pedals are both pulled and pushed. It is just a lot easier to climb a hill that way.
I can also say that that my feet tends to last longer if I try not to press on the pedals all the time. By lifting the feet att the return stroke, I can avoid the aching feet I will otherwise have after some time pedalling. This, btw, seems to be a recumbent problem. For mechanical reasons I assume the force pressing the foot to the pedal is actually higher on a recumbent (with a near horizontal leg) than on an upright (I will do some calculations some day).
My method to get a smooth round pedalling is to imagine my feet following the pedals, instead of pushing them. Try that, it gives a remarkable relaxed, flying feeling (on my Trice recumbent, at least)! The trouble is to keep this up for a prolonged time, some muscles seems to need training...
Sverker