Slow-Paced Breathing: Influence of Inhalation/Exhalation Ratio and of Respiratory Pauses on Cardiac Vagal Activity

Citation

Laborde S, Iskra M, Zammit N, Borges U, You M, Sevoz-Couche C, Dosseville F. Slow-paced breathing: influence of Inhalation/Exhalation ratio and of respiratory pauses on cardiac vagal activity. Sustainability. 2021 Jul 12;13(14):7775.

4 FUNDAMENTALS

 

1. Essential Background Material

 

This study examined the impacts of inhalation:exhalation ratio and breathing pauses on vagal activity using heart rate variability (HRV) measurements.

 

As you probably know by now, slow breathing has consistently been shown to increase HRV.  However, two aspects of it are still poorly understood:

 

  1. Should the inhale and exhale be equal, or should the exhale be longer?

  2. Does adding a pause after inhalation or exhalation increase HRV?

 

For number 1, we know that the parasympathetic nervous system controls exhalation.  Thus, extending the exhale should stimulate it more, resulting in more vagal activity.  However, study results have been mixed, which, according to these authors, might be due to misinterpretation of HRV measurements.

 

For number 2, it’s hypothesized that a pause might increase vagal activity, as heart rate generally slows down when we pause our breath.  However, again results have been mixed.

 

Therefore, this study aimed to fill these gaps by examining how the inhale:exhale ratio and respiratory pauses impact vagal activity as measured by HRV (specifically, RMSSD).

 

 

2. What Did this Research Do?

 

The authors recruited 64 athletes (27 female; 37 male).  They had them perform 6 slow breathing exercises randomly for 5 minutes each.  There was also a 5-minute washout period in between each exercise.

 

The 6 exercises they tested were:

  • Equal

    • 5-sec inhale; 5-sec exhale

    • 4.6-sec inhale; 0.4-sec pause; 4.6-sec exhale; 0.4-sec pause

  • Extended Exhale

    • 4.5-sec inhale; 5.5-sec exhale

    • 4.1-sec inhale; 0.4 sec pause; 5.1-sec exhale; 0.4-sec pause

  • Extended Inhale

    • 5.5-sec inhale; 4.5-sec exhale

    • 5.1-sec inhale; 0.4-sec pause; 4.1-sec exhale; 0.4-sec pause

 

The primary outcome measurement was HRV measured with RMSSD.

 

According to the researchers, RMSSD is the best indicator of vagal activity because it is not influenced by breathing rate.  Thus, if RMSSD increases, this is due to an increase in vagal activity, not some kind of confounding interaction with the breathing rate (as can happen with LF-HRV or HF-HRV power).

 

This is what sets this study apart from others: it’s the first to focus on RMSSD and thus the first to truly focus on vagal activity.

 

 

3. What Were the Major Findings?

 

There were two critical findings.

 

First, RMSSD (and thus vagal activity) increased most significantly during extended exhalation breathing.  However, it is important to note that all the slow breathing practices increased RMSSD compared to baseline.

 

Second, adding slight pauses did not impact the results.  However, the pauses might have been too short (only 0.4 seconds) to have any noticeable impacts.

 

 

4. Why Do These Results Matter?

 

This study confirms that extending the exhalation increases the activity of the vagus nerve.  This made sense in theory; however, these results provide concrete evidence of increased vagal activity through RMSSD measurements.

 

 

 

1 BIG TAKEAWAY

 

Slow breathing with extended exhalations increases vagal activity more than an equal inhale:exhale ratio.  Thus, we can extend our exhales to increase parasympathetic nervous system activity.

 

 

 

1 PRACTICAL APPLICATION

 

Use a slightly longer exhale than inhale for deeper relaxation during a slow breathing practice. The most common approach is the “40:60 Rule”: 40% of your breath should be inhaling, and 60% should be exhaling.

 

Thus, regardless of which rate you breathe at (6/5/4 breaths per minute), you can use the 40:60 rule to lengthen the exhalation and increase vagal activity.

 

And if you don’t know which rate to start at, use this excellent advice from Leah Lagos, Psy.D., in Heart Breath Mind: “The standard rate that works for most individuals is to inhale for 4 seconds and exhale for 6 seconds with no pause in between.”

 

Simple, easy, and highly effective.