In order to determine left ventricular global and regional myocardial functional reserve in endurance-trained and strength-trained athletes, and to identify predictors of exercise capacity, we studied 18 endurance-trained and 11 strength-trained athletes with left ventricular hypertrophy (172+/-27 and 188+/-39 g/m(2) respectively), and compared them with 14 sedentary controls. Global systolic (ejection fraction) and diastolic (transmitral flow) function, and regional longitudinal and transverse myocardial velocities [tissue Doppler echocardiography (TDE)], were measured at rest and immediately after exercise. In endurance-trained compared with strength-trained athletes, resting heart rate was lower (59+/-11 and 76+/-9 beats/min respectively; P<0.001), and the increase at peak exercise was greater (+211% and +139% respectively; P<0.001). In addition, exercise duration, workload, maximal oxygen consumption and global systolic functional reserve (but not peak ejection fraction) were higher in the endurance-trained athletes, and resting global diastolic function (E/A ratio 1.62+/-0.40 compared with 1.18+/-0.23; P<0.01) (where E-wave is peak velocity of early-diastolic mitral inflow and A-wave is peak velocity of mitral inflow during atrial contraction) and long-axis diastolic velocities (E(TDE)/A(TDE) ratio 2.2+/-1.2 compared with 1.1+/-0.3; P<0.01) (where E(TDE) and A(TDE) represent peak early- and late-diastolic myocardial or tissue velocity respectively) were augmented. Systolic velocities were similar. Exercise capacity was best predicted from end-diastolic diameter index and E/A ratio at rest, and end-diastolic volume index and diastolic longitudinal velocity during exercise (r=0.74, n=43, P<0.001). In conclusion, endurance-trained athletes had higher left ventricular long-axis diastolic velocities, augmented global early diastolic filling, and greater chronotropic and global systolic functional reserve. Maximal oxygen consumption was determined by diastolic loading and early relaxation rather than by systolic function, suggesting that dynamic exercise training improves cardiac performance by an effect on diastolic filling.