Heart rate refers to the pace at which your heart pumps blood through your body. An adequate heart rate is important because blood carries oxygen, nutrients and waste products. A number of factors can decrease your heart rate, including external or internal changes, fitness level, illness and medications. The brain stem continually keeps abreast of such changes, sending signals that regulate the pace of your heart.
Resting Heart Rate
At rest, the adult heart normally beats at a rate of 60 to 100 beats per minute, or bpm. Trained athletes may have a normal resting heart rate as low as 40 to 60 bpm, according to the Mayo Clinic. Children below the age of 10 usually have higher resting heart rates than adults.
External Factors
Environmental stressors that challenge your body's temperature regulation system can cause your heart rate to slow down, says FitMed. For instance, wind keeps your heart rate in low ranges by causing body heat to decrease. Certain drugs can also cause your heart rate to drop, including: beta blockers, such as Inderal, Propranolol, and Lopressor; cardiac anti-arrhythmic drugs, such as Cardioquin, Procaine and Quinidine; sedatives, such as barbiturates; tranquilizers; alcohol and the recreational drug quaaludes.
Internal Factors
As Howard University professor of medicine Otello Randall remarks, your heart rate also varies in response to emotional changes. For instance, depression usually lowers your heart rate. A similar effect can result from emotions, such as love, compassion and happiness, according to FitMed. Also, your heart normally slows its pace during the first four stages of sleep, although a 2004 issue of Psychosomatic Medicine reported that chronic stress can affect heart rate variability during your sleep.
Fitness Level
Undoubtedly, the arm muscles of a trained athlete can lift more weights in one count than those of a sedentary individual. Likewise, the cardiac pump of a fit person can pump more blood in one beat than that of an unfit person. Thus, the athlete's heart requires fewer beats per minute in order to deliver enough blood to the body. Since your heart is a muscle, you can strengthen it with training. The fitter you get, the more efficient your cardiac pump becomes. In fact, training effect can lower your resting heart rate by as much as 20 to 30 bpm, says FitMed.
Disease States
Bradycardia, which is the medical term for a consistently below-normal heart rate, results from a disruption of your heart's electrical system, says the Mayo Clinic. A number of disease states can cause this disruption, including: age-related heart tissue degeneration; heart attack; high blood pressure; heart tissue infection, congenital heart defects; heart surgery complications; under-active thyroid gland; blood electrolyte imbalance; obstructive sleep apnea; inflammatory disorders such as rheumatic fever or lupus; and iron accumulation in your organs.
Risk Factors
Admittedly, bradycardia may be normal for you, particularly if you're a healthy, physically fit individual. However, because of bradycardia's common association with heart tissue damage, the Mayo Clinic , argues that lifestyle changes or medications that address heart disease risk factors can also help you reduce the risk of bradycardia. These risk factors include: high blood pressure, high cholesterol, smoking, heavy alcohol use, use of recreational drugs, stress and anxiety.
Warning Signs
Both high or low extremes of heart rate can be a sign of an underlying problem, according to the Mayo Clinic. Because bradycardia can also mean that your brain and other organs are not receiving enough oxygen, be wary of such symptoms as: fainting, dizziness, fatigue, shortness of breath, chest pains, sleep disturbances, mental confusion and quick tiredness during physical activities. Untreated bradycardia can escalate to repeated fainting spells, heart failure and sudden cardiac arrest.
References
- The Mayo Clinic: Bradycardia
- "FitMed": Ways to Change Your Heart Rate
- "Psychosomatic Medicine "; Acute Stress Affects Heart Rate Variability During Sleep; Martica Hall, Ph.D. et al; January/February 2004
- "The A to Z of the Heart and Heart Disease" Otello Randall, M.D. and Deborah Romaine; 2006
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