Postural and Phasic Muscles

Muscle Classification System:

A Position Statement

B y Rodney Corn MA, PES, CSCS and the NASM Performance Team

When reviewing the variety of terms associated with muscle classification, it is apparent that many inconsistencies exist. This can be detrimental to the health and fitness professional who desires to effectively communicate with other related professionals. Furthermore, it can cause confusion and increase anxiety that may exist when learning the intricacies of kinetic chain concepts. Thus it is imperative that the National Academy of Sports

Medicine (NASM) provides a simplistic position on this matter. It must be stressed, however, that categorizations or generalizations made about the human body cannot encompass the vast variability that exist within this complex system. Any generalizations made in this statement are for ease of explanation, description and communication and should be interpreted with caution.

Background

Many different approaches have been taken to categorize muscle function and dysfunction. These include distinguishing muscles based more on their proposed functional abilities (postural/phasic and/or stabilizer/mobilizer) and reaction capacity (tight/overactive/hypertonic and weak/inhibited).

1,2 fiber type distribution (slow twitch/type I/slow oxidative/SO; fast twitch/type IIa/fast oxidative glycolytic/FOG; fast twitch/type IIb/fast glycolytic/FG) 3,4 and structural locale (local/global).

5,6,7

Position

While each of these can be rationalized for validity, the NASM has chosen to use the terms “local” and “global” muscles suggested by

Bergmark.

Ошибка! Закладка не определена.

The following text will expand the meaning of the terms local and global and explain the characteristics these muscles show a tendency to display in response to their environment.

Definition

It is often suggested that there are two interdependent muscular systems that enable our bodies to maintain proper stabilization while concurrently distributing forces for the production of movement. Crisco and Panjabi 8 have stated that this concept may stem from the great Leonardo Da Vinci.

Da Vinci suggested that muscles located more centrally to the cervical

spine (local) provided intersegmental stability (support from vertebrae to vertebrae) while the more lateral muscles (global) supported the cervical column as a whole to produce movement.

Local Muscles

The local muscles are predominantly involved in joint support or stabilization.


,9,10 They are not typically movement producers, but provide stability to allow movement of a joint. They usually are located in close proximity to the joint and often have a poor mechanical advantage for movement production.

11 They also have a broad spectrum of attachments to the passive elements of the joint that make them ideal for increasing joint stiffness and thus stability.


, Ошибка!

Закладка не определена.

,12,13,14

A list of common local muscles include the:


, Ошибка! Закладка не определена.

,15





 Deep cervical flexors

 Rotator cuff

 Rhomboids

Mid and lower trapezius

Transversus abdominis





Multifidus

 Diaphragm

 Muscles of the pelvic floor

Gluteus medius and minimus

 External rotators of the hip

 Vastus medialis obliquus

Global Muscles

The global muscles are predominantly larger and responsible for movement. They consist of more superficial musculature that attach from the pelvis to the rib cage and/or the upper and lower extremities.

Ошибка!





,i16 They are associated with movement of the trunk and limbs and equalizing external loads placed upon the body.


They also are important for transferring and absorbing forces from the upper and lower extremities to the pelvis.


The major global muscles include the:


, Ошибка!



 Sternocleidomastoid

 Upper trapezius

 Levator scapulae

 Pectoralis major

 Deltoid

 Latissimus dorsi

 Rectus abdominis





External obliques

 Erector spinae

Gluteus maximus

 Hamstrings

 Rectus femoris

 Iliopsoas

 Adductors

 Gastrocnemius/soleus

Concepts

To properly rationalize a general classification scheme for muscle function and dysfunction, it is important to review some basic concepts that will help to illuminate how muscles move and respond to movement and their environment. First and foremost, we must highlight some very important constants concerning the human body and movement:


,17,18,19,20

1.

All humans have similar structure and function

2.

All humans act under the constant force of gravity

3.

All muscles are capable of providing stabilization in some capacity

4.

All movement and muscle is controlled by the nervous system

The Nervous System

Ironically, it is the fourth constant, the nervous system, that allows for the most variability within the human body and is often the most overlooked.

Panjabiii 21 has alluded to the importance of the nervous system working in concert with muscular and articular systems in controlling stabilization and movement. Bullock-Saxton


noted that some muscles as a result of the location would work against gravity more so than other muscles. In turn, this will influence the sensory input into the nervous system from muscles and joints that can alter interpretation and responding actions.

Research has also demonstrated that by changing the frequency of stimulation to a motor unit, the biochemical properties can change (i.e. slow twitch muscle fiber that is rapidly stimulated converts to fast twitch fiber and vice versa).

22,23,24,25 This type of response has been noted in the transversus abdominis.


The nervous system also plays a major role in the inhibition of muscles either through pain or as a result of reciprocal inhibition.



,26,27,28,29 Inhibition of a muscle is a decrease in the neural drive to that muscle that reduces its ability to respond to stimuli with proper timing Ошибка! Закладка не определена.

, Ошибка!


and can thus result in a loss of proper strength

(weakness).

Pain is highly influential on the nervous system. Research has demonstrated alterations to afferent and efferent motor responses in the presence of pain.

30,31,32 This often effects the local muscles as they have been shown to have a propensity to inhibition as a result of pain.

Ошибка!


,


,


,iii33

Reciprocal inhibition is a principle whereby a tight muscle will cause decreased neural input to its functional antagonist (inhibition).




, Ошибка!





Electromyographic (EMG) data has demonstrated that tight muscles have a propensity to activate (simulate concentric action) easier and at times when they would normally remain less active.



, Ошибка!


Tightness is characterized by a decrease in the resting length of a muscle as well as the common occurrence of overactivity

(heightened neurological state).






Global muscles show a propensity to becoming tight.

Ultimately, the nervous system dictates the status of muscles and their function. It is the nervous system that creates inhibition either through pain or as a result of antagonistic muscle tightness/overactivity.

Rationale

It is known that non-diseased humans have near identical neuromusculoskeletal structure and perform a variety of similar activities under the constant force of gravity. Thus it can be deduced that the human body will respond to stimuli in a similar manner. Therefore, generalizing musculature within the human body can be justified for ease of description and communication.

The NASM has chosen to address and categorize muscles as “local” and

“global”. These terms, when defined, promote an awareness of the muscles location that has a major influence on their biomechanical function.


,


,


In contrast, muscles that are labeled as “postural” and “phasic”

or “stabilizers” and “mobilizers” make reference to a specific action that can more easily be misconstrued.

Postural and Phasic

Support for this statement lies in the previously mentioned third and fourth constants. The terms postural and phasic denote actions performed based upon fiber type. Postural being predominantly slow twitch/type I/SO and phasic being fast twitch/type IIa/FOG.


, Ошибка!


However, in the fourth constant it is stated that all movement and thus muscle is controlled by the nervous system. As the nervous system is designed to be highly adaptable, it can alter the stimulation and response of effector motorneurons.


,


,


,34

Research has demonstrated that change in nervous stimulation to a motor unit, such as that seen in disuse or injury, can alter the physical characteristics of that motor unit.



,


For example, a type I motor-unit stimulated at a high frequency will change in physical characteristics to a type II and/or vice versa.

35

Therefore it is the nervous system and not necessarily the fiber type distribution within the muscle that is ultimately responsible for the muscle action.

Stabilizer and Mobilizer

The terms stabilizer and mobilizer again refer to a specific action performed by the muscle. Inconsistency can arise from the third constant, which stated that all muscles are capable of providing stabilization in some capacity. The best way around this is delineating primary, secondary and tertiary stabilizers, which many professionals do use. Thus it might be bet ter to just use the term “stabilizers” with varying degrees of stabilization

(primary, secondary and tertiary). In either case, the premise is still being placed on the action of the muscle that can be directly influenced and changed by neural input.

Local and Global

The terms local and global simply refer to the location of the muscle in relation to the joint of motion. Local and global muscles are deemed more prone to stabilization not based upon fiber type, rather on their biomechanical advantage (or disadvantage) relative to the joint. The smaller the moment arm (leverage system) of the muscle, the less torque or motion (concentric/eccentric action) it will be able to induce. Thus by

default, they may be better delegated to stabilizing (isometric action).

Conversely, a larger moment arm generally indicates a muscle’s greater distance from the joint and the greater potential to manipulate movement.



,36

Conclusion

There is much confusion among heath and fitness professionals pertaining to terminology used for muscle classification. Many professionals use terms that are pertinent to specific actions of muscles based upon their fiber type. However, as all motion and muscle is controlled by the nervous system, research has shown that these actions and characteristics can be altered via neural input.



,


,


,



Therefore, classification based upon specific fiber type actions may be misleading.

The NASM has chosen to u se the terms “local” and “global” muscles to denote differences in musculature. This system of classification is based upon physical location and biomechanical properties rather than fiber type distribution.

Local muscles are biomechanically less advantageous to manipulate movement of a joint and thus may be better suited for stabilization. These muscles show a propensity to inhibition, defined as a decrease in the neural drive to a muscle that reduces its ability to respond to stimuli with proper timing



and can thus result in a loss of proper strength (weakness).

Global muscles have greater biomechanical advantages to manipulate movement of a joint(s). These muscles show a propensity to become tight, defined as a decrease in the resting length of a muscle as well as the common occurrence of overactivity (heightened neurological state).

Ошибка!


,


,




Many classifications exist and all can be rationalized to make sense in certain populations. The key is to develop them so they make sense in any population. Ultimately, this can only be achieved through proper definition and rationale that comes as a result of a genuine concern to illuminate the most pertinent applicable information. The NASM has taken the industry up on this offer and delivered a proposal for muscle classification. Please remember that the human body is very interdependent and complex. No categorization that attempts to generalize the systems of the body will be able to precisely simplify this complexity. However, for ease of explanation,

education and communication, we must strive to create accurate simplicity of the human body.

References

1.

Jull G, Janda V. Muscles and motor control in low back pain: assessment management. In Twomey L (ed.). Physical therapy of the low back. New York:

Churchill Livingstone; 1987.

2.

Bullock-Saxton J, Janda V, Bullock M. Reflex activation of gluteal muscles in walking. Spine 1993; 18:704.

3.

Hu J. Stimulation of craniofascial muscle afferents inducing prolonged facilitory effects in trigeminal nociception brainstem neurons. Pain 1992; 48:53.

4.

Liebension C. Integrating rehabilitation into chiropractic practice (blending active and passive care). Chapter 2. In Liebenson C (ed.). Rehabilitation of the Spine.

Baltimore, Williams and Wilkins, 1996.

5.

Bergmark A. Stability of the lumbar spine. A study in mechanical engineering. Acta

Ortho Scand 1989;230(suppl):20-4.

6.

Richardson C, Jull G, Toppenberg R, Comeford M. Techniques for active lumbar stabilization for spinal protection. Australian J Physiother 1992; 38:105-12.

7.

Norris C. Functional load abdominal training. J Bodywork Movement Ther 1999;

3:150-8.

8.

Crisco JJ, Panjabi MM. The intersegmental and multisegmental muscles of the spine: A biomechanical model comparing lateral stabilizing potential. Spine

1991;7:793-9.

9.

Richardson C, Jull G, Hodges P, Hides J. Therapeutic exercise for spinal segmental stabilization in low back pain. London: Churchill Livingstone; 1999.

10.

Bastide G, Zadeh J, Lefebvre D. Are the little muscles what we think they are?

Editorial. Surg Radiol Anat 1989; 11:256.

11.

Boduk N. Clinical Anatomy of the Lumbar Spine. 3 rd edition. New York: Churchill

Livingstone; 1997.

12.

Norris C. Response from Chris Norris. Position statement. J Bodyworks Movement

Ther 4(4):232-5.

13.

Clark MA. Integrated training for the new millennium. Thousand Oaks, CA:

National Academy of Sports Medicine; 2001.

14.

Clark MA. An integrated approach to human movement science. Thousand Oaks,

CA: National Academy of Sports Medicine; 2001.

15.

Janda V: Muscle Function Testing. London: Butterworth; 1983.

16.

Lee D. The pelvic girdle. London: Churchill Livingstone; 1999.

17.

Bullock-Saxton J. Response from Joanne Bullock-Saxton. Position statement: a global view. J Bodyworks Movement Ther 4(4):227-9.

18.

Murphy Dr. Response from Donald R. Murphy. Position statement. J Bodyworks

Movement Ther 4(4):229-32.

19.

Richardson C. Response from Carolyn Richardson. Position statement. J

Bodyworks Movement Ther 4(4):235-36.

20.

Tunnell PW. Response from Pamela W. Tunnell. Position statement. J Bodyworks

Movement Ther 4(4):237-41.

21.

Panjabi MM. The stabilizing system of the spine. Part 1. Function, dysfunction, adaptation, and enhancement. Spinal Disord 1992; 5:383-9.

22.

Buller AJ, Eccles JC, Eccles RM. Interaction between motorneurons and muscles in respect of the characteristic speeds of their responses. J Physiol 1960; 150:417-

39.

23.

Al-Amood WS, Buller AJ, Pope R. Long-term stimulation of cat fast twitch skeletal muscle. Nature 1973; 244:225-7.

24.

Dubowitz V. Cross-innervated mammalian skeletal muscle: histochemical, phyusiological and biomechanical observations. J Physiol 1967; 193:481-96.

25.

Hennig R, Lomo T. Effects of chronic stimulation on the size and speed of longterm denervated and innervated rat fast and slow skeletal muscles. Acta

Physiologica Scand 1987; 130:115-31.

26.

Clark MA. A scientific approach to understanding kinetic chain dysfunction.

Thousand Oaks, CA. The National Academy of Sports Medicine; 2001.

27.

Bullock-Saxton JE: Muscles and Joint: Inter-Relationships with pain and movement dysfunction. University of Queensland. Course Manual, 1997.

28.

Chaitow L: Muscle Energy Techniques. New York: Churchill Livingstone; 1997.

29.

Hammer WI. Muscle imbalance and postfacilitation stretch. Functional Soft Tissue

Examination and Treatment by Manual Methods. In Hammer WI (ed.). 2 nd edition.

Gaithersburg, MD: Aspen Publications; 1999.

30.

Grubb A, Stiller R, Schaible HG. Dynamic changes in the receptive field properties of spinal cord neurons with ankle input in rats with chronic unilateral inflammation in the ankle region. Exp Brain Res 1993; 92:441-52.

31.

Schaible HG, Grubb B. Afferent and spinal mechanisms of joint pain. Pain 1993;

55:5-54.

32.

Mense S, Simons DG. Muscle pain: understanding its nature diagnosis and treatment. Philadelphia: Lippincott Williams & Wilkins; 2001.

33.

Hopkins JT, Ingersoll CD, Krause BA, Edwards JE, Cordova ML. Effect of knee joint effusion on quadriceps and soleus motorneuron pool excitability. Med Sci

Sports Exerc 2001; 33(1):123-6.

34.

Romanul FCA, Van Der Meulen JP. Slow and fast muscles after cross innervation.

Enzymatic and physiological changes. Arch Neurol 1967; 17:387-402.

35.

Gunderson K, Leberer E, Lomo T, Pette D, Staron RS. Fibre types, calciumsequestering proteins and metabolic enzymes in denervated and chronically stimulated muscles of the rat. J Physiol 1988; 398:177-89.

36.

Hodges PW. Is there a role for the transversus abdominis in lumbo-pelvic stability?

Man Ther 1999; 74-86.

Disclaimer

No warranty is given as to the accuracy of the information on any of the pages in this website. No responsibility is accepted for any loss or damage suffered as a result of the use of that information or reliance on it. It is a matter for users to satisfy themselves as to their or their client’s medical and physical condition to adopt the information or recommendations made. Notwithstanding a users medical or physical condition, no responsibility or liability is accepted for any loss or damage suffered by any person as a result of adopting the information or recommendations.

© Copyright Personal Training on the Net 1998 2004 All rights reserved

Postural and Phasic Muscles

Muscle Classification System:

A Position Statement

Related documents

Products

Support

Postural and Phasic Muscles

Muscle Classification System:

A Position Statement

Related documents

Add this document to collection(s)

Add this document to saved

Suggest us how to improve StudyLib