Some studies have suggested that cross-linking of glycated collagen is a major mechanism that governs aging and diabetes-associated loss of cardiac and vascular compliance. We investigated the impact of long-term exercise training (ET) on age-related myocardial stiffness caused by advanced glycation end products (AGEs) cross-linking. Young (6-month-old) and old (25-month-old) male Fischer 344 rats were studied after 12 weeks treadmill ET or sedentary cage life. We compared cardiac performances using the pressure-volume conductance catheter system and amounts of myocardial total and AGEs cross-linked collagen between groups. The maximal slope of systolic pressure increment (P<0.05) increased, and end-diastolic volume (P<0.005) and slope of end-diastolic pressure-volume relation (P<0.05) were lower in old trained group (OT) than in old control group (OC). The maximal slope of diastolic pressure decrement (P=0.07) and time constant of LV pressure decay (課) (P=0.1) showed a tendency to improve by ET. Amounts of total and AGEs cross-linked collagen were increased with senescence. However, amount of AGEs cross-linked collagen was only reduced by ET (P<0.05). The activities and expressions of matrix metalloproteinase (MMP) 2 and MMP9 were higher in OC than in young control group (YC), but were lower in OT than in OC. Furthermore, the expressions of tissue inhibitor of metalloproteinase (TIMP) 1 and TIMP2 in OC and OT were antithetically regulated. In conclusion, long-term ET appears to prevent age-related deteriorations in LV geometry and function. The improvements in myocardial passive stiffness could be attributed to reductions in pathologic collagen cross-linking resulting from augmented collagen turnover.