Here’s a secret—there is a muscle deep within your abdomen that is the key to keeping your core strong. Located behind the rectus abdominis and obliques—which is what most ab workouts focus on —is something called the transverse abdominis.
This is sometimes referred to as the corset muscle because the fibers pull in the core from the front and back (just like a corset), helping to protect and stabilize the spine. As the deepest muscle in the abdominal region, stretching the transverse can result in super toned abs and is safe enough to work during pregnancy.
Stand straight up, with your arms extended above your head. You can stand with your back to a wall if this is easier.
Attempt to elongate your back by using arms to pull your torso upwards. While doing so, you may tighten your buttocks.
Remain in this position until you feel a pulling sensation in your abdomen. Hold for as long as you can. That is one rep. Repeat 10 times.