Optimal Home Blood Pressure Monitoring: Must The Legs Be Uncrossed and The Feet Flat?

The new ACC/AHA guidelines for High Blood Pressure were published late last year and they were in favor of using home blood pressure measurement to aid in the management of hypertension.

I was happy to hear this as I am constantly advising my hypertensive patients to buy a home BP cuff, measure their BP once when they get up and again 12 hours later and report the values to me after two weeks.

I have not spent a lot of time instructing them on  exactly how to make the measurement but the new guidelines do specify in detail how this should be done:

• Remain still:

• Avoid smoking, caffeinated beverages, or exercise within 30 min before BP measurements.

• Ensure ≥5 min of quiet rest before BP measurements.

• Sit with back straight and supported (on a straight-backed dining chair, for example, rather than a sofa).

• Sit with feet flat on the floor and legs uncrossed.

• Keep arm supported on a flat surface (such as a table), with the upper arm at heart level.

• Bottom of the cuff should be placed directly above the antecubital fossa (bend of the elbow).

• Take at least 2 readings 1 min apart in morning before taking medications and in evening before supper. Optimally, measure and record BP daily. Ideally, obtain weekly BP readings beginning 2 weeks after a change in the treatment regimen and during the week before a clinic visit.

• Record all readings accurately:

• Monitors with built-in memory should be brought to all clinic appointments.

I monitor my own BP at home and often wonder whether there is scientific evidence to support such a rigid protocol.  Being a contrarian and a skeptic, I typically violate 3/4 of the recommendations that are listed.

It seems like all of the instructions are guaranteed to give you the lowest BP you are likely to experience during the day. The vast majority of the time I am not sitting quietly with my legs uncrossed, my bladder empty and my back straight so following these directions will underestimate my average daily BP.

I’ve spent some time looking into all the instructions and they generally have some scientific studies to support them. For example, the position of the upper arm in relation to the heart does  heavily influence BP readings (more on that in subsequent posts.)

The Mandate To Uncross The Legs

The instruction that most intrigued me was this one:

Sit with feet flat on the floor and legs uncrossed.

A number of questions came to the skeptical hypertensive:

What if you are on an exam table and your feet don’t reach the ground?

Does it really make a difference if your feet are flat on the ground versus slightly crooked?

Does any degree of leg crossing influence BP? Legs crossed at the ankles? Legs crossed at the knee?

And once I began thinking of leg crossing I realized that I spend a lot of my time with my legs crossed. Was this raising my blood pressure and my cardiovascular risk? Did I cross my legs because I liked the feel of a higher blood pressure?

The ACC/AHA guidelines are not alone in this recommendation-take a look at the British Health Service recommendation:

3.5. Measurements should be taken in silence when the patient is relaxed, with both feet flat on the floor and their back and arm supported. Many patients automatically cross their legs, which raises their blood pressure, so it is particularly important to emphasise the need for the patient to uncross their legs when taking their blood pressure.

Apparently the Brits believe that any ambient sound will alter the blood pressure. Talking is right out!

But if talking, ambient sounds and crossing your legs raises your blood pressure shouldn’t we be advising patients to spend their days wearing ear plugs in silence with their legs uncrossed?

Scientific Studies On Leg Crossing

It turns out there are good studies showing that leg crossing raises your blood pressure.

The first was published in 1999 and involved  53 hypertensive and 50 normotensive subjects.

Participants were randomly assigned, using a cross over design to having seated blood pressures measured with their leg in three different postures

  1. Feet flat on the floor and legs uncrossed

    Here I am demonstrating method 2 with my lateral malleolus carefully placed on my suprapatellar bursa. I actually prefer method 1 which is depicted below.
  2. Legs crossed , method 1-popliteal fossa of the dominant leg over the suprapatellar bursa of the non-dominant leg.
  3. Legs crossed, method 2- lateral malleolus (which the article spells mallelous) of the dominant leg over the suprapatellar bursa of the non-dominant leg.

I love the efforts these Calgarian investigators went to in this study to ensure blinding (although spelling is clearly not their forte’). They state “blood pressures were measured by one investigator who was behind a screen and blinded to the leg position of the patient while a second investighator (sic)  ensured that the subject assumed the proper leg position.”

Systolic blood pressure in patients with hypertension increased by 8 mm Hg by method 1 leg crossing and 10 mm Hg by method 2.

Figure from Adiyaman, et al. demonstrating method 1 on the left.

Another study demonstrated that although crossing the legs at the knees influenced blood pressure, crossing them at the ankles had no effect.

A recent review identified 7 studies which support the influence of leg crossing on BP.

 An Inconvenient Truth
If leg crossing raises the systolic blood pressure  8 to 10 mm Hg why aren’t we doctors recommending patients sit with leg uncrossed the majority of the time. Personally, I had never heard there were any health complications to sitting with my legs crossed.
Apparently the myriad health information sources on the internet are near unanimous in their condemnation of leg crossing but the hypertensive effect of this maneuver is usually not cited.
My favorite title condemning the practice was “The surprising and inconvenient truth of crossing your legs.”
I must admit since doing this bit of research I have substantially reduced the amount of time I sit with my legs crossed. And I’ve pondered extensively whether sitting with legs crossed makes me feel any different and why I suddenly and seemingly randomly decide to cross my legs.
I’ve also started asking  friends and colleagues and medical residents how much of the day they spend with legs crossed.
On teaching rounds one morning recently we tested a volunteer resident’s blood pressure with legs crossed and uncrossed. Sure enough, the systolic BP was 10 mm Hg higher with legs crossed.
Chiasmically Yours,
-ACP

 

For those of you itching to read more about BP and leg crossing here are the references:

 

Pinar R, Ataalkin S, Watson R. The effect of crossing legs on blood pressure in hypertensive patients. J Clin Nurs 2010; 19:1284–1288. [PubMed]
Adiyaman A, Tosun N, Elving LD, Deinum J, Lenders JWM, Thien T. The effect of crossing legs on blood pressure. Blood Press Monit 2007; 12:189–193. [PubMed]
Pinar R, Sabuncu N, Oksay A. Effects of crossed leg on blood pressure. Blood Press 2004; 13:252–254. [PubMed]
Avvampato CS. Effect of one leg crossed over the other at the knee on blood pressure in hypertensive patients. Nephrol Nurs J 2001; 28:325–328. [PubMed]
Keele-Smith R, Price-Daniel C. Effects of crossing legs on blood pressure measurement. Clin Nurs Res 2001; 10:202–213. [PubMed]
Foster-Fitzpatrick L, Ortiz A, Sibilano H, Marcantonio R, Braun LT. The effects of crossed leg on blood pressure measurement. Nurs Res 1999; 48:105–108. [PubMed]
Peters GL, Binder SK, Campbell NR. The effect of crossing legs on blood pressure: a randomized single-blind cross-over study. Blood Press Monit 1999; 4:97–101. [PubMed]

19 thoughts on “Optimal Home Blood Pressure Monitoring: Must The Legs Be Uncrossed and The Feet Flat?”

  1. Love it—“do I cross my legs because I like the feel of higher blood pressure”—LOL. I take my BP regularly and had always heard legs should be uncrossed—now I know there are exhaustive studies as to why : ) . On a sort of related note, it seems the ARB I recently switched to (Valsartan 160mg 1x per day) is not as effective as the Lisinopril I was on before ( 20mg twice per day). I have been on it over 2 mos. now, and am getting readings mostly in the low 120/70’s with occasional 130’s/70’s. The Lisinopril usually had me below 120 systolic /60’s diastolic, or low 120’s. I’ve looked and looked and everything I read says they are both equally effective for BP control. Have you run into this in your practice. Guess I’ll be going back to Lisinopril. Thanks as always for the informative post.

    1. Glad I could make you LOL!
      I have not noted consistent difference when switching patients from lisinopril to valsartan (or any of the other ARBS). With losartan I’ve noticed a tendency to not last 24 hours so i often end up giving that twice daily. You could check to see if the Valsartan effect is wearing off earlier than 24 hours and trying splitting the tablet and dosing twice daily. I usually only make that switch (to ARB from ACEI) if patient develops cough.

  2. I think I’m right in thinking that the net effect of treating high blood pressure is a modest but measurable reduction in QoL (which is why its not much fun being a hypertension doctor). So does it follow that we cross our legs because it feels good?

    1. Letter to the Editor
      Re: ‘‘Call To Action on Use and Reimbursement for Home
      Blood Pressure Monitoring: Executive Summary’’

      To the Editor:
      The injunction contained in ‘‘Call To Action on
      Use and Reimbursement for Home Blood Pressure
      Monitoring: Executive Summary’’against wrist BP
      monitors is arbitrary, prejudicial, lacking in clinical
      experience, and nonsense. Currently, there are so
      many people with large arms that, rather than lar-
      ger cuffs, wrist monitors work uniformly well;
      moreover, wrist monitors fit just fine, are more
      convenient, are easily portable, and can be verified
      as accurate. The method that I use is as follows:
      apply the blood pressure (BP) cuff and record the
      BP (arm or wrist). BP is immediately measured
      again using my (lifetime-certified) upper arm BP
      cuff. This is repeated twice in quick succession. The
      patient’s BP cuff and mine are used on the same
      arm, since there may be an important difference in
      readings between the two arms.

      If the two cuffs measure identical readings or
      provide readings that are minimally different, the
      patient is informed of what to add or subtract from
      the systolic and⁄or diastolic values. Pickering and
      colleagues 1merely and inadequately state that the
      BP cuff is to be verified, with no specific method
      discussed.This article’s recommended method for BP
      recording has nothing to do with the realities of
      life. It is ideal to see what the BP is at any time
      and under any circumstance, as well in the ‘‘9 times
      zones’’: before and after each meal, in between
      meals, and at bedtime. These can be measured over
      3 or 4 days, giving the physician a comprehensive
      picture of daytime and evening BP levels. This is
      more likely to be accomplished with the smaller
      and more portable wrist cuff. Sitting calmly in a
      near-meditative state resembles no part of conscious
      life I am aware of. If the patient smokes, drinks, or
      exercises, I want to know what their BP numbers
      are(!). There is no reason to assume that these wrist
      monitors become inaccurate over time, and if such
      occurs, the discrepancy is usually obvious and
      readily identifiable.—
      H. Robert Silverstein, MD
      ,Hartford, CT

      REFERENCE
      1 Pickering TG, Miller NH, Ogedegbe G, et al. Call to action
      on use and reimbursement for home blood pressure moni-
      toring: executive summary.J Clin Hypertens
      . 2008;10:467–476

      1. Good points on the wrist monitor, something I heretofore have advised my patients against using. That advice is based on the fact that the brachial artery is closer to the central aortic pressure. As you measure more peripherally the systolic goes up the diastolic down but the average remains the same. However, if they followed a calibration as you describe I would be ok with it now.
        It’s probably worthwhile to print Dr. Pickering’s response to your letter.(He seems to take exception to your calling his statement nonsense,)
        Response:
        Dr Silverstein raises 3 issues, which deserve comments.
        Wrist Monitors. Our statement was not ‘‘arbi- trary, prejudicial, lacking in clinical experience, and nonsense,’’ but was based on publications as well as the clinical experience of the authors. The state- ment actually said, ‘‘Wrist monitors are the most convenient type to use and are preferred by many patients. They have the potential advantage that they can be used in obese individuals in whom putting a cuff on the upper arm is difficult. A potential disadvantage is that the wrist must be held at the level of the heart when a reading is being taken, which increases the possibility of
        doi: 10.1111/j.1751-7176.2008.00033.x
        This article’s recommended method for BP recording has nothing to do with the realities of life. It is ideal to see what the BP is at any time and under any circumstance, as well in the ‘‘9 times zones’’: before and after each meal, in between meals, and at bedtime. These can be measured over 3 or 4 days, giving the physician a comprehensive picture of daytime and evening BP levels. This is more likely to be accomplished with the smaller and more portable wrist cuff. Sitting calmly in a near-meditative state resembles no part of conscious life I am aware of. If the patient smokes, drinks, or exercises, I want to know what their BP numbers are(!). There is no reason to assume that these wrist monitors become inaccurate over time, and if such occurs, the discrepancy is usually obvious and readily identifiable.—H. Robert Silverstein, MD, Hartford, CT
        REFERENCE
        1 Pickering TG, Miller NH, Ogedegbe G, et al. Call to action on use and reimbursement for home blood pressure moni- toring: executive summary. J Clin Hypertens. 2008;10: 467–476.
        erroneous readings. A recently introduced model avoids this problem by only taking readings when the wrist is held over the heart. Experience with wrist monitors is relatively limited at present, and most of the monitors that have been tested have failed the validation studies (see http:// http://www.dableducational.org). They are therefore not generally recommended for routine clinical use.’’
        Checking Monitors for Accuracy. Dr Silverstein’s statement that ‘‘Pickering and colleagues merely and inadequately state that the BP cuff is to be verified, with no specific method discussed’’ is incorrect. We actually said, ‘‘When patients get their own monitor, it is very important to have them bring it into the clinic to check their tech- nique and also the accuracy of the monitor. A sim- ple and practical version . . . has been developed for this purpose, and [it] can be done in less than
        VOL. 10 NO. 11 NOVEMBER 2008
        THE JOURNAL OF CLINICAL HYPERTENSION 885
        10 minutes by the physician or other health care provider and the patient. . . . The patient sits at the physician’s desk with the monitor set up and the arm resting on the desk. Five sequential same-arm BP readings are recorded with a gap
        ‘‘It is ideal to see what the BP is at any time and under any circumstance.’’ This statement is not acceptable, because the interpretation of BP levels is only valid when standardized circumstances are used. This is why routine morning and evening readings are recommended.—Thomas G. Pickering, MD, DPhil, New York, NY
        of no more than about 30 seconds readings.’’
        between

      2. “The variation in central-to-peripheral BP could be hard for cuff BP to detect because it measures signals at an isolated peripheral artery with a generic, one-size-fits-all method (either oscillometric algorithms or Korotkoff sounds). These methods potentially overlook subtle but distinct phenotypic differences in the way that BP is transmitted from central-to-peripheral arteries (eg, possibly increased SBP transmission in some people, but not in others).”

        “To our knowledge, this notion has never been raised, but there are other clues to the presence of distinct BP phenotypes,” the researchers suggest. “For example, among people with renal disease, cuff BP becomes increasingly inaccurate as the severity of disease, and vascular dysfunction (aortic stiffness) increases. Also, people with apparently normal clinic cuff BP can still have signs of organ damage related to high BP, suggesting that a sizeable element of BP risk is missed by the cuff BP method.” :
        https://www.medscape.com/viewarticle/895909

    2. I have noticed that when my systolic blood pressure drops below 120 I become a little less sharp and energetic. In the post I allude to the the fact that I’ve been trying to observe if I feel different with legs crossed versus uncrossed. But I can’t say I’ve noticed any more energy with legs crossed. Perhaps other readers can share their experience.

      1. Same thing happens to me when my systolic drops below 95: usually I am 105-110. The response to my letter to the editor was unfair. the info they listed was NOT IN the original article to which I responded to and continue to stand by, In more than 10 tears of using Omron (available online for under $40) verified wrist BP cuffs, I have had 2 instances when it did not fit because of wrist size–both in people over 350 lbs. HRS, MD, FACC

  3. Now I’m really curious as to why feet flat on the floor and sitting on a firm surface? While crossing your legs can make BP high, I wonder what could make it fasely low?

    As an aside, just last week I had a patient who thought the “S” in systolic was for standing, so all the recorded measurements were standing until I corrected her it meant systolic. I wonder why she thought the “S” was standing, and not sitting or sleeping? Been an RN for almost 25 yrs. and this was a new one!

    1. If S was for standing what did the patient think the D was for?
      I was so side-tracked by the crossed legs phenomenon that I haven’t yet looked into the feet flat on the floor issue.
      Those of us with short legs may find it difficult to consistently place our feet flat on the floor when seated.

      1. I wanted to ask her what she thought the D was for as well, but she seemed to be a bit too embarrassed when I explained systolic … She then hastened the conversation along.

  4. This prescribed procedure is exactly what I’ve been following for several years now. It seems to work consistently at determining the lowest pressure of the day, as you describe.
    What I worry about is the highest and the average pressures of the day. Pressure varies according to what we ask our bodies to do, yes? Exercise, fight a cold… worry.
    It would be nice if ambulatory BP devices got as smartly digital as rhythm analysis ones have.
    Or is this all of no concern?

    1. I think these considerations are of concern. All the guidelines for taking BP focus on getting a lower BP. It seems to me what we really want to know is the overall burden of blood pressure throughout 24 hours. This may be why the current guidelines find ambulatory BP monitoring to be the best method for out of office bp measurement.
      As someone who is very rarely still for more than 5 minutes and often sits without a straight back and without feet flat on the ground, uncrossed I could be seriously underestimating the blood pressure that is usual for me.
      On the other hand, major trials (like the SPRINT) utilize techniques that “minimize” if you will the obtained BP

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.