Understanding Your Muscles and Muscle Injury

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Muscles are one type of tissue we take for granted.  They work with us not just when we are running or typing or working or playing, but when we are breathing, sleeping, eating and even thinking.  Injury to muscle tissue is a complicated affair that can not only be disabling, but can mimic other types of illnesses creating symptoms that can be misdiagnosed and mistreated for years. 

So let's begin by understanding everything we can about muscles. 

The Minutiae of Muscle Tissue

Muscle tissue is one of the two highly specialized tissues the body contains, with purposes ranging from generating a contractive force for movement to maintaining posture and even generating heat by converting chemical energy into mechanical energy. The word muscle comes from the words meaning "little mouse" derived from early hunters who would stimulate an exposed muscle in living tissue, creating a tremor that would pass the length of the muscle resembling a scurrying mouse. Muscle tissue by nature is pale white, but appears red because of the large amounts of blood flow in muscle. Muscle tissue constitutes 40-50% of our total body weight and is the way our body generates heat. This is because most muscle contractions produce only 15% movement / work and 85% heat.  Often when you experience excessive body heat it can be from muscles in spasm.

Each muscle has between 200,000 and 300,000 fibers. The muscles utilize the bones and connective tissue in order to provide for posture. They supply the tension that holds the musculature erect much like a suspension bridge. The ability of skeletal muscles to perform efficiently is determined by their relation to gravity and the stability of the structure. By stability, we mean the relation of the structure to the center of gravity, which must fall within the foot base (directly in the center between your feet). Stability will be greater when the center of gravity is lower. Also when muscular work involves lifting, the closer the load amount is to the joint, the less effort it will require. Joint structures are the crucial connections between the muscle tissue and the connective tissue. Consider the effect of muscle relaxants or general anesthesia, which block nerve impulses to the muscles. Not only does it block muscle contraction and movement, it blocks the link to connective tissue.

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Each muscle cell is called a muscle fiber and contains strands of proteins arranged into small compartments called sarcomeres. When a nerve stimulates a muscle fiber or group of fibers, the neurotransmitter chemical acetylcholine is released across the gap between the end of the nerve and the muscle fiber itself. This then stimulates the sarcoplasmic reticulum to release calcium into the cellular fluid. Then ATP is split to release energy, causing the sarcomeres to slide toward each other creating a contraction, the byproduct of which is heat. This contraction will be sustained as long as there is calcium present. An interesting note is that caffeine causes the spontaneous release of calcium, accounting for the energy burst and muscle tension that caffeine creates.

The Creation of Muscle Energy

Muscle cells contain multiple nuclei and large amounts of mitochondria to accommodate the need for various levels of energy. Understanding the creation of energy in the muscle can also help deal with muscle strain and muscle pain. Each muscle, whether voluntary or involuntary has four ways of creating energy, and they operate in a specific order. First, the mitochondria (the "powerhouse" of every cell) utilize glucose and oxygen to synthesize ATP(adenosine triphosphate). The ATP will then be split to release energy when calcium is released within the muscle cell. This stage will last as long as there are sufficiently high levels of calcium and the availability of ATP. There is generally only enough ATP present in the muscle tissue to last a few seconds. When that runs out, additional ATP must be produced to sustain the contraction.

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The next phase is to create additional ATP by using creatine phosphate found naturally in muscles and adding that to ADP(adenosine diphosphate). This will produce enough ATP energy for an additional 15 seconds. When the creatine phosphate is depleted, then the muscle turns to glucose to generate ATP. This is accomplished through a series of reactions known as glycolysis, which produces ATP and pyruvic acid, a process that is anaerobic, i.e. does not require oxygen. This process can provide enough energy for about 30 to 40 seconds. An additional amount of glucose can be derived from glycogen stored in the liver. However, the by-product of this entire phase is lactic acid, which if not removed by the circulation, can be an irritant to muscle tissue. Think of the burning sensation in the muscle.

When muscular activity lasts longer than 30 seconds, the mitochondria begin to oxidize the remaining pyruvic acid created during glycolysis in order to make ATP. Although this is slower, it is longer-lasting than glycolysis and can generate much more ATP. An essential part of this process is the presence of oxygen, which can be derived from the hemoglobin in the blood and the myoglobin in the muscle fibers. So if someone is asthmatic or has a decreased capacity for oxygen absorption, then their muscular energy will be compromised.

All of these chemical reactions can be enhanced by the introduction of heat, which increases molecular motion, thus creating faster muscular reaction time. This is the main reason for "warming up". Another important aspect of muscular contraction is its relationship with the nervous system, as it is the motor nerves that produce muscular contraction. Damage to the motor nerves can deteriorate muscular ability and health. Damage lasting years will cause the cells to break down, dispersing the sarcomere proteins and replacing them with connective tissue or fat. This will make the muscle inactive and atrophied.

Muscles in Movement

So when we look at the body, we see the muscles and bones working together through the action of pulling. By examining the angles of pull, we can see where muscles are pulling too much, even when they should be at rest. This is especially evident in the muscles of posture. Over time, contracting these muscles does not change their length, because they are already semi-contracted, instead only the internal muscle tension increases. This is identical to what happens in isometric or static exercise. These are the muscles that will suffer from fatigue, partly because the static state reduces the pumping action that muscles have when contracting and relaxing. Use of the same muscles over and over cannot only cause fatigue, but spasms and fibrosis. So performing more isotonic movement where muscle tension increases with a change in muscle length is actually healthier for the life of the muscle.

This focus on muscular movement also hones a very important connection with the nervous system: kinesthetic or proprioceptive sense. This is the awareness and continual arrangement of the body during movement and positioning, particularly in relation to the surroundings. It is this connection with the nervous system that gave rise to the concept of kinesiology, the study of the moving body. This sense allows us to be aware without looking, to move without thinking, to judge movement relative to our environment. Proprioceptive receptors allow us to be aware constantly of necessary adjustments that we have to make in our body position. It helps to develop our muscle coordination and our posture. Many of these receptors are found along tendons and ligaments as well as interspersed within the fascia of the muscles. These receptors are also highly sensitive to caffeine, stimulants, alcohol and toxic metabolites. Accumulation of these or regular influxes of these chemicals can change the sensitivity of these receptors making them less sensitive, and therefore we become less coordinated in movement, or more sensitive, causing our stress level to rise with movement.

A muscle's ability to contract or to stretch is greatly controlled by the connective tissue surrounding the muscle as well as the action of stretch receptors. Three layers of deep fascia surround the muscle, extend through the muscle and hold the muscles together in functional groups. These layers provide protection and strength to the muscle tissue, but when stiff and shortened, the fascia can also be a straightjacket. That is because a contracting muscle increases in volume, an expansion that can be confined by the fasciae surrounding the muscle. This increases the pressure between the tissues. By addressing this restricted fascia the pressure and tension in the muscle can be reduced by up to 50%.

Understanding Why Muscles Fail

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Muscles have four characteristics which contribute to muscular dysfunction: excitability, contractility, extensibility and elasticity. Different muscle fibers have different abilities for contraction, extension, elasticity and how much nerve stimulation is required for them to contract.

Then there are two types of voluntary muscles based on the speed of contraction and fatiguability.  Phasic muscles are comprised primarily of fast-twitch fibers which tend to produce rapid contractions and therefore function to produce rapid movements. They have a low capillary supply and so tend to fatigue quickly and will experience a rapid accumulation of lactic acid as a metabolic byproduct. In the presence of muscular dysfunction they tend toward weakening.

Postural or tonic muscles produce a sustained partial contraction of the muscle known as tonic contraction. In this contraction motor units fire consecutively to relieve each other in a smooth and continuous manner, sustaining contraction over a long period of time. They are comprised of mainly slow-twitch fibers and so have a high capillary supply preventing fatigue. When there is muscular dysfunction with these type of muscles, they will tend toward shortening.

If oxygen is present, cells will work to create energy aerobically, whereas when oxygen is lacking, the cells must revert to anaerobic energy production. The number of phasic muscle fibers vs. tonic muscle fibers can determine a person's oxygen endurance and when their muscles will fatigue. For instance, marathon runners need large numbers of tonic muscle fibers which will allow them to sustain muscular function over a long period of time. Many of our somatic muscle cells are designed to be aerobic or anaerobic, but not both. So when an environment exists that is not supportive of cellular energy, only part of our body is able to function.

Sustaining Dysfunction and Injury

  • Pelvic Imbalance - if you are standing, sitting, running or jumping, you are using the pelvis. If the pelvis is not balanced, then the muscles that control lateral movement, rotation or striding, can become fibrotic, inflamed and eventually distorted. This makes them susceptible to shortening, weakening and tearing, and is the primary contributing factor to groin pulls, sciatica and hernations of the lumbar discs.
     
  • Misfitting Furniture - don't laugh, but you need more than just great-fitting clothes. Furniture can oftentimes cause a tiring and strain of postural muscles. Seating should be such that, as the muscles relax and the body tends to sag, correct posture is maintained by the chair and not by sustained effort of the muscles. The chair should do all the work.
     
  • Poor Posture - you can develop distortions in muscle balance and angles of movement simply by the use of the body unevenly.  Examples would be deafness in one ear, sitting on one leg, pulling the left leg up while driving, pitching a baseball over and over and over again.
     
  • Abuse of Muscles - this means especially too many repetitions of the same movement or quick, jerky movements, particularly without allowing sufficient recovery time between times of use. Even something as simple as placing body weight mainly on one leg, pressing down while writing or painting a ceiling can create overuse of muscles. This is the typical issue with "weekend warriors".  Common signs of this are bursitis, sciatica, carpal tunnel and headaches.
     
  • Prolonged Immobility - when a muscle is in the shortened position for a lengthy period of time, it tends to aggravate and perpetuate myofascial trigger points. This commonly occurs when people sleep in a position that places the muscle in its shortest length. Also when the muscle cannot be moved through its full range of motion due to a fracture or articular disease. Even guarding against movement due to pain can cause aggravation to trigger points and resulting contraction and restrictive fibrosis.
     
  • Emotional Posturing - think of something you're afraid of ... your posture will change.  This is an example of emotional posturing.  Painful injury, physical abuse, surgery, accidents, deference, military stances, fear, anxiety, depression ... these are all written across your muscles and your body.  Your body's intention is to protect you by anticipating injury, but this can become a habitual muscular posture.
     
  • Prolonged Constricting Pressure - constriction pressure of a muscle such as by a heavy purse strap or a narrow bra strap which grooves the upper trapezius or may be too tight around the latissimus can wreak havoc with blood flow, lymphatic immunity and removal of metabolites from the muscle tissue. Constriction from support hose compromises the gastrocnemius, a tight shirt collar or necktie constricts the sternocleidomastoid, and everything from headaches to fibrosis can be the result.
     
  • Low Levels of Water-Soluble Vitamins - B1, B6, B12 and folic acid are frequently responsible when only transitory relief is obtained by massage therapy of the muscles. These inadequacies impair the energy metabolism needed for the contraction of muscles and increases the irritability of the nervous system. Vitamin B1 is necessary for the synthesis of neurotransmitters and for energy and is a particular problem in alcoholics. Vitamin B6 (pyridoxine) is essential to the metabolism of many proteins including several neurotransmitters. Forms of Vitamin B12 are critical for energy and protein metabolism. Combined with folic acid, these vitamins are required for the synthesis of DNA and normal development of the nervous system. Vitamin C deficiency causes post-exercise stiffness, particularly in smokers and increases capillary fragility.
     
  • Toxic Levels of Fat-Soluble Vitamins - A, D and E may cause bone or joint pain and severe throbbing headaches if stored in high levels in adipose or fat tissue surrounding the muscles.
     
  • Adequate Amounts of Trace Minerals - calcium, potassium and iron are essential for normal muscle function. Borderline anemia is an important factor and may actually increase the irritability of myofascial trigger points. Calcium controls muscle contraction while potassium is needed for rapid repolarization of muscle and nerve cell membranes after stimulation. Iron is essential within myoglobin and hemoglobin to transport oxygen to and within muscle fibers.
     
  • Low Thyroid conditions - even slightly low thyroid function, even with medication, may still be enough to cause muscular aches and pains or stiffness of muscles. Chronic fatigue upon arising and then worsening at midafternoon as well as cold intolerance and "weather conscious" muscular pain is common.  Constipation is another muscle reaction to low thyroid function. Even if blood testing shows normal TSH levels, there may still be a low thyroid situation. 
     
  • Hypoglycemia - this is a condition where the blood glucose levels critical for energy, are allowed to get too low creating symptoms of dizziness, headaches and irritability.  When glucose availability and processing within the body is impaired, muscles and nerves will suffer, as glucose is the main energy-supplying molecule for their function. Also this may cause an increase in circulating epinephrine leading to anxiety and secondary muscular contraction.  Higher levels of epinephrine can increase heart rate and breathing, both muscular functions, depleting essential reserves for the muscles of movement.
     
  • Hyperuricemia (gouty arthritis) - muscular rheumatic complaints are a common feature of this condition.  Excessive amounts of uric acid is deposited generally in the big toe, the furthest point of circulation.  This irritates, inflames and erodes the joint causing painful muscle cramping and sensitive nerve fibers.  Cases of plantar fascitis are often the result of undiagnosed gout. 
     
  • Dehydration - Another important factor affecting muscle tissue health is hydration. Muscles which are full of metabolic waste materials, such as lactic and pyruvic acid, tend to be in a state of dehydration and hypertension, which will increase postural distortion.  Flushing out muscle tissue regularly with water is essential, but if there isn't enough water, the mineral salts and acids in the muscle tissue can crystallize causing irritation and inflammation. 

The Cascade Effects of Injury

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Once a muscle has been injured, the stroma provides new tissue for repair. This process is called fibrosis and generally occurs in deeper wound healing. A natural part of this repair process is inflammation. Inflammation will be stimulated in the event that natural tissue and its component cells die, a process known as necrosis. In necrosis, there is a degeneration of the natural activity of the cell, whether slowly or suddenly, and so the cell will swell causing it to burst. Sometimes this can even happen as a result of lack of oxygen, which research has demonstrated occurs in brain cells with large amounts of alcohol consumption. The alcohol overwhelms the lysosomes of the cells, causing the cell to begin to degenerate.

Different cells in the body have different periods of time that they can withstand oxygen deprivation, for instance brain cells can survive for 4 minutes while muscle tissue in the leg can survive for 30 minutes. Muscle fatigue is the first sign that the oxygen supply has been depleted in a particular muscle. Once this occurs the toxic metabolic wastes such as lactic acid and pyruvic acid accumulate and cannot be removed because of the fatigue of the. In fact, chronic overuse of muscles causes spasms and fibrosis.

As the body responds to the chemical changes that occur within the affected cells, histamine is released from mast cells. This causes congestion of the area with blood and lymph to prevent infection. A blood clot will immediately form by the platelets of the blood to close the gap produced by the dead tissue. The cascade of the blood clotting factors will cause the release of serotonin, which acts as a sensitizing agent, making the area sensitive to touch and movement. This sensitizing factor can become a chronic problem if serotonin continues to be released, or re-injury occurs.

The excess fluid in the area following the clot and inflammation produces swelling which increases pain by pressing on the sensory nerve endings. Over time, fibroblasts produce the new permanent scar tissue to close the gap left in the muscle fibers. This is because in muscles, the stem cells also known as satellite cells, which are present for repair, do not divide rapidly enough to replace damaged skeletal or cardiac muscle fibers. Therefore the only option for muscle repair is scar tissue. Scar tissue is similar in composition to connective tissue, but lacks its thixotropic nature and flexibility. Think of the body builder whose muscles are enlarged with the presence of large amounts of scar tissue.

Unfortunately, this repair process may not always occur in optimal fashion. Many times toxic material or dead material can become trapped in the area, sustaining the inflammation. This is particularly true if the body is very toxic to begin with, or if blood flow has not been efficient at removing metabolic wastes such as lactic or pyruvic acids. Another problem is the alignment of tissue. When scar tissue forms, the fibers are laid out in patterns that are dictated by movement and physical stress. When aligned properly, they do not significantly restrict proper alignment and movement. However, if extensive range of motion is not introduced during the healing process, because of pain or immobility, and then the fibers are spread out randomly over the damaged area, normal movement will be restricted, future blood flow will be compromised and muscle function will lessen.

Years of Guarding

The end result for many people is years of pain, inflammation and unresolved illness.  And it all began with a simple injury that should have healed, but couldn't.  Many times after an injury, the pain may subside, either naturally or with pain killers and cortisone injections.  But it doesn't mean that healing has taken place.  The muscles will compensate for unresolved injury, creating patterns of walking, breathing, turning the head that are not natural.  Simply by looking in the mirror, you can see the result of these compensations.  Are your shoulders even?  Are you walking with your feet straight or are they turned out?  Are you walking evenly on both legs?  Are your muscles stiff when you wake up in the morning until you get going with your day? 

Chronic pain is often just the body's way of avoiding further injury.  Active trigger points develop habits of guarding that limit movement of the original injury area.  Chronic muscular pain, stiffness and dysfunction are the result. This type of chronic pain will be present all the time as a  dull ache.  But do something out of the ordinary, or a bit extreme and the result will often be deep intense pain that can vary from low-grade discomfort to severe torture. It may occur at rest or only with motion and is rarely completely symmetrical on both sides of the body.

Without identifying the history of injury, it is difficult to identify the path to healing.  But when you are sitting, standing, walking, running or even just lying down, take a moment to truly ask yourself what is the cause of your pain... you will often get exactly the answer you need, and then healing can begin.

Karen Clickner