What if the spike started at your head?
Hey Dana , I dont really like the analogy of that any more , I find it usefull as a median position and postural alignment , and maybe it`s a great tool image for beginners , but works more above the waist and even then gets a little bent out of shape with spinal whip(dragon etc)
I think it encourages more thinking of rotating around the centre than through the centre , centripedal versus centrifugal force .
Back on track though , I think grounding is probably the biggest (key) lesson in mechanics , its the key for generating heavy strikes IMHO , being able to take a shove is just a small benifit when you consider all the advantages to a direct line of force .
as for using it in movement , I feel some form of push hand work is key to this , try maintaining base while someone pushes on your sanchin draw or thrust etc , add footwork , even arm rubbing can give that tactile feedback .
one of the more abstract notions ( to me ) is the concept of grounding upwards , once you have a good base downwards and can maintain it visualising projecting upwards and pushing the energy up can really aid in grounding , creating a slight compression . Not much of a concept to give a beginner though I think , more chi stuff , might get some funny looks
also when projecting down , I dont really think of a depth but think forever , same as on strikes , but i think the tool with a lot of this stuff is what helps you find a feel , and what imagery works for the individual and look at the mechanical science behind it .
Ink Grinding Qi-gong etc and Ricks does some good Sanchin mechanics drills that really help in folks finding there base , and the relatoinships going on .
to me this is the stuff folks would be working on with a three year Sanchin or the like , I could so spend three years working on such mechanics .