How is Somatic Vision Smoothness Calculated? (HRV)

[Ryan Deluz]

Hi All,

I'm posting this response, as I've had a number of people ask the question of how Somatic Vision Smoothness is calculated. People also want to know how it compares with HeartMath Coherence.

First of all, HeartMath calculates coherence, and the exact method is partly patented and partly a trade secret, so I can't comment much on the details. Also, Somatic Vision's smoothness algorithm is proprietary and a trade secret.

Still, for most people the following information is probably more than sufficient regarding how these are calculated:

In both cases (coherence & smoothness) an FFT is first used to determine the power of various spectral bands, this means how much of a certain frequency there is. As you breathe in your heart rate increases, as you breathe out it decreases, so if your breathing is smooth and steady, and you don't have much other stress that would cause rises or variations in heart rate, your heart rate will look something like a sine wave (not perfect, but similar) where the frequency is how fast you are breathing. Therefore, doing frequency analysis on the heart rate allows you, for instance, to see if the breathing is smooth and steady and there isn't a lot of other inputs that would make the heart rate wave jerky. If the heart rate moves up and down quickly, that would be a higher frequency wave.

In heart rate variability (HRV) analysis, there is a concept of low frequency, which includes 0.1Hz (10 seconds per cycle). So a 10 second breathing time would be a 0.1Hz wave. LF technically is 0.04 to 0.15Hz. Higher frequencies (HF) indicate additional, normally irregular but quickly changing inputs that indicate some form of stress or less positive state. So its common to use LF / HF as a basic measure of this sort of coherence/smoothness training.

Somatic Vision Smoothness is more of an LF / Other (LF compared to all other frequencies), and not LF / HF. Also, LF isn't exactly 0.04-0.15Hz in the Somatic Vision algorithm. Finally, different algorithms choose a different length of input data. If you take a lot of input data, it takes longer to detect changes as the changes are sort of averaged over the length of time.

Somatic Vision Smoothness has further optimizations designed to immediately (well it's more like a 1-5 second delay) show changes in your state. Coherence is a slower algorithm that uses more data. We have spent a lot of work optimizing our algorithm to attempt to as quickly as possible reflect changes in stress/emotional state, as it is too confusing, in our opinion, if you make an inner change at a certain time, but only see that change on the screen 15 seconds later. Studies have shown that this delay in feedback creates problems, generally people assume whatever they did immediately before the change caused it, so often times if feedback is slow people think that since they just starting doing B, that B helped them, when it was really A that they did earlier that made a difference.

In any case, this is some additional description of Smoothness and Coherence. To summarize, both are based on frequency analysis of the heart rate, and both reward increases in the low frequency (LF) bands that correspond to slow, relaxed breathing and other positive physiological states (such as nervous system balance).

[willtaylor]

Thanks for this Ryan -
am wondering how the "smoothness" calculation, if based largely on a portion of the classical LF bandwidth, factors out the sympathetic (vasomotor) components of the LF band?

[Ryan Deluz]

Hi Will,

Perhaps you want to post a link to a relevant paper regarding vasomotor influence on the LF band, and an explanation of why it should be filtered. My research indicates this is a VLF activity. Also its good to note that due to the short time windows involved we don't measure much actual VLF.

Ryan

[willtaylor]

In the calculation of Smoothness - is the actual state of the breath pacer (the rate set, and assumption that the client is breathing in sync with this) taken into account? i.e., if a client is not attending to the breath pacer, or is breathing out of sync with this, perhaps using an alternative pacer outside the program, does this impact on the calculation of "Smoothness"?

[Ryan Deluz]

Hi Will,

Breathing with an outside pacer is fine. Smoothness is calculated based on the heart rate data only. We aren't calculating a correlation to the pacer. People are feel to breathe however they like, looking at, or not looking at, the pacer. As long as the heart rate wave is smooth you get a high smoothness.

Best,

Ryan