An acute bout of a controlled breathing frequency lowers sympathetic neural outflow but not blood pressure in healthy normotensive subjects - McClain et al. (2017)

Key Points

  • Controlled breathing reduces sympathetic activity, even when performed at a relatively fast pace

  • The reduction in sympathetic activity might be due to increased focus, or due to increased tidal volume

The Breathing Diabetic Summary

Several studies have shown that slow, controlled breathing has many positive effects.  For example, Oneda et al. (2010) showed that slow breathing reduced blood pressure, heart rate, and sympathetic nervous system activity in hypertensive patients.  A study published in Nature showed that slow breathing increased autonomic function, arterial function, and blood oxygen saturation in type 1 diabetics.  However, in most studies looking at controlled breathing, the breathing rate is controlled and reduced.  What the current study wanted to examine was what role the “controlled” part of the breathing plays.  That is, are the benefits due to controlling the pace of respiration or slowing down the respiration?

To do this, they had participants breathe both spontaneously and at a controlled pace of 12 breaths/min.  A rate of 12 breaths/min was chosen because it is a “typical” breathing rate given in most physiological textbooks.

They found that the controlled breathing lowered sympathetic activity, but it did not lower blood pressure.  Thus, but simply controlling the breathing rate, even at a relatively “fast” pace compared to other studies, sympathetic activity was still lowered.

What was especially interesting about this was that several patients actually had a slower spontaneous breathing rate (~5-9 breaths/min) than the controlled pace.  But, even in these patients, their sympathetic activity was lowered when they switched to the controlled pace.  This makes me wonder if there is a “meditative/focus” aspect of controlling your breath that relaxes you and lowers sympathetic activity? 

I am obviously a fan of light, low-volume breathing.  But, this study also points out that the controlled breathing rate might have increased tidal volume, which also has been shown to reduce sympathetic drive.

Overall, this study highlights that controlling your breathing rate can lower sympathetic output.  Even if you are not able to drop into the 4-6 breaths/min range (which is usually suggested), there still are benefits to using an app to control your respiration rate at a pace that is comfortable to you. 

Abstract from Paper

Controlled or paced breathing is often used as a stress reduction technique but the impact on blood pressure (BP) and sympathetic outflow have not been consistently reported. The purpose of this study was to determine whether a controlled breathing (12 breaths/min, CB) rate would be similar to an individual’s spontaneous breathing (SB) rate. Secondly, would a CB rate of 12 breaths/min alter heart rate (HR), BP, and indices of muscle sympathetic nerve activity (MSNA). Twenty-one subjects (10 women, 11 men) performed two trials: SB, where the subject chose a comfortable breathing rate; and CB, where the subject breathed at a pace of 12 breaths/min. Each trial was 6 min during which respiratory waveforms, HR, BP (systolic, SBP; diastolic, DBP), and MSNA were recorded. During CB, the 6 min average breathing frequency (14±4 vs 12±1 breaths/min, P<0.05 for SB and CB, respectively), MSNA burst frequency (18±12 vs 14±10 bursts/min, P<0.01) and MSNA burst incidence (28±19 vs 21± 6 bursts/100 heart beats, P<0.01) were significantly lower than during SB. HR (66±9 vs 67±9 beats/min, P<0.05) was higher during CB. SBP (120±13 vs 121±15 mmHg, P=0.741), DBP (56±8 vs 57±9 mmHg, P=0.768), and MSNA total activity (166± 94 vs 145±102 a.u./min, P=0.145) were not different between the breathing conditions. In conclusion, an acute reduction in\ breathing frequency such as that observed during CB elicited a decrease in indices of MSNA (burst frequency and incidence) with no change in BP.

Journal Reference:

Shannon L. McClain, Alexa M. Brooks, and Sara S. Jarvis, (2017) An acute bout of a controlled breathing frequency lowers sympathetic neural outflow but not blood pressure in healthy normotensive subjects, Int J Exerc Sci, 10(2), 188-196.