Upper body exercise has many applications to the rehabilitation and maintenance of cardiovascular health of individuals who are unable to exercise their lower body. The hemodynamic loads of upper body aerobic exercise are characterized by relatively high blood pressure and relatively low venous return. It is not clear how the left ventricle adapts to the specific hemodynamic loads associated with this form of exercise training. The purpose of this study was to measure left ventricular structure and function in previously sedentary men, using echocardiography, before and after 12-weeks of aerobic arm-crank exercise training (n=22) or a time-control period (n=22). Arm-crank VO_2peak (ml/kg/min) increased by 16% (P<0.05) following training and significant differences (P<0.05) were found in wall thickness (from 0.86 to 0.99 cm) but not left ventricular internal dimension in diastole or systole. This suggested a concentric pattern of left ventricular enlargement that persisted after scaling to changes in anthropometric characteristics. No differences (P<0.05) were found for any measurements of resting left ventricular function. We conclude that upper body aerobic exercise training results in a specific left ventricular adaptation that is characterised by increased left ventricular wall thickness but no change in chamber dimension.