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Artigo paulo

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Artigo paulo

  1. 1. Downloaded from bjsm.bmj.com on 9 June 2009 Changes in recruitment of transversus abdominis correlate with disability in people with chronic low back pain Paulo Ferreira, Manuela Ferreira, Christopher Maher, Kathryn Refshauge, Robert Herbert and Paul Hodges Br. J. Sports Med. published online 26 May 2009; doi:10.1136/bjsm.2009.061515 Updated information and services can be found at: http://bjsm.bmj.com/cgi/content/abstract/bjsm.2009.061515v1 These include:Rapid responses You can respond to this article at: http://bjsm.bmj.com/cgi/eletter-submit/bjsm.2009.061515v1 Email alerting Receive free email alerts when new articles cite this article - sign up in the box at the service top right corner of the article NotesOnline First contains unedited articles in manuscript form that have been peer reviewed andaccepted for publication but have not yet appeared in the paper journal (edited, typeset versionsmay be posted when available prior to final publication). Online First articles are citable andestablish publication priority; they are indexed by PubMed from initial publication. Citations toOnline First articles must include the digital object identifier (DOIs) and date of initial publication.To order reprints of this article go to:http://journals.bmj.com/cgi/reprintformTo subscribe to British Journal of Sports Medicine go to:http://journals.bmj.com/subscriptions/
  2. 2. Downloaded from bjsm.bmj.com on 9 June 2009 BJSM Online First, published on May 26, 2009 as 10.1136/bjsm.2009.061515Changes in recruitment of transversus abdominis correlate with disability in peoplewith chronic low back pain.Paulo H Ferreira PhD1, 2, Manuela L Ferreira PhD1, Christopher G Maher PhD3, Kathryn RefshaugePhD1, Robert D Herbert PhD3, Paul W Hodges PhD41 Discipline of Physiotherapy, The University of Sydney, Sydney, Australia.2 Departamento de Fisioterapia, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.3 The George Institute for International Health, The University of Sydney, Sydney, Australia.4 Centre for Clinical Research Excellence in Spinal Pain, Injury and Health, School of Health andRehabilitation Sciences, The University of Queensland, Brisbane, Australia.Addresss for Correspondence:Dr. Paulo Ferreira, Discipline of Physiotherapy, Faculty of Health Sciences,University of Sydney, PO Box 170 Lidcombe 1825 AUSTRALIATel: 61 2 93519397 Fax: 61 2 93519601E-mail: p.ferreira@usyd.edu.auChanges in recruitment of transversus abdominis correlate with disability in peoplewith chronic low back pain.Key words: low back pain, motor control, ultrasonography. 1Copyright Article author (or their employer) 2009. Produced by BMJ Publishing Group Ltd under licence.
  3. 3. Downloaded from bjsm.bmj.com on 9 June 2009ABSTRACTObjectives: Although motor control exercises have been shown to be effective in the management oflow back pain (LBP) the mechanism of action is unclear. The current study investigated therelationship between ability to recruit transversus abdominis and clinical outcomes of participants in aclinical trial.Methods: Ultrasonography was used to assess the ability to recruit transversus abdominis in a nesteddesign: a sample of 34 participants with chronic low back pain was recruited from participants in arandomised controlled trial comparing efficacy of motor control exercise, general exercise and spinalmanipulative therapy. Perceived recovery, function, disability and pain were also assessed.Results: Participants with chronic LBP receiving motor control exercise had greater improvement inrecruitment of transversus abdominis (7.8%) than participants receiving general exercise (4.9%reduction) or spinal manipulative therapy (3.7% reduction). The effect of motor control exercise onpain reduction was greater in participants who had a poor ability to recruit transversus abdominis atbaseline. There was a significant, moderate correlation between improved recruitment of transversusabdominis and reduction in disability (r= -0.35; 95%CI 0.02 to 0.62).Conclusion: These data provide some support for the hypothesised mechanism of action of motorcontrol exercise and suggest that the treatment may be more effective in those with a poor ability torecruit transversus abdominis. 2
  4. 4. Downloaded from bjsm.bmj.com on 9 June 2009INTRODUCTIONChanges in recruitment of both the superficial and deep trunk muscles are common in people with lowback and pelvic pain. Activity of the large superficial muscles is often increased, although the natureof the increase varies.[1] Evidence suggests increased superficial muscle activity such as increased co-contraction of the flexor and extensor muscles[2], increased erector spinae activity during gait[3] andduring a sit-up task[4], and increased bracing of the abdominal muscles during an active straight legraise.[5] Conversely, activity of the deep trunk muscle, transversus abdominis is delayed[6-8] orreduced[9,10] during movements of the limbs and trunk which challenge the stability of the spine. Inthe absence of low back pain (LBP), transversus abdominis is generally activated prior to movement ofthe limbs or trunk and this activity appears to be independent of the direction of limb movement.[11-13] Healthy individuals also activate transversus abdominis in response to loading and forceapplication to the trunk.[14] It has been argued that this pattern of activation of transversus abdominisis important for control of intervertebral movement[15], particularly shear forces[16], and for control ofstability of the sacroiliac joints of the pelvis.[17] In LBP, changes in control of the trunk muscles,including transversus abdominis, are therefore thought to compromise control of the lumbar spine andpelvis. As activity of transversus abdominis can be impaired in LBP, one of the aims of contemporaryexercise interventions (such as the motor control exercise program) for patients with LBP is to retrainthe coordination of this muscle, as a component of the intervention.[18]Interventions aimed at training the control and coordination of the trunk muscles, including transversusabdominis, have been shown to be effective in the management of low back[19-23] and pelvicpain.[24] However, we do not yet know whether clinical improvements are associated with changes inthe recruitment of this muscle. Because transversus abdominis is situated deep to the more superficialabdominal muscles, intramuscular fine-wire electromyography (EMG) has been required to evaluate itsactivity.[6-8, 13, 25-29] Recent data using invasive recording methods in small groups of subjects haveprovided initial evidence that temporal aspects of activity of transversus abdominis can be modifiedwith training.[30, 31] More recently ultrasound imaging has been used to evaluate the morphology orrecruitment of deep muscles of the trunk, in an attempt to use less invasive tools.[18, 32-36] Duringcontraction, muscles change shape (e.g. thickness) in association with shortening of the muscle withsliding of actin and myosin filaments (even during isometric contractions because of tendonstretch).[36] There is a curvilinear relationship between changes in TrA thickness andelectromyographic activity, but this is almost linear when activity increases from a relaxed state up to~20% of maximum contraction.[36]A protocol developed to assess activity of transversus abdominis with ultrasound imaging has beenshown to be able to distinguish between people with and without LBP.[10] This protocol showed thatwhen subjects perform an isometric leg flexion and extension task, and the changes in thickness oftransversus abdominis are averaged across the two directions, LBP subjects have ~72% less increase inthe thickness of transversus abdominis, ~53% less in obliquus internus abdominis and ~2% less inobliquus externus abdominis than controls. That study[10] also demonstrated moderate to substantialcorrelations between ultrasound and fine wire EMG measures of muscle recruitment for transversusabdominis and obliquus internus (Pearsons’r = 0.74 to 0.85), but not obliquus externus (Pearson’s r =0.19).Motor control exercise aims to train coordination of the muscles of the trunk to meet the demands foroptimal spinal function. The exercise includes training the recruitment of the deeper muscles of thetrunk such as transversus abdominis.[18] It could be hypothesised that a greater change in thickness ofthe transversus abdominis muscle would be observed following this intervention than after other 3
  5. 5. Downloaded from bjsm.bmj.com on 9 June 2009treatments such as general exercise or spinal manipulative therapy which do not specifically trainactivation of the deep muscles of the spine. To be of clinical importance, a change in ultrasoundthickness should be accompanied by improvements in clinical outcomes.Changes in the ability to recruit transversus abdominis were measured in a sample drawn from chronicLBP patients participating in a randomised controlled trial of motor control exercises, generalexercises, and spinal manipulative therapy.[37] The specific aims of this study were to investigatewhether: 1) The ability to recruit transversus abdominis improves following an 8-week program of motor control exercise, general exercise, or spinal manipulative therapy; 2) Changes in recruitment of transversus abdominis are greater in patients receiving motor control exercise than patients receiving general exercise or spinal manipulative therapy; 3) Changes in the ability to recruit transversus abdominis correlate with improvements in clinical outcomes of perceived recovery, function, disability and pain; and 4) The effect of motor control exercise (compared to general exercise) on the clinical outcomes of perceived recovery, function, disability, and pain depends on the subjects’ ability to recruit transversus abdominis measured at baseline. 4
  6. 6. Downloaded from bjsm.bmj.com on 9 June 2009METHODSA sample of non-specific chronic LBP patients was taken from a randomised controlled trial[37] thatcompared the efficacy of motor control exercise, general exercise, and spinal manipulative therapy. Thefinal 45 subjects to be enrolled in the randomised controlled trial were invited to participate in thisstudy, of whom 34 were eligible to participate. This sample size provided 80% power to detect aPearson’s correlation coefficient between TrA recruitment and clinical outcome measures of at least 0.4(fair)[38] with 95% confidence intervals of 0.2 to 0.6. The study was approved by the Ethicscommittees of the University of Sydney and the South Western and Western Sydney Area HealthServices. Recruitment of transversus abdominis was measured using a published ultrasonographyprotocol.[10] The ultrasound measurement was made before participants were randomised to a motorcontrol exercise group, a general exercise group, or a spinal manipulative therapy group and again afterthe application of 12 sessions of treatment over an 8-week period. The clinical outcomes of perceivedrecovery, function, disability, and pain were also collected at the time of the ultrasoundmeasurement.[37]SubjectsPatients aged between 18 and 80 years with chronic low back pain (symptoms for at least 3 months)with or without pain referral to the leg, but without neurological deficit were recruited for the study. Tobe included in the trial, patients needed to have persistent pain or disability for at least 3 months, andthey had to score at least 3 points on the Roland Morris Disability Questionnaire and at least 2 units onthe 0-10 pain scale at the screening consultation. Exclusion criteria were: spinal surgery in the past 12months; pregnancy at the first assessment; suspected or diagnosed serious spine pathology(inflammatory spondyloarthropathy, fracture, malignancy, cauda equina syndrome, or infection); nerveroot compromise; contra-indications to exercise; or poor English comprehension.InterventionBased on the randomisation procedure, participants received motor control exercise, general exercise,or spinal manipulative therapy. Participants allocated to the motor control exercise group wereprescribed exercises aimed at improving control of lumbopelvic movement and stability. Exercisesincluded training function of specific deep muscles of the low back region, coordination of deep trunkmuscles with diaphragmatic respiration pattern, control of a neutral lumbar posture, and reduction ofany excessive superficial trunk muscle activation.[39] Participants allocated to the general exercisegroup received the program described by Klaber Moffet[40], which is based on a biopsychosocialmodel and aims to overcome a fear of movement and to improve physical function in both the short-and long-term. For subjects allocated to the spinal manipulative therapy group, joint mobilisationtechniques, but not thrust manipulation techniques, were applied to the participant’s spine or pelvisusing grades and techniques that were at the discretion of the treating physiotherapist.[41]Clinical outcomesClinical outcomes were measured at baseline and after eight weeks of treatment. Global impression ofrecovery was measured on an 11-point scale.[42] Disability was measured using the 24-item version ofthe Roland Morris Disability Questionnaire.[43] Average pain intensity over the last week wasmeasured on a numerical rating scale [42] Function was measured with a modified Patient-SpecificFunctional Scale.[42] 5
  7. 7. Downloaded from bjsm.bmj.com on 9 June 2009UltrasonographyUltrasound images were made with a 5.5 cm, 5 MHz linear array ultrasound transducer1*. Thetransducer was placed transversely across the right abdominal wall along a line mid-way between theinferior angle of the rib cage and the iliac crest. The medial edge of the transducer was positioned sothat the medial edge of transversus abdominis was aligned in the right-hand one-third of the ultrasoundimage when the subject was relaxed. The location of the transducer was recorded for standardisation ofplacement across measurement sessions. All ultrasound measures were made blinded to the subject’streatment group.ProcedureA previously published ultrasonography protocol was used to measure change in thickness of TrA as anindirect measure of recruitment during a task that involved generation of flexion and extension torqueat the knee.[10] Unlike other measurements of voluntary TrA recruitment such as the abdominaldrawing-in manoeuvre, this protocol involved measurement of automatic activation of trunk musclesduring the leg task with no conscious attention to the abdominal muscles. Participants were positionedin supine on a bed with arms crossed over the chest, the hips flexed to 50 degrees and knees flexed to90 degrees. Knee flexion and extension force was monitored with a spring scale attached to a beltstrapped around the ankles. Patients were instructed to remain relaxed prior to testing and then toperform isometric knee flexion or extension contractions to target forces of 7.5% of body weight. Theorder of testing movement direction was randomised and patients were provided with verbal feedbackabout force by the examiner reading the spring scale. Two repetitions of each task were performed andstatic transversus abdominis ultrasound images were made both at rest and once the target isometricknee flexion or extension force had been reached. Reliability analysis for this ultrasonography protocolhas been shown to be excellent with an Intraclass Correlation [3,1] Coefficient of 0.85 and a minimaldetectable change score of 1.16%.[44]Data extractionTransversus abdominis thickness was measured using ultrasonography with custom-designed software.A grid was placed over the image and measures of muscle thickness of transversus abdominis weremade at three sites: the middle of the image and 1 cm (calibrated to the image scale) on either side ofthe midline. The average of the three measures from each image was recorded for analysis and thethickness for each direction of movement was expressed as a proportion of the thickness at rest andaveraged over the 2 repetitions of the task. Change in thickness of transversus abdominis was obtainedby averaging the values for both directions of movement.Statistical analysisMeans and standard deviations were employed to describe demographic data, recruitment oftransversus abdominis recorded as a change in thickness measured with ultrasonography, and clinicaloutcomes (perceived recovery, function, disability and pain).Changes in recruitment of transversus abdominis and clinical outcomes within groups were analysedwith paired t-tests. Differences between treatment groups in the ability to recruit transversus abdominiswere analyzed using a one-way ANOVA and Tukey post hoc tests on the change scores. Pearson’s rwas used to analyse the relationship between changes in transversus abdominis recruitment andchanges in clinical outcomes. Linear regression was used to analyze whether the effect of motor controlexercise (contrasted to general exercise) on final clinical outcomes was influenced by subject’s ability1 Logic 100 Pro General Electric 6
  8. 8. Downloaded from bjsm.bmj.com on 9 June 2009to recruit transversus abdominis at baseline after adjusting for baseline clinical outcomes. Asignificance level of 5% was chosen a priori.RESULTSForty-five participants in the randomized control trial within which the present study was nested, wereinvited to participate. Of these, 4 refused to participate, 3 did not tolerate the test procedure because ofpain in the knee or hip joints, and in 4 it was not possible to obtain a clear image of transversusabdominis due to excessive adipose tissue. A total of 34 participants were therefore recruited into thisstudy. The final sample included 11 participants in the motor control exercise group, 10 patients in thegeneral exercise group, and 13 patients in the spinal manipulative therapy group (Figure 1). <<figure 1 approximately here>>Baseline demographic data, recruitment of transversus abdominis, and clinical outcomes are presentedin Table 1. Patients attended a mean (SD) of 8.7 (2.6) motor control exercise sessions, 11.2 (1.5)general exercise sessions, and 9.2 (2.4) spinal manipulative therapy sessions. All 34 patients werereassessed after treatment. There were no significant between-group differences in the baseline clinicaloutcomes or TrA recruitment (one-way ANOVA, p 0.05 for all comparisons). Between-group ≥comparisons were conducted on change scores or ANCOVA-adjusted scores using the baseline as acovariate so that any discrepancies in baseline scores would not cause bias. 7
  9. 9. Table 1 – Baseline characteristics of the study participants. MCE (n=11) GE (n=10) SMT (n=13)Age (years) 47.5 (17.3) 54.9 (11.3) 45.4 (17.7)Weight (kg) 78.7 (13.0) 70.1 (12.0) 72.6 (10.2)Height (cm) 171.0 (10.8) 160.7 (6.6) 165.0 (8.5)Female n (%) 6 (55) 7 (70) 10 (77)Pain duration (weeks) 104 (93) 183 (134) 114 (86) Downloaded from bjsm.bmj.com on 9 June 2009Work status (number (%) Full time 1 (10) 0 (0) 3 (23) Part time 2 (20) 0 (0) 3 (23) Not working 7 (70) 11 (100) 7 (54)Transversus abdominis recruitment 4.6 (7.7) 13.7 (14.9) 8.5 (11.3)Perceived recovery at baseline (-5 to 5) -2.91 (1.64) -3.70 (1.06) -2.38 (2.32)PSFS at baseline (1-30) 11.09 (3.21) 9.70 (4.14) 11.62 (4.66)RM at baseline (0-24) 14.00 (4.94) 12.70 (6.00) 9.77 (5.93)Pain at baseline (0-10) 6.36 (2.20) 7.50 (1.35) 5.38 (2.22)Values shown are means and standard deviations (except for work status).Transversus abdominis recruitment measured as change in muscle thickness as % of resting thickness; PSFS patient specific functional scale;RM Roland Morris disability questionnaire; MCE motor control exercise; GE general exercises; SMT spinal manipulative therapy. 8
  10. 10. Downloaded from bjsm.bmj.com on 9 June 2009The clinical and ultrasound measures are shown in Table 2. All 3 groups improved in the clinicaloutcomes of perceived recovery, function, disability and pain at the 8-week follow-up. Transversusabdominis recruitment improved by 7.8% in the motor control exercise group and deteriorated by 4.9%in the general exercise and 3.7% in the spinal manipulative therapy groups. Paired t-tests revealed thatnone of these changes were statistically significant. However the change in recruitment observed withmotor control exercise approached significance (t10 = 2.02; p = 0.07). 9
  11. 11. Table 2 - Baseline, final, and improvement scores for transversus abdominis recruitment and clinical outcomes, for all groups. MCE (n=11) GE (n=10) SMT (n=13)Transversus abdominis Baseline 4.6 (7.7) 13.7 (14.9) 8.5 (11.3)recruitment (% change from Final 12.4 (11.6) 8.8 (12.1) 4.9 (9.1)resting thickness) Improvement 7.8 (12.8) -4.9 (10.7) -3.7 (10.9) Baseline -2.91 (1.64) -3.70 (1.06) -2.38 (2.32) Downloaded from bjsm.bmj.com on 9 June 2009Perceived recovery (-5 to 5) Final 2.09 (2.88) 1.50 (3.24) 3.08 (1.66) Improvement 5.00 (3.10)* 5.20 (2.94)* 5.46 (2.85)* Baseline 11.09 (3.21) 9.70 (4.14) 11.62 (4.66)PSFS (1-30) Final 18.91 (6.55) 14.50 (6.29) 20.92 (5.66) Improvement 7.82 (7.33)* 4.80 (3.79)* 9.31 (6.55)* Baseline 14.00 (4.94) 12.70 (6.00) 9.77 (5.93)RM (0-24) Final 7.36 (6.59) 9.00 (6.04) 4.15 (2.76) Improvement 6.64 (5.68)* 3.7 (5.06)* 5.62 (5.09)* Baseline 6.36 (2.20) 7.50 (1.35) 5.38 (2.22)Pain (0-10) Final 4.00 (2.37) 4.70 (1.77) 2.92 (1.71) Improvement 2.36 (3.20)* 2.80 (2.70)* 2.46 (2.33)*Values are means and standard deviations. Change scores calculated so positive scores are improvements. *denotes significant at p<0.05. Transversusabdominis recruitment measured as change in muscle thickness as % of resting thickness; PSFS patient specific functional scale; RM Roland Morrisdisability questionnaire; MCE motor control exercise; GE General Exercises; SMT spinal manipulative therapy. 10
  12. 12. Downloaded from bjsm.bmj.com on 9 June 2009There were significant differences between groups with respect to the improvement in transversusabdominis recruitment (F2,31 = 4.09; p = 0.026). Motor control exercise produced 12.7% greaterimprovement in transversus abdominis recruitment than general exercise (p = 0.043) and 11.4%greater improvement than spinal manipulative therapy (p = 0.053). No difference in improvementwas found between the spinal manipulative therapy and general exercise groups (p = 0.963).When data from the 3 groups were pooled (Fig 2), there was a correlation between improvements inrecruitment of transversus abdominis and improvements in the clinical outcomes of perceivedrecovery (r= 0.27; 95%CI -0.08 to 0.55); Roland Morris disability scores (r= -0.35; 95%CI 0.02 to0.62); patient-specific functional scores (r = 0.19; 95%CI -0.16 to 0.50) and pain (r = -0.28; 95%CI0.07 to -0.56). Only the correlation with the Roland Morris disability score was statisticallysignificant. <<figure 2 approximately here>>The effect of motor control exercise (versus general exercise) was greater in subjects who had apoorer ability to recruit transversus abdominis at baseline, however the estimates of this interactioneffect are imprecise and only statistically significant for the pain outcome. The interaction effect forpain was: 18.1 (1.2 to 34.9) p= 0.037. The interpretation of this finding is that a subject who had abaseline transversus abdominis activation score of 0.00 would have 3.6 units less pain at theconclusion of treatment than a subject whose baseline transversus abdominis activation score was0.20 ie (0.00-0.20)x18.1 = -3.6. The interaction effects for the other outcomes were Roland Morrisdisability (effect = 16.1; -34.0 to 66.2; p = 0.506); patient-specific function (effect = -13.7; -67.2 to39.9; p = 0.597); and for perceived recovery (effect = -19.9; -45.3 to 5.5; p = 0.116). 11
  13. 13. Downloaded from bjsm.bmj.com on 9 June 2009DISCUSSIONThis study shows that, in chronic LBP, the improvement in recruitment of the trunk muscletransversus abdominis, measured by changes in thickness with ultrasonography, was greater inthose who performed motor control exercise than in those who undertook a program of generalexercise or spinal manipulative therapy. The motor control exercise group showed an absoluteincrease in recruitment of transversus abdominis of 7.8% compared with a slight decrease inrecruitment of transversus abdominis in the general exercise group (-4.9%) and in the spinalmanipulative therapy group (-3.7%). All these values exceeded the previously reported minimaldetectable change score of 1.16% for the ultrasonographic measurement of transversus abdominis.This magnitude of change demonstrates that changes in recruitment with the implementation oftreatments are above the potential error associated with the measurement.Our results suggest that relieving pain with spinal manipulative therapy or encouraging generalactivity with a general exercise program is not sufficient to maximally improve the ability to recruittransversus abdominis. We found that application of a motor control exercise program was the mosteffective method for improving recruitment of transversus abdominis in people with chronic LBP.Improvements in transversus abdominis recruitment associated with motor control training havealso been identified in the short term (4 weeks) in LBP patients[45] as well as in asymptomaticsubjects.[46] Other studies of fine-wire EMG recordings of transversus abdominis activity havereported changes in timing of muscle activation after motor control training, both immediately[31]and at 6 months.[30] Similar results have been noted for other deep muscles of the spine in anothertrial evaluating physical treatment of acute LBP.[47] Hides et al[47] found in patients with acuteLBP, that motor control exercise, but not usual medical care, reduced multifidus asymmetrybetween the symptomatic and asymptomatic sides. Similar to the present study, the participants inHides and colleagues’ study in both groups exhibited similarly large improvements in pain anddisability at the end of four weeks of treatment, however the group that did not receive multifidusexercise did not restore the symmetry of multifidus. Although the short term outcomes were similarfor pain and disability differences were apparent in the long term, the group who had restoredsymmetry of multifidus experienced a significantly reduced rate of recurrence of episodes.[47]When data from the three treatment groups in our trial were pooled there was a moderate correlationbetween change in recruitment of transversus abdominis and perceived recovery. This correlationwas positive, which means that an increase in recruitment of transversus abdominis correlatedmoderately well with improvements in perceived recovery. There was also a moderate, negativecorrelation between increase in recruitment of transversus abdominis and disability measured withthe Roland Morris questionnaire, which means that an increase in the recruitment of transversusabdominis was associated with reductions in disability. Although neither pain nor function wasstatistically significantly correlated with transversus abdominis recruitment, the effects were in theanticipated direction.An important finding of the study was the interaction between subject’s ability to recruit transversusabdominis at baseline and the effect of motor control exercise (versus general exercise) on painoutcomes. The effect we found was in the direction suggested by clinical theories. In the maintrial[37] we demonstrated that motor control exercise produced better short-term outcomes thangeneral exercise and so on average motor control exercise is superior. However the interactioneffect means that motor control exercise worked best for participants who had a poor ability torecruit transversus abdominis and conversely for participants who have a good ability to activatethis muscle general exercise may be a better treatment option. We are aware that it is possible togenerate spurious findings when looking for treatment interaction effects in clinical trials.[48,49] Toreduce the risk of this we specified our analysis a priori and confined our analysis to one predictorthat was biologically plausible. We used the preferred approach of a statistical test of an interactionand confined the analysis to primary outcomes. 12
  14. 14. Downloaded from bjsm.bmj.com on 9 June 2009Although we have demonstrated that the baseline ability to recruit TrA modifies the treatment effectof motor control exercise (versus general exercise) it would be premature to attempt to apply thisresearch finding to the routine clinical management of LBP. We first need to replicate the result in alarger, independent sample so that we can generate a more precise estimate of the magnitude ofeffect modification and also generate cut-off scores for the ability to recruit TrA. Such data could beused to develop a clinical prediction rule. Lastly the rule would have to be validated in a clinicaltrial and then demonstrate the impact of implementation of the rule on the outcomes of care insubsequent research.[50] We expect this process to take some years.ConclusionIt has been uncertain whether motor control exercises lead to changes in activation of transversusabdominis and whether these changes are associated with clinical improvements. Our findings showthat, after adjusting for baseline values, a greater change in the automatic activation of transversusabdominis, measured by ultrasonography, occurs after a motor control exercise program than afterother interventions, and this change in muscle activity is associated with improvements in disability.The study also demonstrated that the pain-relieving effect of motor control exercise is greater insubjects who have a poor ability to recruit this muscle at baseline. 13
  15. 15. Downloaded from bjsm.bmj.com on 9 June 2009WHAT IS ALREADY KNOWN ON THIS TOPIC • Recruitment of transversus abdominis is impaired in patients with LBP. • Motor control exercises aimed at training the control and coordination of the trunk muscles,including transversus abdominis, are effective in the management of LBP.WHAT THIS STUDY ADDS • Changes in the recruitment of transversus abdominis appear to be specific to theimplementation of motor control exercises and are moderately associated with improvements indisability. • The treatment effects of motor control exercise are greater in those with a poorer ability torecruit transversus abdominis.Acknowledgements: the trial was funded by the Motor Accident Authority of NSW; ChrisMaher, Rob Herbert and Paul Hodges are supported by the National Health and Medical ResearchCouncil of Australia.Competing interests: noneFigure legendsFigure 1 - Flowchart of progress of patients. TrA, transversus abdominis.Figure 2 - Overall correlation between changes in recruitment of transversus abdominis measuredwith ultrasonography and changes in clinical outcomes. Lines represent the r2 line of best fit; PSFSPatient Specific Functional Scale; RM Roland Morris; TrA, transversus abdominis. 14
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  20. 20. Last 45 patients randomised to controlled trial invited to participate in the study 4 patients refused to participate 3 patients did not tolerate test procedure 4 patients did not show a clear image of transversus abdominis on screen Downloaded from bjsm.bmj.com on 9 June 2009 34 patients admitted to study RandomisationBaseline measures• TrA recruitment Motor control General Spinal• Perceived recovery exercise group exercise group Manipulative• Function (n=11) (n=10) group• Disability (n=13)• Pain Treatment (8 weeks)Follow-up measures• TrA recruitment Motor control General Spinal• Perceived recovery exercise group exercise group Manipulative• Function (n=11) (n=10) group• Disability (n=13)• Pain
  21. 21. 6 A B 25 4 20Perceived recovery PSFS change 2 15 R=0.2 0 R=0.3 R=0.4 10 -2 Downloaded from bjsm.bmj.com on 9 June 2009 5 -4 -6 0 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 TrA recruitment change TrA recruitment change C C D 8 4 4 R=-0.4 2 0 R=-0.3 Pain change RM change -4 0RM change -8 -2 -12 -4 -16 -20 -6 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 TrA recruitment change TrA recruitment change

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