Differential: The difference between things.
When the first HRV recordings were created they were based on a simple formula. Make it so that there was a one second difference between how long we breath out vs breath in. The idea is to spend more time in the breathing out state with each cycle of breath so that the brain will send more signals to the heart to slow down.
For instance, if we were talking about 5 breaths per minute, we understand that each breath would need to be a total of 12 seconds long. 5 breaths times 12 seconds equals 60 seconds or a minute.
In this case we started by determining the middle point of each breath, 6 seconds.
From here we increased the length of the Out Breath while also decreasing the length of the In Breath. Breathing in and out for 6 seconds would not have achieved what we wanted to do as this would tell the heart to speed up and slow down for the same amount of time. We needed to make the out breath longer.
The length of the Out Breath was increased while we reduced the length of the In Breath to insure the breath cycle remained 12 seconds long.
In order to make our Out Breath 1 second longer, we subtracted half a second from the In Breath and added half a second to the Out Breath.
The result was a 1 second difference between the In Breath, lasting 5.5 seconds and the Out Breath, lasting a second longer at 6.5 seconds. This is what we refer to as a 1 second differential.
To achieve a long ratio in favor of the Out Breath, we created a 2 second differential by subtracting 1 second from the In Breath and adding 1 second to the Out Breath.
The result for a 2 second differential put the In Breath at 5 seconds and the Out Breath at 7 seconds.
Finally, to achieve an even longer ratio in favor of the Out Breath, we did a 3 second differential by subtracting 1 and a half seconds from the In Breath and adding 1 and a half seconds to the Out Breath.
Now, there are 3 variations of HRV breathing. This customized set now has the ability to provide a deeper experience based on our individual needs.