means spinal column. The asana
is so named because the spinal column is the organ which is greatly benefited by this asana.
Lie down flat on your back. Keep your feet close to each other and hands close to your thighs with palms down and flat on the floor.
Breathe two or three times in the normal manner. Then inhale and raise your right leg up to two feet high without bending the knee. Remember to keep your tiptoe pointing forward. Remain in the position for three seconds. Then inhale and slowly bring the leg down.
Repeat the same with the other leg.