Several substudies were conducted using the Muscatine study population. The subproject on left ventricular mass in childhood was designed to determine the age/sex distribution of left ventricular mass in children 5-14 years of age and whether elevated left ventricular mass, as demonstrated by echocardiography, could be related to higher ambulatory blood pressure, exercise blood pressure and work capacity, or physical conditioning. The study also determined whether there was a familial aggregation of left ventricular mass, whether it was associated with high blood pressure in parents and whether left ventricular mass in children was associated with increased cardiovascular and all causes mortality in first and second degree relatives.