This article reviews Marichyasana and explains:

• Its fundamental principles
• The structural and functional physiology involved
• The Yogic or subtle physiology involved
• How it relates to other asanas in the group
• How it may be sequenced in a practice/class
• Variations according to needs and major pre-cautions and/or contra-indications.
• Main indications for adjustment.

1. Exhale your right knee up placing the foot flat on the floor in line with your right sit-bone.  The right foot is flush against the inner left thigh.
2. Inhale your left arm up towards the sky.
3. Exhale your left arm around the outside of your right knee and clasp your hands.  Lift the chin a bit aristocratically and look to the back of the room, as this will help you find lift in the spine as you twist.  Hold for 5 Ujjayi breaths. ** Note ** If you are just learning to clasp your hands focus on slightly crossing your right thighbone over your left thighbone to decrease the distance the arms have to travel to achieve the clasp.  Once you understand the crossing of the thighbones, try to eliminate space between the torso and the right leg by securing your right foot as closely to your right sit bone as possible.  It is best to have an experienced teacher show you how to properly roll the right arm bone to clasp the hands.
4. Inhale lift your spine.
5. Exhale release.
6. Inhale your left knee up placing the foot flat on the floor in line with your left sit-bone.  The left foot is flush against the inner right thigh.
7. Exhale cross your thighbones.
8. Inhale your right arm up toward the sky.
9. Exhale your right arm around the outside of your left knee and clasp your hands.  Lift the chin a bit aristocratically and look to the back of the room, as this will help you find lift in the spine as you twist.  Hold for 5 Ujjayi breaths.
10. Inhale lift your spine.
11. Exhale release.
12. Vinyasa coming through to sitting.

Twists have the ability to correct posture, improve vertebral alignment and increase range of motion makes it an excellent therapy to reduce the symptoms of spinal problems. 

Twisting poses have been devised to bring a rich supply of blood to the various parts of the spinal column. The Asana work by stretching, bending and twisting the spinal column in different directions to promote the health of the nerves:  i with lumbar and thoracic rotation,  (which are normally never done in daily life) the paraspinal muscles are made flexible and the emerging spinal nerves are freed from their " physiological adhesions " which commonly occurs as one grows older.  Strengthens and stretches the spine, relieves backaches and pain in the hips. 

In twists which involve rotation, disorders like lumbago and slipped disc syndrome are relieved as in the former case the lumbar muscles have been very stiff  (and rotational movements are good to soften them) and in the latter, enough room is given for the herniated disc so that pressure effects are avoided.

Twists purify the body by wringing toxins out of the internal organs. Thus, massaging abdominal organs, toning the liver and spleen and kidneys.

Twists are neutralizing and balancing—they'll stimulate you if you're tired or lethargic and calm you down if you're agitated or excited. 

Balances the front and back of the body.

Stretches the shoulders increasing shoulder range of motion.

Cardio-respiratory capacity improves. The heart and lungs are made to work in a constrained atmosphere as the twisting poses squeeze one side of the body . The intercostal muscles are made elastic - a feature unique to yoga. No other system can do this.  This helps with Asthma, Fatigue  

All abdominal organs are alternatively squeezed and flushed with blood.  Thus, addressing constipation, Digestive problems, Menstrual discomfort

A twist can help to release tight muscles along the spine, improving flexibility of the spinal column; the rotating action of a twist can realign the spine, improve circulation and nourish spinal nerves (therefore benefiting all systems in the body). This action also encourages a free flow of prana through the major nadis of Ida, Pingala and Sushumna.

Twists create a two way movement in the seated twists with grounding and lifting upwards. The restrictions in the low legs locking the lower energies encourages them to move upwards

This enhances pranic flow in Samana region.  This nourishes organs such as the pancreas, kidneys, stomach, small intestines, live and gall bladder and relieves associated disorders and rejuvenate the tissues generally.  Samana is the balancing area of the major organs, so helps to rebalance them.  This helps to clear the nadis with this action

Exercise for opening the second chakra involve working with movement in the hips and lower abdomen.   Ideally this chakra is openned and brings us fluidity and grace, depth of feeling, sexual fulfillment, and the ability to accept change.   This provides greater sense of well being.  Encourages flexible thinking and spiritual strength

Serious back or spine injury: Perform this pose only with the supervision of an experienced teacher.   If your sacroiliac is already out, then twists can be especially problematic.  The only way to prevent further injury and discomfort is to meticulously move the pelvis and sacrum together.  According to Judith Lasater:

"The popular pose Marichyasana III (Marichi's Pose) is an example of this, where practitioners often use the arm to create the torque necessary for the twist instead of twisting from the pelvis. It's better to create as much of the twist as you can before using your arm—this will decrease the possibility of separation and strain at the S-I joint."

One of the easiest twists for beginners is Marichyasana (pose dedicated to Marichi, son of Brahma), performed in a standing position with one foot raised up on the seat of a chair or some other prop. To practice this pose, place a folding chair or other similar prop against a wall, so it won't move while you are performing the twist. Stand directly in front of the chair with your feet parallel and only a few inches apart. Put your right foot on the seat of the chair, keeping both feet pointing straight ahead. Place your left hand on the outside of your right thigh near the knee. Place your right hand on the back of your right hip with your fingers pointing down.

Also avoid this pose if you have:
High or low blood pressure
Migraine
Diarrhea
Headache
Insomnia

You feel the excess of last meal in Marichyasana or if you have eaten within the 3 hours before the practice.  Ideally practice after 3 hours has past after eating.