Causes of a Slow Heart Rate During Exercise

Your heart is composed of complex electrical pathways that dictate your heart rate and send the message to pump blood throughout your body. Checking your heart rate during exercise allows you to track your fitness and ensure maximum benefit from your workout sessions. Determine your pulse by placing your finger on the radial side of your wrist or on your carotid artery. Count the number of times your heart beats in 15 seconds. Multiply this number by four to calculate your heart rate. Occasionally, you may experience bradycardia, or a heart rate less than 60 beats per minute. A slower-than-normal heart rate denies the body an adequate amount of oxygen-rich blood to organs and muscles during exercise. Symptoms may include shortness of breath, dizziness or chest pain. The causes of bradycardia range from benign to potentially serious, so it is crucial to determine its cause with the help of a physician or cardiologist.

Age and Fitness Level

Age and fitness level affect your heart rate. According to the Mayo Clinic, younger, healthy individuals who exhibit a low heart rate likely have little cause for concern. In addition, older adults who are physically fit may experience bradycardia during exercise. However, if you faint or have prolonged chest pain during or after exercise, get immediate medical attention regardless of your age. Age also may affect the heart negatively. For older adults, bradycardia may be caused by long-term tissue damage to the heart and requires the assistance of your physician. Treatments range from medications to surgery, depending on the cause.

Underlying Cardiac Illness

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A variety of underlying cardiac illnesses may result in bradycardia during exercise. The American Heart Association states that issues with your sinoatrial node or other electrical heart abnormalities may present as bradycardia during activity. Other examples include an infection of your heart, known as myocarditis, or a structural issue of your heart present since birth. One percent of the population is born with a congenital defect, but this may or may not become apparent until later in life. Therefore, it is crucial to speak to a physician immediately if you experience any bradycardic symptoms so he can rule out this potentially life-threatening cause.

Underlying Chronic Illness

Chronic illness is another potential cause of slow heart rate. Sleep apnea, a breathing disorder during sleep, may result in bradycardic episodes during the day, as well. Loud snoring at night may indicate this issue, and a sleep study can determine if this is the cause for your bradycardia. Hypothyroidism, or an underactive thyroid gland, may also result in a slow heart rate during exercise. The low level of hormones produced by the gland results in a general slowing of bodily functions, including heart rate. Diagnosis is made through symptoms and a TSH blood test. This is a common disorder, particularly if you are a woman over 50. Treatment ranges from hormone-replacing medication to surgery.


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A number of medications decrease your heart rate during exercise. Certain blood pressure medications and drugs used to regulate heart rhythm cause a low heart rate. Examples include beta-blockers and Digoxin. Despite the vigorous nature of your workout, these medications block the heart's ability to pump at a faster rate. Therefore, it is important to speak to your physician about how to determine your ideal exercise heart rate.