Creatine phosphate (Cr) and its phophorylated form (phosphocreatine, PCr) is catalyzed by creatine kinase (CK) reaction to phosphorylate ADP to ATP, which plays an important role in muscle energetics. This study aims to examine the combined effect of Cr and/or exercise training on myocardial energy reservation, using female hamsters. Fifty female Golden Syrian hamsters were divided into 4 groups of control (n=10), Cr supplementation (Cr+; n=10), exercise training (Ex; n=10), and Cr supplementation combined with exercise training (Cr+Ex; n=10). In the exercise-trained group, wheel-running for exercise (10 min. a day, 5 days a week) was imposed for 2 weeks. All animals were measured for exercise metabolic rate (EMR) on the 1st, 7th and 14th day. After the animals were sacrificed, the hearts were cut and weighed and the contents of Cr, PCr, total Cr (TCr), CK activities and RNA content were measured, using a spectrophotometric method. The animals treated with Cr+Ex on the 2nd week yielded the greatest EMR level with the lowest of oxygen consumption, compared with Cr+ or ex alone. Additionally, all parameters regulating myocardial energy reservation (contents of Cr, PCr, TCr and CK activity) and RNA contents improved greatly in Cr+Ex, treatment. These data indicate that creatine supplementation, when combined with exercise training, have many benefits for oxygen economy and effectiveness for myocardial energy reservation via Cr metabolism