As I indicated in my recent post, Do You Have a Healthy Heart?, I am interested in determining if exercise can improve heart rate variability (HRV). Over the past month, I have made daily measurements in order to establish a baseline for future comparisons. Below are the details of what I am measuring.
Each morning after I wake up, I measure my resting heart rate using a Suunto t6d heart rate monitor. I first measure my resting heart rate in a seated position for three minutes followed by a three minute measurement in a standing position. From each three minute window, I isolate a one minute segment to analyze and record.
The numbers that I have chosen to record are seated resting heart rate, standing resting heart rate, orthostatic heart rate (the difference between standing and sitting), and a heart rate variability measurement.
While there is a wide range of measurements available to evaluate beat-to-beat variation in heart rate, my interest is in understanding the contribution of parasympathetic tone during a short duration measurement of resting heart rate. The key measurement that I am recording is RMSSD or the root mean square of successive differences of R-R intervals.
Over the past month, my seated resting heart rate averaged 75.2 (+/- 3.8) beats per minute, standing resting heart rate averaged 97.5 (+/- 5.2) beats per minute, and my orthostatic heart rate averaged 22.3 (+/- 4.7) beats per minute. The reason that heart rate increases when standing is because the heart is trying to maintain a consistent flow of blood in spite of the fact that gravity is causing blood to pool in the lower extremities.
While I don’t expect most readers to dig into the details of my RMSSD results, for the month my average was 34.8 (+/- 10.9). Let’s just say that this isn’t a stellar result, but it was somewhat expected. My hope is that over the next six months, the RMSSD (as well as resting heart rate) will improve significantly from exercise.
Lastly, I mentioned in Do You Have a Healthy Heart? that there were studies claiming that cold water immersion improved heart rate variability. Being somewhat skeptical, I did a quick experiment. First, I measured my seated resting heart rate as described above, and then I splashed my face with cold water (for about 30 seconds) and repeated the same test. Below are two graphical representations of my HRV as show in “Poincare Plots.” A cigar-shaped plot indicates limited heart rate variability (not ideal) and an oval or circular plot indicates high heart rate variability (ideal).
The plot on the left is the first seated measurement and the plot on the right immediately after the cold water immersion (heart rate decreased from 78.7 bpm to 72.1 bpm following the cold water).
While these graphs aren’t meant as proof that cold water immersion improves parasympathetic activity, they are certainly interesting.
Over the coming months, I will provide regular updates that document my progress.