ResearchReport - BackStrongself-report and physical performance measures seems ideal to represent function and disability. Only one study measured functional performance, and in only

An Intensive, Progressive ExerciseProgram Reduces Disability and ImprovesFunctional Performance in Patients AfterSingle-Level Lumbar MicrodiskectomyKornelia Kulig, George J. Beneck, David M. Selkowitz, John M. Popovich Jr,Ting Ting Ge, Sean P. Flanagan, Elizabeth M. Poppert, Kimiko A. Yamada,Christopher M. Powers, Stan Azen, Carolee J. Winstein, James Gordon,Srinath Samudrala, Thomas C. Chen, Arya Nick Shamie, Larry T. Khoo,Mark J. Spoonamore, Jeffrey C. Wang; Physical Therapy Clinical Research Network(PTClinResNet)

Background. Restoration of physical function following lumbar microdiskec-tomy may be influenced by the postoperative care provided.

Objective. The purpose of this study was to examine the effectiveness of a newinterventional protocol to improve functional performance in patients who haveundergone a single-level lumbar microdiskectomy.

Setting. The study was conducted in physical therapy outpatient clinics.

Design and Participants. Ninety-eight participants (53 male, 45 female) whohad undergone a single-level lumbar microdiskectomy were randomly allocated toreceive education only or exercise and education.

Intervention and Measurements. The exercise intervention consisted of a12-week periodized program of back extensor strength (force-generating capacity)and endurance training and mat and upright therapeutic exercises. The OswestryDisability Index (ODI) and physical measures of functional performance were tested4 to 6 weeks postsurgery and 12 weeks later, following completion of the interven-tion program. Because some participants sought physical therapy outside of thestudy, postintervention scores were analyzed for both an as-randomized (2-group)design and an as-treated (3-group) design.

Results. In the 2-group analyses, exercise and education resulted in a greaterreduction in ODI scores and a greater improvement in distance walked. In the3-group analyses, post hoc comparisons showed a significantly greater reduction inODI scores following exercise and education compared with the education-only andusual physical therapy groups.

Limitations. The limitations of this study include a lack of adherence to groupassignment, disproportionate therapist contact time among treatment groups, andmultiple use of univariate analyses.

Conclusions. An intensive, progressive exercise program combined with educa-tion reduces disability and improves function in patients who have undergone asingle-level lumbar microdiskectomy.

K. Kulig, PT, PhD, is Associate Pro-fessor of Clinical Physical Therapy,Division of Biokinesiology andPhysical Therapy, University ofSouthern California, 1540 E Al-cazar St, CHP-155, Los Angeles,CA 90089-9006 (USA). Address allcorrespondence to Dr Kulig at:[email protected].

G.J. Beneck, PT, MS, OCS, is a PhDcandidate in the Division of Bio-kinesiology and Physical Therapy,University of Southern California,and Lecturer, Department of Phys-ical Therapy, California State Uni-versity–Long Beach, Long Beach,California.

D.M. Selkowitz, PT, PhD, OCS,DAAPM, is Professor, Departmentof Physical Therapy Education,Western University of Health Sci-ences, Pomona, California.

J.M. Popovich Jr, PT, DPT, ATC,CSCS, is a PhD candidate in theDivision of Biokinesiology andPhysical Therapy, University ofSouthern California.

T.T. Ge, PhD, is Biostatistician,Johnson and Johnson, San Diego,California.

S.P. Flanagan, PhD, ATC, CSCS, isAssociate Professor, Departmentof Kinesiology, California StateUniversity, Northridge, Northridge,California.

E.M. Poppert, PT, DPT, OCS, is Ad-junct Assistant Professor of ClinicalPhysical Therapy, Division of Bio-kinesiology and Physical Therapy,University of Southern California.

Author information continues onnext page.

Research Report

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November 2009 Volume 89 Number 11 Physical Therapy f 1145

Low back pain continues to bethe most prevalent musculoskel-etal problem, affecting 70% to

85% of individuals at some time intheir lives.1 One source of low backpain is lumbar disk herniation withresultant sciatica. Cases of sciaticadue to lumbar disk herniation that donot resolve with conservative inter-ventions often undergo surgical re-section of the herniated material.

Early success rates of lumbar diskec-tomy based on pain, function, andpatient satisfaction outcomes rangefrom 65% to 91%.2–9 These figuresshow that in 9% to 35% of cases, thepostsurgical results are unsatisfac-tory and patients continue to havesymptoms and functional deficits.The success rates reported in thesestudies may be influenced by thepostoperative care provided. In thecase of patients with persistingsymptoms and disability, additionalinterventions such as trunk muscletraining exercises often arerecommended.

The postoperative impairment oftrunk muscle performance may ex-plain why the symptoms and func-tional deficits associated with diskherniation do not fully resolve fol-lowing the surgical procedure. Dueto months of pain and reduced activ-ity prior to surgery, back musclefunction may become impaired. Inpatients with disk herniation, nervecompression and inactivity often re-sult in atrophy, weakness, andgreater fatigability of the back exten-sors.10–14 Trunk muscles that areweak and more fatigable allow in-creased stresses on the intervertebraldisks, facets, and ligaments.15 Post-operative muscle atrophy also mayresult from muscle or nerve damagefrom the surgical procedure.13,16

Previous studies that examined theeffectiveness of exercise on patientspostdiskectomy conducted trainingprograms ranging from 4 to 12

weeks, with one program lasting 6months.17 With the exception of onestudy that omitted abdominal muscleexercises,18 most studies includedexercises to promote performanceof the trunk musculature.19–24 Moststudies described their interventionon the trunk muscles as strengthen-ing or stabilization exercise, whereas2 studies described their trunk exer-cises as endurance exercises.19,23 Allexercise programs generally weredepicted as being graded and pro-gressive. Some programs includedaerobic training,18,19,24,25 lower-extremity strengthening,17,18,20,21,23

and trunk or hip flexibilityexercises.19,21,24

An important goal of physical ther-apy interventions is to resolve func-tional deficits associated with lowback pain. Previous studies assessedthe effectiveness of exercise inter-ventions in resolving functional def-icits postdiskectomy primarily bymeans of self-reported question-naires.17–20,22,24 A reduction in dis-ability was reported in 4 studies.19–22

Physical measures of performancemay afford certain advantages overself-reports, but were rarely reportedin these studies. A combination ofself-report and physical performancemeasures seems ideal to representfunction and disability.

Only one study measured functionalperformance, and in only one spe-cific task (ie, lifting).21 In addition,

K.A. Yamada, PT, DPT, OCS, ATC, CSCS, isInstructor of Clinical Physical Therapy, Divi-sion of Biokinesiology and Physical Therapy,University of Southern California.

C.M. Powers, PT, PhD, is Associate Professor,Division of Biokinesiology and Physical Ther-apy, University of Southern California.

S. Azen, PhD, is Professor and Co-Director ofBiostatistics, Department of Preventive Med-icine, Keck School of Medicine, University ofSouthern California.

C.J. Winstein, PT, PhD, FAPTA, is Professor,Division of Biokinesiology and Physical Ther-apy, University of Southern California.

J. Gordon, PT, EdD, FAPTA, is Associate Deanand Chair, Division of Biokinesiology andPhysical Therapy, University of SouthernCalifornia.

S. Samudrala, MD, FACS, is Neurosurgeon,Cedars-Sinai Spine Center, Los Angeles,California.

T.C. Chen, MD, PhD, is Associate Professorof Neurological Surgery, Department ofNeurological Surgery, Keck School of Medi-cine, University of Southern California.

A.N. Shamie, MD, is Assistant Professor ofOrthopaedic Surgery, Department of Ortho-paedic Surgery, Santa Monica–UCLA Medi-cal Center and Orthopaedic Hospital, SantaMonica, California.

L.T. Khoo, MD, is Assistant Professor, Depart-ment of Orthopaedic Surgery, Santa Moni-ca–UCLA Medical Center and OrthopaedicHospital.

M.J. Spoonamore, MD, is Assistant Professorof Orthopaedic Surgery, Department of Or-thopaedic Surgery, Keck School of Medicine,University of Southern California.

J.C. Wang, MD, is Professor of OrthopaedicSurgery, Department of Orthopaedic Sur-gery, Santa Monica–UCLA Medical Centerand Orthopaedic Hospital.

Physical Therapy Clinical Research Network(PTClinResNet) (see list of investigators onpage 1155).

[Kulig K, Beneck GJ, Selkowitz DM, et al;Physical Therapy Clinical Research Network(PTClinResNet). An intensive, progressive ex-ercise program reduces disability and im-proves functional performance in patients af-ter single-level lumbar microdiskectomy.Phys Ther. 2009;89:1145–1157.]

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Intensive, Progressive Exercise Program for Patients After Single-Level Lumbar Microdiskectomy

1146 f Physical Therapy Volume 89 Number 11 November 2009

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with the exception of that study,21

outcomes have not been assessedearlier than 6 months following sur-gery. Therefore, the purpose of thisstudy was to examine the early ef-fects of a recently developed inten-sive postoperative exercise pro-gram26 on self-report and physicalperformance measures of functionand disability in patients who hadundergone a single-level lumbarmicrodiskectomy.

MethodOverall Study DesignThis prospective study was dividedinto 3 phases: a protocol develop-ment phase, an implementation orintervention phase, and a follow-upphase. During the protocol develop-ment phase, a team of researchersand clinicians developed, tested, andstandardized the postsurgical inter-vention and testing protocols. Theprotocol development phase, in-cluding a detailed presentation ofthe methods used in the entireproject, has already been presentedelsewhere.26

ParticipantsA total of 176 individuals (100 male,76 female) between the ages of 18and 60 years were informed aboutthis study through participating sur-geons’ offices. These individualswere scheduled to undergo a single-level lumbar microdiskectomy forthe first time. Microdiskectomy pro-vides a magnified view of the diskand nerve root, which makes it pos-sible for the surgeon to remove her-niated material while minimizingdamage to the surrounding tissues.Surgeons screened these patients forpresurgical inclusion and exclusioncriteria.

As previously reported,26 the pri-mary presurgical inclusion criteriawere diagnosis of disk protrusionconfirmed by magnetic resonanceimaging testing, predominant symp-toms in the lower extremity, radicu-

lar pain distribution, restrictedstraight leg raise, and positive signsof adverse nerve root tension (ie, im-paired mobility, pain, or dysesthe-sia). An additional inclusion criterionwas that the surgery and the 4- to6-week period after surgery werewithout an adverse event. Therewere no enrollment restrictionsbased on sex, race, or ethnic origin.

Presurgical exclusion criteria includ-ed: previous back surgeries, pres-ence of concurrent lower-extremitypathology (other than that associ-ated with low back and lower-extremity pain associated withsingle-level disk injury), neurologicaldisorders (eg, traumatic brain injury,cerebrovascular accident, seizures),uncontrolled cardiovascular disease,evidence of spinal cord compres-sion, infection, severe respiratorydisease, pregnancy, rheumatic jointdisease, peripheral vascular diseasewith sensory loss at the foot, or anycondition the participant identifiedthat was considered to limit partici-pation in physical activity. Researchpersonnel further screened them foravailability and interest in participat-ing in the study.

The Institutional Review Board ofthe University of Southern California(USC) granted approval for this ran-domized controlled trial and its in-formed consent process. A total of98 people who satisfied the inclu-sion and exclusion criteria were en-rolled in the study. The participantssigned the informed consent formafter receiving a detailed explanationof the study.

InterventionsThe participants were randomly allo-cated using blocked randomizationto 1 of 2 groups: a group that re-ceived one session of back care ed-ucation (education-only group) or agroup that received a back care ed-ucation session followed by the 12-week USC Spine Exercise Program

(exercise and education group).There were 2 components to thisexercise program: (1) back extensorstrength (force-generating capacity)and endurance training and (2) matand upright therapeutic exercises.The education session and the exer-cise program were implemented byintervention physical therapists atparticipating physical therapy clinicsin the greater Los Angeles area. Allintervention therapists received stan-dardized training in implementationof the education session, the exer-cise protocol, and the method andprogression of testing. These inter-vention therapists passed a video-taped mock testing and interventionsession with a score of 90% or moreon a checklist of competencies,graded by researchers who devel-oped the interventions, before theyadministered the interventions toparticipants.26

Education. Education comprised a1-hour, one-on-one session with theintervention therapist that occurredafter the preintervention testing ses-sion, 4 to 6 weeks after surgery. Thiseducational session was tailored spe-cifically for individuals who had un-dergone a lumbar microdiskectomy,to help them understand their backproblem and how to care for theirback. It was guided by an educa-tional booklet that was created espe-cially for this study.27

Exercise–USC Spine ExerciseProgram. The exercise programwas initiated 2 to 3 days followingthe education session and occurred3 times a week for the remainder ofthe 12 weeks. The USC Spine Exer-cise Program is unique comparedwith other therapeutic interventionsfor patients with back pain in that itis goal oriented, performance based,and periodized, and it was rigorouslyapplied in a standardized manner.26

It comprised back extensor strengthand endurance training and mat and



therapeutic exercise training, whichwere performed concurrently.

The back extensor strength and en-durance training portion of the pro-gram was designed to load the backextensor muscles in a graded mannerby varying the angle at which thetrunk was held against gravity, usinga variable-angle Roman chair* (Fig. 1).Exercise session intensity for eachweek of the program was deter-mined for each individual at the sec-ond training session of each weekby testing the amount of time he orshe was able to maintain the trunkposition against gravity (using thevariable-angle Roman chair).26 Dur-ing the first half of the program, par-ticipants trained at 2 levels belowtheir maximum tested level. Duringthe second half of the program, theytrained at one level below their max-imum tested level, which repre-sented 60% to 80% of the maximumperformance of the exercise. Theseintensities were shown to have thelargest increases in strength in apopulation of health individuals.28

The goal of the program was for par-ticipants to be able to maintain ahorizontal body position for 180seconds. This position is equivalentto the Sorensen test position, andthe target time reflects Sorensen testperformance by adults who werehealthy.29 After an initial 2-weeklearning phase, participants alter-nated between phases designed toimprove their back extensor strengthand their back extensor endurance,starting with a strengthening phaseand ending with an endurance phase(Flanagan SP, Kulig K; unpublishedresearch).26,30

A team of 20 physical therapists se-lected exercises for the mat and up-right portion of the program andthen ranked them according to thephysical demand of each exercise.The purpose of the mat and uprighttherapeutic exercise portion of theprogram was to progressively anddynamically develop strength, en-durance, and control of movementby the trunk and lower-extremitymusculature.26 The number of repe-titions was based on a widely ac-cepted continuum for endurance

gains.31 The number of sets andfrequency represented the largesteffect size for increases in strengthof a population of healthy individu-als.28 Similarly, rest periods andwork-to-rest ratios were extractedfrom a review of the literature for apopulation of healthy individuals.32

The systematic and individualizedprogression or regression of exer-cise intensity with this protocol com-plements that of the back extensorstrength and endurance training pro-tocol with the variable-angle Romanchair and mimics the clinicaldecision-making process used byphysical therapists.

Three categories of exercises tar-geting the abdominal, back, andlower-extremity musculature wereselected. A progression of these ex-ercises of increasing difficulty wasestablished.26 The exercises were di-vided into 3 categories based on per-formance in supine, quadruped, andstanding positions. Each category ofexercise included multiple traininglevels designed to accommodateparticipants of varying levels of fit-ness and symptoms and to allow forprogression of the workload overthe 12-week training period.26 Partic-ipants performed exercises from all3 categories during the entire inter-vention period. Levels of difficultyof exercises could vary among theexercise categories for an individualparticipant.26 For example, a personcould be training the back extensorsat a very high level and performinglong-duration holds at level 6 of 6on the variable-angle Roman chair,while only being able to exerciseat level 2 of 7 in the abdominalprogression.

A testing procedure was developedto determine the appropriate initialtraining level for each category ofexercise and to modify training lev-els during the training period to al-low for progression, regression, ormaintenance of exercise intensity

* Backstrong International LLC, 710 N BreaBlvd, Ste G, Brea, CA 92821.

Figure 1.Variable-angle Roman chair. Levels of difficulty of the Roman chair, from easiest (level 1)to most difficult (level 6).



within each category. Test perfor-mance was based on each partici-pant’s symptoms, use of correcttechnique, and rate of perceived ex-ertion. The tests were repeated at3-week intervals during the 12-weekintervention.26 No exercises wereperformed as part of a home exer-cise program.

Outcome MeasuresTesting on all outcome measuresbegan 4 to 6 weeks after surgery. Alloutcome measurements were ob-tained by evaluators who wereblinded to the participants’ group al-location. Each evaluator completedstandardization training in the test-ing procedures and passed a video-taped mock testing session with ascore of 90% on a checklist of com-petencies, graded by other researchassociates, before administering theoutcome measures to participants.

The Oswestry Disability Index (ODI)was used to assess the extent towhich each participant engaged inactivities of daily living. The mostrecent version of the ODI was used,in which the question regarding sex-ual activity was replaced with oneregarding employment and home-making.33 Each participant was re-quired to complete the entire ques-tionnaire for it to be considered validand accepted. The standardized eval-uators ensured that all sections werecompleted during each assessment.

Outcome measures assessing ob-served performance in activities in-cluded the Repeated Sit-to-StandTest, the 50-Foot Walk Test, and5-Minute Walk Test. The RepeatedSit-to-Stand Test measured the time(in seconds) needed to complete 5consecutive repetitions of a sit-to-stand sequence as fast as tolerated.The same type of metal folding chairwithout armrests was used by eachparticipant. The 50-Foot Walk Testmeasured the time (in seconds)needed to walk a distance of 50 ft

(15.24 m) as fast as tolerated. The5-Minute Walk Test measured thedistance (in feet) walked in 5 min-utes at a self-selected pace. A stop-watch and a tape measure were usedfor timing and measuring the walk-ing courses, respectively. These mea-sures of functional performancehave been shown to be reliable34,35

and to discriminate individuals withlow back pain from individuals whowere healthy.35

In addition, performance of the backextensor muscles was assessed usinga modified Sorensen test (FlanaganSP, Kulig K; unpublished research).This test was derived from the testdeveloped by Biering-Sorensen,29

who used it to assess the isometricstrength and endurance of the lum-bar back extensors in individualswithout low back pain. The variable-angle Roman chair, used in the exer-cise intervention, also was used toperform the modified Sorenson test.

The variable-angle Roman chair,when used in conjunction with aweighted vest, allows the resistanceto be progressed from much lighterto much heavier than the originalSorensen test. This apparatus allowsthe angle of a mobile frame to varyfrom 75 degrees to 0 degrees relativeto the horizontal in 6 increments ofincreasing difficulty: 75, 60, 45, 30,15, and 0 degrees (Fig. 1). Each anglewas replaced with a level identifier(1, 2, 3, 4, 5, and 6, respectively),with level 6 being the position of theoriginal Sorensen test.26 The depen-dent measure for the modified Soren-son test was “impulse,” defined asthe product of the moment (pro-duced by the mass of the trunk,arms, and head and its lever arm) andthe time the body was held at a par-ticular level. All of the tests used asoutcome measures in this study havebeen previously described.26

Research DesignA 2-group, pretest-posttest (repeated-measure) design was planned. Al-though participants originally wererandomly allocated to the 2 groups(education only and exercise and ed-ucation), not all of the participantsadhered to their group allocation.Instead, after their allocation, someof the participants self-selected acourse of physical therapy at a clinicof their choosing. This created athird group that we called the “usualphysical therapy group.” We wereunable to control what comprisedphysical therapy interventions atthese nonparticipating clinics (seeAppendix for components of theseprograms), but they were not usingthe 12-week USC Spine Exercise Pro-gram. Therefore, for the purpose ofdata analyses, we used both a 2-group design (based on the originalrandomization process) and a 3-group design (based on actual treat-ment received).

Sample SizePower calculations were based ondata from prior published studies.These data indicated that the inter-participant variability, with respectto impairment, activity, and partici-pation outcome measures, was mod-erate to high, suggesting that samplesizes in the range of 40 to 69 partic-ipants per group would detect mod-erate effect sizes. The outcome mea-sures in the current study assessedthe immediate effects of the inter-ventions in addition to surgery; thus,the calculations were made on theassumption that the changes due toexercise and education would begreater than those expected for edu-cation alone. Accounting for attri-tion, we determined that a samplesize of 50 participants per groupwould have 80% power to detect amoderate effect size of 0.50 at analpha level of .05 (one-sided).26



Data AnalysisHard copies of coded data for all out-come measures and relevant inde-pendent measures were transferredby the blinded evaluators to datamanagement and analysis personnel.These data were transferred fromhard-copy recordings to a menu-driven Web-based SQL data entrysystem (PTClinResNet) and then ex-ported to SAS version 8.2† for statis-tical analyses.

Due to a high and disproportionatedropout rate for the follow-up assess-ments, the analyses were conductedon preintervention and postinterven-tion data only. Consequently, the

common method of imputation ofmissing data became unsuitable, soanalyses instead were performedonly on those participants (n�77)with follow-up (ie, evaluable) data.For each outcome measure (ODIscore, 5-Minute Walk Test, 50-FootWalk Test, Sit-to-Stand Test), an anal-ysis of covariance (ANCOVA) wasperformed using the postinterven-tion scores as the dependent variablewith the preintervention scores asthe covariate. Given the exploratorynature of the study, we elected notto control for type I error. This anal-ysis was conducted on each of thevariables for both the 2-group and3-group designs. For the 3-group de-sign, if the ANCOVA for any of theoutcome measures was significant,

post hoc testing was performed us-ing the Tukey method to determinestatistically significant pair-wise com-parisons between the groups.36 Thealpha level for all analyses was set at.05.

Role of the Funding SourceThis study was funded by a grantfrom the Foundation for PhysicalTherapy.

ResultsRecruitment and RetentionA total of 176 patients were screenedfor randomization (Fig. 2). Seventy-eight of these were excluded for thefollowing reasons: 52 declined toenroll and 26 failed to meet the in-clusion criteria. Ninety-eight partici-

† SAS Institute Inc, PO Box 8000, Cary, NC27513.

Figure 2.CONSORT diagram of the MUSSEL randomized clinical trial: number of participants screened, randomized, and retained andanalyses. LBP�low back pain.



pants were randomly allocated usingblocked randomization to receiveexercise and education (n�51) oreducation only (n�47). Of the 98participants, 21 (6 in the exerciseand education group and 15 in theeducation-only group) were inevalu-able because they withdrew fromthe study before completing the 12-week intervention period. In addi-tion, 4 participants in the exerciseand education group did not ad-here to the group allocation; subse-quently, 3 participants received edu-cation only and 1 participant soughtoutside care (usual physical ther-apy). Furthermore, in the education-only group, 21 participants did notadhere to group allocation; subse-quently 2 participants received exer-cise and education, and 19 partici-pants received usual physical therapy.The participants who remained inthe study provided the basis for theevaluable data in 3 groups: exerciseand education (n�43), educationonly (n�14), and usual physical ther-apy (n�20) (Fig. 2).

Of the 98 randomized participants,the majority were employed, had anincome of �$50,000, and attendedat least some college. Overall, 53(55%) of the participants were men,and the mean (�SD) age was 40�10years across both sexes. Table 1 sum-marizes the demographic and clini-cal characteristics for the 98 ran-domized participants, stratified byintervention allocations. No statisti-cally significant baseline differenceswere found among the 3 interven-tion groups (P�.05), nor were signif-icant differences found across the 3actual intervention groups (P�.05)at baseline.

Postintervention OutcomesAnalyses of evaluable data for theoutcome measures for the 2-groupallocation are summarized in Table2. The ANCOVA results revealed asignificant difference in the post-intervention scores for the ODI

(P�.001) and the 5-Minute Walk Test(P�.024) between the 2 groups, withthe improvements exhibited by theexercise and education group ap-proximately twice the magnitude ofthose seen in the education-onlygroup. The postintervention scoreswere not significantly different be-tween groups for the 50-Foot WalkTest (P�.078) and the Repeated Sit-to-Stand Test (P�.430).

Analyses of data for the outcomemeasures for the actual interventionreceived are summarized in Table 3.The ANCOVA results revealed a sig-nificant difference in ODI scoresamong groups (P�.001). Post hoccomparisons showed most improve-ment in the exercise and educationgroup (19.5%�13%) compared withboth the education-only group(9.3%�11% improvement) (P�.016)and the usual physical therapy group(7.9%�11% improvement) (P�.003).No significant difference in post-intervention scores was found be-tween the education-only and usualphysical therapy groups (P�.985).Postintervention scores were signifi-cantly different among groups forthe 5-Minute Walk Test (P�.028)and the 50-Foot Walk Test (P�.010).The 5-Minute Walk Test post hoccomparisons revealed the exerciseand education group showed sig-nificant improvement (293.0�277 ftimprovement) compared with theusual physical therapy group(96.6�152 ft improvement) (P�.038)but not the education-only group(171.4�316 ft improvement)(P�.188). The 50-Foot Walk Testpost hoc comparisons showed mostimprovement in the exercise and ed-ucation group (�1.8�1.9 seconds)compared with both the education-only group (�1.2�1.7 seconds)(P�.033) and the usual physicaltherapy group (�0.5�1.0 seconds)(P�.046). Between-group postinter-vention scores were not significantlydifferent for the Repeated Sit-to-Stand Test (P�.053).

Performance of the BackExtensorsThe exercise and education groupwas trained and assessed using thesame apparatus; therefore, musculo-skeletal performance of the backextensors was not included as anoutcome measure. However, as amatter of interest, preinterventionand postintervention extensor im-pulse during the modified Sorensentest procedure on a Roman chairwas analyzed. In the 2-group analysis(Tab. 4), the ANCOVA results re-vealed a significant difference inpostintervention scores between the2 groups (P�.001). In the analysisof the 3 actual intervention groups(Tab. 5), the ANCOVA results alsorevealed a significant differenceamong groups (P�.001). Post hoccomparisons showed greater im-provement in the exercise and edu-cation group (5,709�4,577 N�m�simprovement) compared with boththe education-only group (860�3,054N�m�s improvement) (P�.001) andthe usual physical therapy group(1,650�3,002 N�m�s improvement)(P�.003). No significant differencein postintervention scores was foundbetween the education-only andusual physical therapy groups(P�.693).

Adverse EventsAdverse events were monitoredand reported according to the proto-col approved by the PTClinResNetSafety Monitoring Board.26 Therewere 3 adverse events that were con-sidered not related to the study (1 inthe exercise and education groupand 2 in the education-only group).Adverse events consisted of a secondmicrodiskectomy for unrelenting sci-atica, elevated blood pressure, and asevere bout of low back pain and legnumbness.

DiscussionThe purpose of this study was toexamine the effectiveness of an in-terventional protocol26 to improve



Table 1.Baseline Demographics, Primary Outcomes, and Participation Measures by Randomization Groups (N�98)a

VariableExercise and Education Group

(n�51)Education-Only Group

(n�47) P

Demographics

Age (y) 39.2 (10.2) 41.4 (9.9) .90

Sex

Male 29 (58%) 24 (50%) .43

Latino or Hispanic 6 (12%) 9 (19%) .35

Race

1.00Black or African American 1 (2%) 1 (2%)

White 36 (71%) 33 (70%)

Unspecified or other 14 (27%) 13 (28%)

Involved in a litigation process with workers’ compensation 4 (9%) 9 (19%) .14

Medical history

Duration of pain episode prior to surgery (mo) 6.7 (9.8) 5.9 (7.0) .66

Time since first onset of low back pain (mo) 82.1 (93.3) 120.7 (125.3) .12

Time since first onset of sciatica (mo) 33.1 (67.6) 38.7 (69.8) .71

No. of previous episodes

.75

�3 13 (32%) 16 (34%)

3–5 3 (7%) 5 (11%)

5–10 5 (12%) 3 (6%)

�10 13 (32%) 18 (38%)

Unspecified 7 (17%) 5 (11%)

Involved spinal level

.35L4/L5 19 (37%) 24 (51%)

L5/S1 31 (61%) 23 (49%)

L2/L3 1 (2%) 0 (0%)

Positive passive straight leg raise 29 (63%) 19 (45%) .09

Oswestry Disability Index (%) 29.4 (15.4) 34.2 (16.2) .15

Physical function

5-Minute Walk Test (ft) 1,423.7 (310.6) 1,418.2 (277.1) .93

50-Foot Walk Test (s) 9.9 (2.8) 9.9 (2.4) .92

Repeated Sit-to-Stand Test (s) 17.9 (7.7) 18.9 (7.0) .53

Modified Sorensen test

Normalized (N�m�s) 5,825.3 (3,432.4) 4,604.9 (3,269.5) .13

a Values are mean (�SD) for continuous variables, frequency (%) for categorical variables. Chi-square tests were used for categorical variables, and one-wayanalyses of variance were used for continuous variables. Missing data for the following variables (exercise and education group, education-only group):involved in a litigation process with workers’ compensation (4, 0), duration of pain episode prior to surgery (10, 0), time since first onset of low back pain(10, 9), time since first onset of sciatica (12, 2), number of previous episodes (10, 0), positive passive straight leg raise (5, 5), physical function (0, 1),modified Sorensen test (2, 3).



functional outcomes in patients whohave undergone a single-level lumbarmicrodiskectomy. In the 2-groupanalyses, the exercise and educa-tion group showed a significantlygreater reduction in ODI scores im-mediately following the intervention(4.5 months postsurgery). The ODIscores were reduced in both groups,but only reached the level of clinicalsignificance in the exercise and edu-cation group.37

A Cochrane review of 200238 con-cluded that there is strong evidencethat intensive exercise is effective inrestoring functional status in patientswho have undergone lumbar diskec-tomy. In the studies cited, exercisegroups experienced a greater reduc-tion in disability following rehabilita-tion for single-level lumbar diskec-tomy.19,20,22 However, there were

several differences among thesestudies and the current study. Theduration of the exercise interventionin these studies ranged from 4 to 8weeks, whereas the duration of theintervention in the current study was12 weeks. In addition, assessmenttime points differed among studies.Of these studies,19,20,22 only Daniel-sen et al20 reported a greater reduc-tion in disability at the first post-intervention assessment (6 monthspostsurgery). A significant reductionwas not achieved in the other studiesat earlier assessment times follow-ing the intervention, but only atfollow-up times of 8 months22 and 12months19 postsurgery. In the studyby Danielsen et al, subjects who re-ceived an 8-week program of vigor-ous medical exercise therapy had asignificantly greater reduction in dis-ability than the control group. How-

ever, in contrast to the current study,Danielsen et al examined the changein disability by subtracting the post-intervention disability scores fromthe preoperative scores. Prior to sur-gery, subjects in the exercise grouphad significantly higher disabilityscores than the control group. Thus,similar within-group changes in dis-ability scores following surgery butprior to the exercise interventionmust be assumed in order to con-clude that the exercise interventionwas responsible for the greater re-duction in disability in the exercisegroup.

Since the Cochrane review,38 onestudy has shown a reduction in dis-ability following a postsurgical exer-cise program in patients who hadundergone a single-level lumbar mi-crodiskectomy.21 In that study, the

Table 2.Mean Change Score (Postintervention-Preintervention) and 95% Confidence Interval for Each Outcome Measure Based on2-Group Analyses of Evaluable Dataa

Outcome MeasureExercise and Education Group

(n�45)Education-Only Group

(n�32) Pb

Oswestry Disability Index score (%) �18.4 (�22.5 to �14.3) �9.4 (�13.0 to �5.8) �.001

5-Minute Walk Test (ft) 281.2 (199.1 to 363.3) 133.6 (53.5 to 213.7) .024

50-Foot Walk Test (s) �1.7 (�2.2 to �1.2) �0.9 (�1.5 to �0.3) .078

Repeated Sit-to-Stand Test (s) �4.8 (�6.7 to �2.9) �4.3 (�6.7 to �1.9) .430

a Missing data for the following variables (exercise and education group, education-only group): 5-Minute Walk Test (1, 5), 50-Foot Walk Test (1, 5), andRepeated Sit-to-Stand Test (2, 5).b The P value is a between-group comparison of the postintervention scores using an analysis of covariance (covariate�baseline/pretest).

Table 3.Mean Change Score (Postintervention-Preintervention) and 95% Confidence Interval for Each Outcome Measure Based on ActualIntervention Receiveda

Outcome MeasureExercise and Education

Group (n�43)Education-Only Group

(n�14)Usual Physical Therapy

Group (n�20) Pb

Oswestry Disability Index score (%) –19.5 (–23.4 to –15.6)c,d �9.3 (�15.1 to �3.5) �7.9 (�12.9 to �2.9) .001

5-Minute Walk Test (ft) 293.0 (210.1 to 375.9)d 171.4 (5.8 to 337.0) 96.6 (29.9 to 163.3) .028

50-Foot Walk Test (s) –1.8 (–2.4 to –1.2)c,d –1.2 (–2.1 to –0.3) –0.5 (–0.9 to –0.1) .010

Repeated Sit-to-Stand Test (s) –5.7 (–8.0 to –3.4) –3.2 (–5.6 to –0.8) –3.1 (–5.1 to –1.1) .053

a Missing data for the following variables (exercise and education group, education-only group, usual physical therapy group): 5-Minute Walk Test (2, 1, 3),50-Foot Walk Test (2, 1, 3), and Repeated Sit-to-Stand Test (3, 1, 3).b The P value is a between-group comparison of the postintervention scores using an analysis of covariance (covariate�baseline/pretest).c Significant difference between postintervention scores using analysis of covariance for the exercise and education group and the education-only groupfrom the post hoc analysis.d Significant difference between postintervention scores using analysis of covariance for the exercise and education group and the usual physical therapygroup from the post hoc analysis.



reduction in ODI scores in the groupthat received lumbar stabilizationexercises was 27%, whereas the re-duction in the current study was18%. This difference may have beendue to the difference in baseline ODIscores between the 2 studies. In thestudy by Yilmaz et al,21 the initialODI score was 44%, whereas thatof the current study was 31%. Thehigher baseline level of disability re-ported by Yilmaz et al may have al-lotted more potential improvementfrom their intervention than in theexercise and education group in thecurrent study. The only functionalperformance measured in that studywas lifting. The subjects in the exer-cise group improved their lifting per-formance significantly more thanthose in the control groups.

The exercise intervention in the cur-rent study consisted of an intensive,graded strength and endurance train-ing program targeting the trunk andlower-extremity musculature, withthe spine maintained in a neutral po-sition. None of the participants inthe exercise and education groupwithdrew due to symptom exacer-

bation from the intervention. Thisfinding is in agreement with thoseof other studies,18,22 indicating thatearly, intensive training of trunkmuscles, initiated 4 to 6 weeks afterlumbar diskectomy, can be a safeform of postoperative rehabilitation.

Walking performance was not re-ported as an outcome measure inprevious investigations studying theeffects of exercise following lumbardiskectomy. In the 2-group analysesof the current study, the exerciseand education group had a signifi-cantly greater improvement in5-minute walk distance comparedwith the education-only group. Thepostintervention walking perfor-mance of the exercise and educationgroup was similar to values of sub-jects who were healthy for both mea-sures.35 This change in walking per-formance may have been the resultof the intensive lower-extremitytraining performed in the currentstudy. Lower-extremity training wasa component of previous exerciseprotocols following microdiskec-tomy;17–20 however, measures oflower-extremity performance were

not reported. A suspected benefitof lower-extremity training was agreater reduction in time to performthe 50-Foot Walk Test and the Re-peated Sit-to-Stand Test. However,the time reduction of both tests inthe exercise and education groupwas not significantly greater thanthat of the education-only group,which suggests a less-discriminatingrole for these tests.

A unique comparison in our studywas the analysis of the actual inter-ventions received. Participants whoopted out of their allocated interven-tion group to pursue physical ther-apy outside of the study agreed toremain in the study, allowing for in-clusion of a third group in the anal-yses. The participants who receivedusual physical therapy care attendedlocal physical therapy clinics wheretheir intervention was determinedby their physical therapists, ratherthan the USC Spine Exercise Pro-gram. The results of the analysis ofthe actual intervention received (3-group analysis) showed a greaterimprovement in performance of theexercise and education group. The

Table 4.Mean Change Score (Postintervention-Preintervention) and 95% Confidence Interval for Back Extensor Impulse Based on2-Group Analyses of Evaluable Dataa



(n�26) Pb

Modified Sorensen test (N�m�s) 5,328.4 (3,948.6 to 6,708.2) 1,261.1 (1,148.6 to 2,407.4) �.001

a Missing data (exercise and education group, education-only group) for the modified Sorensen test (2, 8).b The P value is a between-group comparison of the postintervention scores using an analysis of covariance (covariate�baseline/pretest).

Table 5.Mean Change Score (Postintervention-Preintervention) and 95% Confidence Interval for Back Extensor Impulse Based onIntervention Receiveda



(n�26)Usual Physical Therapy

Group (n�17) Pb

Modified Sorensen test (N�m�s) 5,709.6 (4,341.5 to 7,077.7)c,d 860.4 (�739.5 to 2,460.3) 1,650.0 (334.2 to 2,965.8) �.001

a Missing data (exercise and education group, education-only group, usual physical therapy group) for the modified Sorensen test (4, 1, 3).b The P value is a between-group comparison of the postintervention scores using an analysis of covariance (covariate�baseline/pretest).c Significant difference between postintervention scores using analysis of covariance for the exercise and education group and the education-only groupfrom the post hoc analysis.d Significant difference between postintervention scores using analysis of covariance for the exercise and education group and the usual physical therapygroup from the post hoc analysis.



improvement in ODI scores, 5-minutewalk distance, and 50-foot walk timewas significantly greater in those par-ticipants who received exercise andeducation compared with either theeducation-only group or the usualphysical therapy group. These re-sults suggest greater effectivenessof the current exercise program inreducing disability and improvingwalking performance than that ex-pected from usual physical therapy.The volume and intensity of the in-terventions in the usual physicaltherapy group were lower thanthose of the USC Spine Exercise Pro-gram, perhaps reflecting cautionwhen managing postsurgical cases.Inherent in the usual physical ther-apy group is a lack of standardizedcare procedures, resulting in highvariability in both the durations andtypes of interventions received. Thelack of standardization of care in theusual physical therapy group mayhave influenced the results.

One limitation of this study was thelarge number of participants whochose not to adhere to the originalallocation into the education-onlygroup. This finding suggests thatmore participants preferred exerciseas part of their intervention ratherthan education only. A selection biasof the participants can confound theinterpretation of the results. For in-stance, more highly motivated par-ticipants in the education-only groupmay have withdrawn from the study,which may have led to poorer out-comes in that group. The intention-to-treat analysis is a strategy usedto deal with participants who with-draw from a study. One commonform of intention-to-treat analysis isthe imputation of missing data bycarrying the last observation for-ward. If applied to the current study,the preintervention score would beused again as the postinterventionscore. Because of the greater drop-out rate in the education-only group,this analysis would clearly bias the

results in favor of the exercise andeducation group. Analysis of theevaluable data in the 2-group analy-sis resulted in more-conservative re-sults, in that no data were carriedforward from baseline and some par-ticipants received exercise in physi-cal therapy clinics outside the study.

A second limitation is that the exer-cise and education group receivedsubstantially more time with a phys-ical therapist compared with theother groups. More time with thetherapist may have influenced themeasured outcomes. However, itshould be noted that such time ine-qualities may not necessarily influ-ence disability outcome measures.Three previous studies of interven-tion effects on disability from lowback problems with disparate inter-vention durations showed no differ-ences in the reduction in disabilitybetween these groups, although pa-tient satisfaction was higher in thegroup that received more therapistattention.39–41

A third limitation involves the statis-tical analyses. Univariate analyseswere performed on each of the out-come variables. As the multiple useof a univariate analysis raises the riskof a type I error, the results shouldbe viewed with this fact in mind.

ConclusionThe outcome of microdiskectomyfor a lumbar disk herniation dependson the postoperative regimen of-fered. An intensive 12-week strengthand endurance training program ofthe trunk and lower-extremity mus-culature is safe and results in agreater reduction in disability and agreater increase in walking perfor-mance immediately following the in-tervention. Because only the imme-diate effects of the exercise programwere reported, long-term effects can-not be assumed.

The authors’ contributions to this work wereas follows. Concept/idea/research design:K.K., S.P.F., E.M.P., C.M.P., S.A., C.J.W., J.G.,J.C.W. Writing: K.K., G.J.B., D.M.S., J.M.P. Jr,S.P.F., E.M.P., C.M.P., S.A. Data collection:K.K., G.J.B., D.M.S., J.M.P. Jr, E.M.P., K.A.Y.,S.S., T.C.C., J.C.W. Data analysis: K.K., G.J.B.,J.M.P. Jr, T.T. Ge, S.P.F., E.M.P., S.A., S.S.,T.C.C. Project management: K.K., K.A.Y.,C.J.W., J.G. Fund procurement: K.K., C.J.W.,J.G. Providing participants: K.K., E.M.P., S.S.,T.C.C., A.N.S., L.T.K., M.J.S., J.C.W. Provid-ing facilities/equipment: K.K., G.J.B., E.M.P.Providing institutional liaisons: K.K., C.J.W.,J.G., L.T.K. Clerical support: K.K., K.A.Y. Con-sultation (including review of manuscriptbefore submission): K.K., J.M.P. Jr, S.P.F.,E.M.P., C.M.P., C.J.W., J.G., L.T.K., M.J.S.,J.C.W.

Physical Therapy Clinical Research Network(PTClinResNet): Network Principal Investiga-tor is Carolee J. Winstein, PT, PhD, FAPTA,and Co-Principal Investigator is James Gor-don, PT, EdD, FAPTA (both at University ofSouthern California). Project Principal andCo-Principal Investigators are: David A.Brown, PT, PhD (Northwestern University);Sara Mulroy, PT, PhD, and Bryan Kemp, PhD(Rancho Los Amigos National RehabilitationCenter); Loretta M. Knutson, PT, PhD, PCS(University of Indianapolis); Eileen G. Fowler,PT, PhD (University of California at Los An-geles); and Sharon K. DeMuth, PT, DPT,Kornelia Kulig, PT, PhD, and Katherine J.Sullivan, PT, PhD (University Southern Cali-fornia). The Data Management Center is lo-cated at the University of Southern Californiaand is directed by Stanley P. Azen, PhD. The4-member Data Safety and MonitoringCommittee are: Nancy Byl, PT, PhD, FAPTA,Chair (University of California at San Fran-cisco), Hugh G. Watts, MD (Shriners’ Hospi-tal for Children–LA Unit, Los Angeles, Cali-fornia), June Isaacson Kailes, MSW (WesternUniversity, Los Angeles, California), andAnny Xiang, PhD (University of SouthernCalifornia).

This study was approved by the InstitutionalReview Board of the University of SouthernCalifornia.

This study was funded bya grant from the Founda-tion for Physical Therapy.

This article was received February 18, 2008,and was accepted July 21, 2009.

DOI: 10.2522/ptj.20080052



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Appendix.Characteristics of Usual Physical Therapy Care Received by the Participants Who Elected to Pursue Care Outside of the MUSSELProject

Characteristics of Clinical Physical Therapy Visits Mode Range Percentage

No. of visits attended 12 1–24

Frequency of visits (per week or per month) 3/wk 3/wk to 1/mo

Time in session (min) 45 30–120

Main reason for discontinuing care (% of total participants) 25 met physical therapy goals22 self-discharge15 insurance “ran out”38 other (plateau, no reason given)

Type of intervention

Education 100

Modalities (ice, heat, electrotherapy) 100

Stabilization exercises 100

Stretching 80

Manual therapy 40

Exercise with back equipment 30



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ResearchReport - BackStrongself-report and physical performance measures seems ideal to represent function and disability. Only one study measured functional performance, and in only