Do you know these words?

• まがる（こしが〜/せなかが〜）

  to bend (waist/back) ; to be hunched

• こしを　あげる

  to raise one's rear end ; to raise one's lower back

• こしを　うかす

  to rise one's lower back

• こしを　うかせる

  to rise one's lower back

• こしを　おとす

  to crouch down ; to bend one's knees