Viparita Karani:Legs up the wall pose
In this supported inversion, the hips flex and the knees extend. Lie on your back with your legs up the wall and your tailbone fairly close to the wall. Your back is supported by a blanket, bolster or blocks, placed so that your buttock edges and tailbone hang off the support. Your abdomen is passive, the hamstrings passively stretch and the hip flexors relax. If there are neck issues in other inversions this posture is ideal and is very restful as it is a restorative and a rejuvenator.
Viparita Karani has cardiovascular effects like the shoulderstand and headstand. There is increased blood returned to the heart from the legs through the inferior vena cava which is beneficial. The heart pumps and works more efficiently when the chambers are full so cardiac output increases. Oxygenated blood is pumped out of the heart through the aorta and distributed to the body.
The effect of inversions is to normalise and to homeostatically balance cardiac output and blood pressure. The aorta and carotid arteries have pressure receptors that help to regulate blood pressure. These receptors respond to increased cardiac output or blood pressure by signalling the brain to increase parasympathetic outflow. (The parasympathetic nervous system calms, soothes and relaxes us so Viparita karani is helpful for anxiety, stress and tension.) This results in a slowing of the heart rate and lowering of blood pressure.
When the blood pressure is low signals from the baroreceptors decrease so cardiac output and blood pressure rises. Inversions on people with normal blood pressure increases firing of the baroreceptors, increasing parasympathetic outflow from the vagus and glossopharyngeal nerves. So, lieing on your back so the blood flow moves from your legs into your torso is very good for your wellbeing!