In the sit-ups, if you want to reduce abdominal fat, sit-ups should be bent legs, so that only train the abdominal muscles, can reduce the excessive accumulation of fat in the abdomen. If you also want to exercise the leg muscles, you can straighten the legs in the abdominal muscle contraction when the legs will be flexed, so while training the abdominal muscles, but also to train the leg muscles, on weight loss is also a relatively good effect, but this action to slowly and gradually to carry out.