James Kiernan
The word pelvis is Latin for basin. Our pelvis sits at the base of our torso and is at the very center of your body's design. It is at the center of all movement, and is fundamental to how we manage gravity. The male and female pelvis are generally slightly different in that the female pelvis is more broad to support child birth. At the back of this bowl, the sacrum is wedged into a snug fit between the two sides of the pelvis, allowing great stability for our spine and the rest of our structures above.
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This is the bridge which connects our spine and our legs, and because these areas are so close together, their movements can impact one another.
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Movements associated with the pelvis are typically referred to as anterior and posterior tilts. Its fairly easy to view these orientations from the side. When the pelvis has anteriorly tilted, the public bone drops and the lumbar curve has become more pronounced as the left half of these two images show, with the opposite happening in a posterior tilt, being displayed on the right half. Becoming aware of this movement in Cat-Cow allows for greater awareness and integrity in other postures.
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Our hip flexors are the group of muscles which can engage to bring our pelvis into flexion, relative to our leg bones. These muscles are the psoas, quadriceps, and adductors. They originate at the bottom of the spine, or on the pelvis, and connect to different points on the leg below.
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The first of muscles illustrated is the iliopsoas, which is two muscles comprised by the psoas major and the iliacus. Raising one leg while standing, or bringing the body into Navasana (boat pose) engage this group. This group of muscles tends to get stiff and weak because of common postures like sitting in chairs for extended periods of time. While the primary action of these muscles is to flex the hip, they also act as as an internal rotator of the hip.
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The quadriceps are a group of 4 muscles where 3 act to straighten the knee, and the other known as Quadriceps Femoris is a hip flexor. Because these muscles work with two different joints (they produce knee extension & hip flexion) the position of one joint affects the ability or difficulty of the other action Think about standing on one leg, it would be easier to lift the opposite leg with the knee bent, than it would be to lift the leg while straight. The quadriceps can also impede several postures that we see in yoga. Sitting in Hero's Pose can be restricted because knee flexion is inhibited. Backbends can also be hampered because of the inability to bring the pelvis into an posterior tilt. Sitting in chairs for extended periods of time may allow these muscles to shorten, and so because these are a big group of muscles, if they are stiff, be patient when searching for greater ranges of motion.
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The last of this group are our adductors. Their primary movement is of course adduction, but they also flexors of the hip. Because these muscles attach to the pubic bone, they also have an effect on the positioning of the pelvis. This means that they can pull down the front of the pelvis and contribute to an anterior tilt. The most common poses that are limited in this range of motion are Baddha Konasana (Butterfly Pose) & Virabhadrasana 2 (Warrior 2).
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The Gluteals consist of three muscles on the posterior side of the pelvis. As a group they do a lot: medial rotation, lateral rotation, as well as flexion and extension of the hip. Yes, the same muscle can have different sections that do opposite actions. The Gluteus Maximus is the largest of the buttock muscles and creates hip extension (the back of the leg moving towards the back of the pelvis). The fibers run at an angle, so not only do they extend the hip, but they also create lateral rotation at the leg. The other two glutes are quite similar to the deltoids of the shoulder, where different portions of these muscles create either internal or external rotation of the hip. Collectively this group is responsible for abduction from anatomical position. While abduction is not an extremely common or frequent position we take, we use this group of muscles a lot in our everyday movements. As we walk/run our center of mass shifts to one leg. This results in our standing leg glutes to contract to keep the pelvis stabile while the other leg moves forward. Everytime you take a step, this action happens, so you can imagine, it happens a lot! If the muscle is tight due to a repeated movement like running, cycling, or some other activity, it influences the ability for the joint to create other movements it is responsible for. Therefor rotation of the hip can be affected as well.
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If you want to use the glutes to create hip extension, but not lateral rotation, you have to work to internally rotate as you're going into hip extension. I've heard verbiage in classes I've taken to not use the glutes when going into a backbend (hips move into extension in these postures). Its perfectly fine to use the glutes there, but to also create the effort of internal rotation, so you're not laterally rotating there as well. That lateral rotation can cause problems in the low back.
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Our hamstrings act in a very similar way to our quadriceps muscles, in that they control multiple joints. The Biceps Femoris is the one 3 muscles within our hamstrings, but is muscle in the group that extends thehip, where all 3 bend the knee. The other two are known as Semitendinosus, and Semimembranosus internally rotate the hip joint. something to note here, is that we don't create the action of internal rotation a lot in our yoga practice, but there are a lot of positions where we should be creating the effort of internal rotation. Especially in backbends, because we naturally use Gluteus Maximus,and because that muscle laterally rotates the hip, creating the effort of internal rotation is very important because lateral rotation by itself is problematic in backbending.
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I will cover this last part about the hamstrings in more detail in the Asana Guide, but if hamstrings tend to be stiff, then impacts our how deep we can flex the hip. If that movement is inhibited, then added stress can be loaded onto our low back. This will be covered later, but a good rule is to prioritize the length of your spine over the stretch and sensation of your hamstrings.
Another lateral rotator of the hip are a group of muscles called the "Deep Six". They are the muscles which attach in different places on the pelvis, and connect to the back of the greater trochanter. The piriformis is the most well known of these six . It originates on the anterior sacrum and inserts at the top of the femur. If the piriformis is tight, it can squeeze on the sciatic nerve which runs from down the spine, to the leg and cause symptoms of sciatica.
It's interesting that these muscles are only a lateral rotator when the hips are not in flexion. When the hips are in flexion it is an abductor of the hip. So when we want to stretch these muscles, it is much more accessible to approach it with flexion and adduction of the hips.
Medial rotation of the hip is something we don't see very much in a typically asana practice. Although we do not see the position of medial rotation often, we see the effort of this in plenty of postures. We talked about how when you are in hip extension, in a backbend, the gluteus maximus a major contributor to that position. Because this muscle also laterally rotates the hip, its important to create the effort of medial rotation so that your hips remain neutral with respect to rotation. I've experienced this personally, where I was creating a strong effort of hip extension in backbends, and because of the lack of effort mentioned, my sacroiliac began to experience a high amount of discomfort.
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Pictured here are our internal rotators known as the tensor fascia lata or TFL. The tensor fascia latae works in synergy with the gluteus medius and gluteus minimus muscles to medially rotate the femur. So together these muscles can create an effort of medial rotation. By doing so we keep the hips neutral when working in positions where the gluteus maximus may otherwise bring the hips into external rotation.
