@theprof00
(I'll preface this by saying i'm assuming the vitality sensor works like a pulse ox, it does look exactly the same)
"If your pulse double jumps once in 5-10 seconds," See my above point about sinus arrhythmia. The other thing to note that after this "double jump" the interval to the next heart beat is usually signficantly longer meaning that over several seconds of monitoring it averages out. Try this by feeling your pulse, take a deep breath in, hold, then breath out, it exaggerates the phenomena.
The reason that the machines sample every few seconds as opposed to beat to beat is that it allows for this physiological phenomena. Pulse ox could easily be designed to sample every beat and instantly calculate a rate based on the beat to beat interval but it's not practically useful and would provide readings that would fluctuate wildly due to sinus arrhythmia.
You gave the example of lifting your feat to your chest but honestly how often are you going to do this while playing? It would cause a small change in heart rate but it's not sustained and when you recommence playing your heart rate will have returned to its previous value. Is it any different from your wii-mote cursor going of the screen while you scratch your nose?
When sampled over 5-10 second intervals your heart rate does not vary as much as you are suggesting. By sampling over this 5-10 second interval you get a relatively stable measurement of your heart rate and the pulse ox will only pick up changes in heart rate that are sustained for more than a few beats.
I'll stop now.
