How do you know? Are you using a monitor?

To tell you the truth, I really dunno. I'd have to do some deep research to find this one.

I'm also an avid scuba diver. Quite often at the end of a dive I'll have to have a big underwater burp thru my regulator on the ascent to the surface. I haven't figured this one out either.

Might be your chest strap losses contact for a moment,just a thought.Randall

I know because I can test it on the treadmill wearing a heart monitor and it consistantly does it. No, it's not the chest strap losing contact.

I think I know why it does it, but I want to hear what the science types on the forum say.

Sorry, Richard....I don't have a clue! I could make a couple of things up that might sound plausible, but, I'd just be making something up!

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Quid quid latine dictum sit altum videtur
(That which is said in Latin sounds profound)

This may be from the gases expanding???

I agree on Cerveloguy's diving question. Probably you swallow some air when clearing ears etc. on decending and it expands on ascent. That's why you can't hold your breath when surfacing while using scuba gear. You can rupture your lungs.

Richard

How about direct vagus nerve stimulation from expansion of the esophagus by the gas/air? Or lower down, vagus nerve stimulation in region of diaphragm due to suspension of normal breathing pattern/forced opening of sphincter?

Congratulations, you win. I think that's the correct answer. I think this nerve stimulation effect is much like why people sneeze when looking at a bright light or get a headache from eating too much ice cream too fast.

Richard

Of course, the vagus nerve is cardioinhibitory, part of the parasympathetic autonomic nervous system. Should have thought of it myself but it's been I long time since I've read Guyton. That happens when you've been in practice awhile. You tend to forget everything that isn't directly clinical.

Here is my stab at it...

to perform a belch you do a maneuver called a valsalva maneuver. This is the same maneuver when you bear down or you are trying to do a number 2. This maneuver increases your intra-abdominal pressure... at the same time it will cause a slowing of the pulse (bradychardia) in a normal person. I can't remember why exactly but i think it is due to the baroreceptors in your vasculature, (specifically the caratoid sinus) will sense the change in pressure and lead to the stimulation of the parasymapthetic nervous system (as others have mentioned) You should be able to recreat this by bearing down like you are taking a dump while wearing a polar mointor... better yet wear your heart mointor the next time you take a dump and record the numbers... This will work especially well if you are constipated...

This thread has convinced me that I need to spend less time thinking about these things.