Inclusion of a rest period in diaphragmatic breathing increases high frequency heart rate variability: Implications for behavioral therapy - Russell et al. (2017)

Key Points

  • Slow breathing at ~6 breaths/min increases heart rate variability (HRV)

  • Including a post-exhalation pause enhances relaxation and makes it easier to breathe slowly

  • A post-exhalation pause also enhances some HRV parameters more than continuous breathing

The Breathing Diabetic Summary

We don’t want our hearts to beat like a metronome, but to constantly be changing and adapting to the current conditions.  One way to measure this is through heart rate variability (HRV), which represents the changes in time between heartbeats.  HRV is generally thought to be a marker of overall health: Higher HRV is usually associated with better health. 

Interestingly, many studies have shown that slow breathing can increase HRV.  In particular, it appears that breathing at a pace between 4 and 6 breaths/min maximizes HRV, depending on the individual.  However, there are many ways to achieve a breathing rate of 4-6 breaths/min.  For example, inhale for 5 sec, exhale for 5 sec.  Inhale for 4 sec, exhale for 6 sec, etc.  The most common approach in the literature is to spend equal time inhaling and exhaling, for example, 5 sec in, 5 sec out.  But, this might not necessarily be the best way to maximize HRV.  The current study set out to see if including a post-exhalation pause would increase HRV compared to continuous breathing with equal inhales and exhales.

Specifically, they tested two different approaches to breathing at 5.5 breaths/min: 5-5 and 4-2-4.  The 5-5 protocol used a 5 sec inhale and 5 sec exhale.  The 4-2-4 protocol used a 4 sec inhale, 2 sec exhale, and 4 sec post-exhalation pause.  Forty subjects performed the breathing protocols in a seated upright position.  They performed each breathing protocol for 6 min, followed by a 5 min washout period before starting the next one.  Along with measuring several different HRV parameters, the authors also evaluated which breathing protocol the subjects found more relaxing and easier to perform.

68% of the participants found the 4-2-4 cycle easier to follow and 63% also found it more relaxing.  The authors suspect that this is a result of the shorter inhalation period, which caused less strain on the breathing muscles.  They also suspect that the post-exhalation rest period reduced the risk of hyperventilation.

There is no one single measurement for HRV.  There are high and low frequency bands, along with other parameters such as the standard deviation of the NN intervals.  In this study, they found that the 4-2-4 cycle significantly improved one aspect of HRV, whereas the 5-5 cycle improved others.  Thus, although the title of the paper suggests that the rest period is critical, it is important to note that both breathing protocols improved HRV in different ways.

For us, this study shows that we can improve HRV by voluntarily slowing our breathing rate.  This is important for two reasons.  First, HRV is an overall indicator of health, so if we can improve it by simply breathing slowly, that is great news.  Second, diabetics generally suffer from lower HRV, so any natural way of improving it is very useful for us.  Whether you adopt a post-exhalation rest, or simply do slow continuous breathing, we know we can improve this critical marker of health with just a few minutes of slow breathing.  Pretty awesome.  Let’s wrap up with a quote from the end of the paper that is one of my new favorites:

With breathing interventions being relatively rapid interventions to implement and also demonstrating a wide range of positive clinical outcomes, breathing interventions warrant closer consideration from healthcare professionals.

Abstract from Paper

Heart rate variability (HRV) is associated with positive physiological and psychological effects. HRV is affected by breathing parameters, yet debate remains regarding the best breathing interventions for strengthening HRV. The objective of the current study was to test whether the inclusion of a postexhalation rest period was effective at increasing HRV, while controlling for breathing rate. A within-subject crossover design was used with 40 participants who were assigned randomly to a breathing pattern including a postexhalation rest period or a breathing pattern that omitted the postexhalation rest period. Participants completed training on each breathing pattern, practiced for 6 min, and sat quietly during a 5-min washout period between practices. Participants were given instructions for diaphragmatic breathing at a pace of six breaths/minute with or without a postexhalation rest period. Recordings of heart rate, breathing rate, HF-HRV, RMSSD, LF-HRV, and SDNN were collected before and during each of the breathing trials. HRV indices were derived from Lead 1 ECG recordings. Pairwise contrasts showed that inclusion of a postexhalation rest period significantly decreased heart rate (p<.001) and increased HF-HRV (p<.05). No differences were found for breathing rates (p>.05), RMSSD (p>.05), and SDNN (p>.05). Results indicated that omission of the postexhalation rest period resulted in higher LF-HRV (p<.05). A postexhalation rest period improves HF-HRV, commonly associated with self-regulatory control, yet the importance of a postexhalation rest period requires further exploration.

Journal Reference:

MATTHEW E. B. RUSSELL, APRIL B. SCOTT, IAN A. BOGGERO, AND CHARLES R. CARLSON, (2017) Inclusion of a rest period in diaphragmatic breathing increases high frequency heart rate variability: Implications for behavioral therapy, Psychophysiology, 54, 358 – 365, DOI: 10.1111/psyp.12791.