I've always thought of it this way but recently read that there is not an explanation.

Imagine I am climbing up a ladder, every time I release my grip, I have to use my own energy to get to the next rung.

But if I were anchored to a spot and the ladder were rising upward I could cling to the rung until my grip was broken, then the next ladder rung would come to me.

In this analogy my limbs are myosin heads and my grip is the forming of cross bridges.