Pacemaker's effect on VO2 max and value of workout heart rate data

The current settings on my pacemaker are 60 and 165. I recently had a very good effort on my bike and my Training Peaks software gave me a Threshold heart rate of 161. i understand by definition Threshold Heart Rate is 80 to 90 percent of your max heart rate.... and the VO2 bit for me is that my Garmin Software gives me a VO2 max value of 43/44.. Which fo a 69 year old is decent...

... So the question: Is my pacemaker causing my VO2 max to be understated or overstated?

For training purposes i would like to know what i am dealing with. From the Threshold HR value i surmise my calculated max heart rate is roughly between 170 and 200 so in my workouts i effectivey have a no data zone above 165. I know something is going on as my percieved exertion will vary on my harder efforts within that zone and i suspect my heart is capable of a higher rate. I have thought of lying to one of my platforms, probably Garmin, with a range of 45 to 180 and see what happens. For right now though i know how to go fairly hard on my workouts but i find my HR data unreliable for things like when to back off or take a rest day. I want to improve but under current settings it's like i am going at max effort all the time and i don't think that is right.

I have had my pacemaker for almost 2 years now and have had several adjustment to my high end from 130 to now 165 and have come a long way in my abilities. I am eternaly greatful for that as i am able to ride close to what i was doing 20 years ago, so if this is as good as it gets i would be ok with that.

Any and all advice would be appreciated.

Please advise

Best regards


I wonder if you're over thinking this

by crustyg - 2023-11-15 15:53:04

As a physiologist I know that the only real VO2-max comes from being connected to the appropriate gas sensors and then actually measuring things.  Everything else is just an approximation.

Tim Nokes' bible, The Lore of Running, reproduces a lot of well validated, published work.  VO2-max drops with age, and the sad thing is that the higher your VO2-max, the steeper the slope of decline.

Cardiac output is a key factor in athletic exercise: trained athletes increase stroke volume more than stroke rate, and very few professional athletes in their 40s or later will achieve a maxHR of >175BPM.  Usually you see that they have considerably enlarged hearts with abnormally good lung capacity and gas exchange.  You might increase your capabilties with a maxHR of 170BPM, but probably not by much unless accurately measured.

Have you achieved peak performance?  Probably not, but it depends on what you're aiming for.  I still accrue some PBs on road bike hill climbs, but not many, and we're of an age.  Expecting to keep improving with increasing age is unrealistic: aiming to improve at a particular goal *does* make sense - but you'll probably see your body shape change as your weight is redistributed.  And you know yourself that the effort to achieve a PB increases with every year.

The evidence behind the beneficial effects of interval training is good, and the medical science underpinning it is good.  Just remember that for most of us here, the disease process that led us to need an implanted device is *probably* progressing.  My EP-doc and I have a running bet about whether/when I will end up in AFib.  4.5years in and so far I'm ahead.  But we'll see.

I wonder if you're over thinking this

by Ventum rider - 2023-11-15 19:22:36

Thank you for the input and your time. Haha... i think "over thinking it" is my middle name. The more i think about it though, VO2 max is an output and heart rate is just that a rate. If my VO2 max is constant an increase in rate will improve my ability to work harder... i think i have experienced this from my journey from when my pacemaker was set at 130 after implant and now when it is set at 165. I called to have a session with my cardiologist to discuss the pors and cons of going any higher. At my last adjustment they said i could go to 170 but other parameters would also have to be adjusted. We settled on 165 because i could go there without any other changes. For background i had Flutter, an Atrial block and low heart rate. Two ablations took care of the Flutter and the pacemaker corrected the block and the lower resting heart rate.(was in the low 30;s) and most of this started when i tried to get back in shape for a long distance bike race. I have improved a lot since implant and am fruly greatful for that but i feel i need to maintain my level of fitness for other things i deal with and just can't see myself turning into a couch potato. There is probably a middle ground.... haha let me think about it.... 

Thanks again

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I'm 43 and have had my pacemaker four weeks today. I'm looking forward to living another 50 years and this marvelous device inside me will help me do that.