A Basic Guide to Blood Pressure: Part I

Blood pressure is a key indicator of your health. This is why it is checked at every visit with a healthcare professional. Understanding this measurement will help you make sense of both your blood pressure and your healthcare professional’s advice. This article series will explain what blood pressure is, how to correctly measure it, and what to do when it is high.

Blood Pressure Basics

Blood carries oxygen and nutrients to all the organs and tissues in your body. The heart functions as a pump, squeezing to push blood forward through your blood vessels and then relaxing to refill as blood returns. The flow of blood exerts pressure on the inner lining of blood vessels, and this pressure fluctuates as the heart squeezes and relaxes. Blood vessels are not like simple pipes — they are muscular, living tissues that respond to changes in blood pressure and adapt over time.

Checking blood pressure involves two measurements: one while the heart is squeezing, known as systolic pressure, and another while the heart is relaxing, known as diastolic pressure. Pressure is measured in units called millimeters of Mercury (mm Hg), which describes the height of mercury in a tube. We still use this unit of measure today, even though blood pressure is frequently checked using digital devices. A normal resting blood pressure is generally below 120 mm Hg systolic, and 80 mm Hg diastolic. This is commonly shortened to 120/80.

It is important to specify “resting” blood pressure because blood pressure fluctuates from minute to minute throughout the day depending on what you are doing. It is normally lower while asleep and higher while awake. Psychological or emotional stress, pain, and physical effort such as when we exercise, normally increase blood pressure. Relaxing, deep breathing, and meditating can cause blood pressure to temporarily decrease. Large, sudden drops in blood pressure cause people to briefly lose consciousness in certain situations.

Blood pressure is influenced by multiple factors, including how much the heart is pumping (known as cardiac output), as well as how tightly the muscular blood vessels are squeezed (known as vascular resistance). These two factors are primarily regulated by the nervous system and a variety of hormones. The total volume of blood contained in the system also influences blood pressure. The kidneys regulate this volume by controlling how much salt and water are urinated out or retained in the body. Treatments for high blood pressure work by impacting one or more of these factors; we will discuss these further in part 2.

What is Hypertension?

Hypertension, commonly known as “high blood pressure”, is the condition of having a resting blood pressure measurement that is persistently higher than normal. Note again the emphasis on resting blood pressure, and the long-term persistence of this elevation in blood pressure. This is different from having brief, temporary increases in blood pressure when you feel anxious or perform exercise that normalize afterwards. 

Having a persistently high resting blood pressure over many years can cause progressive damage to the heart and blood vessels throughout the body. This increases the risk of experiencing a stroke, heart attack, heart failure, and many other health complications that can cause disability or death. Lewington 2002 High blood pressure affects half of all adults in the United States and is the leading contributor to premature death worldwide, accounting for 13% of deaths globally each year. WHO 2009 High blood pressure does not cause symptoms in most people, so a large proportion of these people do not know that they have it. The following table illustrates the different stages of high blood pressure.

Category Systolic Blood Pressure
(mm Hg)
Diastolic Blood Pressure
(mm Hg)
Normal Less than 120 Less than 80
Elevated 120-129 Less than 80
High Blood Pressure, Stage 1 130-139 80-89
High Blood Pressure, Stage 2 Higher than 140 Higher than 90

High blood pressure can have many different causes, which we will discuss in further detail in part 2. These include things like genetics, smoking and alcohol use, overweight and obesity, physical inactivity, medications, and diet quality. Other underlying medical conditions like sleep apnea and kidney disease can also contribute to high blood pressure.

High blood pressure does not always clearly present itself. Some people may have high blood pressure when measured in a healthcare setting like a clinic or hospital, but maintain normal blood pressure when going about their everyday life. This is called “white coat hypertension”. Even though people with this condition have normal resting blood pressures when outside of a clinic setting, they still have higher cardiovascular risk if left untreated compared to people who have normal resting blood pressure all the time. Cohen 2019 These findings are not well-understood, but we do know that people with white coat hypertension have much higher risk of developing sustained high blood pressure over the following decade. Mancia 2013 People with white coat hypertension benefit from blood-pressure lowering treatments. As a result, white coat hypertension is not something that should be ignored.

It is also possible for individuals to have normal blood pressure in a healthcare setting despite having high blood pressure when going about their everyday life. This is called “masked hypertension”. Trudel 2019 This is a particularly risky situation given how likely it is that the diagnosis is missed, leading to years of untreated high blood pressure. As a result, it is recommended to periodically check your blood pressure outside of the doctor’s office.

Physical activity produces a temporary increase in blood pressure, with more vigorous activities usually creating a higher increase. This is especially true with lifting weights. Holding your breath and exerting yourself against a resistance causes a large momentary spike in pressure. It does not increase your long-term resting blood pressure, which means lifting weights does not cause hypertension. In fact, the brief variations of blood pressure during lifting weights provide a useful stress to the cardiovascular system, and can lower resting blood pressure over time. This is an adaptation that is good for us, and means that even people with hypertension can benefit from strength training.

How do I check my blood pressure?

Since we are most concerned with resting blood pressure over the long term, diagnosing hypertension requires multiple blood pressure measurements over time. Most people have their blood pressure checked in a healthcare office setting. If this office measurement is high, additional measurements outside the office setting are recommended to confirm before starting treatment. USPSTF 2021 Checking blood pressure at home can be an excellent option, but requires careful measurement technique with the appropriate equipment.

The most accurate way to measure your blood pressure at home involves using an automatic blood pressure machine under the correct conditions. A listing of approved devices is available at ValidateBP.org.

First, the blood pressure cuff should be appropriately sized for your arms — a cuff that is too small will give falsely high readings, and a cuff that is too large will give falsely low numbers. We can correlate the circumference of the upper arm (for example, using a measuring tape around the biceps), to an appropriate cuff size, as shown in the following table. AHA Fortunately, most devices are now sold with variable-size cuffs that will fit most arms from the “small adult” to “large adult” range.

Arm Circumference
Arm Circumference
Recommended Cuff Size
(width x length, in cm)
22-26 8.7-10.2 12 x 22 (small adult)
27-34 10.6-13.4 16 x 30 (adult)
35-44 13.8-17.3 16 x 36 (large adult)
45-52 17.7-20.5 16 x 42 (extra large adult)

When ready measure your blood pressure, follow these steps. For a graphical illustration, see here.

  1. Ensure you have a quiet room, a chair with back support, and a table available.
  2. Place the blood pressure cuff on your arm, lining up the artery indicator line on the cuff over the inner part of your upper arm. When using an upper-arm blood pressure device, the lower end of the cuff should sit about 2–3 centimeters (about an inch) above your elbow crease. 
  3. Rest your arm on an elevated surface, like a table, a box, or a few pillows, so that your arm is at the height of your heart. Ensure your arm is relaxed and your palm is facing upwards.
  4. Once everything is properly positioned, sit upright with your back supported, legs uncrossed, and feet flat on the floor. Sit quietly for five minutes while remaining relaxed in this position before taking the first measurement. 
  5. Start the machine to have it take your blood pressure while staying relaxed. Repeat the measurement a second time for more reliable results. 

When evaluating people for high blood pressure using home measurements we recommend a minimum of three days of measurements, two in the morning and two in the evening on each day. Bello 2018 Even if the resting blood pressure measurements are high, this can be addressed gradually over time with a primary care doctor if no other symptoms are present. Emergency care is rarely needed, only in situations where symptoms like chest pain, shortness of breath, vision changes, confusion, or stroke-like symptoms are present, but otherwise can safely be managed in the primary care setting.

Conditions like white coat hypertension and masked hypertension require blood pressure monitoring outside of the doctor’s office. The preferred method is known as “24-hour ambulatory blood pressure monitoring”, where a special blood pressure monitor is worn continuously for 24 hours and a series of measurements are taken automatically as you go about your day. However, properly calibrated home blood pressure machines can be used if 24-hour monitors are not available. Carefully measuring blood pressure as outlined above, twice in the morning and twice in the evening for at least 3 days, can provide useful information to help your doctor make recommendations.


Blood pressure is an important measurement that can provide valuable information about our overall health. Persistently high resting blood pressure over time increases the risk of heart attacks, strokes, and other complications that can cause disability or death. Fortunately, we have ways to measure blood pressure accurately, and we also have multiple things we can change in order to improve blood pressure. In Part 2 we’ll discuss how to treat high blood pressure by targeting these risk factors with lifestyle interventions, as well as the role of medications.

Thank you to Tom Campitelli for his assistance in editing this article.

Source link: https://www.barbellmedicine.com/blog/a-basic-guide-to-blood-pressure-part-i/ by Austin Baraki at www.barbellmedicine.com