Placing the Risks and Benefits of Physical Activity Into Perspective

ImageGenerally, habitual physical activity reduces risk of death due to heart disease, but in susceptible persons vigorous activity can increase the risk of sudden cardiac death and acute myocardial infarction. Susceptible adult individuals are primarily those with atherosclerotic disease.

The incidence of both acute myocardial infarction and sudden death is greatest in habitually sedentary individuals. Habitually sedentary men are 56 times more likely to experience cardiac death during or after vigorous exercise than while resting; however, very physically active men are only five times more likely to die during or after vigorous exercise than at rest.2 Similarly acute myocardial infarction during or soon after vigorous physical exertion is 50 times more likely in least active than in most active subjects.3

Maintaining physical fitness through regular physical activity may help to reduce premature death because a disproportionate number of fatal cardiac events occur in the least physically active subjects performing unaccustomed physical activity. While sedentary people are advised to change their lifestyle and adopt regular physical exercise starting with low intensity and gradually increasing over time, they may need a preparticipation screening. Subjects with any health limitations need medical clearing and preferably a professional fitness coach. High-risk patients should be excluded from certain activities. For a brief set of guidelines, read “When to consult a health-care provider before engaging in physical activities.”

Even the most restrictive policies will never be able to completely prevent cardiovascular events associated with exercise. For individuals who exercise, it is important to recognize and report prodromal symptoms (symptoms preceding cardiac event). Prodromal symptoms were present in 50% of joggers, 75% of squash players, and 81% of distance runners who died during exercise. Prodromal symptoms may include chest pain/angina, increasing fatigue, indigestion/heartburn/gastrointestinal symptoms, excessive breathlessness, ear or neck pain, vague malaise, upper respiratory tract infection, dizziness/palpitations or severe headache. People who exercise have to be aware of this and physicians should inquire about exercise and these symptoms during exams.

For more details about risk/benefit and strategies to mitigate risks see the paper of Thompson PD et al.

References

  1. Thompson PD et al. Scientific Statement From the American Heart Association Council on Nutrition, Physical Exercise and Acute Cardiovascular Events: Placing the Risks Into Perspective: Physical Activity, and Metabolism and the Council on Clinical Cardiology. Circulation. 2007;115:2358-2368; originally published online April 27, 2007; http://circ.ahajournals.org/content/115/17/2358
  2. Siscovick DS, Weiss NS, Fletcher RH, Lasky T. The incidence of primary cardiac arrest during vigorous exercise. N Engl J Med. 1984;311: 874–877.
  3.  Mittleman MA, Maclure M, Tofler GH, Sherwood JB, Goldberg RJ, Muller JE. Triggering of acute myocardial infarction by heavy physical exertion: protection against triggering by regular exertion: Determinants of Myocardial Infarction Onset Study Investigators. N Engl J Med. 1993;329:1677–1683.

Post written by: Petar Denoble, MD, D.Sc.

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