Try google? One source is the sound of bubbles of air in the liquids in your body containing bubbles of air and these are formed and squeezed making the noise. Another source could be ligaments snapping over a bone.

http://www.loc.gov/rr/scitech/mysteries/joint.html

Shouldn't be coming from your muscles. If your muscles are popping you've got trouble :) The pop is likely coming from your joints, just like when you crack your knuckles. The prevailing theory is that gas, likely nitrogen, builds up in the joint and when you move it, push on it or manipulate it the bubble bursts creating the audible pop. Which also explains why you can't re-pop a knuckle/joint that you just popped. Gotta wait for the pressure to build up again. To my knowledge this is still theory though, nobody knows for sure.

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Dan Hollingsworth

Nobody grows old by merely living a number of years. People grow old only by deserting their ideals. Years may wrinkle the skin, but to give up interest wrinkles the soul." - Douglas MacArthur

it's the sound of lethargy leaving the body....

I notice that my back never pops anymore. It used to make a popping sounds, like cracking your knuckles, when I did certain stretches. Not any more. I suspect it is due to thinning disk space.

Or possibly arthritic and soft-tissue changes which reduce your ability to move a joint far enough to achieve said nitrogen bubble poppage. I used to be able to twist side-to-side and it was like a 21 gun salute, as all my facets wouild let loose. Now, I'm lucky if I can even get one strained little "pop" to emanate from ye olde back. And I am far less flexible than I used to be.

Right !!! pull my finger I eat lots of beans ;-)


just call me gas finger Thom

Instead of popping an already-present nitrogen bubble, I think you might create a bubble in the potential spaces in a joint by manipulation in such a way as to pull apart the membranes that form the walls of the potential space. There's the POP, it's the formation of a bubble, not it's bursting. Also, I'm not sure it has to result in a bubble being formed, fluid could rush into the newly opened space. Or, the space could be a near-perfect vacuum for a millisecond before recollapsing upon itself, with no resultant bubble formation.

If there are already bubbles in the space and you move such that the bubbles pop, it's an entirely different sound...it even has a name: crepitus.

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