Principles of Action and Anatomy

There are several key actions consistently performed in yoga asanas. A brief discussion of anatomy will help you understand the mechanics of the body.

The Importance of Foundation

The rooting of the foundation, or base, allows extension, space, balance, and ease in a pose. If you're looking for proof, sit down on a firm chair with your heels directly under your hips and shoulder over hips. First sit in a slouched position and notice how that feels and be aware of the quality of your breath. Now, sit up tall, without leaning against the chair back. Press your buttock bones (the bony protuberances you sit on), into the chair seat. Observe the rebounding, lengthening action that lifts your spine out of the pelvis. Enhance this by lengthening up through the top of your head. Observe the quality of the breath. Is it fuller and deeper than when you sat in a slumped position?

Hugging Muscle to Bone

The function of muscle is to support the skeletal system. This cannot occur if muscle does not actively adhere to the bone. If muscle is not supporting bone, then the bone cannot stay in its socket. The joints are then not properly supported. This situation has a domino effect throughout the body, underlining the necessity of drawing muscle energy into the bone to create good alignment and integrity.

The hugging muscle action occurs when we draw the muscle in to the bone. This creates support for the bone, lengthens the muscle, and draws the bone into the socket, where it belongs.

Have you seen very flexible people who walk as if their bones are not connected? They need to build strength to support their joints and to hold their bones in the right place. Overly stiff people need to break down some of the strength to create more space and flexibility. However, they are already supporting their joints much more than the overly flexible person.

People who begin yoga with stiffness bemoan the fact that they are inflexible. They tend to look enviously at their loose classmates, who seem to be able to effortlessly ease in and out of postures. However, it is much easier to break down stiffness than to build up muscle strength. And flexible people tend to get injured more frequently because their support system is not in place. So, in some ways, it is better to be stiff with support than flexible without support.

The good news is that yoga is the great equalizer. The poses will develop flexibility and strength where they are needed. Careful attention and practice while in the poses will help correct these problems over time, resulting in better alignment, a balance of strength and flexibility in the muscles, and integrity of the leg joints.

Practice this: Stand with your feet wider apart than your hips. Place your hands on the hips. Press down into your feet and draw the inner thighs away from each other. Observe the hugging muscle action in the thighs, as they draw into the bone. This exercise can also be done standing in a doorway and pressing the outside of the feet against the doorjamb while doing the above actions. Don't your legs feel more solid and stable?

Shoulder Blades and Arms

The job of the shoulder blades is to open the chest and support the upper body. This is very important, as the heart and lungs are housed there, and they need proper space to function well. And when the chest is open and supported, the breath can fully enter the lungs.

In order to do this, the shoulder blades must press into the body, and the muscles surrounding them must actively work and contract, to keep the shoulder blades flush with the upper back. Weight the shoulder blades so they feel as if they are moving down the back toward the waist. This action will naturally lift the chest. The muscles around the upper side ribs also have to hug the body to provide length and support. It takes time and practice to strengthen these muscles, especially if they are only accustomed to stretching.

When a person's upper back is rounded, that is an indication that the shoulder blades are off the back, providing no support. The head may lean forward, placing excessive demands on the neck and upper back muscles, while the chest caves in and the shoulders roll forward, and the arms are forward in the socket. The arms and shoulder blades are disconnected from the upper body and the breath tends to be short and shallow.

In the discussion of poses, you will be reminded to keep your shoulder blades on your back. If this is confusing, try this exercise: Lie down on your back with your knees bent. Extend your arms, with palms facing each other, up to the ceiling. Stretch your fingertips up to the ceiling. Observe how the shoulder blades are now off the back and the arms are also disconnected from the shoulder sockets. Now draw your upper arm bone down to the floor while stretching out through the fingertips. Feel the shoulder blades press onto the floor. Continue stretching into the fingers as you bring the blades to the floor.

This is the dynamic, opposing stretch you want in your arms—going in equally opposing directions, stretching expansively out from the center of the body into the fingertips, and back into the core of the body, with the arms in the socket and the shoulder blades supporting the upper body. Practice this daily, doing ten or twenty repetitions, thus building the strength of the upper back muscles.

Maintaining Extension in the Spine

There must be space between the spinal vertebrae to create a healthy and supple spine. A long spine allows the nerves sufficient room to exit from the spinal cord. Impingement on the nerves can cause nerve pain and damage. Extension of the spine affects every system in the body—the nervous system, the circulatory system, the respiratory system, the digestive system, and the endocrine system.

When we do poses, we inhale to prepare for the pose and to create expansion in the body and length in the spine. Then we are ready to safely do the pose. Remember that is the grounding action in any pose that allows the extension.

The extension of the spine also creates the freedom for opening, broadness of the upper body (chest and upper back), and the spaciousness of the pelvis (the lower back and lower abdomen). Internal space means that the organs have room to do their work and enough room for the breath to enter the cells, bones, organs, and all the places in between.

Spinal Curves

The spine has four natural curves, running front to back, which are designed to absorb the shocks and jolts to the body during daily activities such as running, walking, and sitting in a car. The cervical (neck) spine is concave, the thoracic (upper back) spine is slightly convex, the lumbar (lower back) spine is concave, and the coccyx is convex. Any deviation from the normal curves can cause pain, dysfunction, and disease.

One of the goals in asana practice is to maintain the natural curves of the spine. We do not want to flatten out the neck or lower back, overly round the middle back, or create swayback (excessive lower-back concavity) or shortening of the neck by lifting the chin or jutting it forward.

What is scoliosis?

An abnormal curve of the spine from side to side, with one side becoming contracted while the other side is long. According to Mary Pullig Schatz, M.D., functional scoliosis is a curve that is caused by conditions, such as asymmetrical work, differences in leg length, and back spasms.

Because the spine is attached to the arms, legs, and chest by the shoulder and pelvic girdles and ribs, with the head balanced on top of the spine, every movement affects the spine and vice versa. For example, if the shoulder joints are inflexible, you may compensate by overarching your lower back when your arms are raised in an activity. This places excessive strain on the lower back, and, over time can cause problems.

If the hips are stiff, with little range of movement, the pelvic area will be unable to move fluidly and freely. This distortion will be transferred upward throughout the spine and the body. Various muscle groups can affect the curve of the lower back. They are listed here.


The paraspinals are deep muscles on either side of the spine, which support the spine when it is vertical and are involved in rotating the spine, bending it backwards and sideways. If the paraspinals are too tight, swayback will occur; if they are too lax they can lead to a flat back. When the paraspinals are overworked, they can go into spasm. Yoga helps the paraspinals by stretching and strengthening them.

Hip Flexors

The hip flexors, which allow the thigh to lift, affect the stability of the lower back. Because they attach to the front of the pelvis, tight hip flexors will cause the pelvis to tilt forward, creating a swayback.

Abdominal Muscles

Abdominal muscles function to support the abdominal organs and the lumbar spine. If the abdominal muscles are weak, the pelvis will drop forward, creating excessive strain and shortening of the lower back.

Psoas Muscles

The psoas muscles are extremely important muscles that affect our posture. The pair of psoas muscles, on either side of the body, attach from the groin, internally, through the pelvis, to the anterior lumbar spine and the diaphram (breathing) muscle. If the psoas is tight and constricted, lordosis, an excessive lower back curve can occur. A tight psoas muscle also impinges upon the internal organs located in the pelvic area, creating less space for the organs to do their work. Weakness of the psoas muscle can contribute to rounding of the lower back.


The hamstrings insert onto the ischial tuberosities (buttock bones) and into the back of the knee. Tight hamstrings will tilt the pelvis backward and create a flattened lumbar curve.


Quadricep muscles in the front of the thigh contract to allow the hamstrings to lengthen in forward-bending poses while the hamstring muscles contract during backbends as the quadricep muscles elongate. Contraction of the quadricep muscle while lifting the kneecap sends a physiological message to the hamstrings to release.

The quadriceps and the hamstrings work together as partners in supporting the legs, pelvis, and spine. They are an example of equal and opposite actions in muscular energy, which result in balanced effort. This synergistic relationship between muscle groups occurs throughout the body.

The Rib Cage

The rib cage has a front, a back, and two sides. Most people are only aware of their front ribs because they can see them. The ribs extend all the way up to the collarbones and down to the middle abdomen. Eight of the ribs are attached to the sternum or the spine and four are floating ribs attached to each other. The muscles between the ribs are called intercostal muscles. They are responsible for stretching upon inhalation to allow the rib cage to expand and make room for the lungs to fill up, and to contract with the rib cage when the lungs empty.

The ribs, like the pelvis, must be in a neutral position to facilitate extension of the spine. If the front ribs are thrust forward, the back is shortened and the kidneys are compressed.

The ribs must lengthen away from the hips, to create a long spine. Space is then created between the hips and the armpits and between the ribs (as the intercostal muscles stretch). Breathing becomes deeper and fuller as a result.

Soft Belly

In our society, there is too much emphasis on obtaining a flat belly by sucking the belly in. This creates tightness and hardness in the abdominal area, its organs, the diaphragm and the groins. The breath also becomes restricted and the flow of energy to the pelvis is blocked. Movement becomes restricted.

The belly needs to remain soft and receptive. In poses, there can be a lengthening of the abdominal area by lifting the ribs away from the hips, and a slight drawing in of the lower abdomen, but this must be done without tension, through synchronization of the movement with the energy and the breath.

Soft and Spacious Pelvic Floor

Like the belly, the pelvic floor needs to be soft and spacious, without hardening of the anal or genital area. The pelvis should be in a neutral position to maintain the correct placement of the sacrum and the natural curves of the spine. It may be helpful to visualize the pelvic area as a broad basin filled with water. If it tips too far forward or backward, the water will spill out.

The pelvis has three dimensions in which it moves: front to back, side to side, and up and down. A pelvis that tilts forward increases the lumbar curve, shortens the lower back muscles, and causes a swaybacked position. A backward-tilting pelvis tucks the tailbone, causes the lumbar curve to flatten, and may be the result of a tight psoas muscle. A pelvis that is higher on one side, leans more to one side, or has one side farther forward, also distorts the sacrum, spine, and legs. The pelvis plays a crucial role in connecting the legs to the spine, which is why it is so important to have the thighbones insert correctly into the pelvis at the right angle.

The Hips and the Groin

The hips remain level to one another as much as possible, without forcing the action. Level hips balance the sacrum and a balanced sacrum balances the spine. The iliacus muscles (on the front of the hip) lengthen down, allowing the lower belly to lift up. Then the inner body lifts and the psoas lengthens and the groin remains soft and long. Like the belly and the pelvic floor, we want to keep the groins as soft as possible. The belly and the groin can softly recede into the body. Hardening or pushing the groins forward shortens them, reduces the openness of the hips, and contributes to lower back discomfort.

The Sacrum

The word sacrum means “sacred bone.” The sacrum is a flat, triangular bone formed by the fusion of the last five spinal vertebrae. It is part of the back wall of the pelvis.

The pelvis joins the spine to the legs and the sacrum acts as the fulcrum upon which the spine rests and arises from. The weight transfers from the head, down the spine, and then distributes through the widest part of the sacrum to the thickest part of the pelvis. Then the weight shunts forward to either the sit bones, if one is sitting, or down the femurs (thigh bones) to the feet, if one is standing. From there the feet rebound the energy back up the legs to the top of the head, allowing for extension.

The sacrum's alignment is crucial. Correct use of the feet, legs, pelvic floor, and abdomen allows the downward weight to transfer and the sacrum to be balanced. Many of us do not completely transfer the weight from the sacrum to the sit bones or the feet. The weight may stay at the sacrum, causing undue stress and strain on the vertebral discs just above the sacrum (L3, L4, L5). Indeed, many people have back injuries in this area. The natural curve of the lumber spine (lower back) is concave. The top of the sacrum slightly tilts in to the body.


The knees are a very vulnerable joint, situated between the ankles and the hips, and dependent upon them for stability and alignment. The most important rule is that there should be no pain in the knees during poses. If pain should occur, the pose needs to be modified or skipped. The activity and grounding of the feet, the full stretching of the legs, and lifting of the kneecaps in straight-legged poses, ensures healthy knees by fully supporting and opening the knees.

To get the feeling of the quadricep muscle contracting and hugging the bone and the kneecap lifting, do this exercise: Stand with your feet under your hips. Lift one foot off the ground and just let it dangle. Observe how difficult it is to maintain your balance when the foot and leg are dull and without energy. Now lengthen the heel and the balls of the foot away from the leg. Note the action and energy in the entire leg and foot. Pay particular attention to the upper knee and lower quadricep muscle. They are now actively engaged. This is the action we try to maintain in our straight-legged poses.

Hyperextension of the knee is a common problem that occurs when trying to straighten the leg. Unfortunately, this is a wrong action, which can result in overstretching the tendons and ligaments of the knee. Tendons and ligaments are not meant to be elastic, as their job is to provide support for the joints. The hyperextended knee is pressed back, rounding the back of the knee, overstretching the calf muscles, and bypassing the space and extension in the legs.

Hyperextension of the knees distorts the alignment of the hips, pelvis, and spine and causes abnormal wear and tear on these joints. Drawing the top of the thighbone into the hip socket, and pressing the neck of the big toe down will help prevent hyperextension. In order to lengthen the leg without hyperextending the knee, it is important that the quadricep muscle contracts and firms before the back of the knee stretches.

Most people who hyperextend their knees do so because their hamstrings are tight and the quadricep muscle is weak where it meets the top of the knee. When hyperextending, the shinbones do not insert properly into the knee joint. The shinbone presses back beyond the knees, overstretching the back of the knee and the calf muscles, and then the thighbone does not insert correctly into the pelvis. This affects and distorts the alignment of the leg, pelvis, and the spine and never allows you to connect into your hips.

Fully Stretching the Legs

The legs must be fully opened and stretched for the spine to lengthen out of the pelvis and for the torso to have freedom of movement. Those with inflexible hamstrings often experience back pain or discomfort, due to the rounding of the upper and lower back. The tightness of the hamstrings reverberates up the body, pulling the muscles of the back down, flattening the lower back, tilting the pelvis backward, and tucking the tailbone. If the hamstrings can be progressively stretched through yoga postures, the back muscles will release as well.

To fully stretch the legs, the feet must press down into the floor as the leg stretches up from the grounding of the feet. Remember: For every action there is an opposite and equal reaction. The lifting of the kneecap is also crucial. Lifting of the kneecap is achieved by the contraction of the quadricep muscle on the front of the thigh, where it attaches to the top of the knee. The top of the kneecap becomes imbedded in the lower quadriceps. Remember that this action helps release the hamstring muscle. Simultaneously, the thighbone draws up into the hip socket. These actions create space and extension in the legs.

Try this exercise to feel the full stretch of the leg: Stand and bend your knees. Feel the weight come into your feet. Keeping the weight in your feet and pressing them down, extend from the shins to the heels, lift up the knees and lengthen the muscles from the knees to the hips, like you are pulling socks up your legs. The “socks” are your thigh muscles. Contract the quadricep muscle before and faster than you stretch the back of the knee. Do this without pushing the knees or shins back. See how slowly you can do this, observing the “taffy pull” of the leg muscles as they lengthen away from each other. Also notice that the quadricep muscles are actively working and will strengthen over time from this action. Do this several times and repeat often to strengthen the quadricep and train the leg muscles to stretch fully.

The Active Yoga Foot

The foot in yoga should always be energetic and active (but not tense), unless you are in a relaxing, restorative posture. When standing, begin by spreading the toes away from each other, creating a broad base with your feet. Feel the balls and the bones of the feet spreading apart.

Stretch your toes forward as you lengthen the heels away from the toes to lengthen the feet. Press your feet down strongly, grounding the big toe and little toe mounds of the feet, and the center of the heel. Press down evenly on the inner and outer sides of the feet, and the balls and heels of the feet.

From the rooting action of the feet, lift your inner and outer arches up into the feet. The lift of the arches stimulates muscle action up your legs. If you cannot feel the arches lift, help them by lifting up your (spread) toes. These actions are performed even if the foot is not against something, as if it was pressing into an imaginary surface.

The actions of the feet create a healthy foot from which the alignment of the whole body develops. The support of the legs and pelvis are fully dependent upon the feet. The lifting of the arches is excellent for developing the arches, which support the weight of the body and rebound the energy and extension back up the body. The grounding, broadening, and lengthening of the foot is equally important.

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