limber up vs limber

limber up is not a noun while limber is a noun.

Word	Noun	Adjective	Verb	Adverb
limber up	No	No	Yes	No
limber	Yes	Yes	Yes	No

As verbs, limber up and limber are synonyms defined as:

limber up (noun)	limber (noun)
	a two-wheeled horse-drawn vehicle used to pull a field gun or caisson

limber up (adjective)	limber (adjective)
	(used of persons' bodies) capable of moving or bending freely
	(used of e.g. personality traits) readily adaptable
	(used of artifacts) easily bent

limber up (verb)	limber (verb)
make one's body limber or suppler by stretching, as if to prepare for strenuous physical activity	cause to become limber
attach the limber	attach the limber