Here is how to do air bike crunches video and sitting twists how to video.
There are four distinct muscle groups that form the abdominal wall. Their medical names are rectus abdominis, external obliques, the internal obliques, and the transversus abdominis. More popularly they are known as the frontal abdominals or six-pack, lateral abdominals and the core.
The lateral abdominals are activated when the trunk is rotated and then needs to return back to its original position. All of the abdominal groups help support the spine and protect the body's internal organs. They also help reduce fatigue by absorbing vibrations during high-impact physical activities, they preserve the transfer of energy from the feet to the arms in activities that require the arms to deliver power and they are key to maintaining the body's balance during fast ballistic movements.
The Easy Abs Challenge uses a multi-factorial approach to building strong abs. All the gains you make here are incremental. Each day builds on the previous one. By the end of the month you will be able to feel the difference.