Background Determinants of exercise capacity have not been clearly elucidated in healthy individuals. In previous reports, left ventricular (LV) dyssynchrony is known to be associated with impaired exercise capacity in patients with heart failure. However, few data exist on the effect of LV synchronicity on exercise capacity in physically-competent subjects. Therefore, we investigated whether LV synchronicity is associated with exercise capacity in those people. Methods We studied 22 healthy subjects (mean age 47.6 짹 6.9 years) including 11 male amateur marathon runners and 11 age-matched subjects with mild hypertension (JNC stage 1). Conventional echocardiographic indices were measured before maximal-graded exercise test on a supine bicycle ergometer with gas exchange analysis. Longitudinal tissue velocity and strain were also measured at 12 segments in the 3 apical views at the level of mid and base of LV, using a 2-D based quantitative Velocity Vector Imaging (Siemens, Mountain View, CA). Results Both group had normal LV systolic and diastolic function. But marathon runners had smaller body mass index (BMI) and larger LV end-diastolic volume (LVEDV), cardiac index (CI) and E/A than hypertensive individuals. Maximal oxygen uptake (VO2 max) was significantly higher in the marathon runners group (marathon runners vs. hypertensive subjects, 37.5 짹 3.6 vs. 25.9 짹 4.4 mL/min/Kg, p<0.001). The linear correlation with VO2 max concerned BMI (r=-0.473, p=0.026), LVmass/BSA (r=0.495, p=0.019), LVEDV (r=0.518, p=0.016), CI (r=0.596, p=0.004), E/A (r=0.504, p=0.017), standard deviation of time to peak longitudinal systolic velocity (Tv-SD, r=-0.525, p=0.012) and standard deviation of time to peak longitudinal strain (Ts-SD, r=-0.577, p=0.005). On multivariate analysis, Tv-SD (��=-0.437, p=0.038) and Ts-SD (��=-517, p=0.017) were the independent predictors of exercise capacity. Conclusions Tv-SD and Ts-SD were respectively the independent predictors of exercise capacity in healthy subjects. These data suggest that regular physical training may improve exercise capacity by leading to the synchronous contraction of LV in healthy individuals.