Measuring VO2 max with Apple Watch and pacemaker

I have a watch 7 and it has a cardio fitness function where it measures VO2 max.  I got a Medtronic dual chamber pacemaker 6 weeks ago, and my readings have been going down since it was implanted.  While I see in some of the literature that Pacemakers can impact the accuracy of the Apple Watch's capacity to measure cardio fitness with the health app, I have not seen how or how much it might affect the accuracy.  

Does anyone have any experience with this. 


Apple watch

by AgentX86 - 2023-01-15 02:11:17

I wouldn't use any watch for anything more than a toy.  They too often lie, even under the best circumstances. Pacemakers can throw off readings, which is why they have the disclaimers for pacemaker patients.  This may or may not add to the problems but I certainly wouldn't use one for anything important.  YMMV


by PacedNRunning - 2023-01-15 03:44:06

Has your activity level decreased? Are you outside or inside? It only calculates outside running or walking. So if you haven't been doing that, it will go down. Mine stayed the same. Maybe dropped some but I'm still in the high range. 

it's all new

by Tracey_E - 2023-01-15 21:27:29

I've been paced since before calculating your own VO2 was a thing so I have nothing to compare it to, but when I had a PFT in conjunction with a stress test and it was very close to the same as my apple watch.

Once you are fully healed and achieve your new normal for activity, you'll have to figure out what your new normals are for your targets. 

VO2 max and watch

by jmc43 - 2023-01-16 10:31:41

Thanks for the comments, very helpful.  Re my activity level...I do measure it with outdoor walks, and I am not quite back to what I had before the pacemaker was implanted, but I am close.  Still, I think rate responsive element means my that my h/r during exercise is quite different than before.  In a very brisk workout walk before, my h/r was 70-85, lower because of a beta blocker and calcium channel blocker.  Now, for essentially the same workout, it ranges from 100-115. So quite different.  I think i will recalibrate the watch, see what happens.


by Tracey_E - 2023-01-16 12:58:33

With new meds and pacing controlling your rate going up and down, I would expect your VO2 to change. 

Good to Know

by MinimeJer05 - 2023-01-16 16:18:18


Good to know about the fact that it only tracks when outside. I perform most of my cardio indoors on a treadmill and was wondering why my VO2 was so bad -- I also didn't put too much stock into it, because I have been feeling better and better as I continue to increase my exercise. 

Hope others have answered your question better than I (my only advice would be the same as others that have said not to rely on the watch COMPLETELY -- it is a useful tool, but it's just an imperfect tool)

Take care



by PacedNRunning - 2023-01-17 03:06:22

Rate response could throw it off since your HR is. Artificial now. When I go for a brisk walk my HR barely goes over 89-95bpm. If you feel fine I would leave my settings. If I felt out of breath I would lower it. 

Further thoughts…

by jmc43 - 2023-01-17 09:29:00

Thx much for the comments.  And I would agree with the previous 3 comments, especially pacednrunning.  The pacemaker is rate responsive so the HR is somewhat artificial, both in how fast it goes up and how slowly it returns.  I know that there are warnings that pacemakers can impact Watch measurement, and there probably hasn't been enough research done to adjust for these.  What I do know is this:  I am 79, live in the mountains at about 3000 feet, walk briskly a little under 2 miles 5 times a week, between 110-120 paces per minute -- and feel just fine.  Only difference is my H/R is between 95-105 depending on hills, as opposed to 75-80 before the pacemaker.  So I will rely on how I feel, and not pay so much attention to the VO2 max.  Too many confounding variables with meds and pacemaker. 

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