RMSSD, a heart rate variability metric, represents the input of the vagus nerve into the sinoatrial node of the heart.

“there's a mathematical algorithm that you applied that you applied that called the root mean square of the standard deviation that basically our MSSD that basically turns that number it's a transformation so it's in mathematics we call these things transformations where you basically compress these numbers and you can then now measure how much variability there's going on”

“you get what's called the rmssd again if you just think about that in units you took something that was in milliseconds you squared it so it became milliseconds squared you added them all up it was still milliseconds squared you took the square root of it it's back to milliseconds so rmssd is reported in milliseconds”

“what we are again measuring is that average variability across that time span and what that represents is the input of the vagus nerve the parasympathetic system and it's input into that sinal atrial node of the heart”

“what we are again measuring is that average variability across that time span and what that represents is the input of the vus nerve the parasympathetic system and it's input into that sinal atrial node of the heart”

“the most common one is rmssd root means successive successive Square differences they just do some basic math and they get that number of milliseconds of rmssd”