patients and the association of impaired ΔHR, HRR1, and VO2max may indicate a physiological pathway of impaired CRF, and our results support the need for cardiorespiratory screening and individualized treatment of middle-aged T2DM patients. [ABSTRACT FROM AUTHOR]