How do you get out of bed? Do you sit up in bed then swing your legs over the side and stand up? Can you sit up without using your hands to help?
This is also a basic movement that we should all have the strength to do, but I find many are not able to do this. If one is lying on the floor I think one should be able to sit up, then push oneself onto one's feet into a squat position and stand up.
That said, there are many reasons why this movement might be unsafe for some people. Anyone diagnosed with osteoporosis should avoid flexing the spine, and anyone with a disk problem would do well to avoid it also. Anyone with a back problem should check with their physio or doctor to be certain this movement is safe.
Also we have noticed in our practice that many people's bellies "tent" up along the center line as they attempt an abdominal curl. Any ab curl, crunch, or sit up would be a bad idea if this is happening. There should be no abdominal bulging along the center line of the belly while doing any activity.
This abdominal bulging is an indication of a rectus diastasis, or a splitting of the fascia down the midline of the abdominal wall. Doing anything that creates that bulging is might make the split worse, potentially requiring surgery.
Most people should be able to work on this movement, but use common sense. If you are not sure, consult a doctor.