estimated 2 million injuries, 500,000 doctors visits, and 30,000 hospitalizations annually. this past friday, 16-year-old antonio rovas collapsed on his high school track, running a routine drill. he was taken to the hospital where he was pronounced dead of apparent heat exhaustion. and last week, hayward dennison of central catholic high school in oregon scored the winning touchdown. moments later, dennison felt his heart racing. i got back up and i was trying to breathe a lot more. reporter: then he collapsed of a heart attack. his heart stopped for about two minutes before a nurse in the stands helped revive him. turns out he has a heart condition, something doctors previously diagnosed as asthma. his father is now fighting to mandate heart screenings for all high school athletes. i want this a law. i won t stop. i m going to push it that no other family has to go through it. reporter: dan harris, abc news, new york.