What the breath does
By Mira Lindqvist · Voice & Pace
Breathing is the only part of the autonomic nervous system you can operate on purpose. That single fact is why it turns up in every tradition that has ever tried to calm somebody down, and it is also why so much is claimed for it that cannot be shown.
This article is about the line between the two.
What the studies establish
A 2018 systematic review pulled together the psycho-physiological work on slow breathing and found the effects converge on something quite specific: breathing at roughly six breaths a minute or below is associated with increased heart-rate variability, shifts in EEG activity, and self-reported reductions in arousal and anxiety.1
Note what that sentence does not say. It does not say breathing fixes anxiety, and it does not say the effect is large. The review's own framing is that the physiological correlates are consistent while the psychological ones are more variable across studies.
The mechanism most often proposed is baroreflex resonance. Lehrer and Gevirtz's account of why heart-rate-variability biofeedback works describes it plainly: at a breathing rate near six per minute, the oscillation the breath imposes on heart rate lines up with the natural rhythm of the blood-pressure reflex, and the two reinforce each other.2 That is a real, physical resonance, not a metaphor.
A 2017 randomised study gave one group eight weeks of diaphragmatic breathing training and measured sustained attention, negative affect, and cortisol against a control group. The breathing group improved on all three.3
And in 2023 a controlled trial compared three five-minute daily breathing practices against five minutes of mindfulness meditation over a month. All four arms improved mood; the breathing arms improved it more, with the largest effect from the practice that emphasised a long exhale.4
What that means for a five-minute exercise
The Breathe exercise in this app runs at seven breaths a minute, the Apple Watch default, which we adopted rather than invented. That is just above the six-per-minute figure the resonance literature centres on, and comfortably inside the "slow breathing" band the 2018 review defines.
So the claim we can defend is this: the exercise sits in the range where the measured effects have been found. Nobody should expect five minutes to do for them what eight weeks of training did for the 2017 study's participants.
The limits of the evidence
Three places, and they matter.
The studies are mostly small and mostly short. The 2017 trial had forty participants. The 2023 trial ran for a month. Neither is a weak study; both are the size of study that gets overturned.
Almost none of this work is about speaking. The outcomes measured are attention, affect, cortisol, heart-rate variability. Nobody in these papers gave a talk. The step from "sustained attention improved" to "you will speak better" is a step we are making ourselves; the literature does not make it for us.
A long exhale is doing more work than the count. The 2023 trial's strongest arm was the one with the extended exhale.4 If you take one mechanical thing from this article, take that one rather than the specific number of seconds.
Why a screen and not a course
That last section is the reason this app has a Breathe screen rather than a breathing course.
Five minutes of slow breathing before you speak is very cheap, has a plausible mechanism behind it, and has enough evidence to be worth trying and not enough to be worth promising. That is a perfectly reasonable thing to put in front of somebody. It will not fix a talk you have not prepared.
The most defensible reason to do it is the least dramatic one: it is five minutes in which you are not rehearsing your opening line for the ninth time.
References
- Zaccaro, A., Piarulli, A., Laurino, M., et al. (2018). How breath-control can change your life: a systematic review on psycho-physiological correlates of slow breathing. Frontiers in Human Neuroscience, 12, 353. https://doi.org/10.3389/fnhum.2018.00353
- Lehrer, P. M., & Gevirtz, R. (2014). Heart rate variability biofeedback: how and why does it work?. Frontiers in Psychology, 5, 756. https://doi.org/10.3389/fpsyg.2014.00756
- Ma, X., Yue, Z.-Q., Gong, Z.-Q., et al. (2017). The effect of diaphragmatic breathing on attention, negative affect and stress in healthy adults. Frontiers in Psychology, 8, 874. https://doi.org/10.3389/fpsyg.2017.00874
- Balban, M. Y., Neri, E., Kogon, M. M., et al. (2023). Brief structured respiration practices enhance mood and reduce physiological arousal. Cell Reports Medicine, 4(1), 100895. https://doi.org/10.1016/j.xcrm.2022.100895