Acute exercise increases myocardial tolerance to ischemia-reperfusion (I-R) injury in male but not female rat hearts, possibly due to a decreased heat shock protein 70 (Hsp70) response in the female hearts. This study examined whether repetitive exercise training would increase Hsp70 and myocardial tolerance to I-R injury in female rat hearts. Adaptations in myocardial manganese superoxide dismutase (MnSOD) and endothelial nitric oxide synthase (eNOS) were also assessed. Ten-week old male (M) and female (F) Sprague-Dawley rats (n=40 total) exercise-trained for 14 weeks; the last 8 weeks consisted of running 1 h at 30 m/min (2% incline), 5 days/week. Following training, left ventricle mechanical function (LVMF) was monitored for 30 min of reperfusion following 30 min of global ischemia (Langendorff procedure). Myocardial Hsp70 content was not different in M and F control groups, while increases were observed in both trained groups (M greater than F; p<0.05). Although MnSOD content did not differ between groups, endothelial nitric oxide synthase (eNOS) levels were decreased in F, with no change in M, following training (p<0.05). Hearts from control F demonstrated a greater recuperation of all indices of LVMF following I-R compared to control M hearts (p<0.05). Hearts of trained M exhibited improved recovery of LVMF (LVDP, LVEDP, +dP/dt, -dP/dt) during reperfusion compared to control M hearts (p<0.05). In contrast, hearts of trained F did not show any change in recovery from I-R. Hence, exercise training is more beneficial to M than F in improving myocardial function following I-R injury.