doi: 10.2522/ptj.20060041Originally published online April 18, 2007

2007; 87:737-750.PHYS THER. Lars EngebretsenMay Arna Risberg, Inger Holm, Grethe Myklebust andTrialLigament Reconstruction: A Randomized ClinicalDuring First 6 Months After Anterior Cruciate Neuromuscular Training Versus Strength Training

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Neuromuscular Training VersusStrength Training During First 6Months After Anterior CruciateLigament Reconstruction:A Randomized Clinical TrialMay Arna Risberg, Inger Holm, Grethe Myklebust, Lars Engebretsen

Background and PurposeThe purpose of this study was to determine the effect of a 6-month neuromusculartraining (NT) program versus a traditional strength training (ST) program followinganterior cruciate ligament (ACL) reconstruction.

SubjectsSeventy-four subjects with ACL reconstruction participated in the study.

MethodsThe study was a randomized, single-blinded, controlled trial. The NT and ST groupswere tested preoperatively and at 3 and 6 months. The main outcome measure wasthe Cincinnati Knee Score. Secondary outcome measures were visual analog scales(VASs) for pain and function, the 36-Item Short-Form Health Survey (SF-36), hop tests,isokinetic muscle strength, proprioception, and static and dynamic balance tests.

ResultsThe NT group demonstrated significantly improved Cincinnati Knee Scores and VASscores for global knee function compared with the ST group at the 6-month follow-up. There were no significant differences between the groups for the other outcomemeasures (ie, hop, balance, proprioception, and muscle strength tests).

Discussion and ConclusionThe results of this study suggest that exercises included in the NT program should bepart of the rehabilitation program following ACL reconstruction.

MA Risberg, PT, PhD, is AssociateProfessor and Chairman, Norwe-gian Research Center for ActiveRehabilitation (NAR), OrthopedicCenter, Ullevaal University Hospi-tal; Norwegian Sport MedicineClinic (NMI); and NorwegianSchool of Sport Sciences, Oslo,Norway. Address all correspon-dence to Dr Risberg at:mayarnarisberg@hotmail.com.

I Holm, PT, PhD, is Professor, Riks-hospitalet Medical Center, Univer-sity of Oslo, Oslo, Norway.

G Myklebust, PT, PhD, is AssociateProfessor, Norwegian Sport Med-icine Clinic (NIMI) and NorwegianSchool of Sport Sciences, Oslo,Norway.

L Engebretsen, MD, PhD, is Pro-fessor and Chairman, Division ofNeuroscience and Musculoskele-tal Medicine, Ullevaal UniversityHospital, and Faculty of Medicine,University of Oslo.

[Risberg MA, Holm I, Myklebust G,Engebretsen L. Neuromusculartraining versus strength trainingduring first 6 months after anteriorcruciate ligament reconstruction:a randomized clinical trial. PhysTher. 2007;87:737–750.]

© 2007 American Physical TherapyAssociation

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Anterior cruciate ligament (ACL)rupture is a serious knee liga-ment injury, causing severe

functional problems that seem to beunrelated to the degree of knee jointlaxity.1 The re-establishment of neuro-muscular control of the lower extrem-ity has recently been recognized asone of the keys to restoring dynamicjoint stability and functional move-ment patterns.2,3 Neuromuscular con-trol results in avoidance of subluxa-tions,4 with the subsequent reducedrisk of further injuries. Lack of neuro-muscular control of the lower extrem-ity and muscle strength (force-generating capacity) are 2 of the mainimpairments following ACL injuryand, therefore, are often a componentof rehabilitation after the injury.2,5,6

Activities of daily living and sport ac-tivities require coordinated neuromus-cular control and muscle strength suf-ficient to perform the requiredmovements and activities. Therefore,the aim of rehabilitation programs forpeople with ACL injury is to normalizedynamic knee joint stability and mus-cle strength of the lower extremity.

Some authors7,8 have reported dif-ferences in neuromuscular perfor-mance in ACL-deficient and recon-structed knees. Other authors9 havehighlighted the importance of re-gaining quadriceps femoris musclestrength following ACL reconstruc-tion. Therefore, both muscle strengthtraining (ST) programs and neuromus-cular training (NT) programs havebeen implemented to restore kneefunction after ACL injury and recon-struction. Several NT programs havebeen evaluated for injury preven-tion10,11 and for patients with ACL de-ficiency,12,13 but these programs havenot been studied thoroughly in sub-jects with ACL reconstruction.14 Toour knowledge, only 2 randomizedcontrolled trials14,15 have been con-ducted on NT versus traditional STprograms. Therefore, more evidencefor differences among the exercisesused in clinical practice today for

rehabilitation after ACL reconstructionwas needed.

We hypothesized that NT programswould be superior to traditional STprograms for restoring knee func-tion. The primary objective of thisstudy was to determine the effect ofan NT program versus a traditionalST program on knee function (Cin-cinnati Knee Score)16 following ACLreconstruction. A secondary aim wasto evaluate the effect on musclestrength, other patient-related out-come measures (visual analog scale[VAS] and 36-Item Short-Form HealthSurvey [SF-36]),17 pain, functionalperformance (hop tests), proprio-ception, and balance.

Material and MethodsSubjectsSeventy-four subjects (27 female and47 male) with a mean age of 28.4years (range�16.7–40.3) were in-cluded in this single-blinded, ran-domized controlled trial. All subjectswere scheduled for ACL surgery atour hospital, were between the agesof 15 and 40.9 years, were candi-dates for arthroscopic reconstruc-tion of the ACL using an autogenousbone-patellar tendon-bone (B-PT-B)graft, and lived close enough to par-ticipate in rehabilitation at the 2 out-patient clinics included in this study.The B-PT-B graft was the reconstruc-tion method of first choice at ourhospital. Subjects were excluded ifthe ACL tear had occurred more than3 years prior to surgery, they hadtears of the menisci that required re-pair, they had previous injury or sur-gery to either knee, there was evi-dence of degenerative arthritis onradiographs or articular cartilage fis-sures extending to subchondralbone, or exposed bone was seen onarthroscopy (grade IV).

ProcedureBefore discharge from the hospital,the subjects were randomly assignedto participate in 1 of the 2 rehabili-

tation programs. The participants ofthe NT program were 13 female sub-jects with a mean age of 27.2 years(range�20.6–37.9) and 26 male sub-jects with a mean age of 27.7 years(range�16.7–39.6). The participantsof the ST group were 14 female sub-jects with a mean age of 26.5 years(range�19.8–38.0) and 21 male sub-jects with a mean age of 31.2 years(range�19.4–40.3). Both groupswere given specific instructions bythe research assistant for the comple-tion of the exercise routines. Simplerandomization was used by our stat-istician using a computer-generatedtable of random numbers. One in-vestigator kept the assignmentscheme and provided the assign-ment to the treating physical thera-pists in a series of consecutivelynumbered opaque envelopes. Alloca-tion was concealed from the out-come assessor and participants at alltimes and from the physical therapistuntil the point of treatment.

Sample size was calculated basedon the Cincinnati Knee Score asthe main outcome measure and ona predetermined difference betweentreatment groups of 10 points changeon the Cincinnati Knee Score. This fig-ure was based on the results of a pre-vious study by our group18 and a com-parative study19 and was considered tobe clinically relevant. A standard devi-ation of 13 points for the CincinnatiKnee Score was used in our powercalculations based on previous stud-ies.9,20 To detect a difference of thismagnitude with a power of 90% at theP�.05 significance level, 36 subjectswere needed in each group, requiringa minimum of 72 subjects. We initiallyaimed for 100 subjects to allow fordropouts.

Both rehabilitation programs lastedfor 6 months, which is the custom-ary length of time for rehabilitationprograms after ACL surgery in Nor-way. No knee braces were used fol-

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lowing the knee surgery or duringthe rehabilitation program.

Two sets of 2 senior expert physicaltherapists completed preoperativeand follow-up test examinations, allmasked to the randomization proce-dure and group allocation. Each sub-ject was tested preoperatively forbaseline measurements and returnedfor follow-up evaluations at 3 and 6months. The rehabilitation programswere administered at 2 outpatientrehabilitation centers (the ST pro-gram at the Norwegian Sport Medi-cine Clinic and the NT program atthe Department of Physical Medicineand Rehabilitation, Ullevaal Univer-sity Hospital). At each center, 2 phys-ical therapists were responsible forthe rehabilitation program. All sub-jects signed an informed consentform prior to participation.

Knee Function—OutcomeMeasurementsThe Cincinnati Knee Score was theprimary outcome measurement. Thisinstrument has been well-validatedas an outcome measure.9,16,18 Thequestionnaire consists of the follow-ing variables: pain, swelling, givingway, general activity level, walking,stair climbing, running, jumping,and twisting activities. The maxi-mum score is 100 points, indicating anormal knee. The Cincinnati KneeScore has shown good reliability,with an intraclass correlation coeffi-cient (ICC) of .88 for test-retestreliability.21

Two VASs were included: one forpain intensity and one for globalknee function. For both scales, thesubjects made a mark on a 100-mmline between 2 extremes. For painintensity, the subjects were asked torate their pain intensity during activ-ities or immediately after activitieson the VAS, with 0 representing nopain and 100 representing worstpain (“as much pain as one can pos-sibly imagine”).22,23 For the VAS for

global knee function, 0 representedthe worst possible knee function and100 represented the same knee func-tion as prior to the knee injury.18,24

To our knowledge, the reliability ofdata for the VAS for global knee func-tion, where the subjects themselvesmarked a line on a 100-mm line, havenot been examined, but some au-thors25 have reported reliability datafor a numeric VAS, and other au-thors26 have reported reliability datafor a knee questionnaire using VASresponses for the items.

Muscle strength measurements ofthe quadriceps femoris and ham-string muscles were obtained usingthe Cybex 6000* isokinetic dyna-mometer27,28 preoperatively and atthe 6-month follow-up. The test pro-tocol consisted of 5 repetitions at anangular velocity of 60°/s (strength)followed by a 1-minute rest periodand 30 repetitions at 240°/s (endur-ance). The parameter used for anal-ysis was total work.27 Side-to-side dif-ferences in strength between injuredand noninjured legs were calculatedusing the strength index: (injuredleg/noninjured leg) � 100. Previouswork has shown good to high reli-ability for isokinetic muscle strengthtests, with ICCs ranging from .81 to.97.29

Balance was recorded using staticand dynamic balance tests on an in-strumented unstable platform(KAT2000†), which has been evalu-ated in previous studies.30,31 TheKAT2000 is a circular platform on abase of a pneumatic bladder, inflatedwith air to adjust for test difficultyand to allow for normalization to thesubject’s body weight. A tilt sensoron the platform was connected to acomputer, which registered the de-viation of the platform from a refer-

ence position 18.2 times each sec-ond. The distance from the centralpoint to the reference position wasmeasured at every registration. Fromthe summation of these distances, ascore—the balance index—was cal-culated. A low balance index indi-cates good ability to perform the bal-ance task.

Each subject completed a 1-leg staticbalance test on each leg (3 trials oneach leg) and a 2-leg dynamic test (3trials). The average of the 3 trials wasused as the balance index. The posi-tion of the feet was recorded, andthe same position was identified atthe follow-up tests. The subjectswere not given any practice trialsprior to the testing, but they re-ceived thorough information onwhat to do during the test. Hansenet al30 reported that, for a group of25 subjects tested on the KAT2000, adiminution of 12% from test to retestwas needed for the dynamic balancetest and a diminution of 15% fromtest to retest was needed for thestatic balance test to detect changesin balance due to interventions; oth-erwise, the changes probably wouldbe due only to test or subject varia-tions. However, no other reliabilitydata for the KAT2000 have beenreported.

Proprioception was evaluated usinga joint kinesthesia measure called the“threshold to detection of passivemotion” (TTDPM) device.32,33 Thedevice moves the knee joint intoflexion or extension with a constantangular velocity of 0.5°/s. All testingwas performed at a starting positionof 15 degrees of knee flexion. Sub-jects were told that either leg couldmove into flexion or extensionbeginning at a random time intervalbetween 0 and 45 seconds after theexaminer started the test. Once thesubject detected motion of the leg, abutton was pressed and the subjectstated which leg was moved and inwhich direction (flexion or exten-

* Cybex International Inc, 10 Trotter Dr, Med-way, MA 02053.† Breg Inc, 2611 Commerce Way, Vista, CA92081.

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sion). Each trial consisted of 3 repe-titions for each of the 4 motions(flexion and extension of both legs),resulting in a total of 12 repetitions.In the case of incorrect identificationof the motion, the repetition was re-turned to the randomization list sothat 3 correct repetitions of each mo-tion were completed. The number ofincorrect responses was recorded. Areliability coefficient (ICC) of .83 hasbeen reported for the TTDPM.33

Knee performance was tested with 3functional knee tests (one-leg hoptest, triple-jump test, and stair hoptest) that were used in previous ACLstudies.34,35 The one-leg hop andtriple-jump tests were performed 2times on each leg, and the best value(distances measured in centimeters)was recorded. For the stair hop test,the subjects were asked to hop upand down 22 steps (stepheight�17.5 cm) on one leg and torepeat the activity on the other leg(time measured in seconds). For all 3functional tests, the procedure wasfirst performed on the noninjuredleg followed by the injured leg. Side-to-side differences in performancebetween noninjured and injured legswere calculated using the index:(injured leg/noninjured leg) � 100.The one-leg hop test has showngood reliability, with ICCs rangingfrom .97 to .99.36 Reliability coeffi-cients (Pearson r) ranging from .81to .97 have been reported for thetriple-jump test and the stair hoptest, with coefficients of variationranging from 2.1% to 3.8%.37

Health-related quality of life was as-sessed using the SF-36.17,38 The in-strument is divided into 8 subscales(physical function, role limitations–physical, role limitations–emotional,bodily pain, general health, vitality,social function, and mental health).Each subscale of the SF-36 is scoredon a scale of 0 to 100, with thehigher the score, the better the per-son’s health status. Reliability for the

Norwegian version of the SF-36 hasbeen documented using the Cron-bach alpha.39 All 8 subscales havebeen reported to exceed the .70standard for group comparison, andthe Cronbach alpha exceeded the.90 standard for individual compari-sons on the physical functioning sub-scale.39 Finally, knee joint laxity wasrecorded using the maximum man-ual KT-1000‡ knee arthrometertest.40 The KT-1000 arthrometer hasshown to be a reliable instrument,with reported ICCs between .91 and.9729 for the involved knee, and withbetter interrater reliability for expertraters compared with noviceraters.41

Rehabilitation ProgramsCurrent research on the effects ofNT and ST; knowledge about grafthealing; research on proprioception,neuromuscular control, and quadri-ceps femoris muscle strength deficitsafter ACL reconstruction; and ourclinical experience were consideredduring the design of our rehabilita-tion programs. The traditional STprogram was widely used when westarted the study, whereas the neu-romuscular exercises had started tobe used in physical therapist prac-tices. We included a 6-month reha-bilitation program in this study be-cause of the current practice inNorway in which all individuals un-dergo a 6-month supervised rehabil-itation program after ACL recon-struction, which is covered by thesocial security system.

The subjects were hospitalized for 1to 3 days following ACL reconstruc-tion. After being discharged from thehospital and until the rehabilitationprogram started at the outpatientclinic, the subjects carried out ahome program with the main focuson restoring full range of motion(ROM) and swelling reduction. Both

rehabilitation programs started thesecond week after surgery at the out-patient clinics, with treatment ses-sions 2 to 3 times a week, and con-tinued for 6 months. To reduceswelling, we recommended that thesubjects keep the injured leg ele-vated and perform ankle plantar-flexion and dorsiflexion ROM exer-cises and isometric quadrcicepsfemoris and hamstring muscle exer-cises. Crutches also were used to re-duce swelling and to improve gait.Full knee extension is the most im-portant goal the first week of reha-bilitation. Gravity is used to restorefull knee extension by the use of 2chairs, with the leg elevated on ahard pillow under the heel when sit-ting or with the leg elevated on theedge of the bed in a supine position.

NT program. The NT programwas divided into 6 phases of 3 to 5weeks each and consisted of balanceexercises, dynamic joint stability ex-ercises, plyometric exercises, agilitydrills, and sport-specific exercises(Appendix 1).42 Subjects who devel-oped pain, swelling, or ROM deficitsunderwent interventions (cryother-apy, patellofemoral taping, and ROMexercises) until these impairmentswere resolved. In addition to amountof pain and swelling, criteria used todetermine readiness for progressionwere the ability to maintain balanceof the position (static balance) be-fore movements were superimposedon the position (dynamic balance)and awareness of the position of thebody in space before toleratingmovements or perturbations.

Balance exercises included single-and double-leg stance on even, flatsurfaces, with progression to bal-ance on a mat, a wobble board, anda trampoline. Some of the dynamicjoint stability exercises were per-formed using vectors on the floor toreference the start and the directionof the exercises described by Gray.43

Plyometric exercises (jump training‡ MEDmetric Corp, Street 7542 Trade St, SanDiego, CA 92191.

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exercises) were used to improve orchange technical performance andto improve shock absorption duringlanding. Furthermore, agility trainingexercises were included to allow thesubjects to adapt to quick changes indirection and to acceleration and de-celeration during cutting activities.Further details of the rehabilitationprogram and the specific exercisesare available elsewhere.42

ST program. The ST program con-sisted mainly of ST exercises of thelower-extremity muscles, with em-phasis on the quadriceps femoris,hamstring, gluteus medius, and gas-trocnemius muscles. All exercises inthe ST program were based on Amer-ican College of Sports Medicine(ACSM) recomendations44 and cur-rent practice in our clinic for peoplewith ACL reconstruction. Subjectswho developed pain, swelling, orROM deficits underwent treatmentsuntil these impairments were re-solved. This program has not beendescribed or published previously,and the exercises are described inAppendix 2.

The ST program was divided into 4phases. The goal of phase 1 was toreduce swelling and increase ROM,especially knee extension ROM. Ex-ercises in phase 1 were ROM exer-cises in prone and supine positions,in addition to the use of a stationarybicycle. Initially, subjects used thestationary bicycle with a pendulummovement. After the training ses-sions, cold therapy was applied forapproximately 20 minutes.

Phase 2 started when pain and swell-ing were reduced. Weight bearingduring the exercises was empha-sized to normalize gait and to controlknee movements. The “knee overtoe” position, core stability with pel-vic and hip control, subjects’ aware-ness of position of lower-extremityjoints, and changes in weight bear-ing during the exercises were em-

phasized during the training ses-sions. A mirror was used to providefeedback and to ensure correctmovements. If the subjects did notperform the exercises as intended,they returned to those exercises thatthey were able to perform in a con-trolled manner. Instructions such as“knee over toe” and “hips in plane”were commonly used during theexercises.

In phase 3, a full ST program wasintroduced in addition to one bal-ance exercise (single-leg stance bal-ance exercise in a pulley apparatus).Moderate- to high-intensity ST wasincluded based on each subject’sabilities to tolerate increased loading(weights). Recommended frequencyand dose of exercises (3 sets, 2–3days a week, of 50%–80% of their1-repetition maximum)44 were used,starting out with 12 to 15 repetitionsand progressing to fewer (8–12) rep-etitions. When the subjects per-formed the exercises in a controlledmanner, weights and resistancewere increased. After 13 to 16weeks, depending on their kneefunction and lower-extremity perfor-mance, the subjects started runningon a treadmill with a few degrees ofinclination to reduce the stress onthe ligamentum patellae. Increasedrunning distance, speed, and inclina-tion were used, depending on theirknee function and their preinjury ac-tivity level.

In phase 4, the ST exercises involveddecreased repetitions and increasedweights (3 sets of 6–8 repetitions),which were individually adjusted.For subjects who wanted to return tosports, sport-specific exercises basedon their previous sport activitieswere introduced.

Adherence to the RehabilitationProgramsEach subject was required to fill outdaily log sheets at the outpatient clin-ics to document their adherence to

the rehabilitation program in addi-tion to other exercises or trainingthat they did elsewhere. This infor-mation was reviewed by the physicaltherapist initially and by the researchassistant on a weekly basis. The train-ing diary included both number ofvisits for physical therapy interven-tion and hours spent exercising dur-ing the rehabilitation program, in ad-dition to number of other exercisesessions and hours spent doing otherexercise activities. Eighty percent ad-herence, meaning 80% of the recom-mended physical therapy visits (2times a week for 6 months), was setas the definition for being adherentto the rehabilitation program.

Data AnalysisData were analyzed using a repeated-measures analysis of variance(ANOVA) with time as the repeated-measures factor for the outcomemeasures at the 3- and 6-monthfollow-ups and as the between-groups factor for rehabilitation pro-grams (NT and ST). In addition, Stu-dent t tests were used to determinegroup differences (NT and ST) at the6-month follow-up as well as for timeof test differences. Mann-Whitney Utests were used when parametric as-sumptions were not fulfilled. Effectsize was calculated using change inscores divided by standard deviationat baseline.45 An effect size above 0.8refers to a large change, and an effectsize above 0.6 refers to a moderatechange.45 A probability level ofP�.05 was used to show statisticalsignificance.

ResultsEighty-one subjects were eligible forthe study based on the inclusion cri-teria and preoperative evaluation. Af-ter application of intraoperative ex-clusion criteria, 74 subjects wereultimately included in the study andrandomly assigned to the ST group(n�35) or the NT group (n�39).The 7 subjects who were tested pre-operatively but not included in the

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study had a hamstring muscle graft(surgeon was not aware of the factthat the subjects were eligible for thestudy), had a cartilage injury down tosubchondral bone, did not have acomplete ACL injury, did not showup at the time of surgery, or had ameniscus repair. Mean time from in-jury to surgery was 46.4 weeks(range�7.4–152.9), and there wereno significant differences betweengroups. Thirty-four subjects (46%)had meniscus injuries, and 29 sub-jects (45%) had grade I, II, or III car-tilage injuries. Nineteen subjects(30%) had both meniscus injuriesand cartilage injuries. All of the me-niscus injuries were debrided, and

no additional treatment was requiredfor those with cartilage injuries.

One subject who was included in thestudy moved out of the city soonafter surgery. She could not attendthe rehabilitation program and didnot return for follow-up examina-tion. Sixty-seven subjects (92%) re-turned for follow-up examination at3 months, and 65 subjects (89%) re-turned for follow-up examination at6 months. Of the 7 subjects who didnot return for the 3-month follow-upexamination and the 9 subjects whodid not return for the 6-monthfollow-up examination, only 4 sub-jects (5%) did not return for re-

examination after surgery (either 3-or 6-month follow-up).

After subject number 47 had beenincluded, the proprioception devicefailed and was unable to be repairedwithin the time frame of the study.As a result, proprioception data wereavailable only for the first 47 sub-jects. Similarly, the KAT2000 failedafter subject 51 was included, anddata were available only for the first51 subjects.

Preoperatively, there were no signif-icant differences between the 2groups with respect to sex, age, timefrom injury to operation, knee joint

Table.Mean (SD) Outcome Measurements for the Strength Training (ST) Group and the Neuromuscular Training (NT) GroupPreoperatively and 3 and 6 Months Postoperativelya

Preoperative (n�74) 3 mo (n�67) 6 mo (n�65)

ST Group(n�35)

NT Group(n�39)

ST Group(n�31)

NT Group(n�36)

ST Group(n�31)

NT Group(n�34)

KT-1000 (mm difference) 7.9 (3.6) 7.2 (4.3) 2.6 (2.9) 2.9 (2.8) 3.0 (2.9) 3.4 (2.6)

Cincinnati Knee Score 65.3 (13.0) 65.2 (17.0) 61.4 (11.7) 64.3 (11.5) 73.4 (9.6) 80.5 (12.3)b

VAS for pain during activity (mm) 35.4 (23.3) 35.2 (26.5) 25.9 (18.6) 31.8 (22.6) 24.6 (20.3) 20.7 (21.0)

VAS for knee function (mm) 33.9 (25.3) 39.1 (25.5) 51.7 (26.0) 50.1 (23.8) 59.3 (23.1) 72.4 (22.1)c

Triple jump test (%) 94.6 (10.2) 91.8 (12.3) 83.1 (15.4) 88.5 (10.4)

One-leg hop test (%) 93.7 (11.3) 90.1 (15.5) 81.0 (18.2) 84.9 (10.9)

Stairs hop test (%) 84.8 (18.1) 78.4 (21.0) 79.8 (16.4) 79.8 (25.7)

Balance index, static, uninvolved legd 566 (266) 557 (246) 509 (170) 457 (218) 443 (156) 433 (168)

Balance index, static, involved legd 602 (258) 592 (311) 532 (211) 455 (170) 460 (159) 445 (191)

Balance index, dynamicd 1,100 (451) 947 (266) 911 (335) 850 (311) 917 (394) 769 (235)

Proprioceptione (TTDPM),uninvolved leg (°)

1.22 (0.67) 1.19 (0.66) 1.13 (0.45) 1.04 (0.52) 1.21 (0.52) 1.22 (0.86)

Proprioceptione (TTDPM), involvedleg (°)

1.14 (0.74) 1.02 (0.52) 1.39 (0.90) 1.13 (0.45) 1.22 (0.52) 1.20 (0.76)

Flexion total work 60°/s (%) 80.6 (19.5) 82.9 (20.4) 88.3 (14.4) 86.3 (14.3)

Flexion total work 240°/s (%) 87.6 (18.4) 86.8 (24.2) 94.7 (16.1) 90.8 (21.1)

Extension total work 60°/s (%) 79.0 (18.0) 79.4 (20.6) 67.3 (16.1) 79.1 (17.1)

Extension total work 240°/s (%) 84.7 (12.8) 83.7 (17.9) 78.0 (16.0) 79.0 (16.8)

a There were significantly improved Cincinnati Knee Scores and visual analog scale (VAS) scores for knee function at 6 months in the NT group comparedwith the ST group. TTDPM�threshold to detection of passive motion.b P�.05.c P�.02.d Total number of subjects�51.e Total number of subjects�47.

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laxity, activity level, or any of theother variables that were measured(Table). At 3 months, there were nosignificant differences between theNT group and the ST group for anyof the outcome measurements(Table).

At the 6-month follow-up, after theintervention was terminated, therewere significantly improved Cincin-nati Knee Scores for the NT groupcompared with the ST group(P�.01) (Figure). The effect sizes forthe Cincinnati Knee Scores were0.89 for the NT group and 0.65 forthe ST group. The NT group also hadsignificantly improved VAS scoresfor global knee function comparedwith the ST group (P�.02). The ef-fect sizes were 1.3 and 1.0 for the NTgroup and the ST group, respec-tively. There were no significant dif-ferences between the 2 groups forpain at rest or pain during activity.The effect sizes for pain during activ-ity were 0.55 for the NT group and0.46 for the ST group. Furthermore,there were no significant differencesbetween the 2 groups for any of themuscle strength variables or any ofthe other secondary outcome mea-sures. Both the functional knee testsand the quadriceps femoris muscle

strength data showed that there wassignificant decline in knee functionfrom the preoperative period to the6-month postoperative period inboth groups. These data are in accor-dance with the findings of our previ-ous study9 showing that patients arenot back to normal strength or kneefunction 6 months after surgery.

The effect sizes for the dynamic bal-ance tests showed a small change forthe ST group from baseline to 6months (effect size�0.46) and amoderate change for the NT groupfrom baseline to 6 months (effectsize�0.60). The effect sizes for theinvolved leg and the uninvolved legfor the static balance test showed asimilar change for both legs frombaseline to 6 months (effect sizes of0.52 and 0.48 for the involved legand uninvolved legs, respectively, inthe ST group and effect sizes of 0.49and 0.50 for the involved and unin-volved legs, respectively, in the NTgroup).

Twenty-four subjects in the ST group(77%) and 34 subjects in the NTgroup (100%) turned in the daily logsheets for program adherence data.There were no significant differ-ences in the number of weeks that

the subjects participated in the reha-bilitation program between the STgroup (20.4 weeks) and the NTgroup (18.8 weeks) (P�.30). How-ever, the number of physical therapyvisits was significantly higher for theST group (57.6 visits) than for the NTgroup (42.2 visits) (P�.001), and themean number of hours spent at thephysical therapy outpatient clinicwas 62.9 hours for the ST group and43.8 hours for the NT group(P�.002). There were no significantdifferences between the 2 groups re-garding number of other exercisesessions or hours spent doing otherexercises (P�.09 for the ST groupand P�.38 for the NT group). Themean number of other exercise ses-sions and the mean hours spent do-ing other exercises were 22.0 exer-cise sessions and 16.2 hours,respectively, for the ST group and12.9 exercise sessions and 11.0hours, respectively, for the NTgroup. In the ST group, 91% of thesubjects were categorized as adher-ent to the rehabilitation program. Inthe NT group, 71% of the subjectswere categorized as adherent to therehabilitation program.

Discussion and ConclusionsThe results of this study indicatedthat, although there were small dif-ferences between the NT programand the ST program, the NT programwas superior to the ST program inimproving knee function after ACLreconstruction. Our main hypothesisin this study was supported. Subject-reported knee function after ACL re-construction (as measured with theCincinnati Knee Score and VASs)was significantly better after 6months of the NT program com-pared with 6 months of the ST pro-gram. The magnitude of the treat-ment effect (effect size) for the NTgroup indicated a large change insubject-reported knee function com-pared with a moderate treatment ef-fect for the ST group according tothe Cohen index.45 However, there

Figure.Cincinnati Knee Score at 3- and 6-month follow-ups for the strength training (ST) groupand the neuromuscular training (NT) group. Asterisk indicates significant differencesbetween groups at 6 months (P�.01).

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were no differences between the 2groups for the other secondary out-come measures and no significantdifferences early (3 months) aftersurgery. Both training programs pro-vided similar improvements instrength, balance, proprioception,and hop tests.

Previous investigations of the effectof neuromuscular training13,46,47

have examined subjects with ACLdeficiencies. Despite some limita-tions in these studies, they all dem-onstrated significantly improvedknee function for rehabilitation pro-grams including neuromuscular ex-ercises compared with only strengthtraining exercises for subjects withACL deficiencies. To our knowledge,only 2 randomized controlled tri-als14,15 have been published on theeffect of neuromuscular training af-ter ACL reconstruction. Neither ofthese studies had baseline data (pre-operative data), and both studies hadmajor limitations. The study by Liu-Ambrose et al14 gave limited informa-tion on the clinical effect of neuro-muscular training, included only 5subjects in each group, and includedthe intervention more than 6 monthsafter surgery. They used peak torquetime of the hamstring muscles as themain outcome measure, in additionto concentric and eccentric torquesof the quadriceps femoris and ham-string muscles, one-legged single-hop test, and Lysholm scale score.The NT group demonstrated agreater percentage of change in iso-kinetic torques compared with theST group, but there were no signifi-cant differences between the groupsfor functional ability or subject-reported knee function (Lysholmscale score). The study probably hadlimited power to detect any differ-ences in Lysholm scale scores orother knee function tests. They con-cluded that NT alone induced isoki-netic strength gains and that restor-ing and increasing quadricepsfemoris muscle strength is essential

to maximize functional ability of thereconstructed knee joint.

Cooper et al15 studied the effect ofan NT program versus a traditionalST program during a 6-week inter-vention (n�15 in each group). Thesubjects were included 4 to 14weeks after surgery; the power anal-ysis was based on hop tests, whichwere included as a outcome measureonly at follow-up, and the ST groupwas significant younger than the NTgroup. The authors used 2 differentgraft types (hamstring and patellartendon), there were more femalesubjects in the ST group comparedwith the NT group, and they in-cluded only subjects who could walkwithout crutches, had full ROM, hadno quadriceps femoris muscle lag,and had minimal joint effusion. Theauthors reported no strength mea-surements, and there were no differ-ences between the 2 groups atfollow-up regarding the hop tests.The ST group, however, had lessswelling and improved walking andsquatting compared with the NTgroup. Cooper et al concluded thatthere appeared to be no benefit ofperforming NT early after ACL recon-struction. Similarly, we found no dif-ferences between the 2 rehabilita-tion groups at 3 months aftersurgery, but a prolonged rehabilita-tion program (up to 6 months)seemed to add some benefit for theNT group.

To our knowledge, this is the firstrandomized controlled trial examin-ing differences between a prolongedrehabilitation program including dy-namic knee stabilization exercises,balance exercises, and jump trainingexercises and a program using pri-marily ST exercises—2 commonlyused exercise programs after ACL re-construction. The strength of thisstudy, as compared with the 2 previ-ous studies,14,15 is the length of therehabilitation program, the numberof subjects included in each group

based on power analysis, the base-line measurements obtained preop-eratively, and the thorough descrip-tion of both rehabilitation programs.However, there were similarities be-tween the 2 rehabilitation programsthat could have had an effect on thelack of differences between the 2groups. The strength exercises in-cluded information to the subjectson controlled knee movements, corestability with pelvic and hip control,and subjects’ awareness of positionof lower-extremity joints. This infor-mation is considered necessary foroptimal performance and joint load-ing during strength exercises. How-ever, this information could be re-garded as instructions to improvedynamic stability of the lower ex-tremity during exercises such assquatting and step-up. Additionally,one balance exercise was includedin the ST program (“single-leg stancebalance exercises,” see Appendix 2).Clinical practice today usually in-cludes both strength exercises andneuromuscular exercises,48 there-fore, our aim was to examine poten-tial differences between these 2common types of exercises includedin rehabilitation programs followingACL reconstruction.

Despite some similarities, there wereobvious and significant differencesbetween the 2 rehabilitation pro-grams regarding both the type of ex-ercises and the criteria for progres-sion for the ST exercises versus theNT exercises. All the exercises in theNT program were aimed at increas-ing the individual’s ability to dynam-ically stabilize their knee during ac-tivities,49 activities starting withstatic balance with progression todynamic balance (ie, more multifac-eted balance exercises and complexjump exercises). Criteria for progres-sion of the exercises in the NT pro-gram were control of movements,the subjects’ ability to maintain bal-ance of the position before move-ments were superimposed on the

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position, and awareness of the posi-tion of the body in space before tol-erating movements or perturbations.Exercises progressed from exercisesperformed on an even surface to ex-ercises performed on different un-even surfaces and from jump exer-cises on 2 legs to jump exercises on1 leg, increased hop distance forboth horizontal and vertical jumps,and jumps with change in directions.The progression for the strength ex-ercises was based on the ACSM’s rec-ommendation of dose response withincreased weights and decreasednumber of repetitions.44

Based on the goals for the ST pro-gram included in this study, we prob-ably have expected a larger strengthgain in the ST group compared withthe NT group. After 6 months, therewere no differences between the 2rehabilitation programs for the mus-cle strength tests performed. How-ever, the NT exercises included plyo-metric or jump training exercises.Plyometric exercises, involving pre-stretching the muscle and activatingthe stretch-shortening cycle to pro-duce a subsequent stronger concen-tric contraction, have been shown toincrease muscle strength.50 Adams etal51 showed that the combination ofplyometric exercises and traditionalstrength exercises such as the squatand leg press are superior in increas-ing muscle strength compared withonly traditional ST exercises. Bothtraditional muscle strength exercisesand plyometric exercises probablyshould be included in rehabilitationprograms to improve musclestrength.

The significant differences betweenthe 2 rehabilitation programsseemed to appear from 3 to 6months after surgery, not immedi-ately after surgery. It could also bethat the first 3 months were decisivefor the functional response from 3 to6 months after surgery, but this studycannot answer that question. The ex-

ercises included in the NT programduring the “running, jumping, andagility” phase, from 3 months to 6months, seemed to result in a signif-icantly improved subject perceptionof knee function compared with tra-ditional ST exercises and the runningexercises on the treadmill includedin phases 3 and 4 of the ST program.

The 2 rehabilitation programs werecarried out at 2 different outpatientclinics. This limitation was consid-ered at the start of the study, but dueto possible problems with communi-cation between subjects performing2 different rehabilitation programs atthe same clinic, 2 different clinicswere chosen. Furthermore, the phys-ical therapists who administered theNT program were more familiar withthose exercises and less experiencedwith only strength exercises. Thephysical therapists who were re-sponsible for the ST program weremore experienced in ST exercises,but also had some experience in NT.The physical therapists who were re-sponsible for the 2 different pro-grams were senior physical thera-pists and were all very experienced.

There also were some differences infacilities between the 2 outpatientclinics. The ST program was carriedout in a larger facility with moretraining equipment and more STequipment in particular comparedwith the clinic where the NT pro-gram was performed. This might bethe reason for the significantlyhigher number of visits and hoursspent at the outpatient clinic for thesubjects in the ST group comparedwith the NT group. Based on thedaily log sheets turned in, the adher-ence data indicate high adherence toboth rehabilitation programs (42 vis-its for the NT group�88%, 58 visitsfor the ST group�better than 100%).However, more subjects in the NTgroup turned in the daily log sheets(100%) compared with the ST group(77%). Most of these factors should

have indicated a better potential forthe subjects in the ST group toachieve better knee function, but itwas the NT group that perceived sig-nificantly improved knee function.

Some other limitations of the studyalso need to be addressed. The mostcommon error made or conclusiondrawn from the results of a random-ized controlled trial is the type IIerror. Power calculations were un-dertaken regarding the main out-come measurement in this study,and, despite the fact that there weresome dropouts at the 3- and 6-monthfollow-ups, a significant differencewas detected for the Cincinnati KneeScore. The study did not includepower calculations for the secondaryoutcome measures, and a significantdifference was detected between the2 groups only for the VAS for globalknee function. According to Hansenet al,30 26 subjects should have beenincluded to detect a significant dif-ference between groups for the dy-namic test, and 119 subjects shouldhave been included for the statictest. At the 6-month follow-up, 21subjects in the ST group and 17 sub-jects in the NT group were tested onthe KAT2000. The lack of differ-ences between the 2 rehabilitationprograms for the other outcomemeasures could be due to lack ofpower for these outcome measures,to similarities between the programs(these potential limitations havebeen addressed above), or to the factthat the other outcome measureswere not sensitive enough to detectdifferences. Biomechanical and mo-tion analysis studies probably shouldhave been included to be able toanswer this question. Previous mo-tion analysis studies4,52 have investi-gated changes in knee biomechanicsduring gait and hop tests and havedemonstrated significant changes inmovement patterns for perturbationtraining and jump training exercises.

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This is, to our knowledge, the firstrandomized controlled trial evaluat-ing the effect of prolonged NT exer-cises compared with traditional STexercises starting after ACL recon-struction and including preoperativedata on knee function. There wereno differences between the 2 pro-grams early after surgery, but a sig-nificant benefit of NT exercises wasrecorded by the Cincinnati KneeScore and VAS after the intervention,at the 6-month follow-up after sur-gery. There were no differences forany of the other outcome measures.Long-term follow-up is needed to de-termine whether this modest differ-ence in favor of the NT exercises hasany long-term consequences. Fur-ther research also is needed to dis-close possible mechanisms for thesedifferent exercises.

Dr Risberg, Dr Holm, and Dr Engebretsenprovided concept/idea/research design. DrRisberg and Dr Myklebust provided writing.Dr Risberg, Dr Holm, and Dr Myklebust pro-vided data collection. Dr Risberg and DrHolm provided data analysis. Dr Risberg pro-vided project management. Dr Risberg andDr Engebretsen provided fund procurement.Dr Engebretsen provided facilities/equip-ment. Dr Holm, Dr Myklebust, and Dr Enge-bretsen provided consultation (including re-view of manuscript before submission). Theauthors acknowledge the following physicaltherapists: Hanne Krogstad Jenssen andMarianne Mork, Department of PhysicalMedicine and Rehabilitation, Ullevaal Uni-versity Hospital, Oslo, Norway, and TuridHøysveen and Gitte Madsen, NorwegianSports Medicine Clinic, Oslo, Norway, forperforming the rehabilitation programs andCamilla Ramsland and Siri Elliassen, Ortho-pedic Center, Ullevaal University Hospital,for testing subjects throughout this rehabil-itation study. The authors also acknowledgeLynn Snyder-Mackler, PT, ScD, SCS, FAPTA,Department of Physical Therapy, Universityof Delaware, Newark, Del, for her commentson the manuscript.

This investigation was approved by the Re-gional Committee for Medical ResearchEthics.

An oral presentation of this research wasgiven at a national sports medicine meeting(Idrettsmedinsk Høstkongress); November1–4, 2005; Bergen, Norway.

This study received research grants from theNorwegian Research Council, Oslo, Norway.

This article was received February 6, 2006, andwas accepted February 28, 2007.

DOI: 10.2522/ptj.20060041

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41 Berry J, Kramer K, Binkley J, et al. Errorestimates in novice and expert raters forthe KT-1000 arthrometer. J Orthop SportsPhys Ther. 1999;29:49–55.

42 Risberg MA, Mork M, Jenssen HK, Holm I.Design and implementation of a neuro-muscular training program following ante-rior cruciate ligament reconstruction. J Or-thop Sports Phys Ther. 2001;31:620–631.

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44 American College of Sports Medicine Po-sition Stand: The recommended quantityand quality of exercise for developing andmaintaining cardiorespiratory and muscu-lar fitness, and flexibility in healthy adults.Med Sci Sports Exerc. 1998;30:975–991.

45 Cohen J. Statistical Power Analysis forBehavioral Science. 2nd ed. Hillsdale, NJ:Lawrence Erlbaum Associates; 2005.

46 Fitzgerald GK, Axe MJ, Snyder-Mackler L.The efficacy of perturbation training innonoperative anterior cruciate ligamentrehabilitation programs for physical activeindividuals. Phys Ther. 2000;80:128–140.

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50 Voight M, Tippett S. Plyometric exercisesin rehabilitation. In: Prentice WE, ed. Re-habilitation Techniques in Sport Medi-cine. 2nd ed. St Louis, Mo: Mosby; 1994:88–97.

51 Adams K, O’Shea JP, O’Shea KL, ClimsteinM. The effect of six weeks of squat, plyo-metric and squat-plyometric training onpower production. J Strength Cond Res.1992;6:36–41.

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Appendix 1.Neuromuscular Training Programa

The rehabilitation program starts the second week after surgery, 3 times a week for 6 months. Only the newexercises that are introduced each week are described below. The involved leg is used if nothing else is stated.

Phase 0: Early Postoperative PhaseWeeks 1–2Goal: full passive knee extension and reduced swelling.Patients are hospitalized for 1 to 3 days. After discharge from the hospital and until the rehabilitation program startsat the outpatient clinic, patients do a home program with the main focus on restoring full range of motion andreducing swelling. To reduce swelling, the patient should keep the leg elevated, repeat ankle plantar flexion–dorsiflexion range of motion exercises, and perform isometric quadriceps and hamstrings exercises. Crutches areused to improve gait and to reduce swelling. Full knee extension is the most important goal the first week. Gravityis used to restore full knee extension by using 2 chairs, with the leg elevated on a hard pillow under the heel whensitting or with the leg elevated on the edge of the bed in supine position.

Phase 1: Walking PhaseWeeks 2–4Goals: normal walking pattern; controlled balance double-limb support; controlled balance single-limb support;controlled dynamic stability of the uninvolved leg.

Crutches are used with weight-bearing as tolerated until 2 to 4 weeks after surgery. The criterion for discontinuingthe use of crutches is no limping. Weight-bearing exercises are started as early as possible. If full weight-bearing isnot tolerated during squatting exercises, counterweights are used to avoid swelling or pain.

Cold therapy (glacier packs) is applied for 15 minutes immediately after training as long as swelling is present.• Stationary bicycle to improve range of motion and reduce swelling• Walking exercises on the floor• Walking exercises on a treadmill to improve gait patterns after discontinuing crutches• Squatting exercises: if the patient has persistent swelling or pain, squatting exercises are performed in a pulley apparatus

with the use of counterweights• Gastroc exercises: standing heel rising exercise• Single leg stance exercise, starting on the uninvolved leg• Single leg stance, involved leg• Balance reach leg exercise and balance reach arm exercises on uninvolved leg• Lunge exercises: anterior, anterior/lateral, lateral, posterior/lateral, and posterior directions on uninvolved leg• Step-up exercises: anterior, lateral, posterior, starting with uninvolved leg

Phase 2: Balance and Dynamic Joint Stability PhaseWeeks 5–8Goals: controlled balance double-limb support, uneven surface; controlled balance single-limb support, unevensurface; controlled dynamic stability, double-limb support; controlled dynamic stability, involved leg; step-up andstep-down; squatting, 2 legs; sideways and backwards walking.

Week 5• Single leg stance, eyes closed• Single leg standing on balance mat, appropriate knee and hip position• Wobble board, 2 legs• Balance reach leg, involved leg• Balance reach arm, involved leg• Step-up, both legs

Week 6• Backwards and sideways walking on treadmill• Wobble board, 2 legs with weights• Wobble board, 2 legs, throwing ball• Wobble board, 1 leg• Step-down, uninvolved leg

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Week 7• Single leg stance, trampoline, throwing ball• Step-up and step-down, involved leg, different direction• Balance reach leg, balance reach arm, balance mat, and wobble board

Week 8• Lunge exercise with bars/weights• Single leg stance, trampoline, throwing ball, different directions (front, back, and sideways)• Single leg stance, balance mat, throwing ball• Step-up, wobble board

Phase 3: Muscle Strength PhaseWeeks 9–12Goal: increased muscle strength.

• Slide board exercises• Single leg stance with weights, eyes closed• Wobble board single leg, eyes closed• Squatting exercises, wobble board• Squatting exercises with weights, increased knee flexion• Lunge exercises with weights, increased knee flexion• Step-up with weights, increased height and weights• Jumps: 2 legs, trampoline

Phase 4: Running PhaseWeeks 13–16Goals: running; controlled jumps, 2 legs, trampoline; controlled jumps, 2 legs, turns, trampoline.

• Running on trampoline• Running on treadmill• Running or jogging outdoors• Jump training: 2 legs, trampoline, increased knee flexion• 180-degree jump on trampoline

Phase 5: Jumping PhaseWeeks 17–19Goals: running sideways and backwards; controlled cutting, slow speed; controlled jumping, 2 legs, flat, evensurface; controlled bounding for distance; controlled jumps on steps.

• Running backwards• Bounding for distance• Jumps: 2 legs, 180-degree turns, flat, even surface• Jumps: up and down from a step• Running: figure-of-eight, stop-turn-run• Agility drills, slow speed

Phase 6: Plyometric and Agility Training PhaseWeeks 20–24Goals: controlled single leg jumps; controlled vertical jumps; controlled cutting, full speed; controlled sport-specificactivities.

• Single leg jumps, trampoline• Single leg jumps, balance mat• Single leg jumps, anterior posterior, lateral, flat, even surface• Vertical jumps• Scissors jumps• Series of jumps: 2-footed jump onto 6- to 8-inch step. Jump off step with 2 feet, then vertical jump• Agility drills, full speed on a moveable standing platform• Sport-specific tasks are added during the agility training depending on the kind of sport the patients may return to

a Reprinted from: Risberg MA, Mork M, Jenssen HK, Holm I. Design and implementation of a neuromuscular training program following anterior cruciate ligamentreconstruction. J Orthop Sports Phys Ther. 2001;31:620–631, with permission of the Orthopaedic and Sports Physical Therapy Sections of the American PhysicalTherapy Association.

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Appendix 2.Strength Training Programa

Phase 1 (Weeks 2–4)Goal: reduce swelling and increase ROM.Focus: full knee extension ROM.Crutches with weight-bearing as tolerated 2–4 weeks after surgery (full weight-bearing was allowed). The criterionfor discontinuing the use of crutches was no limping. Cold therapy was applied after the training session for 20minutes as long as swelling persisted.

Number of repetitions: 4 sets of 20–30 repetitions.• Supine position—straight leg raising exercises• Supine position—isometric quadriceps contraction• Supine position—knee flexion and extension ROM exercises, the heel in contact with the bench during the ROM• Prone position—straight leg raising exercises• Prone position—knee flexion ROM exercises• Prone position—knee extension ROM exercises with toes in contact with the bench• Stationary biking—before reaching 100 degrees of flexion, the pedals were used in a “pendulum” movement

Phase 2 (Weeks 5–8)Goal: normalized walking pattern.Progression: stair climbing and strength exercises.Focus: knee over toe position, and controlled full knee extension in weight-bearing positions.

Number of repetitions: 3 sets of 15–20 repetitions.• Standing—full weight-bearing, controlled balance double-limb support during parallel and diagonal stance, controlled knee

extension, emphasis on full knee extension in weight-bearing position• Standing heel rising exercises both legs—progression to one leg• Step-up (start: low height) exercises• Squatting exercises without bars/weights• Hip abduction/adduction exercises• Hamstrings exercises: training in both prone and sitting positions

Phase 3 (Weeks 9–15)Goal: increased weights during strength training exercises.Focus: motivation during strengthening exercises.

Number of repetitions: 3 sets of 12–15 repetitions.• Single leg heel rising exercises• Step-up exercises (increased heights)• Step-down exercises• Squatting exercises with bars/weights• Hip abduction/adduction exercises• Hamstrings, training in both prone and sitting positions• Lunges, anterior and lateral directions• Leg-press exercises• Single leg stance balance exercises in anterior, posterior, and lateral directions in a pulley apparatus• Running on a treadmill (between week 13–16)

Phase 4 (Weeks 16–24)Goal: increased running speed and weights during strengthening exercises.Focus: sport-specific tasks depending of type of sport and motivation during strengthening exercises.Repetitions: 3 sets of 6–8 repetitions.Same type of exercises as phase 3 but now with increased loads and reduced number of repetitions.

a ROM�range of motion.

Neuromuscular Versus Strength Training After ACL Reconstruction

750 f Physical Therapy Volume 87 Number 6 June 2007 by guest on December 28, 2014http://ptjournal.apta.org/Downloaded from

doi: 10.2522/ptj.20060041Originally published online April 18, 2007

2007; 87:737-750.PHYS THER. Lars EngebretsenMay Arna Risberg, Inger Holm, Grethe Myklebust andTrialLigament Reconstruction: A Randomized ClinicalDuring First 6 Months After Anterior Cruciate Neuromuscular Training Versus Strength Training

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