hodges 1999

Manual Therapy (1999) 4(2), 74±86# 1999 Harcourt Brace & Co. Ltd

Review article

Is there a role for transversus abdominis in lumbo-pelvic stability?

P. W. Hodges

Prince of Wales Medical Research Institute, Sydney, Australia

SUMMARY. There has been considerable interest in the literature regarding the function of transversusabdominis, the deepest of the abdominal muscles, and the clinical approach to training this muscle. With thedevelopment of techniques for the investigation of this muscle involving the insertion of ®ne-wire electromyographicelectrodes under the guidance of ultrasound imaging it has been possible to test the hypotheses related to its normalfunction and function in people with low back pain. The purpose of this review is to provide an appraisal of thecurrent evidence for the role of transversus abdominis in spinal stability, to develop a model of how the contributionof this muscle di�ers from the other abdominal muscles and to interpret these ®ndings in terms of the consequencesof changes in this function.

INTRODUCTION

The therapeutic application of exercise of theabdominal muscles has been widely used in themanagement of low back pain (Kendall Mannicheet al. 1988; Robinson 1992). The basis for thisapproach has been that strong abdominal musclescould provide support for the lumbar spine (Robin-son 1992). However, evaluation of the e�cacy ofgeneral abdominal muscle strengthening has yieldedlittle experimental support for this approach (Koes etal. 1991). Recently the focus has turned to transver-sus abdominis (TrA), the deepest of the abdominalmuscles (Miller & Medeiros 1987; Richardson et al.1992; Jull & Richardson 1994; Richardson & Jull1995; O'Sullivan et al. 1997; Richardson et al. 1998),with the assumption that this component of theabdominal muscle group provides a speci®c contribu-tion to spinal stability and that its function isimpaired in the presence of low back pain.

The contribution of the super®cial abdominalmuscles (i.e. rectus abdominis [RA], obliquus ex-ternus abdomininis [OE] and to some extent obliquusinternus abdominis [OI] to spinal stability is relatedto their ability to produce ¯exion, lateral ¯exion androtation moments and thus, control external forcesthat cause the spine to extend, laterally ¯ex or rotate(Bergmark 1989). In addition, co-contraction of the

Dr. Paul W. Hodges, Bphty (Hons) PhD, Prince of Wales MedicalResearch Institute, High Street, Randwick, Sydney, NSW 2031,Australia.

74

trunk ¯exors and extensors has been found toincrease the stability of the spine (Bergmark 1989;Gardner-Morse & Stokes 1998). Correspondingly,activation of the super®cial abdominal muscles hasbeen found to be higher than predicted during speci®ctasks (Zetterberg et al. 1987).

In contrast, the role of TrA in lumbo-pelvicsupport is less intuitive. TrA arises from the iliaccrest, lower six ribs and the lateral raphe of thethoracolumbar fascia and passes medially to the lineaalba (Fig. 1) (Askar 1977; Bogduk & MacIntosh1984; Williams et al. 1989). Due to this horizontal®bre orientation, contraction of TrA results in areduction of abdominal circumference with a resul-tant increase in tension in the thora-columbar fasciaand an increase in intra-abdominal pressure (ifdisplacement of the abdominal contents is pre-vented). TrA has only a limited ability to producetrunk motion (McGill 1996). Due to the mechanicale�ect of TrA contraction it can control the abdom-inal contents (Keith 1923; Goldman et al. 1987;DeTroyer et al. 1990) and contributes to respirationby increasing expiratory air glow rate (Agostoni &Campbell 1970), decreasing end expiratory lungvolume (Henke et al. 1988) and by defending thelength of the diaphragm (De Troyer 1983).

Evidence for a contribution of TrA to spinalstability can come from two sources. Firstly, fromevaluation of the ability of TrA to contribute toaspects of spinal control, or secondly, by indirectevidence from investigation of how TrA is used bythe central nervous system (CNS) during speci®c

Fig. 1ÐAnatomy of transversus abdominis. The attachments oftranversus abdominis to the lumbar vertebrae via middle andanterior layers of the thoracolumbar fascia are not shown. Todemonstrate the bilaminar fascial attachment of the posterior layerof the thoracolumbar fascia it is shown connecting only to thespinous processes. LR ± lateral raphe, LA ± linae alba, SP ±super®cial lamina of the posterior layer of the thoracolumbarfasica, DP ± deep lamina of the posterior layer of the thoraco-lumbar fascia.

Is there a role for transversus abdominis in lumbo-pelvic stability? 75

tasks. While few attempts to investigate the mechan-ical e�ectiveness of TrA have been reported (Snijderset al. 1995), there is accumulating evidence frommotor control research. Through a series of studiesaimed at challenging the hypothesized contributionof TrA to lumbo-pelvic stability it has been possibleto provide evidence for its control and to develop amodel of its speci®c contribution to stability. Thismodel has been used to predict the consequence ofdisruption to this system in low back pain. Thepurpose of this review is to critically appraise thisevidence.

EVIDENCE FROM RECRUITMENTOF TRANSVERSUS ABDOMINIS

The development of techniques enabling measure-ment of TrA electromyographic (EMG) activity using®newire electrodes inserted under the guidance ofultrasound imaging has allowed the direct investiga-tion of the recruitment of this muscle (Goldman et al.

# 1999 Harcourt Brace & Co. Ltd

1987; De Troyer et al. 1990; Cresswell et al. 1992).While many studies of TrA activity have evaluatedthe respiratory function of this muscle (Strohl et al.1981; Goldman et al. 1987; De Troyer et al. 1990;Abe et al. 1996), the ®rst investigations of TrA as apossible contributor to spinal control were performedby Cresswell et al. (1992). These studies werestimulated by the observation that high intra-abdominal pressure was present during isometrictrunk extension, yet little activity of RA, OE or OIcould be detected with surface EMG electrodes(Cresswell & Thorstensson 1989). TrA was postulatedto be responsible for this pressure increase since it cangenerate pressure without opposing the trunk ex-tensor moment (Bartelink 1957; Morris et al. 1961;Cresswell et al. 1992).

In their initial series of experiments, Cresswell andcolleagues investigated the activity of the abdominaland erector spinae (ES) muscles during the perfor-mance of trunk movements (Cressell et al. 1992).When subjects performed isometric trunk ¯exion inside lying, all of the abdominal muscles were active,including TrA. However, a similar magnitude ofTrA EMG was recorded during trunk extension incombination with the ES. In addition, TrA wasrecruited continuously during ¯exion and extensionof the trunk in standing whereas the other abdominalmuscles and ES were phasically active to intiate anddecelarate the trunk movement (Cresswell et al.1992). This unexpected continuous (but varying)activity of TrA and its close relationship to intra-abdominal pressure lead the authors to conclude thatTrA may contribute to a general mechanism fortrunk stabilization rather than the production oftorque or control of orientation of the spine. Similarobservations of activity of TrA in both ¯exion andextension were recorded when movement was per-formed dynamically against resistance (Cresswell1993) and with lifting and lowering (Cresswell &Thorstensson 1993). The activation of OI sharedsome similar features to that of TrA but was not asstrongly related to intra-abdominal pressure and wasmore variable between movement directions.

In a second series of experiments, Cresswell andcolleagues (1994) investigated the recruitment of thetrunk muscles in response to an externally generatedpertubation of the spine by adding a weight to aharness over the shoulders (Fig. 2A). When subjectswere unexpectedly forced into trunk ¯exion, TrA wasactive prior to ES with a latency of 24 ms (Fig. 2B).Since TrA is unable to produce trunk torque theseresults provide futher support to a possible contribu-tion of this muscle to spinal stability. When subjectsadded the load themselves and could predict thetiming and magnitude of the perturbation, TrA wasactive 175+24 ms prior to the loading (Fig. 2B). This®nding provides the ®rst insight into the possibleactivation of TrA in advance of a predictable

Manual Therapy (1999) 4(2), 74±86

Fig. 2ÐRecruitment of the abdominal (transversus abdominis [TrA], obliquus internus abdominis [OI], obliquus extrenus abdominis [OE],rectus abdominis [RA]) and erector spinae (ES) muscles with addition of an unexpected (®lled circles) and expected (un®lled circles) ventralload. (A) Experimental set-up with harness placed over the shoulders and load added ventrally to produce trunk ¯exion. (B) Mean onset(SD) of each muscle relative to the onset of the pertubation. Note the consistent activation of TrA prior to the other trunk muscles and theactivation of all trunk muscles prior to loading in the `expected' loading condition. (Adapted from Cresswell et al. [1994]).

76 Manual Therapy

perturbation. The complicating factor with the modelused by Cresswell et al. (1994) was that the subjectswere conscious of the outcome of the loading andcould make voluntary adjustments. Other methodswere necessary to investigate the preparatory strate-gies of spinal control in a more controlled manner.

EVIDENCE FROM PREDICTABLEPERTURBATIONS

By investigating the recruitment of TrA in a task thatprovides a predictable perturbation to the spinethat is not consciously perceived, it was possible toinvestigate the contribution of TrA to stability and itscontrol by the CNS in more detail. This was achievedby the investigation of spinal control associated withlimb movement. When a limb is moved the con®g-uration of the body is altered and reactive forces areimposed on the body that are equal in magnitude butopposite in direction to those producing the move-ment (Bouisset & Zattara 1981). Thus, when ashoulder is ¯exed, reactive forces act backwards anddownwards on the centre of mass causing the spine to¯ex (Bouisset & Zattara 1987; Friedli et al. 1988;Hodges et al. 1999) and the centre of mass isdisplaced anteriorly by the forward displacement ofthe arm. It has been known since the 1960s that theCNS prepares for the predictable challenge to postureby altering the activation of muscles of the leg priorto the muscle initiating the limb movement (Belen'kiiet al. 1967; Bouisset & Zattara 1987; Friedli et al.

Manual Therapy (1999) 4(2), 74±86

1988; Hodges et al. 1999). In addition, several studieshad identi®ed early activation of super®cial trunkmuscles (RA and ES) prior to upper limb movementin speci®c directions (Friedli et al. 1988; Zattara &Bouisset 1988; Aruin & Latash 1995).

In an initial series of studies, the activation ofthe abdominal and ES muscles was investigated withthe performance of rapid unilateral arm (Hodges &Richardson 1997b) and leg (Hodges & Richardson1997a) movements (Fig. 3A, B). TrA was consistentlythe ®rst muscle activated. Since the onset of activa-tion of TrA preceded that of the muscle responsiblefor limb movement it must be pre-programmed bythe CNS and is consistent with a contribution to thepreparation of the spine for the perturbation resultingfrom the reactive forces on the spine. These resultscon®rmed that the CNS controls spinal stability inanticipation of a predictable disturbance.

Further insight into the contribution of TrA tolumbo-pelvic stability came from the e�ect of limbmovement direction on trunk muscle activation.When limb movement is performed in di�erent direc-tions the direction of force acting on the spine varies.

The initial study identi®ed the activation ofthe trunk muscles (except TrA) varied betweendirections of movement (Fig. 3C) (Hodges &Richardson 1997b). ES was active signi®cantly earlierwith shoulder ¯exion than in shoulder abductionand extension and a converse relationship wasidenti®ed for the ¯exing abdominal muscles (Friedliet al. 1984; Aruin & Latash 1995; Hodges &Richardson 1997a; b). It appeared that the CNS


Fig. 3ÐRecruitment of the abdominal (transversus abdominis [TrA], obliquus internus abdominis [OI], obliquus externus abdominis [OE],rectus abdominis [RA]) and erector spinae (ES) muscles with rapid shoulder ¯exion. (A) Experimental set-up indicating the location of theelectromyography electrodes. (B) Electromyography (EMG) data of a representative subject from a single trial of shoulder ¯exion. Note theonset of TrA EMG prior to that of deltoid. (C) Mean (SEM) times of EMG onset of each trunk muscle relative to that of deltoid formovement of the upper limb in each direction. Note the variation in limb movement direction for all muscles except TrA. (Adapted fromHodges & Richardson [1997b]).


recruited the super®cial muscles earlier when theiraction opposed the direction of forces acting on thespine. In contrast, TrA was active in a consistentmanner, irrespective of the force direction.

It was necessary to con®rm the proposed relation-ship between the trunk muscle recruitment and thekinematics of the perturbation to the trunk. A studywas undertaken that involved measurement of themotion of the trunk with concurrent measurementof trunk muscle EMG during performance of rapidbilateral shoulder movement (Hodges et al. 1999).Infra-red markers were placed over speci®c land-marks on the spine, pelvis, thigh and arm thatallowed measurement of angular displacement be-tween segments (Fig. 4A) As predicted, the resultsindicated that shoulder ¯exion was associated with¯exion motion between trunk segments (Friedli et al.1984; Bouisset & Zattara 1987). The converse reactivemotion occurred for shoulder extension. However, asmall but consistent motion of the spine occurredin the opposite direction to the perturbation thatcommenced prior to limb movement (Fig. 4B). Thismotion was consistent with the pattern of activationof the super®cial trunk muscles, and providesevidence that the CNS deals with the perturbationto spinal stability that results from limb movementby initiation of preparatory motion of the spine to`dampen' the forces rather than simply making thetrunk rigid. The timing and magnitude of TrAactivity did not vary between movement directionsand is thus inconsistent with this function. Anadditional ®nding that was consistent with the initialexperiment of Cresswell et al. (1992) was that TrA


responded in a relatively tonic manner in the majorityof subjects.

The ®ndings of these studies contributed to theevidence that was beginning to accumulate thatsuggested a possible speci®c and independent con-tribution of TrA to spinal stability. Yet before it waspossible to consider the function that TrA maycontribute to stability it was important to determinewhether the activation of TrA was associated with amechanical output.

EVIDENCE FROM MECHANICAL OUTPUT

The mechanical output of TrA can be evaluated bymeasurement of intra-abdominal pressure or tensionin the thoracolumbar fascia. While measurementof fascial tension is technically di�cult, it is possibleto measure intra-abdominal pressure by placement ofa pressure transducer in the gastric ventricle. Cress-well and colleagues (1992; 1994) identi®ed a closerelationship between intra-abdominal pressure andTrA activity. In addition, intra-abdominal pressurewas measured during the performance of rapidshoulder movement. The results indicated thatintra-abdominal pressure increased following theactivation of TrA and was early enough to precedethe onset of limb movement and could contributemechanically to the preparatory process occurringprior to limb movement (Hodges et al. 1997a; Hodgeset al. 1999).

The identi®cation of an increase in intra-abdom-inal pressure prior to limb movement limb provided a

Manual Therapy (1999) 4(2), 74±86

Fig. 4ÐAngular motion of the trunk in the sagittal plane with rapid shoulder ¯exion and extension. (A) Experimental set-up indicating thelocation of the infra-red markers and angles measured. (B) Representative raw data from a single subject with shoulder ¯exion andextension. The onset of shoulder movement is marked in the unbroken line and the onset of preparatory trunk motion is marked by thebroken line. The missing data with shoulder extension was due to movement of the arm between the camera and markers. Note thepreparatory motion occurring between trunk segments in the direction opposite to the movement provoked by the reactive forces from limbmovement. A ± acromion, GT ± greater trochanter. IC ± iliac crest, O ± olecranon, PT ± proximal thigh, PSIS ± posterior superior iliac spine,H-L ± angle between thigh (GT-PT) and lumbar spine (T12-S1), L ± angle between the upper (T12-L3) and lower (L3-S1) lumbar spine,L-P ± angle between the lumbar spine (T12-S1) and pelvis (PSIS-IC), Sh ± angle between upper arm (A-O) and vertical, S-P ± angle betweenthe total spine (C7-S1) and pelvis (PSIS-IC). (Adapted from Hodges et al. [1999]).

78 Manual Therapy

further possibility to test the hypothesized contribu-tion of TrA to spinal stability. Contraction of thediaphragm and pelvic ¯oor muscles is essential toprevent displacement of the abdominal contents andpermit TrA to develop su�cient isometric tension toincrease intra-abdominal pressure and fascial tension.Thus, it was pertinent to evaluate the recruitment ofthe diaphragm in a postural task.

EVIDENCE FROM THE RELATIONSHIP TOTHE DIAPHRAGM

The possibility that the diaphragm may perform apostural task has been considered for many years(Delhez 1968; Massion 1976). Yet studies investigat-ing activation of the diaphragm in decerebrateanimals have been unable to identify a posturalfunction (Massion 1976). Studies of transdiaphrag-matic pressure (pressure di�erence between thethorax and abdomen) have provided indirect evi-dence of diaphragm activity during lifting (Hemborget al. 1985). The experimental paradigm used toevaluate the postural response to limb movementprovided a possible method to investigate thisquestion. For reasons outlined in the precedingsection, the ability of TrA to in¯uence spinal stabilitywould be unlikely if activation of the diaphragmdid not occur in this task. Monopolar needle andoesophageal electrodes were used to make recordings

Manual Therapy (1999) 4(2), 74±86

of the costal and crural portions of the diaphragm,respectively, while subjects performed rapid unilat-eral shoulder ¯exion (Hodges et al. 1997a). Theresults indicated that the onset of diaphragm EMGactivity (costal and crural) preceded the onset ofdeltoid EMG activity (Fig. 5A) and was concurrentwith that of TrA. Measurement of transdiaphrag-matic pressure indicated that the mechanical outputof the diaphragm preceded the onset of movement(Fig. 5B). In addition the length of the diaphragmwas indirectly evaluated by ultrasound measurementof the length of the region of the diaphragm incontact with the internal surface of the rib cage (zoneof apposition) prior to and during the movement.The length of the zone of apposition has been shownto provide an indirect index of the length of thediaphragm (McKenzie et al. 1994). The resultsindicated that shortening of the diaphragm precededthe onset of shoulder movement, and provides furthercon®rmation of the mechanical e�ciency of thefeedforward activation of the diaphragm (Fig. 5C).A further study investigated the diaphragm duringthe performance of a voluntary abdominal man-oeuvre aimed at activation of TrA and found activityof the diaphragm in association with this contraction(Allison et al. 1998). While the results of this studysuggest that TrA and the diaphragm are activatedconcurrently in certain tasks it is di�cult to interpretthe results since surface electrodes were used and it isimpossible to be certain what proportion of the signal


Fig. 5ÐRecruitment of the diaphragm with rapid shoulder ¯exion. (A) Representative electromyographic (EMG) activity of the costaldiaphragm and deltoid and rib cage motion for a trial performed during expiration. Note the onset of diaphragm EMG prior to that ofdeltoid. (B) Representative transdiaphragmatic (Pdi), gastric (Pga) and oesophageal (Poe) pressures for the same trial as panel A. Note theonset of pressure increase prior to limb movement which indicates that the activity of the diaphragm (and TrA) is associate with amechanical response. (C) Representative data of changes in length of the zone of apposition (LZAPP) with shoulder ¯exion. Note the decreasein diaphragm length that precedes the onset of movement. (Adapted from Hodges et al. [1997a]).


arose from the intercostal muscles underlying theelectrode.

The con®rmation that the diaphragm contributesto the feedforward postural response providedadditional support to the contribution of TrA tospinal stability. Yet further questions arise, such ashow the CNS may coordinate the respiratory andpostural functions of TrA and the diaphragm. Whenrapid movement of the upper limb is performedat random throughout the respiratory cycle, there isno di�erence between the onset of EMG of thediaphragm (Hodges et al. 1997a) and TrA (Hodgeset al. 1997b) between movements performed duringinspiration and expiration with normal quiet respira-tion. However, if the respiratory demand is increasedby provision of an inspiratory load or forcedexpiration (which results in expiratory activation ofTrA [DeTroyer et al. 1990]) it has been shown thatthe onset of TrA EMG activity occurs earlier inexpiration than inspiration (Hodges et al. 1997b).Similarly, the onset of TrA activation occurs laterwhen a sub-maximal expulsive manoeuvre is per-formed prior to the limb movement. These ®ndingssuggest that the CNS coordinates the respiratory andpostural function of TrA and interprets the statusof stability in order to plan the recruitment of TrA onthe basis of pre-existing pressure in the abdomen. Yetrapid limb movement provides only a brief challengeto stability and presents as a minor disturbance torespiration. How the CNS deals with a longerduration postural demand is more complicatedand is an area of ongoing investigation. A recentstudy provided evidence that individual TrA motorunits may be recruited di�erently in respiratory and


postural tasks (Puckree et al. 1998). This ®nding pro-vides preliminary evidence for independent control ofthese two tasks and requires further investigation.

A corresponding requirement exists for co-activa-tion of the pelvic ¯oor muscles with TrA. Preliminaryevidence suggests that early activation of the pelvic¯oor muscles does occur (Hodges et al. unpublishedobservations 1996). However, more extensive evalua-tion is required. In summary, there is evidence thatTrA, the diaphragm and the pelvic ¯oor muscles areco-activated to form an enclosed abdominal cavity(Fig. 6) which further suggests that the function ofthis response is to control spinal stability.

EVIDENCE FROM RELATIONSHIP TO LOAD

An additional option to test the hypothesizedcontribution of TrA to spinal stability is to investi-gate how the activation of this muscle is a�ected byvariation in force magnitude. If the activation of TrAis related to spinal stability then it should be relatedto force magnitude and not be active in situationswhere the force is negligible and unlikely to perturbthe spine. The relationship between force magnitudeand the response of TrA has been investigated ina variety of ways. In an initial study subjects wereasked to perform movement at a variety of speeds(Hodges & Richardson 1997c). When the speed oflimb movement is reduced the magnitude of accel-eration and resulting reactive force is reduced.Feedforward activation of TrA was recorded withrapid movement and with movement performed at anintermediate speed. Yet no response occurred with

Manual Therapy (1999) 4(2), 74±86

Fig. 6ÐDiagrammatic representation of the abdominal `canister'formed by co-activation of the diaphragm, transversus abdominisand the pelvic ¯oor. Activation of all muscles of this canister isrequired in order for abdominal contents to be controlled and forcontraction of transversus abdominis to increase the pressure in theabdominal cavity and increase the tension in the thoracolumbarfascia.

80 Manual Therapy

movement performed at a slow speed. A similarexperiment involved movement of progressivelysmaller segments of the upper limb. A response ofTrA was identi®ed with movements of the shoulderor elbow but not the wrist or thumb (Hodges &Gandevia, unpublished observations, 1996). Identicalresults were obtained for the diaphragm (Hodgeset al. 1997a). Further evidence comes from compar-ison of the movement of the arm and the leg. Whenarm movement is performed, the onset of TrAactivity precedes that of deltoid by approximately30 milliseconds (Hodges & Richardson 1997b). Incontrast, when the leg is moved (producing reactiveforces of greater magnitude due to the increasedmass) activation of TrA precedes that of deltoid bymore than 100 milliseconds (Hodges & Richardson1997a). An additional study provided evidence thatthe period between the onset of increased intra-abdominal pressure and trunk movement increasedas the velocity of trunk movement is increased(Marras & Mirka 1996).

Manual Therapy (1999) 4(2), 74±86

While each of these studies provides evidence of athreshold for TrA activation, additional evidencecomes from comparison of the changing forcemagnitude during a movement and the correspondingchanges in TrA activation. For instance, Cresswelland colleagues (1993) identi®ed bursts of increasedEMG magnitude of TrA during periods of highacceleration and deceleration of the trunk duringboth ¯exion and extension. This was in contrast toRA/OE and ES which were only active duringacceleration when they generated the movement andduring deceleration when they opposed the move-ment. Intra-abdominal pressure was found to re-spond in a two-burst pattern consistent with arelationship to TrA. The response of TrA associatedwith rapid shoulder ¯exion occurs in a similarmanner with a greater magnitude burst at theinitiation of the movement followed by continuousactivation at a lower level (Hodges et al. 1999). Inaddition, when subjects perform a lifting task at di�-erent velocities the magnitude of TrA is greatest withthe fastest movement speeds (Cresswell & Thorstens-son 1993). These results suggest that the activation ofTrA is closely related to periods of maximal stress ofthe spine and provides additional support to theproposed role of TrA in enhancing spinal stability.

Tonic low-level activation of TrA has beenreported in standing subjects (DeTroyer et al. 1990;Hodges et al. 1997b). Several authors have postulatedthat continuous activity of speci®c muscles at a lowpercentage of maximum could be bene®cial to spinalstability by raising muscle sti�ness (Gardner-Morseet al. 1995; Cholewicki et al. 1997) and thus, maintaina constantly changeable level of sti�ness to the joints(Johansson et al. 1991). However, it has been arguedthat the tonic activity of TrA in standing is related tothe control of the abdominal contents (Keith 1923;DeTroyer et al. 1990) and thus, the length of the dia-phragm. In support of this proposal, the activity ofTrA has been shown to be related to the gravitationalload on the abdomen. When a subject lies supineactivity in the abdominal muscles is absent but can beincreased by tilting the support surface up to 45degrees (DeTroyer 1983). In addition, the activity ofTrA in relaxed standing can be ceased voluntarily (DeTroyer et al. 1990; Hodges et al. 1997b). Therefore,whether the tonic activity in standing is related toongoing maintenance of spinal stability has not beencon®rmed and requires additional investigation.

DEVELOPMENT OF A MODEL OF THECONTRIBUTION OF TrA TO SPINALSTABILITY

From the preceeding discussion it is apparent thatsubstantial motor control evidence exists for acontribution of TrA to spinal stability. However, it



is important to consider the speci®c components oflumbo-pelvic stability that are controlled by TrAand the super®cial muscles. The contribution of thesuper®cial trunk muscles (RA, OE, OI, ES) to spinalstability is more straightforward than TrA and isassociated with the control of trunk orientation orposture (Fig. 7A). For instance, when dynamic trunkmovement was performed against resistance in sidelying, activation of RA, OE, OI occurred at the endof trunk extension to decelerate the trunk, theconverse relationship occurred for ES (Cresswell1993). Similarly, activation of the super®cial muscleswas linked with the production of preparatory trunkmotion prior to movement in the limb movementparadigm (Hodges et al. 1999). While this prepara-tory activity is consistent with the control of trunkorientation or posture it was also consistent with thecontrol of the centre of mass (Aruin & Latash 1995;Hodges et al. 1999). Thus the activation of thesuper®cial trunk muscles must be controlled by theCNS in a manner that combines the challenges ofcontrolling orientation and the centre of massconcurrently.

From the studies of Cresswell and colleagues (1992;1993) and Hodges and colleagues (1999; 1997b) it canbe seen that the activation of TrA is not related to thedirection of trunk movement (Cresswell et al. 1992),the direction of the acceleration or deceleration of thetrunk (Cresswell & Thorstensson 1993), the directionof perturbing forces acting on the spine (Hodges& Richardson 1997b; Hodges et al. 1998) or thedirection of displacement of the centre of mass(Hodges et al. 1999).

Fig. 7ÐModel for the di�erential contribution of the trunk muscles toobliquus externus abdominis, obliquus internus abdominis and erecorientation or posture of the spine. (B) In contrast, transversus abdointersegmental motion in a general manner by increasing the pressure


Thus, TrA must contribute to an aspect of spinalstability other than the control of spinal orientation.The likely candidate is inter-segmental control(Fig. 7B). The muscle ®bres of TrA have multipleattachments to the lumbar vertebrae via the layers ofthe thoracolumbar fascia and can also in¯uence thelumbar segments via the development of intra-abdominal pressure. Due to the inherent instabilityof the lumbar spine, particularly around the neutralzone (Panjabi 1992b), the control of this feature is ofparamount importance. While muscles such aslumbar multi®dus provide up to two thirds of thecontrol of inter-segmental motion in certain direc-tions (Wilke et al. 1995), there are limitations in thecontrol provided by this muscle. For instance multi-®dus can contribute little to the control of lumbarrotation (Wilke et al. 1995) and the shearing forcesgenerated at the L5 level by maximal contraction ofthis muscle are counterproductive (Bogduk et al.1992).

The mechanisms through which TrA may con-tribute to inter-segmental stability are complex andinvolve either fascial tensioning) (Tesh et al. 1987),generation of intra-abdominal pressure (Grillneret al. 1978; Tesh et al. 1987; Cresswell et al. 1992)or a combination of both (Hodges & Richardson1997b). As such it is likely that TrA can onlyin¯uence segmental stability in a general, non-direction speci®c manner. In the limb movementand trunk loading studies presented earlier theresponse of TrA was consistent with a role inincreasing the sti�ness of the lumbar intervertebraljoints to potentially simplify the control of orienta-

spinal stability. (A) The super®cial trunk muscles (rectus abdominis,tor spinae) have the mechanical advantage to control the overallminis is unable to directly control external forces and may controlin the abdominal cavity and tension in the thoracolumbar fascia.

Manual Therapy (1999) 4(2), 74±86

82 Manual Therapy

tion by the super®cial muscles (Cresswell et al. 1994;Hodges et al. 1999).

This model of di�erentiation in the contribution ofthe trunk muscles to spinal stability is consistent withthe proposal of Bergmark (1989), which de®nesmuscles as either `local' or global'. In Bergmark'sbiomechanical model the `local' muscles were thosewith attachments to the lumbar vertebrae and hencean ability to in¯uence inter-segmental control. Incontrast, the `global' muscles were those withattachments to the thorax and pelvis and weresuitable for control of external forces acting on thespine, in other words, the control of spinal orienta-tion. Although TrA was not considered in Berg-mark's model, the behavioural evidence presented inthis review is consistent with the classi®cation of TrAin the `local' group.

On the basis of the hypothesis that TrA contributesto a separate aspect of spinal stability, it waspredicted that the CNS may control components ofspinal stability independently. This possibility wastested in an attempt to provide further support forthe model. In the limb movement studies it wasidenti®ed that TrA was active at the same latencyprior to deltoid irrespective of movement direction(Hodges & Richardson 1997b; Hodges et al. 1999)while the temporal relationship of the other super-®cial muscles varied. It was hypothesized that if TrAwas controlled independently to provide interseg-mental sti�ness then the CNS would not need toknow which direction of limb movement would beperformed. In contrast the CNS would need informa-tion of movement direction in order to plan theresponse of the super®cial muscles. If there wasuncertainty about the movement direction then theCNS would need to wait until the direction ofmovement was determined in order to initiate aresponse. This hypothesis was tested by havingsubjects perform either shoulder abduction or ¯exionin response to a visual stimulus after receivingpreparatory information about which movement theywould be expected to perform (Hodges & Richardson1998d). In the majority of trials the preparatoryinformation was correct, in other trials subjects weregiven a signal that provided no information of therequired movement direction and in a small numberof trials the preparatory information was wrong. Inthe trials where the preparatory information wascorrect the reaction time was rapid. In the conditionswhere no preparatory information was provided orthe preparatory information was wrong the reactiontimes of deltoid and the super®cial trunk muscleswere delayed. In contrast, the activation of TrA wasunchanged. This ®nding suggested that TrA wascontrolled independently of the other trunk musclesand provided further evidence that this musclecontributed to sti�ness of the spine in a generalmanner.

Manual Therapy (1999) 4(2), 74±86

This ®nding provides initial evidence that the CNScontrols segmental stability and orientation of thespine independently. Several modes of coordinationbetween the anticipatory postural muscle activity andlimb movement have been presented A `hierarchical'model suggests that postural networks in the CNS arecontrolled by pathways involved in limb movementproduction (GaheÂ ry & Massion 1981; Paulingnanet al. 1989; Massion 1992). In this model the latencybetween the activation of the postural and limbmovement commands is relatively ®xed (Paulingnanet al. 1989). Alternatively, limb movement andassociated postural responses may be controlled ina `parallel' manner where separate commands aregenerated in the CNS for each component (Lee et al.1987; Gur®nkel 1994), thus allowing for uncoupledactivation (Brown & Frank 1987).

While a ®xed latency between the postural andagonist limb muscle activity has been identi®ed understable conditions (Lee 1980; Friedli et al. 1984), themajority of studies have failed to ®nd a ®xedrelationship which questions the `hierarchical' model(Marsden et al. 1977; Cordo & Nashner 1982; Brown& Frank 1987). Evidence that interaction occursbetween the voluntary and postural responses alsoquestions the `parallel' model. For instance, limbmovement is delayed in tasks where the posturaldemand is increased (Cordo & Nashner 1982; Zattara& Bouisset 1986) and both limb movement and itsappropriate postural response are intiated by elec-trical stimulation of the cortex in animals (GaheÂ ry &Massion 1981). The most likely hypothesis for thecoordination of limb movement and the associatedpostural muscle activation has been presented byMassion (1992). In this model the coordination ofpostural control and movement occurs at a lowerlevel in the CNS where both the planning ofmovement and postural control are known (GaheÂ ry& Massion 1981; Gur®nkel 1994). Evidence has comefrom studies of patients with absence of the corpuscallosum where postural responses in the contral-ateral limb is retained without communicationbetween the brain cortexes (Massion et al. 1989).

The di�erential in¯uence of preparation for limbmovement on the activation of the trunk muscles(Hodges & Richardson 1998d) adds another dimen-sion to this problem. These ®ndings suggest thatpostural control should be further subdivided andthat the CNS deals with control of segmental stabilityof the spine (and potentially other regions of thebody) in a separate manner. This has signi®cantimplications for the manner in which training of theabdominal muscles should be addressed in clinicalpractice. With this new model of the contribution ofTrA to spinal stability and the evidence that the CNScontrols TrA independently of the other abdominalmuscles it was important to test whether changesoccurred in the presence of pain.



EVIDENCE OF DYSFUNCTION

Interest regarding the relationship between spinalstability and low back pain has stimulated a wealth ofinvestigation of this parameter (Nachemson 1985;Panjabi 1992a). Evaluation of the function of TrA inpeople with low back pain has provided additionalindirect insight into this discussion. A study wasundertaken on a group of 15 patients with chronicrecurrent low back pain and a group of age and sexmatched controls using an identical limb movementmodel to that used previously (Hodges & Richardson1996). The results for the control subjects wereidentical to those found in the initial studies (Hodges& Richardson 1997b). However, when the subjectswith low back pain performed rapid limb movementthe onset of TrA was signi®cantly delayed and failedto occur in the pre-movement period with movementin all directions (Fig. 8). The onsets of activation ofRA, OE, OI were also delayed but only withmovement in a single direction. In addition, the onsetof TrA activity was signi®cantly di�erent betweenmovement directions (along with the super®cialabdominal muscles ) and the response of TrA becamemore phasic. Additional studies revealed that TrAwas delayed with movement of leg (Hodges &Richardson 1998b), that the threshold for activationof TrA was increased (a ®nding consistent for all theabdominal muscles) (Hodges & Richardson 1998c)and that TrA was no longer activated independently

Fig. 8ÐChanges in recruitment of the trunk muscles in low back pain ptrunk muscles (Transversus abdominis [TrA]), obliquus internus abdomand erector spinae (ES) associated with rapid movement of the shouldeto the onset of deltoid EMG at zero. The shaded areas indicated theprogrammed by the central nervous system. Any activity occurring mre¯exly from the pertubation produced by the movement. Signi®canmovement in each direction and the direction speci®c changes of the o


of the super®cial trunk muscles (Hodges & Richard-son 1998a) in people with low back pain.

The implications of these ®ndings are considerable.If the model of the contribution of TrA to spinalstability is correct then the speci®c dysfunction of thismuscle in low back pain implies that it is this aspectof spinal stability that is de®cient. The motion of thespine associated with limb movement has not beeninvestigated in people with low back pain. In order tocon®rm this hypothesis it would be necessary toevaluate both segmental motion and spinal orienta-tion during limb movement. With methods beingdeveloped for the direct measurement of intersegmental motion (Willems et al. 1997) this presentsas an exciting possibility for the future.

Two further groups of studies provided additionalindirect evidence for a change in the activation ofTrA in low back pain patients. Several studies havebeen undertaken to investigate the ability of low backpain patients and control subjects to perform anabdominal manoeuvre thought to activate TrAspeci®cally. In this task subjects gently draw in theirabdominal wall (Richardson & Jull 1995; Richardsonet al. 1998) and the displacement of the abdominalwall is measured as the reduction in pressure in anair-®lled bag placed under the abdomen. Interestinglythe ability to consciously perform this manoeuvre isrelated to the timing of onset of contraction of TrAassociated with rapid limb movement (Hodges et al.1996). A major ®nding has been that the majority of

atients. Mean time of onset of electromyographic activity (SD) of theinis [OI], obliquus externus abdominis [OE], rectus abdominis [RA])r averaged over ten repetitions for 15 subjects. The onsets are alignedtime period in which a muscle must be active in order to be pre-ore than 50 ms after the onset of deltoid EMG may be mediatedt di�erences are noted. Note the delayed activation of TrA withther muscles. (Adapted form Hodges & Richardson [1996]).

Manual Therapy (1999) 4(2), 74±86

84 Manual Therapy

people with a history of low back pain are unable toperform the manoeuvre adequately while people withno history of low back pain can (Jull et al. 1995;Richardson et al. 1995).

A randomized, controlled clinical trial has beenundertaken in which TrA was being trained in peoplewith chronic low back and a radiological diagnosis ofspondylolisthesis/spondylosis (O'Sullivan et al. 1997).Following training these patients achieved a reduc-tion in pain and reduction in functional disability thatwas maintained at 30 months after the completionof the training period. While TrA was not directlymeasured in this study and it is impossible to deter-mine whether the contraction of TrA was altered bythis training, this study provides additional indirectsupport for the relationship of TrA to low back pain.

RELEVANCE TO CLINICAL PRACTICE

With the apparent e�cacy of TrA training in themanagement of low back pain, it is imperative thatseveral points be considered when training thismuscle:

* TrA is controlled independently of the other trunkmuscles and should be trained separately from theother trunk muscles:

* TrA is the principle abdominal muscle a�ected inlow back pain and should be trained separatelyfrom the other trunk muscles.

* TrA should be trained to contract tonically but notat a constant level.

* TrA loses its tonic function in low back pain andneeds to be trained to regain this function.

* The functional interaction between TrA, dia-phragm and pelvic ¯oor muscles should beconsidered.

* TrA has a similar function in many situations andexercise may not need to be performed infunctional positions initially.

CONCLUSION AND DIRECTIONS FOR THEFUTURE

Many questions remain unanswered regarding thecontribution of TrA to spinal stability. While thestudies presented here provide indirect evidence of thefunction of TrA, it is imperative that data is obtainedto con®rm the mechanical contribution of TrA tostability and the consequence of changes in itsactivation in the presence of low back pain. Furtherstudies are required to further document the feedfor-ward and feedback mechanisms of control of thismuscle and the coordination between breathing andspinal stability. Additional investigation is requiredto con®rm, (or exclude) the proposed model of the

Manual Therapy (1999) 4(2), 74±86

contribution of TrA to spinal stability. One questionthat remains unsolved is the possible contribution ofTrA to trunk rotation. While some studies havefound activation of TrA with ipsilateral trunkrotation (Cresswell et al. 1992; Hemborg 1997) othershave failed to ®nd a relationship (DeTroyer et al.1990). In addition, the temporal parameters of theresponse of TrA are una�ected by changes indirection of rotation provoked by unilateral upperlimb movement in di�erent directions (Hodges &Richardson 1997b).

Thus while the initial evidence for a speci®c andcrucial role of TrA in providing stability to thelumbo-pelvic region exists, further work is needed tocon®rm these ®ndings.

ACKNOWLEDGEMENTS

I would like to thank Associate Professor CarolynRichardson, Professor Simon Gandevia, ProfessorAlf Thorstensson and Dr Andrew Cresswell for theircollaboration and input into many of the studiespresented here. I would also like to thank AssociateProfessor Gwen Jull for her input and comments onthe manuscript. Financial assistance was provided bythe NHMRC of Australia.

References

Abe T, Kusuhara N, Yoshimura N, Tomita T, Easton PA 1996Di�erential respiratory activity of four abdominal muscles inhumans. Journal of Applied Physiology 80: 1379±1389

Agostoni E, Campbell EJM 1970 The abdominal muscles. In:Campbell EJM, Agostoni E, Newsom-Davis J (eds) TheRespiratory Muscles: Mechanisms and Neural Control. Lloyd-Luke, London; pp 175±180

Allison G, Kendle K, Roll S, Schupelius J, Scott Q, Panizza J1998 The role of the diaphragm during abdominal hollow-ing exercises. Australian Journal of Physiotherapy 44:95±104

Aruin AS, Latash ML 1995 Directional speci®city of posturalmuscles in feed-forward postural reactions during fastvoluntary arm movements. Experimental Brain Research 103:323±332

Askar OM 1977 Surgical anatomy of the aponeurotic expansionsof the anterior abdominal wall. Annals of the Royal College ofSurgeons of England 59: 313±321

Bartelink DL 1957 The role of intra-abdonimal pressure inrelieving the pressure on the lumbar vertebral discs. Journal ofBone and Joint Surgery 39B: 718±725

Belenk'ii V, Gur®nkel VS, Paltsev Y 1967 Elements of control ofvoluntary movements. Bio®zika 12: 135±141

Bergmark A 1989 Stability of the lumbar spine. A study inmechanical engineering. Acta Orthopedica Scandinavica Suppl230: 1±54

Bogduk N, MacIntosh JE 1984 The applied anatomy of thethoracolumbar fascia. Spine 9: 164±170

Bogduk N, Macintosh JE, Pearcy M 1992 A universal modelof the lumbar back muscles in the upright position. Spine 17:897±913

Bouisset S, Zattara M 1981 A sequence of postural adjustmentsprecedes voluntary movement. Neuroscience Letters 22:263±270

Bouisset S, Zattara M 1987 Biomechanical study of theprogramming of anticipatory postural adjustments associated



with voluntary movement. Journal of Biomechanics 20:735±742

Brown J, Frank JS 1987 In¯uence of event anticipation on posturalactions accompanying voluntary movement. ExperimentalBrain Research 67: 645±650

Cholewicki J, Panjabi MM, Kachatryan A 1997 Stabilizingfunction of trunk ¯exor-extensor muscles around a neutralspine posture. Spine 22: 2207±2212

Cordo PJ, Nashner LM 1982 Properties of postural adjustmentsassociated with rapid arm movements. Journal ofNerurophysiology 47: 287±308

Cresswell AG 1993 Responses of intra-abdominal pressure andabdominal muscle activity during dynamic trunk loading inman. European Journal of Applied Physiology 66: 315±320

Cresswell AG, Grundstrom H, Thorstensson A 1992 Observationson intra-abdonimal pressure and patterns of abdominal intramuscular activity in man. Acta Physiologica Scandinavica 144:409±418

Cresswell AG, Oddsson L, Thorstensson A 1994 The in¯uence ofsudden perturbations on trunk muscle activity and intra-abdominal pressure while standing. Experimental BrainResearch 98: 336±341

Cresswell AG, Thorstensson A 1989 The role of the abdominalmusculature in the elevation of the intra-abdominal pressureduring speci®ed tasks. Ergonomics 32: 1237±1246

Cresswell AG, Thorstensson A 1993 Change in intra-abdominalpressure, trunk muscle activation and force during isokineticlifting and lowering. European Journal of Applied Physiology

Delhez L 1968 Motor activity of the respiratory system. Poumon etLe Coeur 24: 845±888

DeTroyer A 1983 Mechanical role of the abdominal muscles inrelation to posture. Respiration Physiology 53: 341±353

DeTroyer A, Estenne M, Ninane V, VanGansbeke D, Gorini M1990 Transversus abdominis muscle function in humans.Journal of Applied Physiology 68: 1010±1016

Friedli WG, Hallet M, Simon SR 1984 Postural adjustmentsassociated with rapid voluntary arm movements I.Electromyographic data. Journal of Neurology, Neurosurgeryand Psychiatry 47: 611±622

Friedli WG, Cohen L, Hallet M, Stanhope S, Simon SR 1988Postural adjustments associated with rapid voluntary armmovements. II Biomechanical analysis. Journal of Neurology,Neurosurgery and Psychiatry 51: 232±243

GaheÂ ry Y, Massion J 1981 Co-ordination between posture andmovement. Trends in Neuroscience 4: 199±202

Gardner-Morse M, Stokes IAF, Laible JP 1995 Role of muscles inlumbar spine stability in maximum extension e�orts. Journal ofOrthopaedic Research 13: 802±808

Gardner-Morse MG, Stokes IA 1998 The e�ects of abdominalmuscle coactivation on lumbar spine stability. Spine 23: 86±91

Goldman JM, Lehr RP, Millar AB, Silver JR 1987 Anelectromyographic study of the abdominal muscles duringpostural and respiratory manoeuvres. Journal of Neurology,Neurosurgery and Psychiatry 50: 866±869

Grillner S, Nilsson J, Thorstensson A 1978 Intra-abdominalpressure changes during natural movements in man. ActaPhysiologica Scadinavica 103: 275±283

Gur®nkel VS 1994 The mechanisms of postural regulation in man.Soviet Scienti®c Reviews. Section F. Physiology and GeneralBiology 7: 59±89

Hemborg B 1997 personal communicationHemborg B, Moritz U, LoÈ wing H 1985 Intra-abdominal pressure

and trunk muscle activity during li®tng. IV. The causual factorsof the intra-abdominal pressure rise. Scandinavian Journal ofRehabilitation Medicine 17: 25±38

Henke KG, Sharratt M, Pegelow D, Dempsey JA 1988 Regulationof end-expiratory lung volume during exercise. Journal ofApplied Physiology 64: 135±146

Hodges PW, Richardson CA, Jull GA 1996 Evaluation of therelationship between the ®ndings of a laboratory and clinicaltest of transversus abdominis function. Physiotherapy ResearchInternational 1: 30±40

Hodges PW, Butler JE, McKenzie D, Gandevia SC 1997aContraction of the human diaphragm during posturaladjustments. Journal of Physiology 505.2: 239±548

Hodges PW, Gandevia SC, Richardson CA 1997b Contractions ofspeci®c abdominal muscles in postural tasks are a�ected by


respiratory maneuvers. Journal of Applied Physiology 83:753±760

Hodges PW, Cresswell AG, Thorstensson A 1998 Preparatorytrunk motion precedes upper limb movement. ExperimentalBrain Research 124: 69±79

Hodges PW, Richardson CA 1996 Ine�cient muscular stabilisationof the lumbar spine associated with low back pain: a motorcontrol evaluation of transversus abdominis. Spine 21: 2640±2650

Hodges PW, Richardson CA 1997a Contraction of the abdominalmuscles associated with movement of the lower limb. PhysicalTherapy 77: 132±144

Hodges PW, Richardson CA 1997b Feedforward contraction oftransversus abdominis is not in¯uenced by the direction of armmovement. Experimental Brain Research 114: 362±370

Hodges PW, Richardson CA 1997c Relationship between limbmovement speed and associated contraction of the trunkmuscles. Ergonomics 40: 1220±1230

Hodges PW, Richardson CA 1998a Changes in the central nervoussystem organisation of transversus abdominis contractionassociated with limb movement. (submitted)

Hodges PW, Richardson CA 1998b Delayed postural contractionof transversus abdominis associated with movement of thelower limb in people with lower back pain. Journal of SpinalDisorders 11: 46±56

Hodges PW, Richardson CA 1998c Altered trunk musclerecruitment in people with low back pain with limb movementat di�erent speeds. (submitted)

Hodges PW, Richardson CA 1998d Transversus abdominis and thesuper®cial abdominal muscles are controlled independently in apostural task. (submitted)

Johansson H, Sjolander P, Sojka P 1991 A sensory role for thecruciate ligaments. Clinical Orthopaedic and related Research268: 161±178

Jull GA, Richardson CA 1994 Rehabilitation of active stabilisationof the lumbar spine. In: Twomey LT, Taylor JR (eds) PhysicalTherapy of the Lumbar Spine, 2nd Ed. Churchill Livingstone,New York, ch 9, pp 251±283

Jull GA, Richardson CA Hamilton C, Hodges P, Ng J 1995Towards the validation of a clinical test for the deep abdominalmuscles in back pain patients. In: Proceedings of the 9thBiennial Conference of the Manipulative PhysiotherapistsAssociation of Austrialia, Gold Coast, Australia, p65

Keith A 1923 Man's posture: its evolution and disorders. BritishMedical Journal 1: 587±590

Kendall PH, Jenkins JM 1968 Exercises for backache: a doubleblind controlled trial. Physiotherapy 54: 154±157

Koes BW, Bouter LM, Beckerman H, van der Heijden GJ,Knipschild PG 1991 Physiotherapy exercises and backpain: a blinded review. British Medical Journal 302:1572±1576

Lee WA 1980 Anticipatory control of postural and task musclesduring rapid arm ¯exion. Journal of Motor Behavior 12:185±196

Lee WA, Buchanan TS, Rogers MW 1987 E�ects of armacceleration of behavioural conditions on the organisation ofpostural adjustments during arm ¯exion. Experimental BrainResearch 66: 257±270

Manniche C, Hesselsoe G, Bentzen L, Christenesen I, Lundberg E1988 Clinical trial of intensive muscle training for chronic lowback pain. The Lancet: 1473±1476

Marras WS, Mirka GA 1996 Intra-abdominal pressureduring trunk extension motions. Clinical Biomechanics11: 267±274

Marsden CD, Merton PA, Morton HB 1977 Anticipatory posturalresponses in the human subject. Jounral of Physiology 275:47P±48P

Massion J 1976 Postural function of respiratory muscles. In: DuronB (ed) Respiratory Centres and A�erent Systems. Colloques deI'INSERM 59: pp 175±181

Massion J 1992 Movement, posture and equilibrium: interactionand coordination. Progress in Neurobiology 38: 35±56

Massion J, Viallet F, Massarino R, Khalil R 1989 Supplemen-tary motor area region in involved in the coordination bet-ween movement and posture. Comptes Rendus De L'AcademieDes Sciences. Seire III. Sciences de la Vie (Paris) 308:417±423

Manual Therapy (1999) 4(2), 74±86

86 Manual Therapy

McGill SM 1996 A revised anatomical model of the abdominalmusculature for torso ¯exion e�orts. Jounal of Biomechanics29: 973±977

McKenzie DK, Gandevia SC, Gorman RB, Southon FCG 1994Dynamic changes in the zone of apposition and diaphragmlength during maximal respiratory e�orts. Thorax 49:634±638

Miller MI, Medeiros JM 1987 Recruitment of internal oblique andtransversus abdominis muscle during the eccentric phase of thecurl-up exercise. Physical Therapy 67: 1213±1217

Morris JM, Lucas DM, Bresler B 1961 Role of the trunk instability of the spine. Journal of Bone and Joint Surgery 43A:327±351

Nachemson A 1985 Lumbar spine instability: a critical update andsymposium summary. Spine 10: 290±291

O'Sullivan PB, Twomey LT, Allison GT 1997 Evaluation ofspeci®c stabilizing exercise in the treatment of chronic low backpain with radiologic diagonisis of spondylolysis orspondylolisthesis. Spine 22: 2959±2967

Panjabi MM 1992a The stabilizing system of the spine. Part II.Neutral zone and instability hypothesis. Journal of SpinalDisorders 5: 390±397

Panjabi MM 1992b The stabilizing system of the spine. Part IFunction, dysfunction, adaptation, and enhancement. Journalof Spinal Disorders 5: 383±389

Paulingnan Y, Dufosse M, Hugon M, Massion J 1989 Acquisitionof co-ordination between posture and movement in a bimanualtask. Experimental Brain Research 77: 337±348

Puckree T, Cerny F, Bishop B 1998 Abdominal motor unit activityduring respiratory and nonrespiratory tasks. Journal of AppliedPhysiology 84: 1707±1715

Richardson C, Jull G, Toppenberg R, Comerfoed M 1992Techniques for active lumbar stabilisation for spinal protection:a pilot study. Australian Journal of Physiotherapy 38: 105±112

Richardson CA, Jull GA 1995 Muscle control-pain control. Whatexercises would you prescribe? Manual Therapy 1: 2±10

Richardson CA, Jull GA, Richardson BA 1995 Dysfunction of thedeep abdominal muscles exists in low back pain patients. In:

Manual Therapy (1999) 4(2), 74±86

Proceedings of the 12th International Congress of the WorldConfederation for Physical therapy, Washington DC, USA,p932

Richardson CA, Jull GA, Hodges PW, Hides JA 1999 Therapeuticexercise for spinal segmental stabilisation in low back pain:scienti®c basis and clinical approach. Churchill Livingstone (inpress)

Robinson R 1992 The new back school prescription: stabilizationtraining Part I. Occupational Medicine: State of the ArtReviews 7: 17±31

Snijders CJ, Vleeming A, Stoekart R, Mens JMA, Kleinrensink GJ1995 Biomechanical modelling of sacroliliac stability indi�erent postures. Spine: State of the Art Reviews 9: 419±432

Strohl KP, Mead J, Banzett RB, Loring SH, Kosch PC 1981Regional di�erences in abdominal muscle activity duringvarious manoeuvers in humans. Journal of Applied Physiology51: 1471±1476

Tesh KM, ShawDunn J, Evans JH 1987 The abdominal musclesand vertebral stability. Spine 12: 501±508

Wilke HJ, Wolf S, Claes LE, Arand M, Wiesend A 1995 Stabilityincrease of the lumbar spine with di�erent muscle groups: abiomechanical in vitro study. Spine 20: 192±198

Willems PC, Nienhuis B, Sietsma M, van der Schaaf DB, PavlovPW 1997 The e�ect of a plaster cast on lumbosacral jointmotion. An in vivo assessment with precision motion analysissystem. Spine 22: 1229±1234

Williams PL, Warwick R, Dyson M, Bannister LH (eds) 1989 In:Grays Anatomy, 38th Ed. Churchill Livingstone, Edinburgh

Zattara M, Bouisset S 1986 Chronometric analysis of the posturokinetic programming of voluntary movement. Journal of MotorBehaviour 18: 215±223

Zattara M, Bouisset S 1988 Posturo-kinetic organisation during theearly phase of voluntary upper limb movement. I. Normalsubjects. Journal of Neurology, Neurosurgery and Psychiatry51: 956±965

Zetterberg C, Andersson GB, Schultz AB 1987 The activity ofindividual trunk muscles during heavy physical loading. Spine12: 1035±1040


hodges 1999

Documents