VO2max

It took me a while to figure out how to set the Apple Cadio Fitness up in Health App to be able to see the VO2max level. Today I took a 25 min brisk walk (17:40 per mile) and the VO2max finally showed up on my phone. For my age group, it's below average. I am too not surprised because this measurement is generally considered the best indicator of cardiovascular fitness, having Afib does not help.

I am wondering did anyone see improvement on their VO2max after a successful ablation?



Edited 1 time(s). Last edit at 05/23/2023 03:00PM by Yuxi.

My VO2 max is abnormally low, and I am in very good shape. I wonder if my ablation had something to do with that, also. I'm also measuring my VO two max via Apple's health app.

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Que
My VO2 max is abnormally low, and I am in very good shape. I wonder if my ablation had something to do with that, also. I'm also measuring my VO two max via Apple's health app.

Do you have Apple readings from before the ablation? An ablation significantly lowering VO2 max seems unlikely to me.

A proper VO2 max test is a maximum test. It is really testing the glycolytic energy system (the three systems are phosphagen, glycolytic, and oxidative). The phosphagen is used when doing a max effort for ~<10 seconds, the glycolytic system is for relatively short term activities at high intensities and glucose is used anaerobically, the oxidative system uses glucose, fat, lactate aerobically through the cell's mitochondrial electron transport chain. I'm guessing the Apple Watch uses a non max proxy equation like the Rockport fitness test. It is a one mile (1609 metres) walking test (walk as fast as possible). The equation is:
132.853 - (0.0769 × Weight) - (0.3877 × Age) + (6.315 × Gender) - (3.2649 × Time) - (0.1565 × Heart rate).
So what it is testing is how fast you can cover the distance and at what heart rate.

If appropriate in your situation, an actual VO2 max will commonly respond to high intensity training. Book "The One Minute Workout" by Martin Gibala has many options. Gibala is a researcher at McMaster University in Ontario, CA.

I'm not an ablatee and will have had afib for 19 years in July. Early on, I learned that if I used nasal breathing as an exertion governor for long duration exercise, exercise was not a trigger for me. Much later, I learned that this approximates what is known as "Zone 2." It can also be approximated using heart rate with Phil Maffetone's MAF system. I also later learned that Zone 2 should be trained to increase mitochondrial density and size (per the work of University of Colorado Health Sciences researcher, Iñigo San Millán). This training will increase the body's ability to metabolize both fat and glucose aerobically. In this post are links to the Z2 topics. Another way to know you are at the Z2 level: if you were talking on the phone, you could do it comfortably for a long time, however the other person would know you are exercising.

I have found I can do the Z2 training without issue. I can also do short duration training of either the phosphagen or glycolytic systems without afib issues. Once a week or so, I will do a workout on a fan bike where I warm up for 3 minutes then do 8 cycles of 15 seconds absolutely as hard as I can & 15 seconds at 50 watts followed by a 3 minute cool down. I'm guessing the first few cycles use the phosphagen system and the later ones the glycolytic. I also have a VO2 max proxy provided by my Polar heart rate system. I probably do 45 or more minutes of Z2 a day & that plus the infrequent high intensity training maintains this proxy at the top 2 1/2% for my age.

Geoge, thanks for the detailed elaboration, top 2 1/2% for your age is wonderful for your heart health.

Apparently the walk I used to measure VO2max was below my Zone 2 heart rate, I was afraid to walk too fast. I will give a try next time with my Zone 2 HR to see if I get a better result. The One Minute Workout would be an interesting read.

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Yuxi
Apparently the walk I used to measure VO2max was below my Zone 2 heart rate, I was afraid to walk too fast. I will give a try next time with my Zone 2 HR to see if I get a better result. The One Minute Workout would be an interesting read.

From what you've said, my suggestion is to not worry about VO2 Max for the time being. I'd find your MAF heart rate, which is nominally 180-age, but there are qualifiers to fine tune it in the link. It is a good proxy for Z2. Then I would go to a flat place with distance marked, like a school track and do a MAF test. Do it at your MAF heat rate and see what the time is. Then work on doing frequent work at your MAF heart rate. Longer times/distances are better, if you are able. Then go back to your track or whatever in a month or so and retest. This will work on optimizing your mitochondria, which has many benefits. If you decide you want to try some more intense exercise, like in Dr. Gibala's book, if you are doing on the same day as your MAF/Z2 exercise, do it after. This is because the higher intensity will be glycolytic and will produce more lactate. Lactate is a good fuel, but above the Z2 level, it will accumulate in the blood and inhibit the Z2 mitochondrial adaptations (per Dr. San Millán). However, once the Z2 is done for the day, some high intensity intervals will be OK (again, per San Millán).

Interpolating from what you've written, the glycolytic system is not a system you are using right now. That is OK. You will get a lot of benefit from just doing the MAF/Z2 work. Realize that the mitochondrial adaptations take time, so be patient.

I'm sure there are some afibbers where Z2 is too intense. However, I think for most, it should not cause issues. I think longer duration high intensity work is where the trouble can be for some. In my case, when I used to do high altitude races, I know that after the race, my resting heart rate would be elevated for a few days, then it would drop below my pre-race resting heart rate and then finally return to normal. It was the time that it was below the pre-race level that was a risk period for me for afib. It was an indicator of stress. For me, even intense mental stress is a risk. In January, I drove for 13-14 hours through high winds, blowing snow and very icy roads. When I stopped for the night and relaxed, I had an afib episode. A classic vagal trigger for an event. So the stress can be physical or mental. At the Z2 level, there is enough stress to cause an adaptation, but not so much as to cause an episode. At least this has been my experience and many others who have communicated with me.