Bandha Yoga - Scientific Keys to Unlock the Practice of Yoga

Gravity and Side Plank
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The shoulder is the most mobile articulation in the body. The muscular stabilizers, including the rotator cuff play an important role in maintaining the congruency of the shoulder joint. When the capsule and ligaments are loose, then the muscles must compensate. This is why we focus on strengthening the muscles... (to gain stability).
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Img1 - ...in this (1st) position, the body weight is directed at an angle to the alignment of the arm bones. When the hand is placed below the shoulder, the supporting arm is aligned in a position such that the bones are perpendicular to the direction of gravity. Practicing the pose in this (2nd) way requires less muscular effort because it uses the inherent passive strength of the bones to aid in supporting the body weight. When the hand is placed forward of the shoulder, greater muscular effort is required to maintain the pose.
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Img2 - People with joint hypermobility depend to a greater degree on the muscular stabilizers of the joint. Placing the hand so that the arm is angled against gravity means that these muscles must also work to support the body weight that would be borne, in part, by the bones. You can experience this concept yourself by standing near a wall and leaning against it. Then, move the feet a bit further from the wall. Which one requires less muscular effort?
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Img3 - Vasisthasana with the supporting muscular stabilizers. I go over a step-wise approach to engaging these muscles and the other core stabilizers of the trunk and legs in Yoga Mat Companion Four Anatomy for ArmBalances and Inversions.
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Img4 - The three factors that contribute to mobility and stability of a joint are the bone shape, the capsulo-ligamentous structures and the muscles surrounding the articulation (1-supraspinatus, 2-subscapularis, 3-infraspinatus, 4-triceps, 5-biceps(short head), 6-biceps(long head), 7-deltoid, 8- pectoralis major, 9-pectoralis minor)

The Posterior Oblique Subsystem
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The posterior oblique subsystem is comprised of the gluteus maximus on one side of the body and the latissimus dorsi on the other side, with the thoracolumbar fascia between (as shown in the inset illustration). These structures operate synergistically with other groups of muscles, ligaments and fascia, particularly during rotational movements such as a golf swing.
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The fibers of the gluteus maximus and opposite side latissimus dorsi run perpendicular to the sacroiliac joint. Co-contracting these two muscles can be used to tension the thoracolumbar fascia, thus stabilizing the sacroiliac joint.
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Bird Dog is an excellent pose for strengthening the core and engaging the posterior oblique subsystem. A good cue for activating the latissimus dorsi muscle in this pose is to straighten the arm forward and then imagine pushing down with the hand against an immovable object (as shown with the dotted arrow). Alternatively, imagine pulling down on a rope with the forward hand. Combine this isometric contraction of the lats with engaging the glutes on the side of the lifted leg to augment the stabilizing effect on the SI joint.

Gomukhasana For Stiff Shoulders
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This Scientific Key focuses the drishti on the lower arm in Gomukhasana and uses a facilitated stretch of the infraspinatus, teres minor, and posterior portion of the deltoid to allow deepening of the pose. A belt connects the upper and lower arms.
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1. Gently drawing the lower arm up the back creates a mild stretch of the infraspinatus, teres minor and posterior deltoid in the lower arm.
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2. Pulling down on the belt while pressing the back of the hand on the lower arm into the back creates an eccentric contraction of the stretching muscles. This activates the Golgi tendon organs of these muscles and creates a “relaxation response” that frees the muscles to lengthen. (For more on the Golgi tendon organ please see “The Key Poses of Yoga”).
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3. Relaxing the rhomboids frees the scapula to move away from the midline, allowing the lower arm to be drawn further up the back to stretch the target muscles. The hand is then held in place by the upper arm.
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4. The rhomboids then activate to draw the scapula back towards the midline, accentuating the stretch.
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These steps are repeated once to deepen the stretch. Do not attempt to attain your maximum in one practice. Rather, build your flexibility over time with consistent, gentle practice.

Movements of the Trunk
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Figure 1 - Flexing the Trunk
The abdominal muscles that flex, or bend, the trunk forward include:
The rectus abdominis: a flat band of muscle extending from the front of the rib cage to the front of the pelvis at the pubis.
The abdominal obliques: two sheets of muscle with fibers running diagonally from the sides of the rib cage to the iliac bones of the pelvis.
The transversus abdominis: the innermost sheet of muscle wrapping around the abdomen from the lower ribs to the top of the pelvis.
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Figure 2 - Extending the Trunk
The muscles on the back that extend, or arch, the trunk include:
The quadratus lumborum: a deep rectangular-shaped pair of muscles running alongside the lumbar spine from the top of the back part of the pelvis to the lower ribs and upper lumbar spine.
The erector spinae muscles: a group of band-like muscles running along the back through its length.
The latissimus dorsi: a large flat muscle that runs from the back of the pelvis and lower back to the upper arm bone (the humerus).
The trapezius: a trapezoid-shaped muscle running from the top of the lumbar spine, over the shoulder blades, and up to the back of the neck.
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Figure 3 - Laterally Flexing the Trunk
The muscles that bend the trunk to the side include:
The psoas: a combination of the iliacus and psoas major muscles that run from the the lumbar spine and inside the pelvis to the upper inside part of the thigh bone (the femur).
The quadratus lumborum: a deep rectangular-shaped muscle running alongside the lumbar spine from the top of the back part of the pelvis to the lower ribs and upper lumbar spine.
The erector spinae on one side of the back: a group of band-like muscles running along the back through its length.
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From "The Key Poses of Yoga"
by Ray Long MD

Movements of the Pelvis
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Image 1 - Tilting the Pelvis Back and Down (Retroversion)
The muscles that tilt the pelvis back and down:
The gluteus maximus: a large muscle forming the bulk of the buttocks that flows from the back of the pelvis to insert on the side of the thigh bone (femur). Part of this muscle also attaches to the iliotibial band, a sheet-like tendon that attaches to the knee.
The hamstrings: four tube-shaped muscles running from the back of the pelvis on the sitting bone, the ischial tuberosity, to the top of the lower leg bones (tibia and fibula).
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Image 2 - Tilting the Pelvis Forward (Anteversion)
The muscles that tilt the pelvis forward:
The psoas: a combination of the iliacus and psoas major muscles that run from the lumbar spine and inside the pelvis to the upper inside part of the thigh bone (the femur).
The rectus femoris: a long tube-shaped muscle that is part of the quadriceps and runs from the front of the pelvis to the kneecap.
The sartorius: a narrow band-like muscle that runs diagonally across the surface of the thigh, from the front of the pelvis to the inside of the knee.
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From "The Key Poses of Yoga"
By Ray Long MD

Yoga Is Just a Technology

“Technology comes from the mind, and religious technology also comes from the mind – yoga, mantra, yantra. Yoga means body postures, which can help you to go deep inside yourself; they are created by the mind. That is religious technology. That’s why Yoga is not part of any particular religion. There can be Christian yoga, there can be Hindu yoga, there is certainly Buddhist yoga, Jaina yoga – there can be as many yogas as there are religions. Yoga is just a technology. No machine is Hindu; no machine is Mohammedan. You don’t go into the marketplace to purchase a Mohammedan car or a Hindu car. Machines are simply machines. Yoga is technology. Mantra is technology; it is created by the mind. In fact, mantra comes from the same root as mind – both come from the Sanskrit word man. One branch becomes mind, another branch becomes mantra – both are part of the mind.”

Osho, Philosophia Perennis, Vol. 1, Talk #9