The incidence of both acute myocardial infarction and SCD is greatest in generally sedentary individuals, especially those who engage in unaccustomed physical activity. A paper published in the New England Journal of Medicine found that habitually sedentary men were 56 times more likely to experience cardiac death during or after vigorous exercise than when at rest; by contrast, very physically active men were only five times more likely to die during or after vigorous exercise than when at rest. Another New England Journal of Medicine paper reported that an acute myocardial infarction was 50 times more likely during or soon after vigorous physical exercise in the least active than in the most active subjects.
So while sedentary individuals are advised to change their lifestyle and take up regular physical exercise — starting with low-intensity activities and gradually increasing the intensity at which they exercise — they may require pre-activity screening. Individuals with any health limitations need both medical clearance and, preferably, a professional fitness coach. Individuals identified as being at high risk for cardiac problems should abstain from certain activities. For relevant guidelines, read "When to consult a health-care provider before engaging in physical activities."
It is important to emphasize, however, that even the most restrictive practices will never be able to completely prevent cardiovascular events associated with exercise. It is thus essential that individuals who exercise recognize and report the symptoms that often precede a cardiac event; these are known as "prodromal symptoms" and may include one or more of the following:
- Chest pain (known as "angina")
- Increasing fatigue
- Indigestion, heartburn or other gastrointestinal symptoms
- Excessive breathlessness
- Ear or neck pain
- A feeling of vague malaise
- Upper respiratory tract infections
- Dizziness, palpitations or a severe headache