Roger Cole's reply:
Cold hands and feet are often caused by excessive constriction of the blood vessels of the fingers and toes. If the condition is severe, you may have Reynaud's Syndrome-check with your doctor. The fingers and toes have specialized connections between the arteries and veins (called arterio-venous anastomoses, or AVAs) that allow your brain to quickly switch the blood flow from a torrent to a trickle, or vice-versa. This helps regulate body temperature.
To reduce blood flow through the AVAs, the brain sends signals along sympathetic nerves. The nerves release a chemical (norepinephrine, also called noradrenaline) that causes the diameter of the arteries to get smaller, thereby allowing less blood through. If the sympathetic nerves are overactive, too little warm blood gets through, so the fingers and toes get cold.
In general, sympathetic nerves prepare the body for action or emergencies. The sympathetic branch of the nervous system is stimulated by things like stress, fear, anger, upright posture, and a cold environment, among others. Activities that calm the sympathetic nervous system can help warm the hands and feet.
Yoga can be very useful-especially if you practice the right postures in the right way in the right environment with the right attitude. The right postures are head-down positions practiced in a restorative way, such as Salamba Sarvangasana (Supported Shoulderstand) on a chair, Viparita Karani (legs up the wall with hips elevated on a bolster or blankets), supported Setu Bandha Sarvangasana (Bound Bridge Pose on bolsters or long, folded blankets), and supported Halasana (Plow Pose, with the thighs supported on a bench or similar prop).
Head-down postures stimulate baroreceptors (blood pressure sensors) in the neck and upper chest. This triggers a powerful reflex (the baroreflex) that inhibits the sympathetic nerves, causing the muscles surrounding blood vessels in the fingers and toes to relax.
Practice these postures supported by props to allow for complete muscle relaxation and comfort. Stay in each posture for a long, uninterrupted period of time to avoid additional stress or activation, and to allow plenty of time for excess norepinephrine that is circulating in the bloodstream to break down (this can take an hour or more).
The right environment is warm and free from disturbances. Turn up the thermostat, cover the body (especially the hands and feet) with a blanket, close the door, and turn off the phone.
The right attitude is passive. Let the postures do the work. Once you set up your props and move into the pose, you don't have to do anything.
This supported, head-down yoga practice will not only warm your hands and feet, it will leave you calm and refreshed.
Roger Cole, Ph.D., is a certified Iyengar Yoga teacher and a research scientist specializing in the physiology of relaxation, sleep, and biological rhythms. He trains yoga teachers and students in the anatomy, physiology, and practice of asana and Pranayama. He teaches workshops worldwide. For more information, visit http://rogercoleyoga.com.