change - undergo a change; become different in essence; losing one's or its original nature; "She changed completely as she grew older"; "The weather changed last night"

straighten - get up from a sitting or slouching position; "The students straightened when the teacher entered"

get up, stand up, rise, arise, uprise - rise to one's feet; "The audience got up and applauded"

fall - drop oneself to a lower or less erect position; "She fell back in her chair"; "He fell to his knees"

fall down, fall - lose an upright position suddenly; "The vase fell over and the water spilled onto the table"; "Her hair fell across her forehead"

right - regain an upright or proper position; "The capsized boat righted again"

sit down, sit - take a seat

lie down, lie - assume a reclining position; "lie down on the bed until you feel better"

drop down, sink, drop - fall or drop to a lower place or level; "He sank to his knees"

hump, hunch, hunch forward, hunch over - arch one's back

straighten, unbend - straighten up or out; make straight

bow - bend the head or the upper part of the body in a gesture of respect or greeting; "He bowed before the King"

uncurl - move out of a curled position; "He uncurled himself"

sit up - change to an upright sitting position; "He sat up in bed"