I continue crunching my data, and in today’s post, will discuss a simple heart rate test that I have been performing last month every morning in order to evaluate its predictive power. It’s called orthostatic test, and it is widely used by athletes to assess their physical condition after the training. My theory was that since orthostatic heart rate (OHR) measures the “recovery” of the body, perhaps, by looking at OHR in the morning, I would be able to predict how I will feel later that day. My self-tracking data partially confirmed that hypothesis: the morning OHR numbers can predict physical and mental performance later in the day.
NOTE: this post was originally published on this blog in February 2013. I am unarchiving and reposting it as a part of the Measured Me 2.0 initiative. You may see comments that date back to the time of the original posts.
To perform orthostatic test, you need is a stopwatch or a heart rate measuring app (I personally used Azumio’s Instant Heart Rate app). The moment you wake up, try to stay still in bed and take your pulse measurement. That would be your resting heart rate (RHR). Then get out of bed and after standing for approximately 15-30 seconds without making any sudden movements, measure your standing heart rate (SHR). Now calculate the orthostatic heart rate (OHR): OHR = SHR – RHR. If you track your OHR for several weeks, you will notice that most of the times its values stay around the same, but occasionally will go higher. Those “spikes” in OHR happen the night after you overtrain at the gym, or if you don’t get a good night rest, get sick or because of some other disturbance in your autonomic nervous system. After collecting my morning heart rate data for a couple of months, I looked at the relationship between OHR and several indicators of my wellbeing, including physical and mental.
I started by tagging the days with OHR of 30 or and higher as high-OHR days. I then compared some other data points from my daily log across the normal and high-OHR days. The first thing I did was to look at my subjective measurements of physical, mental and emotional energy, which I measured every morning, afternoon, and evening, using a 10-points sliding scale in rTracker. Here is the chart of the differences in my physical energy (the data points for normal days are shown in blue, high-OHR days are in red):
As you can see, my average physical energy ratings on high-OHR days tend to be lower throughout the day (differences were statistically significant for afternoon and evening scores). Further, if you chart the changes in energy throughout the day as a trendline, and then compute the rate of the changes (calculated as a slope of the curve – you can use slope function in Excel), you can see that I am getting tired much faster on high-OHR days, compared to normal days.
The same pattern holds for my mental energy(differences were statistically significant only for afternoon scores):
If high OHR indeed reflects disturbances in my autonomic nervous system, these effects have been also captured by cognitive tests. I used Mind Metrics app to test my alertness and memory in the morning and in the afternoon, and as you can see, both my reaction time and recall quality were slightly lower on high-OHR days (none of the differences were statistically significant though, but I attribute that to not having enough data points):
Interestingly, there was no noticeable changes in my emotional energy, and the same was true for my mood and emotions.
There were, however, some interesting patterns for sleep. In January, I included in my log another question for tracking sleep quality: “How easy was it to get out of bed”, and the scores for this question were much lower on high-OHR days (2.4), compared to regular days (4.4). According to my Zeo, during the nights prior to high OHR mornings, I also had more REM (~14 minutes longer) and deep (~10 minutes longer) sleep. It is as if my body was trying harder to recover on those nights!
In summary, while not all differences were statistically significant (I attribute that to not having enough data points), overall patterns suggest that if I have a higher than usual OHR in the morning, my physical and mental performance are likely to be compromised later that day. Perhaps, I should start relying on OHR test in the mornings in order to plan my days.