AUSTIN, Texas -- High school athletes are now gearing up for the fall. One or two-a-day practice for sports like football, call for kids to exert themselves in the Central Texas heat -- a combination that has proven to be deadly.

A medical condition called Hypotrophic Cardio Myopathy (HCM) can go undetected and kill an otherwise healthy teenager in an instant.

Joseph Collins loves golf and hopes to play in the PGA. But Joseph's golf swing started with a bat. He used to play baseball, but in July of 2006, that changed when his heart stopped in the middle of practice.

“They just told me that I was running; that's all I remember,” said Collins.

Joseph was then diagnosed with HCM. It’s a condition that causes the thickening of the heart walls and eventually cardiac arrest.

Doctor Silvana Lawrence says HCM is the reason why seemingly healthy athletes - whom have passed physical exams - drop dead.

To diagnose it, doctors have to see the heart using an echo-cardiogram.

“The echocardiogram actually images the heart, the chamber, and the walls, and we can actually see if the walls of the ventricle -- the pumping chamber -- are thick,” said Dr. Lawrence.

The echo cardiogram is essentially a sonogram. Non-invasive, it takes just a few minutes to detect trouble.

Patients with HCM must immediately cut back on physical activity.

“These patients are recommended not to participate in competitive sports, usually they are placed on medications,” said Dr. Lawrence.

Joseph is now on medication, and there's a small defibrillator in his chest. But the hardest change was trading in his bat swing for one with a club.

“It took a while - I got better and better, and I just love it now, I play it everyday,” said Collins.