The hands-to-knees sit-up is a good way of working your abdominal muscles.
Lie on your back with your knees bent, making sure your feet are flat on the floor.
STEP ONE
Start off with your hands resting on your thighs and, as you do the exercise, slowly slide them up your leg, towards your knees.
Control the movement on the way down, remembering the slower you work, the harder but more effective the exercise.
If you are doing the exercise correctly you should feel your abs working.
STEP TWO
Make sure more powerful muscles in the leg and hips are not doing most of the work.
Make sure you can feel your abdominal muscles working.
Keep your chin off your chest, and if your neck aches, support your head with one hand.