Myocardial blood flow, oxygen consumption, and fatty acid uptake in endurance athletes during insulin stimulation

We have previously demonstrated reduced myocardial glucose uptake rates in hearts of endurance athletes, which could be due to increased use of altern ative fuels or reduced energy demands. In the present study myocardial bloo d flow, oxygen consumption, and free fatty acid uptake were measured with [ O-15]H2O, [O-15]O-2, [F-18]FTHA, and positron emission tomography (PET) in 9 endurance athletes and 11 sedentary men during euglycemic hyperinsulinemi a. Compared with sedentary men, athletes had 33% lower myocardial blood flo w, 27% lower oxygen consumption, and 20% lower estimated myocardial work pe r gram of tissue. Myocardial fatty acid uptake rates were not significantly different in endurance athletes (0.83 +/- 0.29) and sedentary men (1.0 +/- 0.31 mu mol.100 g(-1).min(-1), P = 0.232). In conclusion, myocardial blood dow and oxygen consumption per unit mass of myocardium are reduced at rest in endurance athletes. This can be explained by reduced energy requirement s per gram of tissue due to anatomic and physiological changes of the athle te's heart.