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Understanding The Nature of Muscles‏

Updated on March 6, 2014

Functions of Muscles

Our posture and ability to move, as well as our ability to operate physiologically in the most optimal way; are all affected by patterns of muscular constriction; whether they are due to emotional or physical patterns of overuse.

All of us have patterns of constricted muscles, contracted in varying degrees that maintain a pattern of tight chronically utilized muscles. In order to understand the nature of injured muscle we first have to understand the nature of normal muscle.

In humans the musculature represents 40 to 50 percent of the total body weight and is considered as a single entity. It can be regarded as the body's largest internal organ. This distinguishes it from the body's largest external organ which would be the skin.

There are 3 primary functions of the muscles. First of all, they support the internal organs and allow movement of the organ infrastructures. Secondly, they support the body as a whole and allow movement of the whole body. Third, this movement creates heat, which helps the body to regulate the temperature.

Integrated Functioning

This movement of the musculature involves both voluntary and involuntary types of movement. Voluntary movement would have more to do with the integrated functioning of bones, joints, tendons, ligaments, muscles and fascia.

Fascia for those who don't know, is a clear thin membrane that wraps around every individual muscle in the body. If you've ever cleaned chicken, you've seen this clear, kind of whitish membrane around the chicken muscle. It's very strong and difficult to pull off the chicken. This is the fascia that is wrapped around all of our muscles as well. When the fascia gets tight, it restricts muscular activity.

Muscular activity includes the maintenance of our upright posture as well as all body movements - like walking, sitting, writing, chewing, breathing and so forth. The movement of internal organs relies on muscular activity. From the beating of the heart to the movement of the blood to the arterial vessels. From digestion to peristalsis to elimination; including the emptying of the bladder and the very ability to draw breath; all of these things are functions of the muscles.

Types of Muscle

There are 3 types of muscle: skeletal, visceral, and cardiac muscles, which provide these functions. These muscles have 4 principal characteristics. They are excitability, contractility, extensibility, and elasticity.

Excitability or irritability is the ability to receive or respond to stimuli via nerve impulses.

Contractility is the ability of the muscle to shorten when sufficient internal or external stimulus is received.

Extensibility is the ability to be stretched. Our muscles are much like rubber bands. If they're not used, their elasticity or extensibility weakens.

Finally, elasticity is the ability to return to normal shape after contractions or extension.

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Functional Capacity

Normal or healthy muscle feels supple and elastic, making the underlying structures easy to palpate through skeletal muscle. The consistency and plasticity of a normal muscle is uniform and there's no tenderness when its palpated. Healthy muscle contracts in response to nervous impulse, and returns to its normal shape after the contraction.

Dysfunctional muscle will contract but it will not return to normal shape after the contractions. Instead, it would be fixed in a short position and often results in local reduction of blood flow, lymph drainage and range of motion. Time causes dysfunctional muscles to become chronic, resulting in changes that are characterized by an increase in muscle tone, greater resistance to palpation and decreased suppleness.

A chronically dysfunctional muscle can no longer perform its activities at optimal levels. Because it's shortened, it can no longer perform at full range of contraction and release due to impaired range of motion, resulting in a weakened functional capacity.

Alignment & Postural Habits

There are 2 types of contraction of skeletal muscle. A phasic contraction is a contraction that is sufficient for the muscle to produce movement of the attachments. Phasic muscles tend to fatigue quickly because of a generally low capillary supply resulting in less blood flow.

Phasic muscles include the rhomboids, the middle thorasic portion of erector spinae, the lower and middle trapezius, the abdominal portion of the pectoralis major; triceps brachii; vastus medialis and vastus lateralis; gluteus maximus gluteus medius and gluteus minimus; rectus abdominus and the external and internal obliques. Most of these are muscles that are either in, or surrounding and supporting the back.

Tonic contractions happen when muscles produce a sustained or partial contraction of the muscle. At any given time, a portion of the muscle cells in the tonic muscle are contracted while others are relaxed. During a tonic contraction, individual motor units within the muscle fire asynchronously, there by relieving one another in a smooth and continuous manor. The individual motor unit does not function continuously, which results in a muscle contraction that can be held for long periods of time. However, because the fibers are not contracted at the same moment in time; the contractions do not produce movement of the skeletal attachments.

Postural or tonic muscles are considered to be anti-gravity muscles, in that they act in the maintenance of upright posture. The capillary supply to these muscles are generally high, therefore they do not fatigue rapidly. And contrary to phasic muscles, lactic acid production is minimal.

Postural muscles are generally considered to be the scalenes, sternocleidomastoid, levator scapulae, pectoralis major, biceps brachii, the cervical and lumbar portions of the erector spinae, quadratus lumborum, iliopsoas, the hamstring group (biceps femoris, semitendinosis, semimembranosus), rectus femoris, tensor fasciae latae, the adductor group ( aductor magnus, longus and brevis), pectineus, gracilis, piriformis, gastrocnemius, and soleus.

Constricted muscles contract in varying degrees and maintain patterns that can typically be seen in common postural habits. Habits such as holding the shoulders elevated, the chest constricted and dropped, the upper back rounded, or the lower back strongly arched, all contribute to chronically utilized muscles.

Proper body alignment and proper foot alignment are crucial in maintaining the suppleness of your muscles. Bad posture can be attributed to either habits or misalignment. Regardless, it's important to correct the alignment problems in order to prevent chronic muscular dysfunction.


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    • Etherealenigma profile imageAUTHOR

      Sandra M. Urquhart 

      6 years ago from Florida

      You're welcome Inglenook. Glad to be of service. Thanks for stopping by.

    • InglenookObserver profile image


      6 years ago from Southwestern Wisconsin

      These explanations with diagrams are very helpful. Thanks.

    • Etherealenigma profile imageAUTHOR

      Sandra M. Urquhart 

      6 years ago from Florida

      Thank you. I really try to educate people on this because most people do not understand very much about their bodies, and the medical community is misleading people for the most part, for a profit. Every day at work, I see evidence of how little people understand their bodies and why they are in pain. Since my job involves releasing their pain and thereby causing relaxation, I try to instruct them on how they can take a more proactive and preventative approach to self-care. Thanks again for stopping by.

    • The Dirt Farmer profile image

      Jill Spencer 

      6 years ago from United States

      Hi! I really learned a lot from this hub! Voted up & awesome. (:


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