When is an "involuntary" not an "involuntary&

When is an "involuntary" not an "involuntary" ?

The combo of bigguy's post this last weekend, popo's stomach post and Darwin's once mention of armpit-stim dredged up an old idea that my bod might have some alternative orgasmic triggers. (This springs from childhood memories when rib or foot tickling produced a massive mental and physical frenzy -- a sort of "kid's orgasm." )

We've done several partnered stomach sessions working with popo's sole-of-the-foot stim to see what it produces. I got my wife involved (another story) since I couldn't stim my feet when in my favorite stomach posture.

Once I'm aroused and producing involuntaries that echo my voluntaries, my wife strokes the soles of my feet with a quill and that triggers a contraction. The path I feel is: quillstroke --> thigh+hamstring twitch --> anal contraction.

Eventually, I'm able to cease voluntary contractions, hold a base contraction and let her continue triggering contractions. If I'm sufficiently aroused, the ratio of anal contractions per 'footstroke' starts at one-for-one then increases; 2:1, 3:1 ...etc. Somewhere beyond 4:1 it goes automatic and she stops the footstrokes. The "automatics" either fizzle out or become steady enough to lead to a mini-O. Cool, easy ride where I can focus just on base contraction and breathing.

From a terminology viewpoint, is the anal contraction that results from the quill stroke classified as "voluntary" or an "involuntary?"

I've not used a tens unit or e-stim like Dr. Erector so don't know if those produce a 1:1 ratio of contractions. If they do, then the classification of 'involuntary' or 'voluntary' might be similar.

Which raises another question -- might a tens unit with pads on the soles of the feet do the job (eliminating the need for a partner) ?

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Note: Restraints are used to minimize leg movement.