This is an exploration of the personal data I gathered from wearing a Fitbit health tracker over the course of 2019.
2019 - A Year of Change
2019 was a very different year for me; aside from having an activity tracker for the entirety of it. Over the course of the year I developed and grew a more focused effort in being active and exercising regularly. In January I purchased a spin bike to use at home in the evenings and I began walking outside with my family more often. We lived near a high school that I taught at so we would go walk around the track after I got off work and sometimes later that evening as well. Once Spring rolled around this happened nearly every day.
In the month of May I deliberately put effort into walking even more and saw several days accumulate more than 20,000 steps. We moved at the end of that month and our ability and willingness to exercise together as a family and be engaged outdoors grew. We went on regular walks in our new locale and began regularly biking together. We even went so far as to say that we would only ride our bikes if we wanted to go to the grocery store. This proved to be a challenge, a worthwhile one, as our new home was at the foot of a mountain. Going to the store was a breeze but coming home, uphill with two children in a trailer, was a bear. With most things, though, I noticed that with each instance of this ride I was getting better and faster.
Soon we began going for bike rides to locations farther away and ended up feeling like there was nowhere we couldn’t reach. And so began our nearly weekly extended bike rides accumulating distance over 30 miles. One of these rides was for the longest I had ever done at a total distance of 64 miles (no kids were in tow that time, though)! Throughout this time I was also moving from simply walking to jogging and eventually running. In all, 2019 was a year of learning to enjoy being active for myself and with my family.
Resting Heart Rate
In this experience of tracking my fitness with a Fitbit I became interested in my resting heart rate (RHR). This is the frequency that your heart beats while awake but not actively moving around; think along the lines of when you’re sitting and watching TV. As the year went on and my fitness increased I noticed that in general my RHR was getting lower. From a small amount of research I found that this is usually a good thing as it indicates an overall lower effort by the heart to circulate blood. That is, the more fit you are the easier it is for your heart to do its job so the less work it has to do. Obviously there is a limit here and you should seek advice from a professional if you have questions or concerns.
I noticed that on a day of intense, extended exercise (by extended I’m thinking in excess of 120 minutes) that my RHR had little change from the day prior. The following day, though, mt RHR would increase by 3-5 beats per minute (BPM). This was an indication that my heart was still recovering from the high effort day and was to be expected. On such days if you were to push yourself again can quickly find yourself in a state called “over-training” where your body will take even longer to recover. So high-intensity days should be following with restful days before more intensity.
After these restful days, usually just one, I noticed that within the next day or two my RHR would drop below where it had been leading up to the day of intense exercise. Reflecting on this is how I ended up with the subject of this very post.
Step It Up
A good, though not complete, way of looking at your activity levels is to check how many steps you take in a day. This can be an overview of how much you were moving around rather than being sedentary on a couch or chair. In my investigation it seemed to only make sense to begin there. Here is a graph of my 2019 year of daily steps counts graphed along with my RHR.
Of interest to me for this story is the spike in steps per day that occurs in May and precedes a sharp drop in RHR in June to the lowest RHR of the year (at 50 BPM on June 10). Additionally, there appears to be some kind of relationship in the first half of the year of the daily step count beginning low, the RHR beginning higher, and the two changing over time. As the daily step count increases the RHR appears to decrease. Aside from these there does not appear to be a major connection between step counts and RHR.
Accounting for Calories
As stated above, while the amount of walking I did in 2019 did increase from previous years, walking was not the only form of exercise. I could list each exercise tracked but different exercises work the body in different ways and aside from that, not all exercises were tracked. Another trait that Fitbit tracks is “Active Calories.” These are calories burned by the body in excess of the amount you need to simply exist. If you were to only lie in bed all day your body would still burn calories. These calories are known as your basal metabolic rate (BMR). The calories beyond your BMR that you burn through walking around and exercising are your active calories. Think of these as the calories you burn actually doing stuff.
Here is a graph of my active calories tracked against my RHR.
A cursory view of this graph shows much more than the step counts graph. Of note are the two overall increases in active calories burned beginning in February to the end of May and then again from July to October. During both of these periods there seems to be a general decline in the RHR. Note the increase of days at the end of May with a high amount of calories burned as compared to the fewer days of high steps counts. Additionally, around September are many days of very high calorie burn that do not show up in the step count graph.
The scale of these graphs is small because they cover the entirety of 2019 so I prepared a couple, focused graphs. This first one shows the months of May and June and points out the drop associated with the cluster of high calorie burn days and a lower RHR.
This next graph surrounds September and shows that of the six high calories burned days that five of them were following by drops in RHR.
Moving Forward
This look at my RHR and how my activity over the course of 2019 impacted it has been quite enlightening. By no means have I exhausted this investigation nor will it end for me here. I still have many questions to answer. Why did one of these days in September not experience a similar drop in RHR? I’m not sure that is even a question I can answer but it has made me realize that I have more to track. I also need to experiment to try intentionally manipulating the data. By that I mean to try varying the high burn days and rest periods to see what happens. There are also other thangs that influence RHR such as water and electrolyte levels and sleep. I intend to track these better over the course of 2020 and beyond to accumulate even more data to explore. I would also like to look into getting a device that measures heart rate variability (HRV). Let’s say that your RHR is 60 BPM. You might think that means your heart is beating once per second but it’s really only beating once per second on average. HRV measures the variation in time between beats. I would love to be able to see that data for myself.