So much of life is invisible, hard to define, harder to be sure of. So finding evidence of something you’ve maybe felt for weeks comes as a shock.

I came down with Covid on October 20 last year. For the first time, as far as I’m aware, and that makes me lucky. And I didn’t get long-Covid, which makes me doubly lucky. Still, it knocked me out entirely for a few days, and then I felt fatigued for weeks afterward, which I found profoundly frustrating.

My thoughts went like this: Is my breathlessness; my inability to concentrate; this subtle dislocation from reality – is it real? Am I being pathetic? Do other people cope better with whatever this is? Do I deserve to languish like I want to? Is this real? Am I pathetic?

At least, this is what part of my head was saying throughout November and even into December. Another part of my head was saying, “You had Covid. Recovery is proving slow. Just accept it.”¹

And even now, I don’t feel I’m quite back to normal when I’m walking the dog up the many hills around Bath. They’re more of a struggle than I remember, but the bad voice is asking, maybe that’s just because I lost fitness and I’m not really working hard enough.

And then I took a look at the Cardio Fitness page in the iOS Health app that my Apple Watch has quietly been correlating since I got it in late September. This feature uses the watch’s blood flow and heart-rate measurements to estimate my rough maximum VO₂ levels, which is how much oxygen my body can use when exercising.

And what do you know? The graph almost precisely matches up with my personal sense of my fitness: I’m still recovering my pre-Covid level.

I’m sure the figures aren’t precise, and is that first data point in November weird? It would have been my first, tentative, walk, which I kept gentle and found incredibly hard. But they otherwise correlate so closely to my subjective experience that there must be some truth here.

And I guess there’s a moral in it all. Trust your feelings?