Your heart should beat between 60 and 100 times each minute. This will allow adequate blood to flow throughout your body, carrying oxygen and nutrients to your cells so they can continue to function adequately. Unfortunately, sometimes the heart is not regulated properly and beats too quickly or too slowly. However, you can check it anytime and determine your heart rate.
Assessment
The American College of Sports Medicine's Health-Related Physical Fitness Assessment Manual lists several ways to assess your heart rate: electrocardiography, electric heart rate monitor and watch, auscultation with a stethoscope or palpation. Palpation is the simplest. Feel the front of your arm near your wrist, just inside of your radius, which is your arm bone at the base of your thumb. Press lightly in different areas until you find a pulse. Count the beats for 30 seconds and multiply by 2 to find your heart rate in beats per minute.
Significance
Two factors control cardiac output, which is the amount of blood that your heart pumps: how much blood is pumped per beat (called stroke volume) and how often your heart beats. Your stroke volume may be normal, but if your heart rate is 30 beats per minute, your heart will only pump half the blood that it should pump. In addition, if your heart rate is too fast, there is not enough time for your ventricles to fill with blood between beats, decreasing cardiac output.
Regulation
Your autonomic nervous system is one of the main regulators of your heart rate, according to "Principles of Anatomy and Physiology" by Gerard Tortora and Bryan Derrickson. It works through the sinus node in your right atria, which initiates the electrical signals that cause your heart muscle to contract.
Stimulation
Hormones, especially epinephrine, norepinephrine, and thyroid hormones, cause tachycardia (resting heart rate greater than 100 beats per minute), per Tortora and Derrickson. In addition, they state that high body temperature and high intracellular calcium can result in tachycardia. However, tachycardia is usually caused by stimulation of the sympathetic nervous system from exercise, fear, or stress, according to Karen Ellis in "EKG: Plain and Simple."
Depression
Any heart rate below 60 beats per minute is called bradycardia. Hypoxia, hypothermia, acidosis and alkalosis can lower heart rate too, according to Tortora and Derrickson. They also explain that people who exercise regularly tend to notice a decrease in resting heart rate because endurance training makes the heart more efficient by increasing stroke volume. Hypernatremia and hyperkalemia, high sodium and high potassium, also cause bradycardia, per Tortora and Derrickson.
References
- "ACSM's Health-Related Physical Fitness Assessment Manual"; American College of Sports Medicine; 2005
- "Principles of Anatomy and Physiology"; Gerard J. Tortora and Bryan Derrickson; 2006
- "EKG: Plain and Simple"; Karen M. Ellis; 2007
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