The heart is a muscular organ. Its function is to push the blood into circulation. The two-way circulation of our body purifies the blood in the lungs while delivering oxygen and nutrients to every body cell. The heart beats at a specific rhythm and rate. The heartbeat is felt as a pulse, which can be felt against the wrist, among other sites. Heart rate varies, depending upon the situation a body undertakes. For example, it rises during exercise and slows down while you sleep.

Despite changing as per body demands, the heart rate ranges between 60 beats per minute to 100 beats per minute. If it goes beyond either extreme, it becomes a dangerous heart rate.

Heart rate is also affected by some conditions. For example, fever, pregnancy, stress and anxiety, aging and use of certain medications, etc. 

Dangerous heart rate levels for a person are marked after following their subjective heart rate pattern.

What is an ideal heart rate: or Normal heart rate

You can check your heart rate by calculating your heartbeat per minute. This should be done at rest and during physical activity.

Measuring the heartbeat on various occasions gives an estimate of one's average heart rate. Deviation from the average should alert you.

Factors affecting the heart rate are;

• Age affects the heart rate inversely. The heart rate decreases with an increase in age.
• An increase in body temperature increases your heart rate as it happens in fever or hot weather.
• The emotional status of a person is directly linked to heart rate. Being anxious, stressed, excited or nervous increases your heart rate.
• Body mass index also affects the heart rate. Obese people have a heart rate towards the higher side as their heart has to put in more effort to supply the same amount of blood compared to people with a healthy weight.
• The position of the body may also have an impact on heart rate. Heart rate increases when you stand after sitting for a long time.
• Certain medications also impact the heart rate. For example, beta-blockers lower your resting heart rate.
• Lifestyle habits such as smoking or dietary ingredients (alcohol, caffeine) impact resting heart rate. Smoking increases the heart rate.
• Physical fitness levels also influence heart rate. Trained athletes may have a heart rate as low as 40 beats per minute. 

Heart rate at rest

For adults, the average heart rate lies between 60-100 beats per minute. The American Heart Association states these figures.

The resting heart rate is defined as the one when the heart is pumping a minimal amount of blood required by your body. It is because the body is at rest; its requirements for oxygen and nutrients are minimal.

The exact figure may vary from person to person and situation-wise, but the resting heart rate range is about 60-100 beats per minute. 

The normal resting heart rate for children is a bit high than for adults. It is about 70-100 beats per minute for a child between six to fifteen years of age.

Heart rate while exercising

Physical activity and exercise increase one's heart rate. This is usually the highest a heart rate can go without causing an ill-effects.

It should be noted that some situations are exceptions. For example, sixty beats per minute heart rate are healthy and normal for a trained athlete. Similarly, the heart rate declines with age, be it at rest or during physical exertion.

When do you call a heart rate as fast?

A heart rate faster than 100 beats per minute is called tachycardia.

However, age and level of physical fitness affect the heart rate.

Children usually exhibit higher heart rates when compared with adults.

The same is true for a pregnancy-induced increase in heart rate. The blood circulation of a pregnant woman increases owing to the increasing demand for pregnancy. This forces the heart to pump blood more forcefully and speedily.

People leading a sedentary life may experience a faster heart rate on minimum activity, climbing stairs, or moving from one room to another. At the same time, individuals who perform regular exercise may require intense activity levels to get their heart rate up.

Different situations also influence heart rate. Depending on the cause, tachycardia is of different types. The type of tachycardia is also dependent on the part of the heart affected. These include;

• Sinus tachycardia
• Supraventricular tachycardia
• Atrial fibrillation
• Atrial flutter
• Ventricular tachycardia
• Ventricular fibrillation

Causes of tachycardia

Possible causes of tachycardia may include;

• an underlying medical condition
• anxiety and stress
• panic attacks
• fatigue
• excessive caffeine consumption
• excess alcohol intake
• fluid and electrolyte imbalance
• high-grade fever
• anemia
• congenital heart disease
• any heart condition with disturbance in blood flow
• hyperthyroidism
• injury to the heart as in a heart attack
• intense exercise or physical activity
• side effects of certain medicines (for example, serotonin intake or drugs for ADHD)
• smoking
• drug abuse as cocaine use
• sleep deprivation
• hypertension
• Postural orthostatic tachycardia syndrome

Postural orthostatic tachycardia syndrome (POTS) causes an increase in a person's heart rate upon standing.  The increased heart rate is also accompanied by a drop in blood pressure and a temporary spell of dizziness.

This is attributed to the disturbance in the autonomic nervous system, which fails to regulate heart rate, blood pressure, or breathing rates under normal circumstances.

When is a heart rate termed slow?

A heart rate less than sixty beats per minute is called bradycardia or slow heart rate. It may occur during physiological conditions like sleep or aging, or it may have an underlying cause.

While sleeping, the heart rate of a normal healthy individual drops down to the lowest margin, sixty beats per minute or even lower. This is true in people who have a slow heart rate under normal conditions. This may also happen while you are in a deep sleep.

Physiological bradycardia is also considered normal in athletes.

Generally, a lower heart rate indicates a healthy heart muscle. However, bradycardia is also a sign of disturbance in the heart's electrical system that relays impulses to keep the heart going. This is particularly true if you are not athletic or suffer from some other underlying medical condition.

Causes of bradycardia

Your heart rate may slow down due to;

• fluid and electrolyte imbalance
• obstructive sleep apnea
• an underlying medical condition
• malfunctioning of the electrical relay system of the heart
• sepsis
• bleeding inside the brain
• heart disease as heart attack, pericarditis, myocarditis, etc.
• trauma to the chest or any other injury
• sick sinus syndrome
• radiation therapy
• amyloidosis
• Lyme disease
• congenital heart disease
• Damage to the heart either due to aging, heart disease, etc.
• hypothyroidism
• inflammatory diseases (lupus or rheumatic fever)
• collagen vascular disease
• muscular dystrophy
• side effects of certain drugs as beta-blockers, calcium channel blockers, digoxin, clonidine, reserpine, adenosine, cimetidine, lithium, amitriptyline, and narcotics
• substance abuse as the use of cannabis

When is the heart rate labelled dangerous?

Except for the physiological causes of increased or decreased heart rate, either extreme can indicate an underlying medical condition. Appropriate medical evaluation and treatment are essential for either bradycardia or tachycardia.

Experiencing a too low or high heart rate for an extended period can result in many complications. These include;

• Formation of blood clots anywhere in the vascular system
• Heart failure
• Dizziness and recurrent fainting
• Sudden cardiac arrest and death

Some symptoms that accompany a low or high heart rate and indicate a severe underlying phenomenon is;

• shortness of breath
• fainting episodes
• frequently feeling dizzy, lightheaded, or confused
• a sensation of fluttering or palpitations in the chest
• pain or discomfort in your chest with low or high heart rate
• signs and symptoms of an infection with heart rate changes
• bleeding with bradycardia (post-partum or heavy menstruation)

The symptoms mentioned above should be promptly checked with your doctor. If you experience the following, it indicates a medical emergency and urgent care;

• chest pain that does not seem to get better and lasts more than few minutes
• difficulty in breathing
• fainting
• sudden changes in heart rate
• a heart rate that makes you anxious
• irregular heart rate
• heart rate changes after starting a new medication

Diagnosis of dangerous heart rate

A consistent abnormality in heart rate accompanied with dangerous signs and symptoms should be vigilantly checked and investigated.

 The following tests give an insight into any possible underlying condition. These may also be labeled as baseline tests for investigating a low or high heart rate.

• Blood tests

These are done to identify any underlying medical condition. There could be many of them, and your doctor will call for the ones suggested by your presenting complaints.

For example, checking for hemoglobin levels is done for everyone. Still, thyroid function tests may be done for some specific cases where the accompanying signs and symptoms indicate a thyroid disorder.

• Electrocardiogram

Also called an ECG or EKG, the test measures and recorded the electrical activity of the heart.

• Imaging tests

Imaging tests are beneficial in indicating any structural abnormalities of the heart. These include an echocardiogram, CT scan, and MRI scan of the heart.

Depending upon the results, your doctor may refer you to a medical specialist or a heart specialist (a cardiologist) for further evaluation and treatment.

How to keep your heart rate at healthy levels?

Heart rate can be maintained with lifestyle modifications. This includes;

• Healthy and balanced diet
• Adopting regular exercise
• Maintaining healthy weight
• Reduce stress; adopt yoga, meditation, or a hobby

Get regular medical check-ups. If you are suffering from a medical ailment, get proper follow-up for your condition. Discuss the side effects of any medication you take with your doctor. Remaining aware of the side effects can keep you a step ahead of any developing complications.

This goes for any heart ailment as well. Always remain in touch with your physician. Take your medicines religiously. Get any unusual signs, and symptoms checked vigilantly.

Some additional precautions you can take include;

• Limiting caffeine intake
• Consuming alcohol in moderation
• Quit smoking

Steps to bring the heart rate down are;

• Maintain a diet rich in omega-3 fatty acids, unsaturated fats, magnesium, and fibers, like salmon, nuts, legumes, green veggies, and lean meat.
• Practice mindfulness by staying focused at the moment and breathing.
• Avoid stress by adopting something that you like. A hobby, friends-meetup, walk in the park, listening to music, reading a book, etc.

Some steps to bring the heart rate up are;

• Do some exercise or stretching.
• Lift some weights.
• Do some house chores or aerobics.

Take home message

The body has an excellent ability to respond to different requirements, be it urgent or otherwise. It does so by increasing or decreasing your heart rate. However, sudden unusual changes, persistent changes, or deviations accompanied by worrisome signs and symptoms require medical check-up. Following your medications and getting appropriate help should keep your heart rate at ideal levels without touching dangerous benchmarks.