slow down vs loosen up

slow down and loosen up both are verbs.

Word	Noun	Adjective	Verb	Adverb
slow down	No	No	Yes	No
loosen up	No	No	Yes	No

As verbs, slow down and loosen up are synonyms defined as:

Other synonyms of slow down include decompress, relax, unbend, unwind.

slow down (verb)	loosen up (verb)
become less tense, rest, or take one's ease	become less tense, rest, or take one's ease
lose velocity; move more slowly	cause to feel relaxed
become slow or slower	make one's body limber or suppler by stretching, as if to prepare for strenuous physical activity
reduce the speed of	cause to become unblocked
cause to proceed more slowly	become less tense, less formal, or less restrained, and assume a friendlier manner