Norris Functional Load Abdominal Tring Part 1

*c 2001 Harcourt Pub

Original Research

C. M. Norris

MSc MCSP,

Barkers Lane, Sale,

Cheshire M336RP,

UK

Correspondence to:

C.M.Norris.Tel.: 0161

972 0512; E-mail:

cnorris500@AOL.

com

Functional load abdominaltraining: part 1C. M. Norris

This article reviews the principles of muscle imbalance relevant to abdominal training. Mobilisor

and stabilisor muscle categories are described and muscle length adaptation is discussed.

Examples of individual muscle tests to determine muscle lengthening and muscle shortening are

given. Concepts of trunk stability are considered and integrated into abdominal training.*c 2001 Harcourt Publishers Ltd

Introduction

Abdominal training is a popular aspect of any®tness programme. Recreational ®tnessactivities tend to emphasize the cosmeticaspects of training, seeking a `¯at stomach' or`slip waist'. Sport-based programmes on theother hand often stress the importance of astrong mid-section to enhance sportsperformance and reduce the risk of back injury.Both of these approaches hold merit fordifferent target populations. The aim of thisarticle is to review abdominal training withrespect to both training effectiveness, and injuryprevention, opening abdominal training tosubjects from a wider range of ®tness levels.

Muscle imbalance

New concepts of muscle training

Popular training programmes for theabdominal muscles tend to emphasize strength

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Box 1 Muscle categories

Stabilisors

. Deeply placed

. Aponeurotic

. Slow twitch nature

. Active in endurance activities

. Selectively weaken

. Poor recruitment, may be inhibited

. Activated at low resistance levels (30±40% MVC)

. Lengthen

by using the muscles as prime movers. Sit-upactions with or without rotation, and leg raiseexercises often form the bases of manyprogrammes. However, one of the mostimportant functions of the abdominal musclesis to stabilize the spine (Norris 1995) a featureoften neglected, especially in sport.

Owing to anatomical, biomechanical andphysiological features muscles may becategorized into two groups, stabilisors andmobilisors (Richardson et al. 1992). The maindifferences between these two musclecategories are shown in Box 1. The structuraland functional characteristics of the two musclecategories make the stabilisors better equippedfor postural holding with an `anti gravity'function. The mobilisors are better set up forrapid ballistic movements and are often referredto as `task muscles'. In the case of theabdominal muscles (Box 2), the rectusabdominis and lateral ®bres of external obliquemay be considered as the prime movers

Physical Therapy In Sport (2001) 2, 29±39 29

032, available online at http://www.idealibrary.com on

Mobilisors

. Super®cial

. Fusiform

. Fast twitch nature

. Active in power activities

. Preferential recruitment

. Shorten and tighten

. Activated at higher resistance levels(above 40% MVC)

30 Physical The

Physical Therapy in Sport

Box 2 Trunk muscle categorization

Stabilisors Mobilisors

Primary Secondary. Transversus abdominis . Internal oblique . Rectus abdominis. Multi®dus . Medial ®bres of external oblique . Lateral ®bres of external oblique

. Quadratus lumborum . Erector spinae

(mobilisors) of trunk ¯exion, while the internaloblique and transversus abdominis are themajor stabilizers of trunk movement in general.These muscles are the only two which passfrom the anterior trunk to the lumbar spine(Miller & Medeiros 1987), and are criticallyinvolved in stabilization (Cresswell et al. 1994,Hodges & Richardson 1996).

Further categorization may be made intoprimary and secondary stabilisors. The primarystabilisors are those muscles which cannotcreate signi®cant joint movements, such as themulti®dus and transversus abdominis. Thesemuscles act only to stabilize. The secondarystabilisors, such as the internal oblique, haveexcellent stabilizing capacity, but may alsomove joints. Taking this categorization further,mobilisors could be termed `tertiary stabilisors'in that they primarily move the joint, but canstabilize in times of extreme need, an examplebeing muscle spasm in the presence of pain. Inthis situation, however, stability has moved onto become rigidity and does not allow normalmovement patterns.

75o/sec150o/sec195o/sec

70

60

50

40

30

20

10

Vastuslateralis

Rectusfemoris

Mus

cle

activ

ity

Vastusmedialis

Lateralhamstring

Fig. 1 Changes in muscle activity with increases in speed.Reproduced from Norris 1994, with kind permission fromButterworth Heinemann.

Muscle length adaptation

Muscle adaptation to reduced usage has beenextensively studied using immobilized limbs(Appell 1990). The greatest tissue changes areseen to occur within the ®rst few days of disuse.Strength loss has been shown to be as much as6% per day for the ®rst 8 days, with minimalloss after this period (Muller 1970). The reactionof type (I) and (II) muscle ®bres differsconsiderably, an important factor in the muscleimbalance process. Type (I) ®bres show agreater reduction in size and loss of total ®brenumbers within the muscle than type (II). Infact, the number of type (II) ®bres actuallyincreases demonstrating a process of selectiveatrophy of the type (I) ®bres (Templeton et al.1984). However, not all muscles show an equal

rapy in Sport (2001) 2, 29±39

amount of type (I) ®bre atrophy. Atrophy islargely related to change in use relative tonormal function, with the initial percentage oftype (I) ®bres that a muscle contains being agood indicator of likely atrophy pattern.

Selective changes in muscle may also occur asa result of training (Richardson & Bullock 1986).In the knee, rapid ¯exion-extension actions havebeen shown to selectively increase activity inthe rectus femoris and hamstrings (biarticular)but not in the vasti (monoarticular). In thisparticular study, comparing speeds of 758/sand 1958/s, mean muscle activity for the rectusfemoris increased from 23.0 uV to 69.9 uV. Incontrast, muscle activity for the Vastus medialisincreased from 35.5 uV to only 42.3 uV (Fig. 1).The pattern of muscle activity was alsonoticeably different in this study after training.At the fastest speeds the rectus femoris andhamstrings displayed phasic (on and off)activity while the vastus medialis showed atonic (continuous) pattern (Fig. 2).

Even in the more functional closed kineticchain position similar changes have been found(Ng & Richardson 1990). A 4-week trainingperiod of rapid plantar ¯exion in standing gave

*c 2001 Harcourt Publishers Ltd


Functional load abdominal training

Hamstrings

Rectus femoris

Vestus medialis

Knee angle

45o

0o

Fig. 2 Pattern of muscle activity during rapid alternatingknee ¯exion±extension. Biarticular muscles are phasic,monoarticular muscles are tonic. Reproduced from Norris1994, with kind permission from ButterworthHeinemann.

signi®cant increases in jump height re¯ectinggastrocnemius activity (mobilisor) but alsosigni®cant losses of static function of the soleus(stabilisor).

In the trunk, recruitment patterns of theabdominal muscles have also been shown tochange depending on the type of training used(O'Sullivan et al. 1998). Subjects followed a10-week training programme involving eitherabdominal hollowing or gym exercise includingsit-up type activities. In the hollowing groupEMG activity for the internal oblique increased,while that of rectus abdominis remainedrelatively unchanged. Those subjects

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1000

500

0

Eng

(m

v)

Trunk curl

Rectus abdominus

First block of each muscle grtraining, second block after 1

Fig. 3 First block of each muscle group shows Emg activityprogramme.

incorporating sit-up type actions (but nothollowing) showed an increase in rectusabdominis activity and a reduction in that ofthe internal oblique (Fig. 3).

Stabilisor muscles tend to `weaken' (sag)whereas mobilisors tend to `shorten' (tighten).The length tension relationship of a muscledictates that a stretched muscle, where the actinand myosin ®laments are pulled apart, canexert less force than a muscle at normal restinglength. Where the stretch is maintained,however, this short term response (reduced forceoutput) changes to a long-term adaptation. Themuscle tries to move its actin and myosin®laments closer together, and to do this, it mustadd more sarcomeres to the ends of the muscle(Fig. 4). This adaptation, known as an increasein serial sarcomere number (SSN), changes thenature of the length tension curve itself.

Long-term elongation of this type causes amuscle to lengthen by the addition of up to 20%more sarcomeres (Gossman et al. 1992). Thelength±tension curve of an adaptivelylengthened muscle moves to the right (Fig. 5).The peak tension such a muscle can produce inthe laboratory situation is up to 35% greaterthan that of a normal length muscle (Williams& Goldspink 1978). However, this peak tensionoccurs at approximately the position where themuscle has been immobilized (point A, Fig. 5).If the strength of the lengthened muscle istested with the joint in mid-range or inner-range (point B, Fig. 5), as is common clinical



1000

500

0

Eng

(m

v)

Abdominal hollowing

Internal oblique

oup shows Emg activity before0 minute training programme

before training, second block after 10 min training

32 Physical The


A

B

C

Fig. 4 Muscle length adaptation. (A) Normal musclelength. (B) Stretched muscle-®laments move apart andmuscle loses tension. (C) Adaptation by increase in serialsarcomere number (SSN), normal ®lament alignmentrestored, muscle length permanently increased.Reproduced from Norris 1994 with kind permission fromButterworth Heinemann.

A

B

ShortenedControlLengthened

10

8

6

4

2

80 90 100 110

% Muscle belly length of control

Act

ive

tens

ion

(g)

Fig. 5 Effects of immobilizing a muscle in shortened andlengthened positions. The normal length±tension curve(control) moves to the right for a lengthened muscle,giving it a peak tension some 35% greater than thecontrol (point A). When tested in an inner range positionhowever (point B), the muscle tests weaker than normal.Reproduced from Norris 1994, with kind permission fromButterworth Heinemann.

practice, the muscle cannot produce its peaktension, and so the muscle appears `weak'.

In the laboratory situation the lengthenedmuscle will return to its optimal length withinapproximately 1 week if placed in a shortenedposition once more (Goldspink 1992).Clinically, restoration of optimal length may beachieved by either immobilizing the muscle inits physiological rest position (Kendall et al.1993), and/or exercising it in its shortened(inner range) position Sahrmann 1990).Enhancement of strength is not the priority inthis situation, indeed the load on the musclemay need to be reduced to ensure correctalignment of the various body segments and

rapy in Sport (2001) 2, 29±39

correct performance of the relevant movementpattern.

Serial sarcomere number (SSN) may beresponsible partly for changes in musclestrength without parallel changes inhypertrophy (Koh 1995). SSN exhibits markedplasticity and may be in¯uenced by a numberof factors. For example, immobilization ofrabbit plantar¯exors in a lengthened positionshowed an 8% increase in SSN in only 4 days,while applying electrical simulation to increasemuscle force showed an even greater increase(Williams et al. 1986). Stretching a muscleappears to have a greater effect on SSN thandoes immobilization in a shortened position.Following immobilization in a shortenedposition for 2 weeks, the mouse Soleus has beenshown to decrease SSN by almost 20%(Williams 1990). However, stretching for just1 h per day in this study not only eliminatedthe SSN reduction, but actually producednearly a 10% increase in SSN. An eccentricstimulus appears to cause a greater adaptationof SSN than a concentric stimulus. Morgan andLynn 1994 subjected rats to uphill or downhillrunning, and showed SSN in the vastusintermedius to be 12% greater in the eccentrictrained rats after 1 week. It has been suggestedthat if SSN adaptation occurs in humans,strength training may produce such a change ifit were performed at a joint angle different fromthat at which the maximal force is producedduring normal activity (Koh 1995).

Rather than being weak, the lengthenedmuscle lacks the ability to maintain a fullcontraction within inner range. This shows upclinically as a difference between the active andpassive inner ranges. If the joint is passivelyplaced in full anatomical inner range, thesubject is unable to hold the position.Sometimes the position cannot be held at all,but more usually the contraction cannot besustained, indicating a lack in slow twitchendurance capacity.

Clinically, reduction of muscle length is seenas the enhanced ability to hold an inner rangecontraction. This may or may not represent areduction in SSN, but is a required functionalimprovement in postural control. Muscleshortening has been shown in the dorsi¯exorsof horseriders. Clearly this position is not heldpermanently as with splinting, but rather shows




Tightness(mobilisor muscles)

a training response. Following pregnancy, SSNincreases in the rectus abdominis incombination with diastasis. Again, length of themuscle gradually reduces in the monthsfollowing childbirth. Inner range training thenis likely to shorten a lengthened muscle(Goldspink 1996).

Poor inner range endurance,leading to lengthening(stability muscles)

Change in body segment alignment(owing to muscle imbalance)

Fig. 6 Muscle alteration as part of the imbalanceprocess.

Assessment and correction of muscleimbalance

Structural and functional alterations of muscleswhich occur as part of the imbalance processshow as three important signs (Fig. 6). Firstly,tightening of the mobilisor (two joint) musclesand secondly, loss of endurance (holding) withininner range for the stabilisor (single joint)muscles. These two changes are used as testsfor the degree of muscle imbalance present.

The combination of length and tensionchanges alters muscle pull around a joint andso may draw the joint out of alignment.Changes in body segment alignment and theability to perform movements which dissociateone body segment from another forms the basesof the third type of test used when assessingmuscle imbalance.

The mixture of tightness and weakness seenin the muscle imbalance process alters bodysegment alignment and changes theequilibrium point of a joint. Normally, theequal resting tone of agonist and antagonistmuscles allows the joint to take up a balancedresting position where the joint surfaces areevenly loaded and the inert tissues of the jointare not excessively stressed. However, if themuscles on one side of a joint are tight and theopposing muscles are lax, the joint will bepulled out of alignment towards the tightmuscle (Fig. 7). This alteration in alignmentthrows weight bearing stress onto a smallerregion of the joint surface increasing pressureper unit area ( focal loading). Further, the inerttissues on the shortened (closed) side of thejoint will contract over time. These alignmentchanges are highlighted during the assessmentof static posture in standing and sittingespecially. Taking pelvic alignment duringstanding as an example which is highly relevantto abdominal training, the lordotic posture isone which combines muscles lengthening andshortening. In an optimal posture (Kendal et al.

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1993) the pelvis should be level such that theanterior superior iliac spine is horizontallyaligned to the posterior superior iliac spine andvertically aligned to the pubis (Fig. 8). In thelordotic posture, the pelvis tilts forwards, analignment which is associated with lengtheningof the abdominal muscles (especially rectusabdominis) and gluteals combined withshortening of the hip ¯exors, the so called`pelvic crossed syndrome' (Janda & Schmid1980). Individual muscle tests are used to assessthe degree of muscle length change. TheThomas test may be used to measure hip ¯exortightness (Fig. 9) while inner range holding ofthe gluteals in this case is used to assesssarcomere adaptation of these muscles (Fig. 10).

Imbalance also leads to a lack of accuratesegmental control. The combination of stiffness(hypo¯exibility) in one body segment andlaxity (hyper¯exibility) in an adjacent bodysegment leads to the establishment of relative¯exibility (White & Sahramann 1994). In a chainof movement, the body seems to take the pathof least resistance, with the more ¯exiblesegment always contributing more to the totalmovement range.

Figure 11 shows a toe touching movement.The two areas of interest with relation torelative ¯exibility are the hamstrings and



34 Physical The


Fig. 7 Muscle imbalance altering joint mechanics: (A) symmetrical muscle tone ± normal joint; (B) unequal muscle pull(imbalance) ± joint alignment poor; (C) joint surface degeneration. Reproduced with kind permission from Norris(1999), The Complete Guide to Stretching, published by A & C. Black Ltd. # A & C Black Ltd.

shoulderjoint

through ear

cervical vertebrae

lumbar vertebrae

centre of knee joint

ankle bone(lateral malleolus)

pelviccrest

pubis

hip joint

Fig. 8 Optimal postural alignment. Reproduced with kindpermission from Norris (1999), The Complete Guide toStretching, published by A & C Black Ltd.#A & C Black Ltd.

lumbar spine tissues. As we ¯ex forwards,movement should occur through a combinationof anterior pelvic tilt and lumbar spine ¯exion.

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Subjects often have tight hamstrings and farmore lax lumbar tissues due to excessivebending (lumbar ¯exion) as part of everydayactivities. During this ¯exion action, greatermovement and, therefore, greater tissue strainwill always occur at the lumbar spine. Relative¯exibility in this case makes the toe touchingexercise ineffective as a hamstring stretch unlessthe trunk muscles are tightened to stabilize thelumbar spine at the same time.

Trunk stability

Lack of stability (instability) of the lumbar spinemust be contrasted with hypermobility. In bothconditions the range of motion is greater thannormal. However, instability is present whenthere is `an excessive range of abnormalmovement for which there is no protectivemuscular control'. With hypermobility, stabilityis provided because the `excessive range ofmovement . . . has complete muscular control'(Maitland 1986). The essential feature ofstability is, therefore, the ability of the body tocontrol the whole range of motion of a joint, inthis case the lumbar spine.

When the lumbar spine demonstratesinstability, there is a failure to maintain correctvertebral alignment. The unstable segmentshows decreased stiffness (resistance tobending) and as a consequence movement isincreased even under minor loads. Both thequality and quantity of motion is thereforealtered. Clinically, with reference to the lumbarspine, this description of instability means thatthere is no damage to the spinal cord or nerve



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Fig. 9 The Thomas test. The subject is positioned at theend of the treatment couch. His / her spine is passively¯exed by bringing the knees to the chest. One knee isheld to the chest to maintain the pelvic position whilethe other is lowered. Optimal alignment occurs when thefemur is horizontal and tibia vertical (A). If the femur isheld above the horizontal, hip ¯exor tightness isindicated. Extending the knee will take the stretch offrectus femoris (B), if the knee then drops down, tightnessin the iliopsoas is present. The position of the tibia in thefrontal plant indicates the presence of hip rotationrequiring further examination (C). Reproduced fromNorris 1994, with kind permission from ButterworthHeinemann.

roots, and no incapacitating deformity.However, because movement is excessive, painsensitive structures may be either stretched orcompressed and in¯ammation may occur(Kirkaldy-Willis 1990, Panjabi 1992).

To maintain spinal stability, three interrelatedsystems have been proposed (Fig. 12). Passivesupport is provided by inert tissues, whileactive support is from the contractile tissues.Sensory feedback from both systems providescoordination via the neural control centres(Panjabi 1992). Importantly, where the stability



Fig. 10 Inner range holding tests. The limb is taken tofull passive inner range and the subject is instructed tohold this position. Optimal endurance is indicated whenthe full inner range position can be held for 10±20seconds. Muscle lengthening is present if the limb dropsaway from the inner range position immediately.Endurance is poor if the inner range position ismaintained for less than 10 seconds. Tests for possiblelengthened muscles around the hip include the illopsoas(A), gluteus maximus (B), and posterior ®bres of gluteusmedius (C). Reproduced from Norris 1994 with kindpermission from Butterworth Heinemann.

36 Physical The


Fig. 11 Relative ¯exibility in the body. (A) Tighterhamstrings, more lax spinal tissues. (B) Forward ¯exionshould combine pelvis tilt and spinal ¯exion equally. (C)Tight hamstrings limit pelvic tilt, throwing stress on themore lax spinal tissues. Reproduced from Norris (1994),with kind permission from Butterworth Heinemann.

Control(neural)

Passive(spinal column)

Active(muscular)

Fig. 12 The spinal stabilizing system consists of threeinterrelating sub-systems. Reproduced from Norris(1994), with kind permission from ButterworthHeinemann.

provided by one system reduces, the othersystems may compensate. Thus, the proportionof load taken by the active system may increaseto minimize stress on the passive systemthrough load sharing (Tropp et al. 1993). Thisgives the individual the opportunity to reduce

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Control

SEMG(root meansquared)

0.90.80.70.60.50.40.30.20.1

0

Fig. 13 Abdominal muscle activation in chronic low back p

pain and improve function by restoring backstability through exercise. Such improvementmay be accomplished by augmenting both theactive and neural control systems. Simplydeveloping muscle strength is insuf®cient.Moreover, many popular strength exercises forthe trunk actually increase mobility in thisregion to dangerously high levels (Norris 1993,1994). Rather than improving stability, exercisesof this type may reduce it and could thereforeincrease symptoms, especially those associatedwith in¯ammation.

In terms of spinal stabilization, rather thanthe strength of the abdominal muscles, it is thespeed with which they contract in reaction to aforce tending to displace the lumbar spinewhich is important (Saal & Saal 1989).Additionally, the ability of a patient todissociate deep abdominal function from that ofthe super®cial abdominals is also vital, as it isthe deep abdominals which have the moresigni®cant stabilizing function. An abdominalhollowing action rather than a sit-up movementhas been shown to work the transversusabdominis and the internal oblique (stabilisors)rather than the rectus abdominis and theexternal oblique (Richardson et al. 1992).Patients with chronic low back pain (CLBP)have been shown to be poorer at using theinternal oblique than the rectus abdominis andexternal oblique, re¯ecting a shift in the patternof motor activity (O'Sullivan et al. 1997a,1997b). As an abdominal hollowing action isattempted, there is a substitution of thesuper®cial muscles which override the deepabdominals (Fig. 13). When expressed as a ratioof internal oblique over rectus abdominis (IO/RA) the value from the control group (non-LBP)was 8.74, while the CLBP group had a ratio ofonly 2.41 indicating a much larger proportional


CLBP

RectusabdominusInternaloblique

ain. (Data adapted from O'Sullivan et al. 1997).



Non-back pain Back pain

150

100

50

0

-50

-100

-150

Em

g tim

ing

Flexion

Abduction

Extension

Fig. 14 Activity of transversus abdominis muscle duringshoulder movements. Note that subjects with back painhad a longer transversus reaction time. 0 emg timingrepresents the onset of shoulder movement. (Data fromHodges and Richardson 1996.)

contribution to hollowing by the internaloblique in the normal group. It seems that paininhibition in these subjects may have lead toaltered muscle recruitment and compensatorystrategies when performing motor tasks(O'Sullivan et al. 1997a, 1997b). The ratio ofmuscle activity rather than the intensity ofmuscle activity is therefore relevant.

The rectus abdominis will ¯ex the trunk byapproximating the pelvis and ribcage. EMGinvestigation has shown the supraumbilicalportion to be emphasized by trunk ¯exion,while activity in the infraumbilical portion isgreater in positions where a posterior pelvic tiltis held (Lipetz & Gutin 1970, Guimaraes et al.1991).

By assessing EMG activity of the trunkmuscles it has been shown that the muscles donot simply work as prime movers of the spine,but show antagonistic activity during variousmovements. The oblique abdominals are moreactive than predicted, to help to stabilize thetrunk (Zetterberg et al. 1987). During maximumtrunk extension, activity of the abdominalmuscles varied from 31% to 68% of the activityin longissimus. In resisted lateral ¯exion, aswould be expected, the ipsilateral musclesshowed maximum activity, but the contralateralmuscles were also active at about 10±20% ofthese maximum values (Zetterberg et al. 1987).

In maximum voluntary isometric trunkextension, transversus abdominis is the onlyone of the abdominal muscles to show markedactivity. The coordinated patterns seen betweenthe abdominal muscles have been shown to betask speci®c, with transversus abdominis beingthe muscle most consistently related to changesin IAP (Cresswell et al. 1992). The transversusabdominis not only contracts with multi-directional trunk activities, its activity alsoprecedes the contraction of the other trunkmuscles (Cresswell et al. 1994).

Where repeated movements are concernedthe onset of the load is predictable, and so thebody anticipates the load and braces the musclesaccordingly. This action is commonly seen instance, but has also been found to occur withthe transversus abdominis during rapidshoulder movements. Using ®ne wireelectrodes, Hodges and Richardson (1996)assessed abdominal muscle action duringshoulder movements. They found that

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transversus abdominis and internal obliquecontracted before the shoulder muscles by asmuch as 38.9 msec. The reaction time for thedeltoid was on average 188 msec, with theabdominal muscles, except transversus,following the deltoid contraction by 9.84 msec.With subjects who had a history of lower backpain, however, none of the abdominal musclespreceded contraction of the deltoid, indicatingthat they had lost the anticipatory nature ofstability (Fig. 14).



38 Physical The


Contraction of the abdominal muscles beforethe initiation of limb movement has beenhighlighted by a number of authors, as anexample of a feed forward postural reaction(Friedli et al. 1984, Aruin & Latach 1995). Inthese cases, as would be expected, the erectorspinae and the external oblique are seen tocontract before arm ¯exion while the rectusabdominis contracts before arm extension. Ineach case, the trunk muscles act to limit thereactive body movement towards the movinglimb. Contraction of the transversus before theother abdominal muscle has been described byCresswell et al. (1994) in response to trunkmovements, but anticipatory contraction duringlimb movements is a newer ®nding. Thetransversus abdominis seems to be contractingduring posture, not simply to bring the bodyback closer to the posture line, but to increasethe stiffness of the lumbar region and enhancestability (Hodges et al. 1996).

Importance of imbalance for functionalabdominal training

A number of important points concerningimbalance and muscle adaptation have directrelevance to improving the standard ofabdominal training. Firstly, rapid movementspeeds and higher resistances have been shownto selectively recruit mobilisor muscles, and inthe case of the abdomen, the rectus abdominisespecially. To reduce the recruitment of thismuscle and increase the work on transversusabdominis and internal oblique, lower resistancesand slow movements should be used.

Secondly, eccentric actions have been shown tobe better suited for reversal of serial sarcomereadaptation. In the lordotic posture, the pelvis isanteriorly tilted, and the rectus abdominislengthened. A signi®cant relationship existsbetween angle of pelvis tilt and abdominalmuscle length, but not between pelvic tilt andabdominal muscle strength (Toppenberg &Bullock 1990). To modify the abdominalmuscles in a lordotic posture, therefore, innerrange movements should be used ( full lumbar¯exion combined with posterior pelvic tilt) withan emphasis on eccentric training initially. Thisshould be combined with hip ¯exor musclestretching to allow full posterior pelvic tilt.Clearly to determine whether muscle

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shortening or muscle lengthening is required, amuscle imbalance assessment should be made toassess static posture and then individualmuscles tests used to determine muscleshortening (range of motion) or lengthening(inner range holding). Full details of tests of thistype are described elsewhere (Norris 1998,Norris 2000).

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Norris Functional Load Abdominal Tring Part 1

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