If you sit up while doing this, it is not good for your spine, and don't put your hands behind your head when doing it.
Just hold your ears with your hands, otherwise it will cause damage to the cervical spine. Do at least 3 groups every day, with 20 in each group.
Lower abdomen: it is a "small belly". Lie flat, legs straight, feet together, slowly lift, at 90 degrees to your body.
Angle, and then slowly put it down. This action will be very tiring, but it can reduce the fat on the front side of the thigh. Do at least 2 groups a day,
A group of 15.