What is the Slow Breathing Workout?
I heard Richard Gervitz talking about a slow breathing workout as part of a daily discipline on the Quantified Body Podcast. I had started doing slow breathing sessions back in May 2014 though I had never specifically looked at the effect on my daily heart rate variability (HRV) reading. And I had fallen out of the habit so I was interested in trying it again.
A slow breathing workout means taking your respiration to a slower pace than normal with inhalations and exhalations of equal length. This is not normal breathing as it synchronizes the cardiac and respiratory systems. Gervitz recommended 20 minutes per day.
The beneficial effects of doing this breathing include a more flexible autonomic nervous system, increased resilience to physical or psychological stress, and sharpened mental clarity. Motivated by what I heard on the podcast, I decided to jump back into a disciplined slow breathing workout.
Could doing 20 minutes a day of deep, meditative breathing in the afternoon improve my morning HRV readings?
What I Did
I had a standing practice of measuring my HRV for five minutes on waking each morning. This provided a baseline of 24 readings. I began doing 20 minutes of evenly paced breathing each afternoon. This provided 18 additional morning readings that were impacted by the slow breathing workouts. I controlled for confounders by removing readings where circumstances were out of the norm like low amounts of sleep or too much food.
How I Did It
Prior to the five minute readings I would listen to 10 minutes of soft music to settle in and ensure I was relaxed. For my afternoon HRV breathing workouts, I used a basic breath pacer app for iOS. With it, I could set the number of seconds per inhalation and exhalation. This would allow me to breath slowly and at a steady pace for the sessions.
I also like to get biofeedback as I do my slow breathing, so I used Heartmath Pro to track how effectively I got I aligned my cardiac and respiratory systems. The Heartmath dashboard shows the HRV in the top panel and the heart beat frequencies in the lower left panel.
The useful thing about the biofeedback is that I could adjust the length of my inhalations and exhalations until I found the highest level of alignment. Without feedback I would have to use levels derived from published data. With the biofeedback I had set up slow breathing exercises tailored for my physiology.
What I Learned
Starting an afternoon slow breathing workout regime increased my average morning HRV readings to a significant degree. You can see the lift in the scores on the graph of readings through the period:
Looking at my readings pre-program my rMSSD averaged 42.8 for the morning session and post-program it averaged 54.8, a 28% increase. Doing a TTest comparing the readings before and after being on the slow breathing workout showed a p-value of .037, meaning the change was statistically significant. You can see the raw data that is the basis of the calculations.
I found my optimal breathing came out at 7 seconds for each inhale and 7 seconds for each exhale. I started with 5.5 seconds per inhale and exhale and kept moving it up until I found my level.
That said, the biofeedback application is not necessary to get the benefit of a slow breathing workout. Though it is helpful to get the biofeedback readings, a simple breathing app with 20 minutes of practice each day will give you all the benefits. And I will continue with it now that I have established its value.