An unsupported arm while measuring blood pressure is a mistake made too often. This error is unexpectantly committed on occasion at the doctor’s office. Unfortunately, the examining table is not blood pressure friendly. This can make one wonder, how does an unsupported arm affect blood pressure?
An unsupported arm can increase blood pressure because it forces you to perform an isometric exercise to steady your arm in the proper position. The muscle contraction raises your heart rate and blood pressure. Studies have shown an unsupported arm can raise blood pressure by as much as 10%.
Since the exam table doesn’t have an arm rest, I’ve had nurses support my arm for me. However, it’s still challenging to totally relax your arm when someone else is holding it up. This article will provide real-life examples indicating the differences in blood pressure, with a supported arm compared to an unsupported arm.
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Unsupported Arm Blood Pressure
An isometric exercise is when you contract a muscle to hold it in place without being moved. I would like you to perform an isometric exercise. Don’t worry, it won’t take long or strain you much.
Sit in a chair as if you were going to measure your BP. Instead of supporting your arm, raise it to the position it typically would be and hold it there. You may not realize it, but you’re using your shoulder muscle to hold your arm in place. If you place your other hand on your shoulder as you raise and lower your arm, you can feel it working by tightening.
The tensing of any muscle in your body can raise your heart rate and increase blood flow. The little increase is enough where it can raise your blood pressure 1. This is the reason why the American College of Cardiology includes a supported arm in their blood pressure measuring guidelines 2.
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Unsupported Arm With High Blood Pressure
Research has shown, in addition to elevated readings with an unsupported arm; those with high blood pressure have a more serious problem. The higher blood pressure associated with isometric exercise is greater in hypertensive people and those taking certain high blood pressure medication 3.
Researchers evaluated the measurements of people with high blood pressure and without. They measured with the arm in the horizontal supported position compared to the arm in an unsupported lowered position, below heart level.
The people with normal blood pressure had a systolic increase of 8 mmHg and a diastolic increase of 7 mmHg with their arms unsupported in a lowered position. The people with high blood pressure also increased, but by 23 mmHg systolic and 10 mmHg diastolic. The people with high blood pressure increased much more than those with normal blood pressure 4.
Unsupported Blood Pressure Studies
Study 1
This study is interesting to me because of the third comparison made. The first part of the study measured blood pressure in the left arm and supported, the way it’s supposed to be performed. The second part of the study measured with the left arm unsupported. The third part measured with the left arm supported, but raised the right arm unsupported at the same time. The purpose of the third part was to assess the effect of isometric contraction on an arm being unmeasured. The results are shown in the table below.
| Study Part | Systolic | Diastolic |
| Part 1 – Supported | 109.6 | 72.6 |
| Part 2 – Unsupported | 111.8 | 73.6 |
| Part 3 – Opposite Arm Unsupported | 109.3 | 73.1 |
With the left arm unsupported, both systolic and diastolic blood pressure were higher compared to supported. With the opposite arm raised, diastolic increased but systolic remained the same 5.
Study 2
Researchers evaluated 240 people and compared their blood pressure readings with different arm positions. Blood pressure averaged 8 mmHg higher when pressure was measured with the arm unsupported and lowered compared to supported at heart height. In addition, blood pressure was lower with a supported arm at heart level compared to an unsupported arm at heart height. They mentioned measuring BP with an unsupported arm may increase the number of people diagnosed with hypertension. In addition, their dosages may be prescribed higher because of the false readings 6.
Study 3
A report published in the BMJ noted if there is no arm support, the nurse should hold the patient’s arm under the elbow. This can be very helpful when trying to support the arm when there’s no arm rest present. They noted when an arm is extended and unsupported, diastolic may be raised by as much as 10% 3.
An Unsupported Arm Can Cause Wrong Arm Positioning
In addition to performing an isometric exercise, an unsupported arm can cause your arm to be in the wrong position. It’s very easy for your unsupported arm to fall down and have the cuff at lower than heart level. When this occurs, your blood pressure typically increases 7.
The opposite may occur as someone might raise their arm higher than heart level while unsupported. This may happen as someone struggles to keep their arm from falling lower. If the cuff is higher than your heart, the blood pressure measurement may be lower 8.
At Home
An unsupported arm at home is just as important as in a physician’s office. It’s easy to get lazy and complacent when measuring your blood pressure at home. In addition, numerous distractions are around that can easily cause mistakes.
Make sure where you measure blood pressure every day is optimal for your arm. Your chair should be next to a surface that places your arm at the correct height and position when supported. If it’s not, find another surface or a soft object you can place under your arm to adjust its height. Typical objects may include a small pillow or folded blanket.
If you’re using a side arm support on a chair, check your cuff level to make sure it’s correct. If not, adjust the height or find another surface to support your arm on. If you’re not sure what the correct height is, you can read about it in complete detail in my blog post, Effect of Arm Position on Blood Pressure.
If you don’t measure your pressure at home, you’re missing out on a great way to manage it. You can read about the blood pressure monitor I recommend in my blog post right here, Monitors.
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- National Center for Biotechnology Information: Heart rate at the onset of muscle contraction and during passive muscle stretch in humans: a role for mechanoreceptors[↩]
- Hypertension: Measurement of Blood Pressure in Humans: A Scientific Statement From the American Heart Association[↩]
- National Center for Biotechnology Information: Blood pressure measurement[↩][↩]
- National Center for Biotechnology Information: Arm Position and Blood Pressure: A Risk Factor for Hypertension?[↩]
- National Center for Biotechnology Information: The unsupported arm: a cause of falsely raised blood pressure readings[↩]
- National Center for Biotechnology Information: Effects of Arm Position and Support on Blood-Pressure Readings[↩]
- Wiley Online Library: Arm Position During Ambulatory Blood Pressure Monitoring: A Review of the Evidence and Clinical Guidelines[↩]
- Hypertension: Measurement of Blood Pressure in Humans: A Scientific Statement From the American Heart Association[↩]
