tighten up vs confine

tighten up and confine both are verbs.

Word	Noun	Adjective	Verb	Adverb
tighten up	No	No	Yes	No
confine	No	No	Yes	No

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

Other hypernyms of tighten up include bound, limit, restrict, throttle, trammel.

tighten up (verb)	confine (verb)
severely restrict in scope or extent	place limits on (extent or amount or access)
	to close within bounds, or otherwise limit or deprive of free movement
	prevent from leaving or from being removed
	deprive of freedom; take into confinement
	close in