Slow breathing is usually described in round numbers and borrowed words — coherent, resonant, diaphragmatic — with very little said about what the numbers are or why anyone chose them. Here are the ones Long Exhale uses, and the reasoning behind each.
A session ends up at 5.5 breaths a minute. That is roughly eleven seconds per breath, against a resting rate of maybe twelve to sixteen breaths a minute for most adults sitting still.
Around that pace, breathing and heart rate fall into step: heart rate rises through the inhale and falls through the exhale, and near six breaths a minute those two rhythms line up rather than interfering. That alignment is what "resonance" refers to, and where the term coherent breathing comes from.
The exact figure is personal, which is why the floor is adjustable between 5 and 7 breaths a minute. If the slowest pace ever feels like you are short of breath, the pace is wrong for you — not the other way round. Raising it is the fix, and the app says so in its own settings.
Long Exhale opens at 10 breaths a minute and takes about eight minutes to arrive at the floor, along an exponential curve rather than a straight line — most of the slowing happens early, and the last part of the approach is almost imperceptible.
Starting at the destination would be the obvious design and it does not work. Ten a minute is already slower than most people are breathing when they get into bed, but it is close enough to follow without effort. Being asked to jump straight to half your natural rate is a demand, and a demand is a thing you have to concentrate on. Concentration is the opposite of the goal.
The ramp is gradual enough that you are unlikely to notice it happening, which is the entire trick. Nothing about it should feel like an instruction.
A breath is not just a duration; it has a shape, and the shape changes as the pace slows.
At the start, the exhale is 1.5 times the inhale. By the floor it is twice the inhale. Around the ends of the cycle sit two small pauses: about 8% of the cycle held at the top of the inhale, and about 12% at rest after the exhale.
At 5.5 breaths a minute, that works out to roughly:
The lengthening exhale is the part the app is named after. A longer out-breath is the half of the cycle associated with settling, and stretching it as the pace slows means the two changes reinforce each other instead of arriving separately.
Most apps in this category keep their parameters to themselves, which is a strange choice for something you are meant to trust with the last twenty minutes of your day. The numbers above are not secret and they are not arbitrary; they are in the source, in a file whose comments explain each one.
If they are wrong for you, the app would rather you changed them than gave up on the idea. That is why the floor is a setting rather than a fixed value, and why the safety note points at it directly.
Long Exhale is not a medical device and is not a treatment for a diagnosed sleep disorder. It is a pacer: a tone that rises and falls, slowing down, and then getting out of the way.