Hope this makes sense:
I was riding today along the LA river. This is basically two dikes lined with concrete, and at each street bridge the path dips down and comes up again on the other side. So it is a long steady effort punctuated by sharp efforts to keep up momentum.

I was feeling sort of tired and my speed was gradually dropping. But rather than stalling out on the underpasses, I easily powered up the other side and ended up going faster on the exit. OK, I asked myself, what am I doing different here? I wasn't standing, or shifting position, just laying down a whole lot of power easily.

Finally it occurred to me: I was powering from the hips. Not like my hips were moving noticeably, either on the flats or when powering up a rise, but maybe my new saddle and bibs were freeing things up a bit. Somehow this seemed to bypass the tired muscles and kick in fresh ones. So I continued this subtle change on the flat, and suddenly I was flying along on fresh legs.

I have noticed this effect after exiting a crowded path and opening it up on the road. Or doing a short fast ride instead of endurance mode. It feels easier, even though the watts are way higher. I wonder if this comes back to using core strength, and giving the large muscles a firm base to act against.

Either way, it will be my focus of training for a while, trying to make this my normal pedaling mode.