I read a Frederic Delavier’s book « Strength Training Anatomy » and I learned good stuff.
Sitting on the bench with your feet under the pads and your hands behind your neck. Inhale and tilt your torso without ever exceeding 20° :
Move your torso back up by slightly rounding your back to better target the effort on recuts abdominis
Exhale at the end of the movement.
This exercise work the entire rectus abdominis muscles and iliopsoas, rectus femoris and tensor fasciae latae (these last 3 muscles help pelvis anteversion). This movement is to do with high sets.
When you back up, you can do a rotation of your torso to transfer a part of the effort to the obliques.
A rotation to the left work more intensely right abdominal external oblique, left abdominal internal oblique and rectus abdominis on the right. Twists can be done alternately or unilaterally. The goal is to focus on the muscular sensation and it’s unnecessary to incline the bench too much.
Diagram showing the senses of action of abdomen muscle and the system of viscera’s compression
Abdominal external oblique
Abdominal internal oblique
With quadrupeds, the entire rectus abdominis muscles passively support the viscera (like a hammock ) and help a little in locomotion.
With human being in bipedal mode, the entire rectus abdominis muscles have hugely strengthened so that the torso and pelvis is upright and prevent the pelvis from tipping excessively during walking or running. They became powerful muscles of contention and they built a strong core to maintain viscera in an active way.
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