stand up vs change posture

stand up and change posture both are verbs.

Word	Noun	Adjective	Verb	Adverb
stand up	No	No	Yes	No
change posture	No	No	Yes	No

As verbs, change posture is a hypernym of stand up; that is, change posture is a word with a broader meaning than stand up:

stand up (verb)	change posture (verb)
defend against attack or criticism	undergo a change in bodily posture
refuse to back down; remain solid under criticism or attack
be standing; be upright
put into an upright position
rise to one's feet
rise up as in fear
resist or withstand wear, criticism, etc.