One of the most classic exercises to tone the abdominal muscles is the crunch. To perform it, you start from the supine position and lift only the upper torso keeping the legs and pelvis still.
Very important is the posture. Let’s start from shoulders and neck. The neck must not bend and, for this not to happen, it is advisable stare at a point in front of you even while lifting the torso. The shoulders, on the other hand, must not come close to the ears but remain wide open and “low”.
Also there position of the pelvis it is essential: it is important that no “holes” form between the basin and the mat or floor. The navel, for the entire duration of the exercise, is sucked towards the sacrum. To help you keep one correct posture at home, you can use it the fitball as a support for the legs (which must be bent at 90 °).
They are recommended 3 sets of 12 repetitions each.