keep step vs keep up

keep step and keep up both are verbs.

Word	Noun	Adjective	Verb	Adverb
keep step	No	No	Yes	No
keep up	No	No	Yes	No

As verbs, keep up is a hypernym of keep step; that is, keep up is a word with a broader meaning than keep step:

keep step (verb)	keep up (verb)
maintain the same pace	prevent from going to bed at night
	keep informed
	maintain a required pace or level
	keep in safety and protect from harm, decay, loss, or destruction
	lengthen or extend in duration or space