Influence of deep breathing exercise on spontaneous respiratory rate and heart rate variability: A randomised controlled trial in healthy subjects - Tharion et al. (2012)
Practice of slow breathing for one month reduces spontaneous breathing rate
Practice of slow breathing for one month increases resting heart rate variability
The Breathing Diabetic Summary
We know by now that heart rate variability (HRV) is important: it essentially measures regulation of autonomic balance, blood pressure, and much more. Unfortunately, diabetics generally have lower HRV than non-diabetics, especially if we suffer from complications. This is true of anyone with a disease causing chronic autonomic dysfunction, not just diabetics. However, this paper gives us hope and, more importantly, scientific evidence that we can improve our HRV by practicing slow breathing.
The study aimed to assess if regular practice of slow breathing could do two things. First, could it reduce the subjects’ natural breathing rate? Second, could it also improve resting measurements of HRV?
I really want to emphasize one unique aspect of this study. Many of the papers we review on slow breathing and HRV measure HRV before a breathing exercise and then after. Thus, we see the direct, acute effects of the breathing exercise itself. This study, on the other hand, measured baseline HRV indices at the beginning of the study and then one month after daily practice of slow breathing. Thus, the final measurements were not taken directly after an “exercise”, but represent the subjects’ new baseline values. So any positive changes we see represent long-term improvements.
The study had 36 participants, a control group with 18 and an intervention group with 18. Participants in the intervention group were instructed to breathe at 6 breaths/min using a 4 sec inhale and a 6 sec exhale. They were provided a CD with a recording to guide them through the exercise each day. They were instructed to practice for 30 min/day, with the flexibility to practice sitting or lying down, and to break the 30 min into two 15 min sessions. This flexibility in the protocol makes it much more applicable to everyday life.
After one month, subjects in the intervention group had lowered their resting breathing rate by ~2.5 breaths/min. They also significantly increased their high frequency HRV, which is a direct measure of modulation of parasympathetic tone. Thus, they found that a reduction in spontaneous breathing rate was associated with an increase in HRV. Finally, the intervention group also had a lower mean arterial pressure.
Overall, this study is very motivating for us diabetics who suffer from lower HRV. Practice of slow breathing can increase our HRV 24/7, not just during and immediately following the exercise. Thus, if we adopt Principle 1, all we have to do is show up consistently and know that the benefits will accumulate and compound over time.
Abstract from Paper
Studies show that yogic type of breathing exercises reduces the spontaneous respiratory rate. However, there are no conclusive studies on the effects of breathing exercise on heart rate variability. We investigated the effects of non-yogic breathing exercise on respiratory rate and heart rate variability. Healthy subjects (21-33 years, both genders) were randomized into the intervention group (n=18), which performed daily deep breathing exercise at 6 breaths/min (0.1 Hz) for one month, and a control group (n=18) which did not perform any breathing exercise. Baseline respiratory rate and short-term heart rate variability indices were assessed in both groups. Reassessment was done after one month and the change in the parameters from baseline was computed for each group. Comparison of the absolute changes [median (inter-quartile ranges)] of the parameters between the intervention and control group showed a significant difference in the spontaneous respiratory rate [intervention group –2.50 (–4.00, –1.00), control group 0.00 (–1.00, 1.00), cycles/min, P<0.001], mean arterial pressure [intervention group –0.67 ( 6.67, 1.33), control group 0.67 (0.00, 6.67), mmHg, (P<0.05)], high frequency power [intervention group 278.50 (17.00, 496.00), control group –1.00 (–341.00, 196.00), ms2 P<0.05] and sum of low and high frequency powers [intervention group 512.00 (–73.00, 999.00), control group 51.00 (–449.00, 324.00), ms2, P<0.05]. Neither the mean of the RR intervals nor the parameters reflecting sympatho-vagal balance were significantly different across the groups. In conclusion, the changes produced by simple deep slow breathing exercise in the respiratory rate and cardiac autonomic modulation of the intervention group were significant, when compared to the changes in the control group. Thus practice of deep slow breathing exercise improves heart rate variability in healthy subjects, without altering their cardiac autonomic balance. These findings have implications in the use of deep breathing exercises to improve cardiac autonomic control in subjects known to have reduced heart rate variability.
ELIZABETH THARION, PRASANNA SAMUEL, R. RAJALAKSHMI, G. GNANASENTHIL AND RAJAM KRISHNA SUBRAMANIAN, (2012) Influence of deep breathing exercise on spontaneous respiratory rate and heart rate variability: A randomised controlled trial in healthy subjects, Indian J Physiol Pharmacol., 56 (1), 80 – 87.