Help. Precisely what muscles (leg, back, etc) are engaged on a recumbent?

I'm almost always distracted when on a longish ride, training or otherwise, by this question.

The three primary pedaling actions seem to include:

1. pushing
2. pulling
3. ankle pedaling

And then there is `bridging.'

My specific question applies to a high racer, front wheel drive recumbent.  For example the Bacchetta CA2 and Ti Aero. 

I would really appreciate a reference and/or explanation.