Atrial Fibrillation, training advise, and chest strap reliability

AFib has impinged as a new “feature” that I need to accommodate in my training plan. It has really crashed the party in an acute and emergent way over the course of only a month. Maybe, being 67 has something to do with it. Dunno yet.

The point of this post is that I am getting really inconsistent HR readings from a variety of sensors. My Venu watch uses LED and it’s readings are generally in line with my blood pressure cuff, which is in line with my Kardia EKG unit. The outliers are my TICKER and TICKR-X that sometimes are in the ballpark and most of the time way higher by 15 to 30 or more bpm.

I have been told that “moderate” exercise is important. So, the other day I got on my Wahoo trainer wearing the TICKR and fired up Sufferfest for an easy endurance ride. Where only a month ago I would have had a heart rate of 104-110bpm warming up, I was clocked in straight away at 155bpm. Exertion that would haveI required 130bpm was taking 180bpm. I have plenty of experience with heart rates around 160bpm, which is my lactate threshold, but 180bpm is new territory. Sufferfest gave me a new medallion award for this record heart rate, even a special attaboy for this “accomplishment." In my acceptance speech for this award I thanked my Atrioventricular Nodes for their current undying support. (Ta-dum)

Does anyone know if AFib is going to confuse a chest strap monitor. I can’t think of another reason and really doubt the reliability of these readings.

A second question is about others who train with AFib. I would look forward to hearing about your experience. I am told that the Beta-blockers I just started really put a governor on your heart rate which likely means real limitations on performance. I am trying to figure this out, so thanks in advance.

Can’t really answer your medical questions ( Not a medical professional, but have studied human biology) but I guess in theory yes A fib could spook readings, but given you’re on B-blockers I’m surprised your BPM goes so high (I think they should keep heart rate down) .
I’ve heard that Beta blockers also basically stop the body being able to use fat during exercise ( as B- blockers interfere with hormones involved) so if you exercise hard and use up your “sugar” store you will bonk badly … but I think you should speak to a medical expert about your treatment!!

On the other hand - I have had LOTS of trouble over the years with HR straps that read wrong - either not at all or far too high. Trying another strap/new battery usually pinpoints the problem, but a good wash can also bring things back to reasonable for a few sessions. Also some straps are very sensitive to static electricity (e.g combination dry winter weather and nylon based clothing), not being wet/hard enough in place etc. Borrow or buy a new strap?
Hope you can get cycling again! /liz

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Also if you are connecting via Bluetooth, there can be all kinds of interference from other Bluetooth devices, routers, etc… It is a lousy protocol if you ask me, but we are stuck with it.

Polar H10. Yes, I know, I know…$$$. But if you want to see what’s really there and going on then there isn’t another option besides a wearable ekg.


FontierX is available. It is EXPENSIVE. It has a monthly fee as well. However, it is not as expensive as a Mobile Telemetry device. You might want to contact them. I get spammed on my Facebook feed due to having to wear one earlier this year due to a finding from my hiking fall.

+1 for the Polar H10.

I’m 57 and suffer from Tachycardia which is similar but not the same as A-fib and have found that reducing the volume of intensive training made a difference in that I haven’t triggered my racing heart beat for a number of months and my fitness is as good, if not better, than what it was before. I’m typically doing one sweet spot, one threshold and one VO2max workout per week, with the rest of the week being Endurance/Tempo

I’m not on beta blockers, so can’t add anything with regard to their effect.

I got the Polar H10 so i could measure HRV with the HRV4 Training & Logger Apps, and have found it very reliable with no periodic odd readings like i got with my TICKR

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You certainly need the Polar H10 (Garmin Dual should do as well).
With the Android FatMaxxer app you can then even record your ECG which logs anomalies.
Have a look here:

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@Potsiea I had a similar experience. My hunch is that it has something to do with the H10 strap being more rigid. I would get decent HRV readings with the Tickr when I was very careful not to move. With the H10, small movements don’t matter as much.


Also, every single HRV application advises to be ‘very quiet’ and be seated in a rigid chair. or laying down. That prevents body movement from causing anomalies with the reading. Also, they recommend a length as long as you can tolerate but no less than five minutes.

I have been doing more research and found the Velopress book, The Haywire Heart to be outstanding. Velopress really stepped up to the plate and did a real service for the cycling community. I have been a long time fan of Lennard Zinn. As tall as he already is, he has achieved an even larger stature with my reading of this book. His candor, generosity, and humanity really come through. And, it is inspiring.

See also:

The issue of heart rate monitors reading a reliable heart rate with atrial fibrillation is one of algorithms that work for normal hearts and don’t know what to make of irregular hearts. Algorithms seek to distinguish signal from noise, the actual heart beat from sensor movement and other artifacts. They get “misled” by irregular heart beats. Some people have episodic arrhythmia and some have chronic arrhythmias. Chronic folk need something that is set up to deal with the arrtymia. Holter monitors and the Fourth Frontier HRM use algorithms that anticipate and record more complex signals than a Polar or Wahoo is capable of. No criticism of Polar or Wahoo. I got my first Polar in the late 80’s and they have been as accurate as anything I used on a University lab erg doing lactate threshold testing back in the day. I have also been very happy with my TICKR’s over the past 7 or so years. I don’t blame them for not being set up for atrial fibrillation.

I ordered the Fourth Frontier X monitor “on sale” for $399. This is not inexpensive, but to put this in perspective, it is a quarter the cost of a decent carbon wheel set, the equivalent cost of a decent computer head unit, y’all get the point. I look forward to sharing how this works.


It may be blasphemy, but I know several long time bicyclists who are going e-bike solely because they have aged out of riding a regular bike. Sad as it may be, they wouldn’t be on a bicycle otherwise. I know one who is on his second and third and will never return to a regular bicycle. I’m also considering, but haven’t bought one. Why? Because heart disease doesn’t get better when you overstress that muscle. However, I’m also working with a medical team to see if the vessel changes can be reverted. As to AFib, there are three courses of treatment: Drugs, External Ablation, and MAZE. These should be done in order unless there is a life threatening condition and emergency treatment is needed.


I wanted to put this separate. If you are under the case of a cardiologist, you might want to consult with them before getting the FontierX. I was monitored for a month, and my insurance paid for it. They will NOT pay for the fees for the FontierX. I had a lengthy discussion with my medical team as well and they stated if you need ECG/EKG monitoring, it is best to use one of the available monitoring solutions rather than something that may raise issues unnecessarily.

I am a 63yo female who only rides inside on a Wahoo Kickr bike. I am on metoprolol succinate 100mg daily for blood pressure control. As a pharmacist I understand how beta blockers suppress heart rate but I am wondering if because my hr is artificially constrained if this also suppresses my power metrics when I do a full frontal and half Monty test. Before I started metoprolol I could get my hr into the 160s. Now I can’t exceed 140bpm regardless of how hard I ride. Should I manually increase my power and cadence metrics to allow for the metoprolol?

As a Pharmacist you know the effects of the drug. As to should I adjust? No. Not until you have a few rides under your bum and you are certain that the drug will not, in any way, affect your ability to hit power and cadence targets. BTW, have you discussed this with your medical team? I say this as I’m on several medicines that, if I exceed my capabilities, can cause extreme harm to myself. This is a risk only you can assume. As I stated before, get with your medical team before going any further.

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This is me actually but I’m 48. Before Metoprolol and Lisinopril, max heart rate was north of 160bpm but almost despite hard effort, I’ve not had seen anything greater than 145bpm.

I’m also wondering if this is a performance limiter. Can I still aspire to get to 3w/kg?

Hey @yodakramer,
There is no real concrete answer to your question. If you aren’t already, I’d suggest working closely with your doctor to get the best health and fitness outcome possible for you. Sorry I can’t give a definitive answer on your quest for 3w/kg.
Here are a couple of articles that you may have already seen.



Yeah, working with my cardiologist. Just kinda bummed since I’ve put in so much effort this past year and set a bunch of cycling goals for the coming year.

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I hear you. Those goals may still be attainable. Working on all aspects of fitness may increase your odds of achieving them. We’re here to help.




Chest straps will work better than wrist based (LED) monitors. The LED monitors rely on variation in peripheral blood flow. The problem with AF is that peripheral blood flow / perfusion is variable and some impulses come so quickly together they can’t be discerned. So measuring your pulse at the wrist/arm can be misleading and typically underestimates your true heart rate.

A chest strap which measures electrical activity will be more reliable, but I don’t know of any data on how they perform in AF, and the algorithms are closely guarded secrets. They can’t measure too fast a heart rate though - they typically top out at 255bpm.

Most people with AF tend to run fast. And your heart is less efficient - because you lose a co-ordinated atrial kick the heart fills less well, so it tends to pump less volume each heart beat - bluntly it’s like losing a cylinder in a car. So it tends to have to rev harder to generate the same blood flow per minute. But to add to this, the optimal heart rate for each exercise load varies from person to person. Some people are better with digoxin/beta-blockers. But you have to get the dose right.

Most “young and fit” people with AF - which tends to be athletes - do really well with an AF ablation. But you have to recognise that endurance sport seems to predispose (men) to developing AF. So, arguably, you shouldn’t do too much.

I am a cardiologist. And also a hypocrite.





One really heavy suggestion: Work with a Cardiologist who also is a bicyclist. I got ‘lucky’ and got one. He is acutely aware of the limitations and has me on a combination of drugs for HBP and those actually eased an issue that Sir Spencer and I found. Now to building myself back up and becoming more pain free.

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