A little about HRV

HRV (Heart Rate Variability) is one of the metrics that the Oura ring tracks. I’ve begun to learn a bit about it, and thought I’d share what I’ve learned so far, and then share a small personal observation.

Very briefly, HRV has to do with the variations in the timings between heart beats. If your heart rate is 60 beats per minute then about one second will pass from one heart beat to the next—but only about one second. In actual fact, sometimes it will be a few milliseconds more, and other times it will be a few milliseconds less. Those “more or less” amounts are your heart rate variability or HRV.

Most of what I know about the HRV comes from an interview on Human OS Radio podcast with Phyllis Stein, Director of the Heart Rate Variability Laboratory at the Washington University School of Medicine in St. Louis, called Introduction to Heart Rate Variability (HRV). It’s definitely worth a listen, if you do the podcast thing.

A lot of HRV is related to respiration. I noticed this when I got my first heart rate monitor thirty years ago: Every time I inhaled my heart rate speeded up, and every time I exhaled my heart rate slowed down. This effect is pronounced enough that the Oura ring can calculate your respiration rate just by watching your heart rate speed up and slow down with each breath.

HRV is widely used as an indicator of the balance between your parasympathetic and sympathetic nervous systems: If your parasympathetic nervous system is functioning well you’ll see quite a bit of variation. When it’s not functioning well—for example, when you’re persistently stressed—the amount of variation in your heart rate will decline.

Since I got my Oura ring, I’ve been tracking my HRV, looking to see if this or that bit of self-care practice will increase it, and I’ve noticed one thing that seems kind of interesting: Very often my HRV will be quite low in the first half of the night, and then be higher (and with higher variability in the variations) in the second half of the night. Here are three recent examples:

I speculate that this is related to the fact that I’m still digesting supper at bedtime, or perhaps that alcohol I’ve consumed is not fully metabolized yet. I’ve been hoping that life would produce a natural experiment to test those two theories, but so far haven’t gotten one. (That is, days when supper or cocktail hour were very early or had to be skipped have also been days when some other factor—such as illness, an unusual bedtime, or unusual stress—confounded things such that I couldn’t really draw any conclusion about the effect on my HRV.)

Maximizing the Oura ring activity score

First, let me say that maximizing my Oura ring activity score is, in and of itself, of no value whatsoever—except to the extent that it reflects and reinforces my efforts to get an appropriate level of physical activity.

Happily, I find that getting an appropriate amount of activity generally results in a higher score. So it works at that level, with perhaps a few mismatches between what I think is appropriate and what the Oura software thinks is appropriate, the main one being their idea of what counts as a recovery day.

Periodization of training—getting a mix of training days and recovery days—is a great idea. In fact, the lack of periodization is one of the limitations with Google Fit, whose model is to have a daily activity goal which is a little aggressive—a goal that motivates you to to get out and walk just a little more than you otherwise might. The problem is that a goal that’s even a little bit aggressive is going to be excessive for your recovery days, while still being much less than you probably want for your training days.

This is where the Oura ring software is a big step up from Google Fit. It strongly encourages both training days and recovery days. Unfortunately, its idea of a recovery day seems a bit too strict for me:

For Oura, an easy day means keeping the amount of medium intensity level activity below 200 MET minutes (200-300 kcal/day), and high intensity activity below 100 MET minutes (100-150 kcal/day).

In practice this can mean doing lots of low intensity activities, getting healthy amounts of medium intensity activity (30-60 min), but only a small amount of high intensity activity (below 10 min).

Now, that’s all well and good, except that ordinary walking is a medium intensity activity, and (except when the weather is crappy) it’s a very rare day indeed that I don’t end up walking more than an hour—meaning that I basically never get a recovery day in Oura ring terms.

The result is that whenever the weather is nice my activity score starts dropping, because I’m not getting what my ring thinks is appropriate recovery. Then, when there’s a couple of days of crappy weather and I sit around the house all day, my score will climb (as my recovery time value improves). Then, as soon as the weather gets nice again and I can get out and be active, my activity score can shoot up into the high 90s:

However, I can only get five days of such high levels. Since I need to have at least two recovery days per week, a string of more than five nice days means my recovery suffers once again, turning into lower activity scores.

I haven’t fully characterized the behavior so far, but it seems like the software may well be doing just what the quoted text above says: Getting between 30 and 60 minutes of medium activity makes a day a recovery day, with a hard end to any “recovery” at 61 minutes.

If true, that would probably be the place to make a fix. That is, I’m not trying to suggest that I have any data to show that an average person could walk more than 60 minutes and still recover as well, nor do I have any good metric for identifying some subset of people who can walk more and recover well. But I am pretty sure that the 1 h 3 min of medium activity that I got the day before yesterday is not so much more than the 60 I got yesterday that the former should count as a training day rather than a recovery day.

Sleeping with my Oura ring: Body temperature

As a big ol’ data geek, I’m by default interested in any metrics that I can get, especially ones related to me.

One of the metrics tracked by the Oura ring is body temperature, which is a metric don’t normally pay much attention to unless I think I might be sick, and I haven’t wanted to get sick just to explore this feature of the Oura ring. But a couple of days ago I did something much better: I got my shingles vaccination.

(I’ve been trying to get my shingles vaccination for months now, since they changed the recommended age from 60 to 50 and my insurance company started covering it for young folks like me. But with all the younger boomers thinking the same thing, the vaccine became scarce. Jackie and I finally tracked down shots last week.)

My immune system viewed the shot as something of a stern challenge, and sure enough my body temperature became elevated. In the graph below observe the last three data points, which show a spike to 0.7℉ above my baseline, followed by a 0.6℉ elevation the second night. Last night was only 0.3℉ above the baseline and back down in the normal range. (Near the middle you can see another spike to 0.7℉ above baseline followed by a negative deviation of a similar amount. That excursion was, I think, related to life stress.)

Graph of body temp, ending with a sharp spike gradually returning toward normal
My average nighttime body temperature deviation from baseline for February 10 to March 16 2019.

Observing that I was under some stress, the ring has been advising me to take it easy for the past couple of days. Knowing that the stress in question was a healthy one, I didn’t take the warning too seriously. The weather was nice the day after the shot, so I went out for a run, despite my ring’s advice.

Despite disregarding that particular day’s advice, I’ve actually been paying rather close attention to the ring’s indications as to my readiness. For example yesterday, when my body temperature and other factors suggested that I was still not recovered, I did take it easy—and I have been rewarded with an excellent night’s sleep and a moderately high readiness score for today:

Sleep panel from Oura ring dashboard.

Perhaps today will be a good day for a long walk. By the middle of the week we’ll have some more excellent running weather, and hopefully I’ll be ready for it.

Deadly actinic rays

I shared a link to this article by Rowan Jacobsen, with the comment “This article falls so squarely in the sweet spot of reinforcing my own preconceptions, I almost hesitate to tweet it.” But I did, with a few brief quotes.

Freed of the limitations of twitter, here’s a more extended excerpt:

Lindqvist tracked the sunbathing habits of nearly 30,000 women in Sweden over 20 years. Originally, he was studying blood clots, which he found occurred less frequently in women who spent more time in the sun—and less frequently during the summer. Lindqvist looked at diabetes next. Sure enough, the sun worshippers had much lower rates. Melanoma? True, the sun worshippers had a higher incidence of it—but they were eight times less likely to die from it.

So Lindqvist decided to look at overall mortality rates, and the results were shocking. Over the 20 years of the study, sun avoiders were twice as likely to die as sun worshippers.

There are not many daily lifestyle choices that double your risk of dying. In a 2016 study published in the Journal of Internal Medicine, Lindqvist’s team put it in perspective: “Avoidance of sun exposure is a risk factor of a similar magnitude as smoking, in terms of life expectancy.”

Source: Is Sunscreen the New Margarine? | Outside Online

Jacobsen later mentions the app dminder, which I’ve been using for several years now. It helps you optimize your sun exposure (getting maximum vitamin D production without getting sunburned, based on time of year, time of day, location, and skin pigmentation). I just checked the app, which tells me that it’s just 8 days until the vitamin D window reopens here in Savoy, Illinois!

I concluded my little tweet storm with this: Pretty much every nice day of the spring, summer, and fall, I announce to my wife around midday that “I’m going out to expose my integument to the deadly actinic rays of the sun.” And then I do. I feel so much better since I started doing this.

The odd motivating power of an unbroken streak

I have mixed feelings about using the motivating power of maintaining a streak.

Lots of people do it. Lots of writers write every day. Lots of runners run every day. There’s probably no virtuous activity out there that doesn’t have someone who has done it every day (or every week, or every year) for decades.

I understand the power. I feel it too, as I’ll describe in just a moment. But I have mixed feelings about it, primarily for two reasons.

First, it tempts people into doing things they shouldn’t just to maintain the streak.

Any runner who has run every day for years has almost certainly gone for a run even though he or she was sick. If it’s just a cold, that’s merely pointless. But going for a run with the flu is life-threatening.

Second, the demotivating power of a broken streak is huge.

For example, I had a streak going in the game Ingress, where there’s a badge for maintaining an unbroken streak of playing every day. I’d gotten my badges for 15-, 30-, and 60-day streaks. When my 180-day badge was due, I found that had apparently missed a day—my streak had ended at 172 days. I immediately abandoned any thought of getting that badge, and quit making any effort to play Ingress on a daily basis. I still play, but my current streak is 4 days.

Because of those issues, I try to be careful about motivating myself by trying to maintain a streak. I still do it though.

I went for a walk yesterday, only because I’m trying to get out for a walk every day this month.

After I hurt my knees in late October, my ability to walk was constrained for several weeks. It was very sad. I missed the last nice days for outdoor exercise, stuck inside resting my knees.

I find it easy to exercise in the summer, and hard in the winter. Every year I imagine that, if I can just keep going through the fall, I’ll preserve the habit and be able to keep going through the winter. It hasn’t worked very well in general, and certainly is out for this year, so I figured I’d do something different: Establish a new habit. I am perfectly capable of just deciding that I’ll get out and exercise in the winter in particular.

So I did decide that. Specifically, I decided that I’d try to meet the goal I’ve established in Google Fit, to get at least 90 minutes of movement every day.

Google Fit’s evaluation is just a bit odd. It’s central metric is minutes, but what it actually counts is steps, and I have no idea exactly how it translates occasional steps into minutes. It works very well when I go for a walk, but when I do taiji, for example, I get essentially no credit for having moved during that hour.

(As an aside, I should mention that I could just manually enter the hour or two I spend doing taiji. I did that for a while, but it isn’t really satisfactory. Among the great thing about Google Fit are that it’s simple and objective—there’s no need to do anything other than just carry my phone all the time, which I do anyway. Manually entering activity misses the whole point.)

Anyway, yesterday was a cold, wet, snowy day. Just the sort of day on which any sensible person would decide to simply stay inside. But I had this unbroken streak going, and a plan to hit 90 minutes of movement each day in December. So, I went out in the cold, wet snow and walked the remaining forty minutes or so to hit the mark.

Cold, wet, snowy day
Cold, wet, snowy day

During the summer, one can just stay in when the weather is bad, and still get plenty of exercise. Do that in the winter, and it’s all too easy to end up spending three months indoors. So, I am using the power of an unbroken streak to prevent that.

Another couple of weeks, and it will be a habit. A couple of weeks after that, and I’ll have met my movement goal for the month of December—and having gotten that far, I expect I’ll be able to move enough in January and February as well.

For now, though, I’ve just checked—and I see that I need another 24 minutes of walking today.

At least it’s not snowing.

A fitness regimen that’s working

After years of getting into shape during the summer, only to gain weight and lose fitness over the winter, I think I’ve finally put together an exercise program that’s working year-round.

It’s pretty simple:

  • Three times a week we go to the Fitness Center and lift weights, then go to the Savoy Rec Center and do an hour of taiji.
  • The other four days of the week, I try to spend at least an hour walking.

We’ve been very good about the lifting and the taiji—we’ve scarcely missed a session for many months now. I’m a bit less consistent about the walking, but I’m hardly ever entirely sedentary, even for one day.

I often get the bulk of the walking just by running errands in the neighborhood—I can get 10 or 20 minutes of walking just by going by foot to the bank or the grocery store. When the weather is nice, it’s easy to get myself out to walk around Kaufman Lake.

On the grounds of the mansion at Allerton Park.

Even better is when we can get out someplace like Allerton and hike over some more interesting terrain.

At a minimum . . . . Well, it takes seven minutes to walk around the block here in the apartment complex. I can hardly ever get myself to do the eight or nine laps that would amount to a full hour, but I can almost always get out for at least one lap—and once I’m out, I can usually convince myself to do a second.

What’s great about this is that it’s working. For the first time in my adult life, I weigh less in January than I did in October. My usual metrics for aerobic conditioning (running time and distance) don’t really apply, but the ease with which I can do ordinary stuff like carry groceries up stairs suggests that I’m in adequately good condition.

I’m looking forward to summer, when I can get back to bicycling and running, but I’m not waiting for summer to work on my fitness. This is a huge improvement.

Tracking words

I go back and forth about tracking words as a useful metric when writing fiction.  Currently, I’m back on again.

Over the past few days, I’ve created a spreadsheet along the lines of the one Toby provided in his post on creativity and word tracking.  Mine is simpler than his; I don’t have a deadline, so I don’t need to track progress toward one.

My main input is simply the length of the current draft.  From that I calculate the words written that day.  I’m also tracking a 5-day moving average (although I’m thinking of changing that to a 7-day moving average, to smooth out the impact of weekday issues).  I calculate a “words to go” value (by subtracting words written from an estimated final length) and a “days to go” value (“words to go” divided by the moving average).  Currently I’m using 60,000 words as my estimated final length–a reasonable value for a short novel, I think–but if I come up with a better guess as I proceed I can change my estimate.

I’m currently at 7555 words and my current 5-day moving average is 745 words per day, so my estimated days to completion of a first draft is 70.  We’ll see.

Is this useful?  I’m not sure yet.  But I do know that I wrote 318 words of fiction yesterday, even though I also wrote a new Wise Bread post and was feeling a bit burned out.  The fact that I’d otherwise have had to plug a zero in for words written yesterday was significant motivation for getting me to put in the time to get some fiction written.