What is the core exactly?
The core consists of a variety of group muscles running from the hips to the shoulders. A strong core is not only about having nice six packs. It is about stabilizing the spine, the pelvis and the shoulder girdle. While contracting, the core muscles squeeze the abdomen/belly, helping the trunk to move, to bend and to rotate. The core muscles maintain the upright posture. It allows your body to make and control movements.
Core muscles are therefore key to our daily life. Especially in modern life, we sit all day long with a rounded back. The muscles of our lower back become de-conditioned. We lost our muscles endurance and awareness, leading to injuries and pain.
=> While performing an asana (yoga posture), exhale deeply to better activate the abdominal muscles. Plank, Dolphin and Bridge variations are really good exercises to strengthen these muscles (please refer to ASANAS section).