Dear Doctors: I meet up with friends a few days a week to go running. One of them always skips the cooldown and hops right into his car to drive to work. A trainer once told me that’s a recipe for sudden cardiac death. Do you know if that’s a myth, or is there something to it?
Dear Reader: The term “sudden cardiac death” is used to describe a medical emergency that, because it compromises the cardiovascular system, results in the person’s death within an hour of the onset of symptoms. Most often the problems directly involve the heart. These include various types of heart arrhythmias, cardiac arrest, heart attack, cardiomyopathy or stroke. Although not as common, sudden cardiac death can occur due to a drug overdose, trauma or poisoning. Sometimes a cause for the sudden cardiac death cannot be determined. The death occurs because something has caused the heart to stop altogether, or to function so poorly that it was unable to deliver enough blood throughout the body to sustain life.
The most common factor in sudden cardiac death is the presence of coronary artery disease, or CAD. This is a condition in which the interior walls of the arteries that deliver blood to the heart grow narrow, or become completely blocked, due to a buildup of plaque. In younger adults, a heart arrhythmia, such as ventricular or atrial fibrillation, or ventricular tachycardia, is often the cause. These are conditions in which the electrical signals that coordinate the heartbeat go awry, which swiftly disrupts the flow of blood throughout the body.
The good news is that sudden cardiac death during or after exercise is rare. However, the trainer you spoke with is on the right track in discussing the importance of a cooling down period after exercise. When you exert yourself in any way, your heart begins to beat faster and more forcefully in order to deliver the additional oxygen and nutrients needed by the muscles. This, in turn, leads to an increase in systolic blood pressure, which is the force of the blood on the walls of the vessels during a heartbeat. Both the added demands on the heart and the increase in systolic blood pressure will persist for as long as you maintain the pace and intensity of the exercise you are doing.
A cooldown period immediately following prolonged vigorous exercise is beneficial to the heart. It lets you slowly reduce the demands you have been making on your muscles, and thus on your heart. As the muscles work less, their need for oxygen decreases. This allows a return to a slower and less vigorous heartbeat, which in turn begins to ease systolic blood pressure. A cooldown doesn’t have to be elaborate or prolonged. Simply taking the time to slow the pace of your run, to jog for a bit as you regain your breath and then wind down to a few minutes of brisk walking should be enough for both the heart and your blood pressure to have a safe and gradual recovery.
(Send your questions to [email protected], or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)
