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post apnea bradycardia

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growingupninja

growingupninja

Lance (@socalspearit)
Mar 20, 2011
712
162
83
I apologize in advance for all these numbers, but I am wondering if anyone can shed light on this: I have been doing some dry statics, and trying to be a little more systematic in my observations and approach--wearing a pulse O2 meter, and experimenting with no warm-up, etc (I am really trying to wrap my head around the effects of spleenic contraction). My resting HR is about 55 bpm, and my diving/cold water/DYN HR is anywhere from 30's to 40's depending on various factors. With dry statics I typically don't experience much bradycardia, except on the first hold or unless my O2 is truly getting low (<90%).

I just now did a couple dry holds, one to 4 mins, followed by another to 5 mins. What is interesting is that a few minutes after the 5 min hold, while in my recovery period and after initial recovery breaths, my pulse dropped back to 46 bpm and held there for a minute before climbing back to my normal resting. Pulse signal was very strong (no vasoconstriction during that episode). Does anyone know what might be causing this? I was very relaxed and breathing shallow, but those numbers are atypical for me.
 
I don't have a device to record and store real time info but I will sketch out what typical numbers are when I have time. This incident was curious to me since HR dropped back to solid dive levels, WHILE I was breathing, and AFTER it had gone up to higher than normal resting when I started initial recovery, which is 'normal' for divers and non-divers alike. I will pay attention next time I do tables and see if happens more often than I realize.
 
I can't say that I know exactly why, but I is what I can tell you:

I am blessed with relatively strong diveresponse as far as I can tell. And I experience post-apnea bradycardia after practically every breath-hold. It goes very much like what you described, allthough I'd say it only take a minute for pulse to get back to the second post-apnea low... What is interesting is also that my pulse hit allmost exactly the same low + 1 or 2 bpm. So if I hit 36 during apnea, I will hit 36-38 app. a minut after I started to breath.

My own theory is this: During last 10-20 % of breath-hold the para-sympathic nervous system is intensily activated and firing heavily... when I start to breath it still fires, but the O2/CO2 imbalance is forcing puls to beat fast... After short time, 1 or 2 minutes, there's no more need for high puls, and the still active para-sympathic nervous system is for some reasons still firing, and hence puls drops to same low. Maybe it's still firing because lack of O2/high CO2 is no jokem it's a possible life/death situation, so just to be prepared for another possible emrgency/breath-hold it is in "low-consumption mode". But that's all just speculation...

The apnea low pulse is associated with extreme high blood pressure I think, like the heart is really pumping big time... the post-apnea low is just a slow beat, allthough sometimes it can be a little strong also...
 
Hmm thanks Baiyoke, yes what you are describing is what I experienced. Fingertip pulse was slow but very strong and regular, no vasoconstriction. Perhaps it is more common than I realized. Probably less than 3% of my training is static so it would be easy for me to miss, and the DYN work I do is very short rest interval and straight up hypoxic cardio so pulse would not have time to drop back down.
 
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