All athletes underwent a standard presport medical history, physical examination, and ECG. Every athlete also had echocardiography. Echocardiography is more difficult to perform and read than ECG, which makes it less feasible for presport evaluation. However, the researchers used the echocardiograms to find out which athletes truly had heart problems that might make sports participation dangerous. They then saw how many cases of echocardiogram-proven heart disease were found with history and examination alone compared with plus ECG.