For core body strength
Lie on your back, hands behind your head, and then lift your head and shoulders up, eighty times.
Now, with hands by your sides, lift your feet six inches off the ground and criss-cross them eighty times. Both are good for abdominal muscles and the muscles of the spinal column, and they are collectively called the core muscles .
To maintain and improve suppleness stand straight with feet apart and slide one hand down the side of your thigh , then go to the other side, repeat twenty times. Now bend forward and back ten times and finally, hands on hips rotate at the waist ten times each way
Never watch the weather forecast without doing this exercise. You need to build these exercises in a daily routine
Here is a good report on core strength from Harvard