there`s one particular exercise which i think is effective, but rarely done.

learned it from breakdance class

known as catepillar

1) do push up style with your hand infront instead of side
2) move your feet slowly infront till your body bends as letter A
3) move your hand infront again till it is flat in position 1)
4) repeat

then were forced to to round the hall 10 times....

pass out next day