Your heart's conduction system creates a steady heartbeat that increases in response to exercise. The physiological changes of the heart during exercise are reflected in EKG tracings. The electrical activity of your heart recorded by the EKG allows doctors to determine if your heart is healthy at rest and during exercise. Cardiac abnormalities that sometimes are not evident at rest can be revealed by EKGs obtained during exercise.
The Heart
The heart is the engine whose pumping action delivers the oxygen and nutrients required for the metabolic processes of every cell in the body. Your heart beats automatically because it is wired to do so by means of a sophisticated system of nerves known as the cardiac conduction system. The heart's conduction system causes the heart to contract or pump by means of timed electrical impulses. These timed electrical impulses are measured in real time by the electrocardiogram.
The EKG
The EKG machine consists of electrodes and leads that are placed on the arms and legs, and across the precordium, which is the area in the left chest where the electrical impulses from the heart are picked up and transmitted to a tracing mechanism. An EKG tracing consists of a combination of 12 leads or images based on the electrical impulses from the inferior, posterior, anterior and lateral aspects of the heart.
Effects of Exercise on the EKG
During exercise, adrenaline causes the heart rate to increase. The increased heart rate also varies during exercise. As the heart rate increases, the distance between R waves gets shorter. The heart rate for an athlete's EKG is slower than that of people who are sedentary. People who are physically fit also have greater heart-rate variability on the EKG than people who are sedentary. According to a study in "Oxford Journals," increased heart rate at rest and during exercise and decreased heart-rate variability during exercise are associated with an increased risk of sudden death. An exercise EKG can also reveal irregular heart rhythms and signs that the heart is not getting enough blood to meet the increased demands of exercise. EKG interpretation can pinpoint the location of the blood-flow blockage within the system of coronary arteries.
Improvement of Your Cardiac Status
Heart disease is the major cause of death in the U.S. Exercise is an essential component for improvement in risk factors for heart disease such as obesity, diabetes, hyperlipidemia, hypertension and coronary artery disease. Exercise plays an important role in the prevention of cardiovascular disease and improves the risk of sudden death following myocardial infarction or heart attack. This protective effect of exercise in believed to be in part due to the action of the vagus nerve, a part of the parasympathetic nervous system that acts to lower heart rate. Failure to engage in exercise presents a serious hazard to your cardiac health and puts you at risk for serious debilitating diseases and sudden death. If your lifestyle does not include an exercise plan, ask your doctor to help you develop one that will safely and effectively maximize your cardiac health.
References
- "Oxford Journals"; Effects of Exercise Training on Heart Rate and QT Interval in Healthy Young Individuals: Are There Gender Differences?; Simonetta Genovesi, et al.; Oct. 3, 2006
- ADI Instruments; Cardiovascular Effects of Exercise; Dec. 7, 2005
- UAB Medicine; Electrocardiogram (EKG)/Stress Test/Holter Monitor: What is an Electrocardiogram?; 2008
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