Why, sometimes, you should ignore your watch.

Wearable fitness tech has become a pretty normal part of life. Even non sporty people often have a wearable watch that counts their steps and measures their resting heart rate and all of this has a whole world of integration with your smartphone and I don’t think the suggestion that this tech is here to stay is a particularly bold proclamation. These watches are, generally speaking, quite good. There’s plenty of evidence that suggests those who wear them are more likely to make long term changes of habit towards being more active – which is obviously good for everyone, except maybe runners?

As I write this I do so with a Garmin watch on my wrist, on which I track all of my runs, I look at all sorts of statistics such as the fact that I’ve burned 864 calories this morning, have a resting heart rate of 48bpm and slept for 8 hours and 4 minutes last night. All of these metrics are useful to me as a means of evaluating why I feel like I do on any given day. However, it also has a bunch of other performance metrics which it calculates from my heart rate and pace while I’m training. The one I’m going to talk about in this article is VO2 max as it’s the one talked about mostly.

It’s just wrong, a lot. My watch thinks my VO2 max is 57, my actual VO2 max is closer to 75. Obviously this is a huge under estimation which could really damage the confidence of a runner which is also an important factor in performance. Imagine being judged as 24% slower than you actually were without the knowledge that this judgement isn’t accurate. This also goes the other way, sometimes people’s performance metrics are over estimated. It’s the same when it judges your ‘performance condition’ or ‘training productivity’. Ignore it. The problem this tech has is the age old problem. Crap data in gives you crap data out.

Watches measure your heart rate using an optical sensor which, in short, doesn’t work very well when you exercise. This is because you sweat, it moves around, it could be on too tight or not tight enough. There’s a series of factors which essentially ruin this calculation. They work ok, but still not amazingly, at rest. You could wear a heart rate strap while you train which yields a better quality of measurement but the easiest solution is focus on performance. If you’re getting faster then you’re getting fitter, even if your watch calls you unproductive.

In summary, focus on performance. Don’t allow the numbers, which are often wrong, on your watch to dictate how you feel about yourself. Your watch isn’t useless though, the data it does give you, especially sleep, can explain why you feel good (or bad) in training. If you want to get faster at running then focus on race results and paces hit in training, not a badly calculated VO2 max number. The best way to improve is through a well structured training plan that allows you to achieve consistency over time.

Happy running!

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