Causes of a Slow Heart Rate During Exercise

During exercise, you will notice changes in your heart rate. Specific heart rate ranges based on the person's age, gender, exercise intensity and type and fitness level. A slow heart rate, called bradycardia if under 60 beats per minute, sometimes happens during exercise. Shortness of breath, dizziness, lightheadedness, fatigue and confusion may indicate a slow beat.

Your heart rate may mean something. (Image: Wavebreakmedia Ltd/Wavebreak Media/Getty Images)

Fitness Level

Being a muscle, your heart gains strength from exercising just as your shoulders and biceps would. As you improve your level of fitness through regular cardiovascular exercise, your heart becomes more efficient and beats slower both during exercise and at rest.

Underlying Heart Problem

Heart defects can also cause a slow heart rate. The heart receives electrical impulses that make it beat. Sometimes these impulses become blocked. When blocked, the heart rate slows down. Additionally, there may be a blocked artery or other congenital undiagnosed heart defect. If you suspect any of these, seek medical help.

Thyroid Issue

The thyroid plays a crucial role in the efficiency of the heart. When the thyroid does not make enough thyroid hormone, called hypothyroidism, individuals often experience a slower heart rate due to the weakening of the heart muscle. In situations of someone with underlying heart disease, this will be more obvious.


Medications such as beta blockers do not allow the heart rate to increase above a certain level to prevent heart problems. Any antiarrythmic and blood pressure medications impact the heart rate as well. Digoxin is used to help the heart beat more efficiently. This causes a slow heart rate that may not match your exercise intensity.

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