Tag Archives: Heart Rate Variabiltiy

Exercise and the Daily Energy Curve

One critical task that I solve for is ensuring that I maximize my energy during daily negotiations. I want to be present and balanced when I engage with others and not have my physiology defaulting me to Vapor Lock because the night before I had a bad batch of cannoli. So I look to maximize my Daily Energy Curve.

To measure my state of balance I use Heart Rate Variability (HRV).  I know that my balance and energy goes down over the course of a day as I shared in a past post. If that was the case, was a hard workout in the morning depleting my energy before I went into negotiations?


Logic said that using energy early in the day would leave less for the remainder of the day. So I had to test it.

My Question

Was exercising early in the day lowering the remaining energy I had for the remainder of the day when I would be in negotiations with others?

The Resulting Potential Action

If exercise first thing in the morning had no effect on my energy levels I would continue to exercise in the morning. If it did have an impact on energy levels on the days when I was engaged in important negotiations I would either skip the workout or workout later in the day after the negotiations.

What I Did

I created a random list of Workout/No Workout days to ensure that the results were not skewed by some personal bias. On days I was to workout, I exercised for 30 minutes on an elliptical machine either at my house or in a hotel on the road.

I took a measure of my HRV at least three times a day, one on waking, one in the afternoon and one on going to bed in the evening. The combination of these three measures I put into a Google spreadsheet and calculated the slope of the three measures. To measure my HRV I used a Polar H7 heart rate belt, an iPhone6 and the Heart Rate Variability app.

I took 25 readings over the course of a month. 19 of the readings were from randomly generated instruction, 6 were due to life events (elliptical not available, had an opportunity to workout).

What I Learned

The difference in my HRV slope on days I exercised had no statistically significant difference than on days that I did not exercise. There was no correlation between exercise and my energy levels.

The idea of the HRV slope reflecting my Daily Energy Curve which would steadily drop over time  means that we would expect the slope to be nearly always negative. Supposedly HRV starts high and ends low. With that assumption, the workout would drop the early day energy and the negativity of the slope would increase. The Daily Energy Curve in the Exercise or Not Exercise would look something like this:

Slide1In the actual readings, there were 9 days that the slope of the curve was positive, with close to an equal number of those positive days being on both Exercise and No Exercise days. You can see the positive days in the scattergram of the readings over time:


And a scattergram of the Exercise (1) vs. No Exercise (0) showing the distribution during the study:

Slope Exercise or Not

Running a few statistical tests on the data it came back that there was no difference between the HRV slope on days of exercise and a random sample of HRV slope readings. On both a T Test and Pearson Correlation the difference was not significant.

So in a (semi) randomized test of exercise effect on the Daily Energy Curve I dispelled a cherished personal myth. In the past, when I would wake up on the day of an important negotiation I would say “I should save my energy for the discussion” and blow off the workout. A study and a bit of math now tell me that I’m not really saving up energy if I skip the workout. I’m just blowing off the workout.

I have to give full credit for the randomization method to Cara Mae Cirignano of Whatify. I did use Whatify for a portion of this study but because I did not get the entire study done with them they are off the hook for methodological irregularities. I highly recommend you check out their service.

So going forward my workout decisions are independent of my pending negotiations. And I have to take more of a look at the HRV Slope. If sometimes it is positive, what is driving that? For a future study.


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