HOW: Start by laying flat on your back with your feet tucked under something sturdy or someone holding them to help with keeping them flat on the ground. Begin the exercise by placing your hands behind your back followed by performing a sit up and curling all the way up so that your torso touches your thighs. Slowly lower down and repeat.
FEEL: This should feel like an ab exercise, you shouldn't feel stress and strain on your low back.
COMPENSATION: The best way to avoid low back strain is don't let your low back excessively arch with the lifting and lowering. If it is too hard, take your hands off your head and have them reaching forward.