YOU CAN DEVELOP GOOD JUDGMENT AS YOU DO THE MUSCLES OF YOUR BODY, BY JUDICIOUS, DAILY EXERCISE.
—GRANTLAND RICE
WE SPEND A lot of time in asana class stretching and strengthening muscles. While many students may not know much about their bodies when they begin the practice, they usually know the names of certain muscles, like the hamstrings, the biceps, and the abdominals. But as a yoga teacher, knowing where the muscles are, and how they work to create and shape actions, is a critical and useful skill. First, however, it helps to understand the relationship between muscles and bones.
BONES
Muscles are attached to bones at two locations; one is called the origin and the other the insertion (Figure 2.1). Muscles arise at the origin. This site is the more proximal of the two ends of the muscle and is considered to be the fixed end of attachment of the muscle during most movements. The muscle inserts at the distal end.
Muscles can originate and insert in the same region, like the muscles that start and stop on the hand. These are called intrinsic muscles. Extrinsic muscles arise in one region and pass to another, like the iliacus muscle, which originates on the pelvis and inserts on the femur.
However, origination and insertion can reverse, depending on the actions that are occurring. An example of the origin and insertion switching places can be seen with the latissimus dorsi muscle. It originates on the pelvis, on the connective tissue of the lumbar and sacral areas, on the thoracic and lumbar vertebrae, and on the lower ribs. It inserts on the intertubercular groove of the humerus, near the top medial portion of this bone, in the armpit area.
In most normal movements, the humerus is brought down toward the origin point, the pelvis, and other nearby areas. One example of this movement is swimming the butterfly stroke. The humerus, or insertion point, is brought toward the origin in the lower body.
However, when climbing a rope, the action is reversed. The origin (lower body) is now brought upward toward the insertion (humerus) instead. To climb a rope, you fix, or stabilize, your arm and lift the pelvis toward the arms. Thus the origin and insertion points switch places in the action of rope climbing. Another movement that brings the insertion toward the origin occurs when pressing the humerus bones down while supporting your back with your hands in Salamba Sarvangasana. In this case, you fix the insertion, the humerus, and move the origin toward it to move your pelvis backward, to create the slight back bending movement needed to lift the chest in the pose.
2.1 HAMSTRINGS: ORIGIN AND INSERTION OF A TWO-JOINT MUSCLE
Therefore it should be remembered that, while the origin and insertion are usually proximal and distal, this can vary, depending on what is stationary and what is moving at any given moment.
It is helpful to learn and remember as many origins and insertions as you can. Knowing where a muscle arises and where it ends will help you to understand not only the action that that muscle can make but also what might be going wrong if that muscle is not doing its job. Additionally, in order to stretch a muscle most effectively, knowing its attachments are critical. Take some time to memorize the origins and insertions of major muscles and their opposing muscles as they are specifically discussed in this book. Then use part of your of asana practice time to review and observe the origins and insertions in your own body. More details on the origins and insertions of individual muscles are presented in subsequent chapters.
JOINTS
Joints and muscles are intimately interactive. In fact a muscle can only act on a joint if it crosses that joint. For example, the brachio-radialis only crosses the elbow joint, so it can only act on the elbow joint. This type of muscle-joint relationship is the most common.
However, a muscle like as the biceps brachii of the humerus can act on more than one joint because it crosses two joints, in this case, the shoulder and elbow joints. This type of muscle is called a two-joint muscle. Some examples of two-joint muscles are the hamstrings, the quadriceps femoris (though only one head crosses two joints), and the biceps brachii (one head only). Since yoga practitioners are very familiar with the hamstrings, consider this example of how two-joint muscles work.
The hamstrings have four origins: three are on the ischial tuberositiy of the pelvis and one is on the linea aspera, the raised ridge on the posterior side of the femur. All of these heads of the hamstrings cross the knee, two inserting the knee at the medial tibia and two inserting at the lateral side of the knee. Because the hamstrings cross the hip joint and the knee joint, they can act on both joints and are two-joint muscles.
When the hamstrings contract, they extend the hip joint, bringing the femur backward from the anatomically neutral position. They flex the knee as well. The hamstrings can also help to rotate the tibia laterally or medially. The biceps femoris helps to rotate the tibia laterally after the knee joint is flexed. The semitendinosus and the semimembranosus help to rotate the tibia medially after the knee is flexed.
To feel these rotations, sit at the edge of a simple, straight chair, with your knees at an approximate angle of 90 degrees. Hold your distal femur so your hands make a circle around it, thumbs on top and the fingers to the back. You should be able to feel the hamstring tendons, especially on the medial side just proximal to the knee joint.
Now flex your hip joint about one-third of the way toward your chest and hold it there. Externally rotate your knee out to the side as for Padmasana. Notice the contraction under your fingers on the lateral hamstring tendons, the biceps femoris. Then reverse the rotation of the femur and tibia, as for going into Virasana. You will notice a contraction of the medial hamstrings, the semitendinosus, and the semimembranosus just above the medial knee joint, as they rotate the tibia.
Here is another suggestion that may help you understand the actions of the hamstrings better. Stand in Tadasana on a nonskid mat. Now move one leg backward (so you are standing only on one leg), and bend that knee so the heel of the foot lifts toward the ceiling. The position you are in is of being ready to kick a ball.
These two actions are largely created by the hamstring muscles. You can do these actions, extending the hip and flexing the knee, separately or together, but in either case these actions are mainly created by the hamstring muscles acting as two-joint muscles across two joints.
CONNECTIVE TISSUE
The fascial planes, or sheaths, are a network of connective tissue throughout the body that helps to hold it together and to maintain its shape. Specifically the connection of muscles to bones occurs through aggregates of connective tissue fibers known as tendons.
A tendon grows out of the bone matrix and periosteal covering of the bone, then becomes a connective tissue matrix that goes through and around the muscle, and then attaches at the other end to the bone by a tendon as well. Thus tendons are named for the muscle of which they are a part. Probably the best way to think of a tendon is as an extension or part of the muscle, not as a separate structure. Tendons, of course, do not have the same contractile elements as muscles.
Most muscles connect directly to the periosteum of the bone via tendons, but some muscles are attached to an aponeurosis. This is, in effect, a flattened tendon, a broad, flat, fibrous sheet of connective tissue that attaches to bone and to muscle. One example of an aponeurosis is the structure that the abdominal muscles attach onto at the anterior surface of the body.
MUSCLES
To understand how to stretch a muscle well, you must first know the origin and insertion points. Stretching a muscle happens by reversing the action or actions that it creates when contracting. Consider the abdominal muscles, which run all along the front of the body. When contracted, they approximate, or bring together, the rib cage and pelvis, such as when doing a sit-up. Therefore, to stretch the abdominals, it is necessary to perform the opposite of flexion, which is extension of the trunk. Back bends extend the trunk and therefore stretch the abdominal muscles.
In order to stretch effectively in the case of two-joint muscles, the stretch must be created over both joints simultaneously. For example, the hamstrings are hip extensors, and, to stretch them, hip flexion is needed. They are also knee flexors, so knee extension is needed as well. Thus an effective hamstring stretch is a position in which the hips are in flexion and the knees in extension, which happens in all forward bending asana.
The opposite of stretching a muscle is contracting it using metabolic energy. There are a number of specific characteristics of muscle contractions. One of these concerns contractibility and elasticity. Muscle fibers can contract to one-half of their resting length. They can also be stretched to half again as long as their resting length. Remember, muscles can contract, which requires metabolic work, and they can be stretched, but that is a passive process unless it is a lengthening contraction, such as in the example of lowering a book in your hand.
The second point to keep in mind when considering muscle contraction is the all-or-none law. This states that in each motor unit, other than in cardiac tissue, the individual muscle fiber is either contracting or not, just as a light switch is either on or off. Of course not all the motor units are involved each time you contract a muscle. The body uses only the number of units necessary to complete the movement. The harder the task, the more units are recruited. But each unit itself is either off or on.
The normal motor unit at rest is not firing at all. When measured on an electromyograph machine (EMG), there is no electrical potential or measurable charge in a muscle at rest. Interestingly enough, the concept of muscle tone is therefore not easily definable. Tone is not the state in which a muscle feels slightly contracted or firm to the touch, though we tend to use the word tone to mean this. One way to think of muscle tone is as the readiness to respond, but remember that at rest a normal muscle is not firing. Only a pathological muscle fiber fires at rest.
One of the most interesting characteristics of muscle contraction is that muscle motor units fire their fibers asynchronously. Keeping in mind the all-or-none law, imagine what would happen to your movement if groups of fibers or all the fibers fired together, all at once. If this happened, your movements would be jerky; each time you reached for something it would look like a car starting and stopping, as if the driver were pushing first the gas, then the brake, then the gas again. But the motor units do not fire this way. Because the motor units fire asynchronously, in more of an overlapping time sequence, the effect is that the movement is smooth. As some fibers stop firing, some are just starting, and vice versa, so that the movement is even.
Another characteristic of muscle firing is that a muscle contracts most efficiently when it contracts at a moderate speed. When it does so, its efficiency is approximately 20 to 25 percent, which is considered high compared to most machines. Quick movements are not as efficient, meaning that the extra energy needed for the quick movement is not proportionate to the speed gained. It is somewhat analogous to driving 55 mph; the higher your speed, the less efficiently the car burns fuel. Most asana are practiced at a moderate speed.
NERVES
A muscle receives its stimulation to contract from a motor nerve. The muscle and the nerve join at the neuromuscular junction (Figure 2.2). Each motor nerve branches to innervate many muscle fibers, but there is only one junction per muscle fiber. An electrical wave travels down the nerve fiber and is translated into a chemical reaction at the neuromuscular junction; this chemical energy travels across the gap between the nerve and muscle membranes. When the chemical transmitter reaches the muscle membrane, it is translated back into an electrical impulse that causes the muscle fiber to contract. The disease myasthenia gravis occurs when there is a chemical problem with the neurotransmitter found at the neuromuscular junction.
KINESIOLOGY
The single most important factor to understand when analyzing the movements created by muscles is the force of gravity. All movements are shaped by the force of gravity. Sometimes students of anatomy overlook this principle because it is so obvious.
Please recall the example in chapter 1 about coming down from Salamba Sirsasana (described on page 13). It was mentioned in the context of a lengthening contraction of the hamstrings. When your student comes out of Salamba Sirsasana, the force or power that creates the movement is gravity. There is no reason for the student to use any muscular effort to create the movement, because in this case gravity is the most efficient force to bring the legs down.
What the hamstring muscles are doing in this particular movement are acting as a brake to slow the descent of the legs toward the floor, thus protecting the muscles from too quick a descent. The hamstrings are not needed to act as creators of the movement, because gravity creates the movement with less metabolic energy expended by the body. The hamstrings only need to guide or shape the movement.
Another example of gravity creating a movement occurs during the practice of Uttanasana. Try this: stand on a nonskid mat, with your feet 12 inches apart, knees straight. On your next exhalation, bend forward to place your hands on the floor. As you do so, notice what is happening to your hamstrings, gluteus muscles, and erector spinae muscles. These muscles are not flexors of the hip, but extensors of your hip joint and vertebral column. Yet they act to create flexion of the hip by letting go with gravity to help control the downward movement. Gravity is already pulling down on the trunk, and the extensors just need to slow down the movement, not create it. To use hip flexors to create Uttanasana would be redundant and would waste energy. Instead the body chooses to create the movement with the least energy necessary, a lengthening contraction of the hip extensors and erectors.
2.2 MUSCLE MOTOR UNIT
All joint movement either with or against gravity is synchronized through the interplay of three different functions that muscles can assume at different times. The first is when a muscle acts as the prime mover, or agonist. This is the term for whatever muscle creates the specific movement. An example of an agonist is the deltoid muscle in the upper outer arm initiating abduction of the humerus. Another example is the anterior tibialis of the lower anterior leg initiating the movement of dorsiflexion of the foot. Both of these muscles are originating the movement and thus are said to be agonists.
The second way a muscle can function is when it acts as the antagonist, in direct opposition to the agonist. The antagonist is the stabilizer of the movement. It acts as a brake on the movement. An example of a stabilizer, or antagonist, is the hamstring muscles when you run.
2.3 HAMSTRINGS, AS ANTAGONISTS OF HIP FLEXORS DURING RUNNING
During the act of running, one of the agonists is the hip flexors, that is, the iliopsoas muscles. When they contract, they bring the femur forward into flexion; the hamstrings, which are hip extensors, contract to slow the powerful momentum of the swinging leg as it goes forward. In this case, the hamstrings are the antagonists (Figure 2.3). They help to shape or stabilize the positioning of the femur as it moves forward, to keep it from going too far. If the hamstrings did not slow down the strong forward movement of the femur during running, the femur would move forward into a high kick.
Agonists and antagonists act together in a very special way that is controlled by a principle called reciprocal innervation. Innervation is the stimulation of a muscle by a nerve. In this case, the principle states that as contraction occurs in an agonist, or prime mover, contractile activity diminishes at an equal rate it its antagonist. An example is the action of the muscles around the knee.
When the quadriceps femoris muscle contracts, it extends the knee joint. When the hamstrings at the back of the thigh contract, they help to flex the knee joint. If both muscles are contracting at the same time with the same force, no movement will be possible. This may be very desirable if one wants to hold a position, for example, a partially bent but stabilized knee in Virabhadrasana II. But in order for movement created by the agonist to occur, the antagonist must release at the same rate that the agonist contracts. This allows for smooth and efficient movements.
The third type of muscle function is slightly more complicated to understand. This is when a muscle acts as a neutralizer. A neutralizer is a muscle that prevents one of the actions of an agonist. A perfect example is the action of the adductors of the thigh during Urdhva Dhanurasana. In order to practice this pose, the extensors of the hip joint must all be contracting strongly to overcome the force of gravity and thus lift the body up. These extensors include the extensors of the vertebral column and the extensors of the hip joint, which are the hamstring muscles, the posterior gluteus medius, the gluteus maximus, with some help from the hip external rotators. The actions of the gluteus maximus are twofold: extension of the hip joint (as previously mentioned) and external rotation of the hip joint.
When practicing Urdhva Dhanurasana, many teachers instruct their students not to externally rotate the hip joints, thus separating and rolling out the thighs, yet is it common to see students doing it. This external rotation is evidenced by the student’s feet turning out and the knees separating wider than the feet. When the femur externally rotates, this new relationship between the acetabulum and the femoral head interferes with the ability of the pelvis to move backward over the femoral head. The pelvis gets a bit stuck while trying to move backward when the femurs are in external rotation.
To feel this inhibition, stand on a nonskid mat with your feet 14 to 16 inches apart, turn your feet out, thus externally rotating the femurs, and move backward, as if you are going to drop back into a back bend. Note how your pelvis seems to get stuck in the process. Now try the same action with your feet turned inward; it will feel much easier and may relieve pressure or stress in your lower back as well.
Remember that the gluteus maximus does two things: extends the hip joint and externally rotates it. In Urdhva Dhanurasana, we want the hip extension aspect to lift the body from the floor. But most teachers do not want the external rotation aspect. What teachers often recommend is for the student to push the knees together, perhaps even adding a yoga block between the knees to press against.
This adduction movement of the thighs is created by the adductor muscles. The adductor muscles are the internal rotators of the hip joint, the opposite of the external rotators. Thus, by using the adductors in Urdhva Dhanurasana, the student is activating the adductors to act as a neutralizing agent against the external rotation component of the gluteus maximus muscle, while at the same time fully allowing the hip extension function.
EXPERIENTIAL ANATOMY
For Practicing
2.4 ANJANEYASANA, WITH BACK KNEE BENT
Applied Practice 1: Stretching Two-Joint Muscles
Props: 1 nonskid mat • a wall
Take Care: Balance can be a challenge, so use the wall if you need it.
PLACE THE SHORT END of your nonskid mat against the wall. Stand on the mat, facing the wall, and begin in Tadasana. For stability, you can place your left hand on the wall. Bend the right knee and catch your ankle with your hand, keeping your knees close together. Gently but firmly press your heel toward your buttock. This action will stretch the quadriceps femoris muscle over the knee joint. But because your hip is in neutral, you are not completely stretching the muscle. To do so, try the following pose.
Kneel on your mat and bring your right foot forward between your hands in Anjaneyasana (Figure 2.4). Keep your back leg straight at first, with your toes curled under, and press your pelvis down. Notice the stretch in the front of your back thigh. Now slowly begin to press your pelvis down, while slightly resisting from your back thigh. Lower your back thigh slowly but persistently. This will cause the quadriceps femoris to stretch, not only over the knee joint but also over the hip joint. The stretch will be more intense because it is over both joints of a two-joint muscle.
To continue the stretch, gradually bring your back knee to the floor, and then press forward a bit with your pelvis. You will feel even more stretch if you bring your back heel toward your buttock (as shown). If you try this movement, make sure you keep your pelvis down, and do not let it lift as the heel comes up.
2.5 GASTROCNEMIUS STRETCH, AT THE WALL
Make sure that your knee remains directly over your front heel throughout all these variations to protect your knee joint from strain. Hold each variation for several breaths and then release. Now get up and walk around the room to notice the difference in how your leg and hip feel. Be sure to repeat to the other side.
Another way to experience the effect of stretching a two-joint muscle is to stretch the calf. Two big muscles make up most of the calf, the more superficial gastrocnemius and the deeper soleus. The gastrocnemius arises from the medial and lateral epicondyles of the femur and the posterior head and upper shaft of the fibula, while the soleus arises solely from the posterior tibia. Both muscles insert with a common tendon, the Achilles, which is attached to the calcaneus bone.
To feel the difference between stretching the soleus, a one-joint muscle, and the gastrocnemius, a two-joint muscle, try the following. Face the wall and stand in Tadasana on your nonskid mat, and place your hands at shoulder level. Now step your right foot back about 12 to 18 inches. Make sure that your foot is straight, so the outside of your foot is parallel to the edge of your mat. Now lean forward by bending your left knee, while keeping your back heel firmly on the floor (Figure 2.5). You may need to adjust the position of your back foot by moving it backward or forward a bit. Continue to be meticulous about not turning your heel inward. This pose will stretch the gastrocnemius muscle across both joints, the knee and the ankle.
Now bend your back knee directly over the forefoot, without lifting your heel. This movement takes out the stretch of the gastrocnemius across the knee joint by releasing the stretch at that end of the muscle, thus focusing the stretch on the other end of the joint and on the soleus muscle (Figure 2.6). You will probably feel the stretch just from the mid-calf downward in the soleus as well as in the Achilles tendon. Throughout this stretch, remember to keep your breathing relaxed and natural. After stretching on one side, be sure to repeat on your left side.
2.6 SOLEUS STRETCH, AT THE WALL
Applied Practice 2: Focusing on Stabilization
Prop: 1 nonskid mat
Take Care: Lie in a symmetrical position. Do not lie on your back if you are more than four months pregnant.
LIE DOWN on your back on your nonskid mat as for Savasana, with your feet comfortably apart and your arms away from your torso, palms up (Figure 2.7). Close your eyes and relax for several cycles of breath. When you feel relaxed, try this experiment. First simply imagine that you are going to lift your straight right leg. Pay exquisite attention to what is happening in your body as you think the movement before actually performing it.
2.7 SAVASANA
The very first thing you will probably notice is your left abdominal muscles contracting. Very quickly you will probably begin to feel other muscles contracting, for example, your left gluteus maximus, left hamstrings, lower back muscles, even your shoulder muscles. Notice how you gradually recruit more and more muscles. The stronger the action (that is, the higher you lift your leg) either in reality or in your imagination, the more muscles are needed to stabilize the desired motion
For Teaching
2.8 UTTANASANA
Applied Teaching 1: Isolating the Hamstrings as a Limitation to Forward Bends
Prop: 1 nonskid mat
Take Care: Avoid this if your student is uncomfortable bearing weight on her knees. MANY YOGA STUDENTS have problems bending forward because of tight hamstring muscles, and yoga teachers are often concerned with how to help them. First have the student stand on a nonskid mat and come into Uttanasna (Figure 2.8). Notice how her pelvis is tilting forward to create the forward bend. Is her back rounded, or is her sacrum tilting down? Remember, the healthiest forward bends for the lower back are done with the pelvis tilting. The more the sacrum tilts, the more the hamstrings have to lengthen, and the more the action is created through the hip joints and not by the more delicate lower back flexing too much, thus putting pressure on the intervertebral discs.
Now, to ascertain whether the student’s difficulty is the direct result of tight hamstrings or instead a problem with her hip joints or lower back, try the following. Have her kneel down on all fours on a nonskid mat. Then ask her to move her tailbone down, which will create lumbar flexion, and then tailbone up, which will create lumbar extension (Figures 2.9 and 2.10). Her pelvis will very likely move quite freely up and down over the hip joints, even if she has tight hamstrings.
2.9 ALL FOURS, TAILBONE DOWN
2.10 ALL FOURS, TAILBONE UP
By placing her in the bent-knee position, you have eliminated the stretch of the hamstrings over the knee joint. Most students will find the tipping of the pelvis, which they found difficult in a standing forward bend, much easier to do on all fours.
If trying this movement on all fours has not improved her ability to move the pelvis, there is very likely some problem other than tight hamstrings, possibly a problem with her hip joint(s), and I would suggest she get a diagnosis from a health care professional trained in orthopedics. Once the student has experienced the ease of tipping her pelvis in a forward bend-like movement on her hands and knees on the floor, she will have a better idea of how to do it in Uttanasana. And as her teacher, you will have more confidence that her hips and back are healthy.
2.11 PRASARITA PADOTTANASANA
Applied Teaching 2: Making Hamstring Stretching Easier
Prop: 1 nonskid mat
Take Care: Make sure the student does not experience any lower back pain during this practice.
HELPING STUDENTS bend forward more easily is related to how far apart the legs are. When the legs are close together, the hamstrings are stretched directly in a straight line from hip joints to knees. When the student widens his legs in a pose such as Prasarita Padottanasana, the hamstrings are no longer in a straight line, and the stretch on them is less direct (Figure 2.11). The student will no doubt feel less stretch on the hamstrings in this position, and if hamstrings are his primary limitation, he will find Prasarita Padottanasana a much easier pose to practice.
LINK
To continue an in-depth study of the muscles and their actions, I recommend Muscles: Testing and Function, 4th ed., by Florence Peterson Kendall and Elizabeth Kendall McCreary (Philadelphia: Lippincott Williams & Wilkins, 1993).