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A magnificent physical specimen

The Apple Watch can estimate your “cardio fitness” level when you do certain activities, and show you how it changes over time. From their website:

Cardio fitness is a measurement of your VO2 max, which is the maximum amount of oxygen your body can consume during exercise. Your cardio fitness level is a strong indicator of your overall physical health and a predictor of your long-term health. Your Apple Watch gives you a cardio fitness estimate by measuring how hard your heart is working during an outdoor walk, run or hike.

I didn’t use this when I first got my Watch because I didn’t go running and I never started A Walk (never mind A Hike) when living in London. I walked, but it was only Going For A Coffee, or Going To The Cinema, not an Activity I felt the need to track. I tracked my swimming and my weight workouts (2-3 times a week each) but neither generated cardio data.

The first time I used the Watch to track an Outdoor Walk was in 2019 when we came here, to Herefordshire, on holiday and I tracked eight Walks over ten days in August and September. The watch said my cardio fitness level was about 41 VO2 max which, for my age and sex, put me just below the middle of the Above Average band shown on this chart as the pink stripe:

A graph with the x-axis stretching from August 2019 to June 2022, and the y-axis from 30 to 60. There is a pink band stretching across the graph, from 38 up to 47. There is a red line that goes from about 42 in August 2019 down slightly to 41 in September 2019

That seems alright! Above Average is good. There are four possible bands:

  • High
  • Above Average
  • Below Average
  • Low

I have no idea how much exercise most people do, or how fit most people are or aren’t, so being Above Average was fine with me.

I didn’t track any more cardio-fitness-eligible activities again until we moved here in January 2020, when I started tracking Outdoor Walks – because most of our walks here are for the sake of walking, getting exercise, rather than travelling to places (because there’s hardly anywhere to walk to).

I was pleasantly surprised to find that somehow I’d become much fitter in the previous five months:

The same as the previous graph but with the red line shooting up from 41 to about 53 in January 2020

I was now in the High fitness level! Brilliant! I had no idea what had changed. I hadn’t altered my fitness routine over the previous year or so, which made this change unexpected. But I wasn’t complaining. I was some kind of superman! I wanted to go back and tell PE-hating child me what a magnificent physical specimen I’d become.

But, over the next few months, my cardio level began dropping:

Now the red line continues for each month from January through June 2020, slowly falling to about 50, still above the pink band

It was still High! I was still brilliant! I’d stopped swimming when we moved, given I was no longer two minutes walk from a pool, and started Couch-to-5K, so I was soon tracking Outdoor Runs as well as Walks. I wasn’t going to a gym for a couple of months until we joined the closest one to here (four miles away) but then had to stop going again a few weeks later because, of course, lockdown arrived that March.

Unfortunately, the decline continued into the summer, with alarming consequences for my sense of brilliance:

The red line runs through to September 2020 and has continued to fall, dropping into the pink band in August. It has now reached about 45.

I was now only Above Average again! Ugh. Almost like a normal person.

If my fitness level had stayed within Above Average over the previous year, this level would have been great – I was fitter than I had been 12 months earlier. But having had a taste of, apparently, being High fitness for a few months this felt like a big comedown.

It was around this time I googled for other people’s experiences with the Apple Watch and its cardio fitness level. I should not have been surprised that people split broadly into two groups: those who were pleased with how fit their Watch told them they were, and so thought it must be very accurate, and those who were disappointed at their rating and thought the Watch must be doing something wrong.

I continued tracking my walks and my 5K runs. I was also doing some HIIT exercise around this stage, using the 7 Minute Workout app (for 21 minutes a time). But this wasn’t enough to improve things and my level settled in the middle of Above Average towards the end of 2020:

Now the line stretches into January 2021. In August 2020 it dropped into the pink band, at about 48, then continued to fall until November 2020 where it settled at around 43

That’s OK but the overall trend wasn’t looking good. If it dropped much further then I would – horror! – become of Below Average fitness, which didn’t feel quite right. It wasn’t like I was crushing it for hours a day but 5K runs twice a week, plus some HIIT, plus occasional 8+km walks, and eating pretty healthily, all seemed like it shouldn’t make me Below Average. The media keeps telling me the country is full of obese couch potatoes eating junk food, smoking fags and boozing, so how could I be heading for Below Average fitness?

But, a saviour! It turns out that the fitness levels are adjusted for your age, changing every decade. And in March 2021 I turned 50 which meant that what counted as Above Average fitness suddenly changed:

The pink band is no longer a straight horizontal band. It shifts from March 2021 and instead of sttretching from 38 to 47 it now goes from 33 to 41. The red line remains the same as the previous graph

Ha ha! Yes! Lots more room to fall before I need worry. What a great birthday present. Thanks Tim Apple.

My fitness did fall a little, so I didn’t quite squeeze into the High fitness level for those aged 50+, but I was now at the upper edge of Above Average:

The red line continues, dropping to 41 in February 2020 and staying there for March. Before, the line was in the middle of the pink band but, now that the band has dropped, it is at the top of the new level of the band.

Phew, plenty of breathing room to get things back on track.

Around this point I started using Apple Fitness+ for strength and HIIT workouts, in addition to my 5K runs twice a week. I’ve really enjoyed using it but, unfortunately, we can see that it wasn’t enough to slow the fall of my fitness over the following twelve months through to April 2022:

The red line continues from March 2021, stretching through April 2022. It continues to fall gradually, aside from a handful of months where it stays level, down to about 35, near the lower edge of the pink band (and below what was the bottom of the band's lower edge before March 2021).

Bummer. Last autumn I stopped running, having done something odd to my knees – maybe due to running, or an over-enthusiastic-if-futile attempt at pigeon pose, or too much kneeling while painting skirting boards, or all of the above.

I stopped and started HIIT for a while before deciding it wasn’t helping, so my exercise for the past few months has been strength workouts three times a week and daily Walks, between 20 and 60 minutes. It’s clearly not enough cardio to keep me clear of the dreaded Below Average zone. And maybe that’s fair enough. For the most part my Walks aren’t much more activity than many people would do as part of their daily commute, or their job. Three lots of 20 minute mild strength workouts every week on top of that probably shouldn’t see me soaring towards the High fitness level. Until my knees are better I’m not sure what cardio I should or could be doing (the nearest swimming pool is a half-hour drive away, and I’m still too covid-cautious for that).

I’ve been intending to write this post for some time but didn’t want to end it on a down note. Which, as you can see, has meant not writing it at all given the lack of any statistically significant positive changes.

But, then, last month:

One more month is added to the red line, May 2022, and it has risen slightly from about 35 to about 36

Yes! My cardio fitness level went up, on average, from 34.6 to 35.6 VO2 max! In a way I’m about back where I started, about a third of the way up the Above Average level, ignoring the fact this level shifted downwards dramatically on my 50th birthday.

For some time I’ve been obsessively checking my level after every single walk, pleased at even a 0.1 increase or getting fed up with a 0.1 decrease. During May I made an effort to walk faster which, I guess, helped. But there’s a limit to how fast one can walk, and walking 3km in 25 minutes is a grim march – neither a pleasant stroll nor an ultimately satisfying run.

I find the whole thing quite strange. Why did my fitness level jump from 41 to 53 VO2 max over those early five months, despite not changing my routines? Is there a limit to how high it can set your fitness if you’re only recording Walks and not Runs? Why did it continue to fall so far when I was exercising every day? How much exercise would I have to do to get it higher? Isn’t it weird to have fitness levels that change so suddenly at arbitrary divisible-by-ten ages?

I want to keep fit, mainly for future-me, knowing that the best way to be fit as an old man is to be fit as a (relatively) young man and to keep that going. But it seems very hard to satisfy whatever code and sensors are gaging my health.

I don’t have a good conclusion. Other than “apparently, somehow, I need to do more cardio exercise,” I’m mainly mystified by exactly how my fitness level could rise so much and then fall so much, without me feeling noticeably different.

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1 comment

  1. I'm the same age, have similar activity levels and have been on a similar trajectory. Perhaps this metric just isn't accurate.

    The resting heart rate figures seem more believable. I can make a noticeable impact on them with a month of good sleep, zero alcohol and a decent amount of exercise.

    (Thanks for the previous 'use hiking' to track walks tip!)