I have questions about how the musculature and more-solid structures
(e.g., bones, discs, etc.) interact and function in the trunk of the
body and especially the back and neck.  For instance, when I do a push
up, which muscles of the back work?  How much does each muscle
contribute to the effort (e.g., muscle A does 90% of the work while
muscle B does 10%)?  Most of this isn't info that seems to be
available in book format.

I'd like to buy a CD or DVD (for my PC, not the TV) which is
interactive.  Ideally, it would go two ways.  (1) I could ask "how do
the muscles handle a push up?" and also (2) "what different movements
stress/exercise this muscle?"  A graphical interface is a virtual
necessity.  My question is: WHERE can I find such a CD or DVD?

I would suspect that this isn't something commonly available to
consumers, but rather more of a "trade tool" for physical therapists,
spine doctors, personal trainers, etc.

I promise a nice tip for someone providing multiple potential product
sites with such CD(s)/DVD(s)
to purchase (especially products with prices that won't make my jaw
drop too much!)

Many thanks!