Heart Rate Variability relationship to Coherence scores
Question: What are the low, medium and high coherence ratios on the Freeze-Framer? How is it related to heart rate variability? Is there any mathematical equation to derive the scores? Also, how do I interpret the results of the ratios?
A. The coherence scores are based on how wave-like the HRV pattern is. The low coherence score is the percentage of time there is no wave-like activity in the HRV wave. Medium coherence is percentage of time that there is some wave-like activity, and high coherence is the percentage of time there is very wave-like activity.
If you look at the power spectrum screen you see three colored regions – blue bars in the brown region on the left are an indication of sympathetic activity. Blue bars in the purple region on the right are an indication of parasympathetic activity. Blue bars in the yellow region indicate that the sympathetic and parasympathetic are synchronizing. In low coherence, the blue bars tend to be scattered across the graph, with more blue typically in the brown sympathetic region. As you move towards high coherence, the blue bars focus in the yellow region and can get very large in amplitude.
We don’t publish the mathematical algorithm that is used to produce the coherence ratio scores. Note that the coherence scores do not have much of a relationship to traditional HRV parameters like SDNN Index which primarily measure HRV amplitude, not how wave-like the HRV pattern is. If you are interested in generating traditional HRV measures, you’ll need to use another piece of equipment to record HRV data, as the Freeze-Framer program stores interpolated data – the inter-beat interval in milliseconds stored every half second.