Ushtrasana Part II

Ushtrasana Part II–Coming out of the pose
Coming out of ushtrasana should be done slowly and with care.  One should imagine “rolling up” one vertebra at a time to a kneeling position.  Start by returning the palms of the hands to the sacral area.  This is achieved by flexing the elbows (concentric contraction—biceps, eccentric—triceps), supinating the elbows and hyperextending the wrists.  Place the hands so that the fingers are facing toward the floor.
Come up slowly, performing the following actions together—extending the neck, extending the spine (concentric–pectoralis, levator scapulae, rectus abdominus, rectus femoris, iliopsoas; eccentric–rhomboids, trapesius, erector spinae), internally rotate the shoulders to return them to neutral.  The glutes are already contracted here but will also work eccentrically to help extend the hips.  The arms are released by extending the elbows (eccentric—triceps, concentric—biceps), extending the wrists, and pronating the elbows back into neutral.    
Flexing the hips (concentric–rectus femoris, iliopsoas, rectus abdominus; eccentric–glutes, erector spinae, trapezius) will bring the body forward while flexing the shoulder joint (concentric-anterior deltoid; eccentric–posterior deltoid) into the counter pose, balasana.
Ushtrasana should be avoided by individuals with serious spine injury such as lumbago or herniated discs.  The pose can be modified as needed by keeping the hands on the hips (not fully dropping and grasping the ankles).

Pose Breakdown: Ushtrasana, Part I

Ushtrasana:  Part I
Ushtrasana opens the chest (pectoralis major/minor) and fronts of the shoulders (anterior deltoids), stretches the hip flexors (iliopsoas), and front thighs (quadriceps) while increasing flexibility and strength of the spine and strengthening glutes.  Benefits also include stimulation of the spinal nerve and stretching of the digestive organs.  With long term practice, it can also relieve sciatica, asthma and kyphosis (hunching of thorasic spine).   Ushtrasana is also beneficial in stimulating the thyroid and parathyroid glands.
Getting into the pose:  Ushtrasana is approached from a kneeling position (vajrasana).  Extension of the hip joint will take the practitioner to a “standing position” on the knees (which are flexed, with feet plantar flexed).  From here, one must hyperextend and internally rotate the shoulder joint, flex and pronate the elbows and hyperextend the wrists to get the palms on the sacral area with fingertips pointing downward.  “Roll back” the shoulders (external rotation) through concentric contraction of the rhomboids (agonist) and eccentric contraction of the pectoralis (antagonist) to retract the scapula open the chest.   The glutes must engage isometrically to stabilize the lumbar spine and hips as the backbend is performed.  One must lean back, engaging trapezius, latissimus dorsi and erector spinae (concentric) coming back with the control provided by the (eccentric) contraction of rectus abdominus and rectus femoris, and hyperextending the cervical spine to gaze upward.
Once the back bend is achieved, the hands are placed one at a time on the ankles, by extending and supinating the elbow joints.  Now all of the above mentioned muscles must work in isometric contraction–without movement–to stabilize the pose (aside from those used in respiration).