A strong, straight lower back is the foundation of every correct position and is consequently important in any Yoga pose. In this exercise, you strengthen the lower back and the legs and by doing so, you create more space in the chest and belly.
Steps of Chair_Poses -
Start with the Mountain Pose (Tadasana). Inhale and stretch your arms, lengthen the spine, and be careful not to press the lower ribs to the front. Exhale and bend your knees and move your upper body forward at 45 degrees.

See to it that your lower back is straight. You can do this by letting your hand feel whether there is a "groove" in the middle of the lower back. If this is not the case, then stand up straight again, bend your body forward, and feel if the "groove" is there. Let the weight of the upper body sink into the pelvis, relax the calve muscles so that the weight of the body can be most efficiently directed into the ground.

The chest bone is moved slightly towards the belly. The breathing is relaxed and goes through the belly or towards the chest bone. Build up the exercise quietly and remain focused on a correct position of the back, chest, and pelvis.

This posture helps in strengthen the spine, calves, thighs and ankles. It stimulates the heart, diaphragm and abdominal organs and stretches the chest and shoulders. As this is a squatting posture, it is considered to be helpful for easy childbirth in women. In addition, it prevents constipation, keeps calf muscles healthy and prevents nervous weakness.

it is essential that the lower back has a natural, slight degree of being sunken. Otherwise, the space disappears from the chest, the movement no longer falls back towards the pelvis and it becomes impossible to breathe through the belly correctly. This means that before you start building up strength in your lower back, it is important to place the lower back in the right way.