I'm new to this site. I'm a 74 year old man living in York, UK.
My Fitbit gives me a score of 42 which is supposed to be excellent for my age. Not long ago I had a proper VO2 max test where I rode an exercise bike with a mask on and they measured my respiratory gases. I was given a score of 13. This is the sort of number that makes you eligible for a lung transplant.
I have mild COPD but can run 10k in about 80 minutes. The entire run is usually in peak heart rate zone, but I'm not alone so don't worry about this. It drops back quickly when I stop running and my resting heart rate is about 58 bpm.
The VO2 max test at a BUPA clinic only ran me up to 90% of predicted max HR and to me this was pretty effort free. They told me the result was taken by extrapolating my graph up to my predicted max. I've since found my actual max is somewhat greater than the 220-age formula they used.
Does anybody have any insight into this? How can these two results be so massively far apart?
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Andyv1
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Welcome to HealthUnlocked, and to the Bridge to 10K community!
I'm not sure if this will be true for all models, but Fitbit has been shown to overestimate VO2max. Fitbit uses your heart rate data to estimate VO2max, but no wrist heart rate monitor is especially accurate (chest straps are better), and the method of measurement used by the Fitbit is very different to that of the laboratory test. So all in all you need to take your Fitbit's measurement of VO2max with a large pinch of salt!
However, your score does reflect the fact that your heart is working hard and recovering quickly - which is very good news! I assume that you have checked with your doctor that you are OK to exercise at this level, so I would think you have no reason to worry. You can use this VO2max estimate as your baseline, and see if you can increase it over time, so it will still have value.
A study comparing accuracy of the Fitbit Charge 2 VO2max estimate with lab treadmill test: ncbi.nlm.nih.gov/pmc/articl...
Many thanks. I've just spent some time going over my BUPA test results. They provided me with loads of graphs correlating time, heart rate, oxygen uptake, CO2 expelled. There may also have been a factor for work done on the exercise bike. It's pretty comprehensive, though they only took me up to 85% of my max HR (not 90% as I previously stated).
The most significant factor that I can see is that as the test progressed and my HR was rising, my breathing rate was going up normally, but oxygen uptake wasn't going up much. It might be an age thing but perhaps my muscles can only deliver so much work and won't use any more oxygen, even though they're signalling the heart to pump faster.
Regarding HR measurement, I've tried two other devices, a chest band and a finger tip clip and my Fitbit is pretty much the same.
The Fitbit assumes higher HR equals more oxygen to the muscles. It doesn't know that only a fraction of the oxygen inhaled is getting used, the rest being exhaled. In making the comparison between VO2 max and cardio fitness it probably works for the bulk of people in the trial. Maybe they didn't include many oldies like me in their study.
Sounds very interesting, what advice did they give to you based on the results?
I think that the definition of "fitness" relates to the ability of muscle cells to take up oxygen and use it efficiently, and age is certainly a factor - but as health allows, fitness can still be improved at any age.
Interesting comment about the HR monitoring - which Fitbit do you have?
Yes, the subjects in that study were much younger than thee or me 😊
The main advice I got was to do as much aerobic exercise as I can. They didn't think it's harmful. However the reason I'm asking right now is that I've let my exercise slide for a good while as I've not gone to classes for a year, and I need to pick it up again and I want to understand the best way.
My Fitbit is a Charge 4. I was using a Charge 2 before. They both work by shining a light into your wrist and responding to the blood flow pulses. The Charge 4 uses a slightly more advanced calculation for cardio fitness, and has built in GPS tracking.
The finger tip device also shines a light into your skin. It measures percentage oxygen in the blood but it also does HR at the same time. The chest band picks up electrical signals from the heart, but often used to lose contact.
Likewise - and it's got a row of bars showing your pulse in real time, but I gave up using it for running when it was indicating 200+ bpm. My theoretical max is 146.
Have you tried using it on a plane or up a mountain where the atmospheric pressure is low? My percent O2 drops into the 80's.
I've not been on an aeroplane since August 2019 (a quick hop to Ireland for work). And there aren't that many proper mountains in the UK.
I do remember feeling quite light headed when we stopped for a bite at a cafe at the top of a pass on the French side of the Pyrenees twenty years ago. The car struggled the last few hundred metres, too.
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Back to 'peak' fitness at last!
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