Sunday, November 29, 2020

Night Watchman

Last night, for the first time ever, I wore my Garmin Forerunner as I slept. So, when I awoke today I was treated to a mountain of data. Whether any of it proves useful remains to be seen.

The big number, as far as I’m concerned, is the total amount of sleep. If you had told me last night that I could expect almost 7 hours of sleep, then I would have thanked you heartily because that is not typical. But it was Saturday night and I had had a fairly active and yet not stressful day. I do sleep better on weekends, but 7 hours is still really good for me. The deep/light breakdown, though, leaves something to be desired.

I can’t account for that moment of wakefulness shortly before 6 a.m.  Being awake briefly at 6:30 was the result of my alarm clock. I had set it for that time in hopes of finding a live stream of today’s UCI Cyclocross World Cup race, but I quickly abandoned that effort and went back to sleep.

My overnight resting heart rate was 40 beats per minute:

From about 12:30 until about 1 a.m., the watch measured my heart rate at 33 bpm. I think that’s a data collection error; maybe I shifted my arm and the watch wasn’t making good contact with my skin … I don’t know. It’s certainly an anomaly. The long periods at 40 bpm argue strongly for the accuracy of that measurement. And 40 bpm is a number I have seen before in my own manual sampling, while 33 bpm is not. The highest number on the chart is 67 bpm, the result of jumping out of bed to silence the alarm clock. I know heart rate is a very individual thing and that it can be affected by a big variety of factors, but in general a low resting heart rate is a good indicator of fitness. So, I’m happy with 40 bpm … happy, but not surprised.

Now the question is what to do with this data. Are these just numbers, interesting but trivial, or by collecting this kind of data over time can I identify opportunities to improve my sleep and thereby improve not just my athletic performance, but also my life in general?


  1. I've been wearing an Oura ring for over a year, which is a sleep tracker. With the Oura ring, it tries to analyze my activity the past day and how well I slept, then gives me a report telling me if it thinks I can "push hard" that day or if I need to take it easy because you didn't rest well. For the most part, it seems pretty accurate.

    Using sleep data, you could potentially save yourself from doing harm to yourself. For example, if you train hard several days in a row and you're not getting good sleep, your training might not be doing what you think it's doing as your body hasn't been able to repair from the previous day's efforts.

    I use the data to experiment and see if there is anything I can do to make my sleep better... or worse. For example, a few days ago I had a handful of dark chocolate chips about an hour before bed. Obviously not a great idea due to the sugar and caffeine in chocolate. Unsurprisingly, my Oura ring showed my resting heart rate was unusually high until well into the night.

    I've also confirmed from my data that sleeping in a cool environment makes a big difference. My deep sleep in the summer was typically less than an hour where as it's now consistently over 2 hours.

    There's also the HRV (heart rate variability) aspect. I don't fully understand HRV, but it seems to be something that athletes track.

    So enjoy your new-found sleep data and I look forward to future blogs with results from any "sleep experiments" you try!