expression, ichidan verb
get off one's backside; bestir oneself; finally get moving
Idiomatic expression for reluctantly rousing oneself to do something one has been putting off. Often implies overcoming inertia or laziness. Related to 腰が重い (to be slow to act).
See also: 腰が重い
彼はなかなか重い腰を上げなかったが、ようやく掃除を始めた。
He was slow to get moving, but finally started cleaning.
重い腰を上げて、ジムに行くことにした。
I finally bestirred myself and decided to go to the gym.