Lumbering pace refers to a slow and heavy gait. There are several synonyms to describe this kind of movement. One could say that someone is trudging along or moving at a sluggish pace. Another alternative is to describe the person's movement as plodding or shuffling. An individual who is walking heavily or laboriously might be described as tramping or slogging along. Additionally, you could use the phrase dragging one's feet to depict this slow pace. Regardless of the word used, it's clear that a lumbering pace is a slow and deliberate movement that is easy to notice.