Why Does Heart Rate Increase?


The body is always in a state of maintaining a delicate balance of providing oxygen and nutrients to human body tissues for it to function properly. An increased heart rate, also known as tachycardia, is the involuntary result of a multitude of influences on the body. External influences include drinking caffeine, exercise and illness. Internal influences include low blood volume or low oxygen and can signal that the body is compensating from a deficit.

Panic or Anxiety

When the brain senses that the body is under attack, usually by a startling or frightening event, it goes into what is called a “fight or flight” mode. This natural and involuntary response prepares the body and its systems to stay and “fight” whatever it is threatened by or to take “flight” from it. Either circumstance requires the body’s reaction to immediately supply additional blood and oxygen to the muscles of the legs and arms more quickly, requiring an increased heart rate.

Low Blood Oxygen

The heart and lungs rely on each other through an interdependent series of blood and blood vessels to function properly. The lungs provide oxygen for the body by the exchange of oxygen and carbon dioxide to the blood cells, while the heart provides the mobility of the blood to circulate that oxygen to all the living tissues of the body. When the lungs are not functioning properly due to conditions such as asthma, chronic obstructive pulmonary disorder (COPD) or infection, the available oxygen to the body becomes reduced, but the tissue demand remains the same.

The same condition exists when the overall blood volume is depleted, either through dehydration or active internal bleeding. The available oxygen and nutrient levels are decreased, but the demands of the tissues remain the same. In both cases, the heart rate increases to push blood through the vessels faster to compensate for the difference.

Stimulating Substances

Stimulating substances, or stimulants, come in prescription and nonprescription form and act to increase the level of activity in the body. Prescription medications may include Ritalin and Dexedrine, and are used to treat specific health conditions. Nonprescription forms of stimulants include caffeine, nicotine and energy drinks, and many diet aids have stimulating effects on the body, including an increase in heart rate. Illicit drugs such as amphetamine, cocaine and ecstasy also mimic the stimulating effect.

Heart Rhythm Changes

The heart rate is controlled by steady electrical impulses from specialized nerve fibers within the heart at a rate of 60 to 100 beats a minute. Sudden or chronic changes in this conduction system cause an increase in heart rate.

Seeking Medical Attention

An increased heart rate may be an early sign that something is going awry in the body. The main symptom is heart “palpitations.” Depending on the underlying cause of the increase, additional symptoms may include a faint or dizzy feeling, difficulty breathing, feelings of increased anxiety and possibly fainting. Seek medical attention if any of these symptoms arise.

About this Author

Daniel Schellenger Jr. started writing in 1992 with his first publication in an EMS trade magazine. Over his 16 years in public safety, he has published in professional magazines, including “Disaster Recovery Journal” and “EMS Magazine.” Awards include a certificate of achievement by the Emergency Management Institute, and he is currently pursuing a degree in emergency management at the University of Colorado at Denver.