Contracting your abdominal muscles when performing stomach exercises helps to increase strength, but it can also make the muscles shorter. Stretching your abs in the opposite direction, such as by lifting or extending your spine backwards, can help to loosen and elongate the muscles.
The abdominal group consists of three different muscles. The deep-seated transversus abdominis, the top-lying rectus abdominis and the side obliques work together to provide stability and balance to your body. The rectus abdominis is most affected by torso contractions and therefore is the main muscle to be elongated when stretching.
Arching your back and extending your shoulders behind you can help to elongate your abs. This can be accomplished through various exercises and in yoga poses. For example, Cobra pose consists of lying prone on the floor and lifting your head and shoulders toward the ceiling. Standing on your knees and extending your spine backwards is Camel pose. Lying on your back with your feet flat on the floor with your hips raised toward the ceiling is Bridge pose.