I agree with NFH and I would add sit-ups.

You could also do toe touches:

Stand up straight.

Legs apart and arms stretched out at your sides.

Touch your left toe with you right finger tips(or bend over as far as possible)

Repeat using the left hand to touch your right toe.

Do repetitions of 12 , rest and repeat twice more

Add music to make it fun or do it during your favorite TV program