Thursday, 31 December 2015

Heart Rate Monitoring: Numbers!

Heart rate monitoring, as a means of pacing activities, is without doubt a very useful tool for people with ME.  

At its simplest, it is a means of avoiding activities that elevate heart rate (HR) into the aerobic exercise zone.

Does the word "aerobic" conjure up thoughts of lycra, leg-warmers and some rather Eighties work-out routines? Maybe you think that being so ill, means that there is little risk of you entering the "aerobic exercise zone"? Well think again. All is not what it seems for people with ME.

In this post I am going to explore the various means of calculating optimal HR numbers, and then share a few of my own thoughts on using these calculated numbers in real life.


Maximum Heart Rate (HRmax)
Exercise recommendations for ME are generally based on limiting HR to a percentage of each individual's HRmax - which is the theoretical maximum rate a healthy individual's heart can work at, before physical damage occurs.

The simplest method of calculating your age-related theoretical maximum is by subtracting your age from 220.  The result is your estimated number of beats per minute (bpm) at HRmax.

220 - [your age] = HRmax                    (for me: 220 - 52 = 168bpm)

Apparently other calculations (1) are now regarded as more accurate, but it seems that this simple calculation still remains the most used.  

 HRmax can then be used to calculate a Personal HR Limit:
There is now good evidence (2) that ME patients cannot ramp up their energy production systems normally. Consequently, people with ME should try to avoid spending time with their HR elevated into the aerobic zone.  It is generally accepted that aerobic exercise is achieved when exercising with a HR of 60% of HRmax or above, and so keeping below this level has been suggested by various ME specialists.

Calculating 60% of HRmax (My Personal HR Limit): 

[Your HRmax] x 0.6 = 60% HRmax          (for me: 168 x 0.6 = 101bpm) 

It is thought that if ME patients can keep their heart rate below this level, that this avoids doing further damage to their already compromised health.  Less ongoing damage, in theory means more opportunities for the body to heal itself.  However the reality of living within this self-imposed limitation is no easy task - more thoughts on that below.

Other recommendations on Limiting HR for ME:

The NICE guidelines for ME (3) suggest using a HR monitor during periods of "exercise", however they are more generous with their upper limit, suggesting 70% of HRmax as the number to remain below.  I wrote a blog post about this, because it seemed to me that doctors are ignoring HR monitoring advice altogether, and that this higher limit is better than no limit at all.

A Two Day CPET Test can be used to make more precise individual HR recommendations.  Unfortunately the test itself is not without risk for ME patients, because it involves two periods on an exercise bike. However the test does show clear differences between ME patients and de-conditioned controls (a possible biomarker?) and can also be useful for proving disability(2).

Whatever number is used, the lifestyle restrictions imposed by this method of pacing are significant.


Using an Alarm: 
I have been wearing a HR monitor daily for over a year now.  At first I used the alarm feature to warn me every time my HR exceeded 100bpm.  Doing so was certainly a useful exercise to help me learn what elevates HR, but ultimately I found it so intensely irritating that I now have it permanently turned off. However, I know others who find it helpful, so I guess it is a personal choice.

Life Adjustments:
I glance at my HR readout every couple of minutes whilst I am active. If it is raised above 100 I then adjust or stop what I am doing until it drops again.  This means most tasks take longer to accomplish because of the rest breaks, but I am convinced that doing so helps me to avoid the worst of the post exertional effects a couple of days later. However I'm not always perfect as chatting raises my HR, and socially I'm not comfortable with breaking off a conversation immediately my HR spikes.  I also can't always control exactly what happens when I'm away from home.

Keeping a Record:
I use an app called Endomondo (4) on my phone to collate data from my HR monitor.  This lets me see how long I spend above 100bpm each day.  This can vary each day from only a few minutes (when things are really good) up to several hours (when I had a urine infection and my HR went bonkers).

A screen shot from my Endomondo account online taken just now looks like this.  (My labels added)

I have changed the boundaries that Endomondo sets for the various zones so that they fall on multiples of 20bpm. (Therefore the zone names shown are not correct.) I can see here that my HR is averaging a little bit higher than normal, which is hardly surprising as it is the holiday period, but the pattern is not unusual for me.

Obeying Exact Numbers?
So here's a thing. If you look at how my heart rate changes through the day you can see that it spikes up quite quickly, but also that it can drop quickly. For this reason, it may not matter what precise number I use as my upper HR limit, because in truth my heart rate changes so quickly that it would shoot past all those exact numbers anyway.  More important, in my view, is to attempt to control were heart rate settles for any length of time, and to try to keep that low.  I also watch where my average HR for each day falls.

Knowing when to pull back:
Tonight it is New Year's Eve.  I had an invitation to go out, but I'm not going.  I know that were I to be out in company tonight my HR would spike easily, and that it would not drop as quickly as usual either. The decision to stay in was not just based on today's higher than usual HR data, but also on the fact that yesterday was a busier than normal day - meaning today is a day to be ultra cautious no matter how I actually "feel".

"Dangerously Okay!"
This phrase was used by a good friend of mine recently to describe what happens when adrenalin masks our symptoms and tricks us into believing we are more "well" than we really are.  I find that this can sometimes happen to me in the 36 hours after a fun event. In fact, during this day-after period my HR may actually be deceptively low - so even HR is not always an accurate measure of well-being.  For this reason, I always try to ensure I have a full two days quiet time after any slightly more active day. To be sure, to be sure! ;)

On Balance:
Heart rate monitoring is an incredibly useful way of monitoring activities in the moment,and regulating them to cause minimum damage.  However, I think using HR data for pacing is slightly more of an art, than an absolute science. If I were to stick strictly to keeping my HR below 101bpm at all times, I would never leave my bed.  However I know I can spend some short periods each day with my HR above this number and still avoid post exertional effects.  Thus I think the numbers need to be read within the context of each individual's own experience.

Looking forwards:
I admit I'm fascinated by numbers, so over the past year (& more) I've been collating much of my daily data into a large Excel spreadsheet.  Using that data I've created some pretty graphs whilst looking for patterns in the data.... So - Next Year - I hope to share some of those graphs and my musings about what they might mean.

Let's hope 2016 is a big year for medical breakthroughs for ME....  

Happy New Year! 


Further Information:
1)Wikipedia on HRmax
2) Workwell paper describing use of 2 Day CPET test for ME (CFS)
3) NICE Guideline for ME:  [CG53]
4) Endomondo (I pay a small monthly premium for the version I use).

Other HR posts on Just ME:
Starting Heart Rate Monitoring for ME Dec 2015
Heart Rate Monitoring & NICE Guideline for ME Nov 2015
Rhythm+ and Endomondo: HR monitoring for ME Aug 2014
A few notes on using a HR Monitor for Pacing Feb 2014


  1. Good post.

    "If I were to stick strictly to keeping my HR below 101bpm at all times, I would never leave my bed. However I know I can spend some short periods each day with my HR above this number and still avoid post exertional effects. Thus I think the numbers need to be read within the context of each individual's own experience."

    That's the thing, most of us probably shouldn't leave our beds, even if we can briefly. This type of heart rate monitoring shows just how severely limited we actually are.

    A couple of days in a row of going over these limits caused a (so far permanent) worsening of the severity of my ME. It happens without warning and the level of exertion it took to cause it was pathetic. The closer you heed these limits, the safer you will be.

    1. 100% agree with you there. It is such a difficult balance between doing what we can within our boundaries, and not risking a relapse that we can't recover from. I think what you say about "a couple of days" is important to think about, as a little over on one day may be okay, but repeating the same the next day is not. That has been my experience anyway. Thanks for you comment.

  2. This has given me a great starting point.Thank you
    Again 103 will be a challenge with moving!!
    But I need to do something drastic now to give my body healing time.
    This will be really tough when back to work but I have 4 weeks to get some idea of where I need to be to be in healing mode.

    1. So glad you have found it helpful. I think we all need to become experts in our own health don't we. Best wishes for 2016

  3. I've had CFS for 27 years, but just finally got off my duff and got a chest-strap monitor working.

    And found out, as I suspected, that I easily go over the 92 I'm supposed to stay under by climbing stairs too fast. And other stuff.

    Have you a feeling or data that says you're getting better by staying under you limit? Or are the crashes less frequent and shorter, but you don't think you're getting much better?

    1. I think the latter Alicia. I am not convinced that the HR monitoring is causing any improvement, but that it is a form of damage limitation, as it prevents crashes and so helps me to stabilise my condition. Perhaps with time this will allow my body to work things out and healing will occur. Maybe. xx

    2. Better than nothing.

      But I've read a lot of anecdotal accounts of people getting better by exercising to or close to their limit, without going over it, and getting better.

      If there is anything I can do, and it's legitimate, I'm going to try. I just hope it's not a waste of time, but hope is important, too.

      I don't know about you, but I still have a dream/hope that one day I'll get better - with or without external help. It would be even sweeter if I did it for myself - the 'external' part of help is taking a very long time.

      I still don't get it: they figured out AIDS. They found a vaccine for Ebola in what, one year? They're curing malaria. Why was I so lucky as to get something with no known cause, cure, or treatment? (Rhetorical question)

      I'm going to wear the monitor when exercising, and take it easy on the stairs.

    3. I honestly think change is around the corner for us .... soon. In the mean time we need to protect ourselves from further harm. I'll be honest I will never like the word "exercise" in relation people suffering from the active illness of ME...maybe "gentle activity within sustainable envelope" would be better... hmmm GAWSE? LOL xx

  4. ELE? (energy-limited exercise?) EME? (energy-monitored exercise?) ELEE? (extremely limited energy exercise?)

    The ultimate goal IS exercise, but exercise that makes us very slowly better, if possible.

    I know 'exercise' has been totally ruined by the GET fiasco as a goal for us, but I'm hoping for better, preferably by my own efforts (since the world is doing such a crappy job of it AND blaming the victims), and I'm doing exercises.

    I have hopes for this year - don't know why. Maybe it's the visibility, which seems to have increased after all these years. Maybe it's just that I have looked for - and found - online support. Maybe it's that I finally managed to publish my book with a CFS main character after working on it since the turn of the century. SOMETHING is in the air.

    I don't know how much I can 'exercise' safely, or how much I can improve. I don't know if I'll then run into a wall: this far and no further. But I keep trying. We all keep trying.

    Hope is a tough taskmaster.

    1. Should have said, 'I'm doing exercises with the HR monitor to stay within safe limits.'

    2. Going now to have a search for your book... presumably it is on Amazon. Love the other acronyms. And totally agree the word "exercise" is permanently tainted. xx

    3. Thanks. No obligation at all. And IF you'd rather, I can send you an electronic Review Copy (and anyone else who prefers), and you may write a review if you wish.

      Alicia (who just took a LONG nap - typical)

    4. Please could I have an electronic Review Copy? Thanks for your blog, it appears balanced and hopefully helpful. I'm going to try and monitor my HR and see what happens.

    5. Sure, Rex. I need your email address. You can write me at abehrhardt [AT] gmail.

  5. This is an amazing post! I never knew about this but I experience PEM so much with my ME so I really want to try this! I've just started blogging my ME experiences too! :)

    Keep up the fight!

    Love, Cat xxx

    1. Really glad to hear this is helping you. PEM is such a killjoy. Maybe you'll join #May12BlogBomb this year... see my current post. :)

  6. Curious why you went from a Fitbit to a Mio?

    1. My Fitbit is the Fitbit One. It pre-dates Fitbit adding heart rate monitors. So when I chose the Mio the Fitbits doing HR had still not come out. Things changed quickly in that market for a while.

    2. My Fitbit is the Fitbit One. It pre-dates Fitbit adding heart rate monitors. So when I chose the Mio the Fitbits doing HR had still not come out. Things changed quickly in that market for a while.

  7. Heart is the most important part of our body and we have to do many things to maintain our heart health. Sometimes our effort works and sometimes not. If you really want to maintain your heart health eat a balance diet with plenty of high fiber foods, do some exercise and try to be happy. Actually I have found a website in which I have read about what is healthy heart rate and according to me it is very important thing to know if we want to maintain our heart health.

  8. Hi, this is such an excellent post. I started heart rate monitoring one week ago and while my digestion has improved, and I feel calmer in general because I'm not doing things at a frantic pace and then crashing, I am nevertheless having a horrible time sleeping. My threshold is 96 and staying within that limit is actually making me feel more lethargic than ever. Or is that from the lack of sleep? It's hard to tell. And I had a massive headache the first few days. Is it normal to feel worse before you feel better? I feel like it may be worth a try to hit the 70% threshold instead of 60% and see if that makes a difference. The "perfectionist" in me wants to "do it right" but it's not worth only getting a tiny bit of sleep. Do you have any advice for me?????

    1. I am obviously not in a position to offer medical advice, but I would suggest that you probably “feel worse” due to other factors that are not to do with HR monitoring.

      Perhaps for a week you should wear the monitor without using it to change your behaviour, but instead just pacing as you normally do. Then you can see what your heart rate is doing without the monitor changing anything.

      Check out this post too, and some of the links I added at the end that you might find useful.

      Remember th HR monitor is just another thing to help you judge when PEM is approaching, but you should not ignore the other signals from your body that you are already familiar with.

    2. PS. Really glad you found the post useful. Here’s to new research finding better answers for us all soon xx