How Can People Who Exercise Die Suddenly?

QUESTION: I thought exercise promoted a long and healthy life, but some of
the things I've been reading in the paper says otherwise. How can people who
exercise regularly die suddenly?
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ANSWER: Although some experts argue that it's just a coincidence when people
happen to die suddenly while they are exercising, others believe that
strenuous exercise may increase the chance of sudden death in certain people,
even if they are in good condition.
Studies of apparently healthy and fit people who died during exercise
have shown that, even though they may have had no symptoms of heart disease,
many had at least one coronary risk factor, such as high blood pressure, high
cholesterol, or a family history of heart disease. Autopsies revealed that
the majority of these people had clogged arteries or other heart problems that
would endanger them during strenuous exercise, without providing any warning
symptoms.
In most cases, the cause of death was clogged arteries--coronary
atherosclerosis. Everyone over 30 years old should be checked for this
condition before beginning to exercise, and see a doctor if they develop any
symptoms that might be related to heart problems.