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Reliability and discriminative validity of sudden ankle inversion measurements in patients with chronic ankle instability

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Reliability and discriminative validity of sudden ankle inversion measurements in patients with chronic ankle instability
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  Reliability and discriminative validity of sudden ankle inversion measurementsin patients with chronic ankle instability Christophe Eechaute a, *, Peter Vaes a , William Duquet b,1 , Bart Van Gheluwe b a The Physical Therapy Department of the Vrije Universiteit Brussel, Laarbeeklaan 103, B-1090 Brussels, Belgium b The Human Biometry and Biomechanics Department of the Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium 1. Introduction Lateral ankle sprains are very common sports related injuries.Ankle sprain recurrence rates range from 19% to 70% [1,2]. Up to72% of individuals who sustain a lateral ankle sprain have beenreported to have residual symptoms and/or to develop chronicankle instability (CAI) [2–4].One of the predisposing factors of CAI is thought to bea delayedperoneal muscle reaction time during sudden ankle inversions, butwhetherthemusclereactiontimeoftheperonealmusclesisdelayedin unstable ankles, still is a matter of debate. Results of studiesinvestigatingreactiontimesoftheperonealmusclesinpatientswithCAIduringsuddenankleinversionsareconflicting[5–15].Thismaybe due to differences in test protocols, patient populations beingstudied, equipment or techniques to detect the first electromyo-graphic signal. However, the validity of clinical measurements isprimarilybaseduponthemagnitudeofthereliabilitycoefficientandthe standard error of measurement [16,17]. No study reportedresults of reliability and accuracy of muscle reaction times duringsudden ankle inversions in patients with CAI.In previous research, the reliability of sudden ankle inversionmeasurements was investigated in subjects with healthy ankle joints [18]. Results of that study showed that the latency time andmotor response time of the peroneus longus muscle, the totalinversion time, the mean and maximum inversion speed and thetimes of onset of the first and second decelerating momentdemonstrate acceptable reliability in healthy subjects. Subse-quently, the purpose of this study was to investigate the reliabilityof sudden ankle inversion measurements in patients with CAI andtoidentifywhetherdeficitsinfunctionalanklejointcontrolexistinpatients with CAI when compared to healthy subjects. 2. Methods  2.1. Subjects 40 patients with CAI (20 men; 20 women; age 21.0  3.2 years, body height175.8  8.6 cm, body weight 69.5  9.0 kg, duration of ankle problem 43.7  41.9 Gait & Posture 30 (2009) 82–86 A R T I C L E I N F O  Article history: Received 28 April 2008 Received in revised form 19 March 2009 Accepted 21 March 2009 Keywords: Ankle joint Joint instabilityAnkle inversionValidation studiesAccelerometry A B S T R A C T Background:  Studies investigating peroneal muscle reaction times in chronically unstable ankle jointspresent conflicting results. The degree of reliability and accuracy of these measurements is unknown inpatients with chronic ankle instability (CAI). Methods:  40 patients with CAI and 30 healthy subjects were tested using a sudden ankle inversion of 50 8 while standing on a trapdoor device. Sudden ankle inversion measurements were registered usingelectromyography, accelerometry and electrogoniometry. For reliability testing, intra-class coefficients(ICCs; model 3,1) and standard errors of measurements of the latency time, motor response time andelectromechanical delay of the peroneus longus muscle, the time and angular position of onset of decelerations, the meanand maximum inversion speed and the total inversion timewere calculatedin15patientswithCAI.Toassessbetween-groupdifferences, t  -testsforindependentsamples(  p < .05)wereused. Results:  ICCs ranged from .20 (angular position of onset of the second deceleration) to .98(electromechanical delay of the peroneus longus muscle). Significant between-group differences wereobserved in only 2 of the 12 variables (for the electromechanical delay of the peroneus longus muscle,  p  = .001; time of onset of the second deceleration,  p  = .040). Conclusions:  The latency time and motor response time of the peroneus longus muscle, the totalinversion time and the mean inversion speed demonstrate acceptable reliability in healthy subjects andpatients. The latency time and motor response time of the peroneus longus muscle are not delayed inpatients with CAI. Ankle inversion measurements are not discriminative for CAI.   2009 Elsevier B.V. All rights reserved. * Corresponding author. Tel.: +32 477 43 26; fax: +32 477 43 26. E-mail addresses:  christophe.eechaute@belgacom.net (C. Eechaute),pvaes@vub.ac.be (P. Vaes), bvangheluw@vub.ac.be (B. Van Gheluwe). 1 In memoriam. Contents lists available at ScienceDirect Gait & Posture journal homepage: www.elsevier.com/locate/gaitpost 0966-6362/$ – see front matter    2009 Elsevier B.V. All rights reserved.doi:10.1016/j.gaitpost.2009.03.006  months,talartilt9.1  7.0 8 asmeasuredduringroentgenologicstressradiographs)and30subjectswithhealthyanklejoints(22menand8women;age21.9  2.8years;bodyheight 177.4  8.0 cm; body weight 68.6  6.5 kg) were selected. Both groups arecomparableforage,heightandweight(  p > .05).PatientswithCAIwererecruitedfromthe Orthopaedic Department and the Emergency Department of the UniversityHospitalandfromtheonlineinjuryregistrationdatabaseoftheHumanPhysiologyandSports Medicine Departments. The inclusion of patients with CAI was based upon the completion of astandardized questionnaire containing the criteria of CAI. CAI was defined as: ahistory of a traumatic lateral ankle sprain (i.e. an ankle sprain followed by pain,swelling, stiffness interfering with active participation in sports, recreational orother activities for at least 3 weeks) requiring two or more medical consultations,complaints of repetitive lateral ankle sprains for at least 6 months, presence of fearof the ankle ‘‘giving way’’ and reporting an ankle-related decreased performancelevel of recreational, competitive or professional activities.Exclusioncriteriaforpatientswere:ahistoryofanklesurgery,vestibulardeficits,presenceofmusclefatigueorpaininthelowerextremitiesatthemomentoftestingpreventing the subject from putting full body weight on the tested leg.Inclusioncriteriaforthehealthysubjectswere:agebetween17and40yearsandbeing activeinrecreational orcompetitivesports. Exclusioncriteria were:a historyof a traumatic lateral ankle sprain, signs of recurrent ankle sprains or feeling of ‘‘ankle giving way’’, a history of an injury in the lower extremities during the last 3months before testing, a history of ankle surgery or ankle fracture, vestibulardeficits,presenceof musclefatigueorpaininthelowerextremityatthemomentof testing preventing the subject from putting full body weight on the tested leg. Theeligibility of both healthy subjects and patients was checked by using astandardized questionnaire containing the criteria for CAI, questions related tothe presence or absence of a history of ankle surgery, vestibular deficits, musclefatigue or painin thelower extremities andalso questionsreferring to thetype anddegree of sports activities. At the moment of testing, participants completed thesame standardized questionnaire to check their eligibility. Further on, the lowerextremity of all healthy subjects and patients with CAI was clinically examined. Alleligible subjects were informed about the purpose of the study and gave theirwritten informed consent. The Ethical Committee of the University Hospitalapproved the research protocol.  2.2. Test procedure The test procedure was conducted in the same manner as described in the studyof Eechaute et al. [18] and full details can be found in that report. Subjects werestanding on a custom-designed ankle inversion platform, with both feet tightlyfixed on independently movable trapdoors (constructed by the Physical TherapyDepartment and the Human Biometry and Biomechanics Department). Subjects,puttingfullbodyweightonthetestedankle,lookingforwardandlisteningtomusicin headphones (and therefore oblivious to external noise) were then exposed to asudden ankle inversion of 50 8  (Fig. 1).With respect to the reliability study, all patients were tested by the sameexaminer, with an interval of 1 week between the two test sessions. The order of testingwasthesameforbothtestoccasions.Sixinversionsofalltestedankleswererecorded. In patients with CAI, the unstable ankle was tested. In patients withbilateral ankle instability and also in subjects with healthy ankles, the side of thetested ankle was randomly chosen.In order to avoid observer bias during the processing of the data, the observerwas blinded for the assessment of the variables on the accelerometric,electrogoniometric and electromyographic curves. To this aim, the identity of thehealthy subjectsandpatientsandalsotherecordingdateofthefiles andgraphswere randomly changed into numeric values.ThemeasuredvariableswereassessedmanuallyasrecordedbytheVarioportdatalogger. Special measuring tools of the accompanying Varioport software allow onscreenextractionofamplitudeandtimeofanydatapointonadisplayedcurve(Fig.2).The following variables were assessed from the curves representing the timehistories for inversion speed (hardware integrated from the accelerometer signal),for electromyographic activity of the peroneus longus muscle and for electro-goniometric inversion displacement of the platform: -  Latency time of peroneus longus muscle (nr. 4, Fig. 2): time between start of theinversion (A, Fig. 2) and onset of EMG (E, Fig. 2). Criterion for onset of EMG: an increase of the signal over twice the noise level. -  Total inversion time: total time between start (A, Fig. 2) and end (B, Fig. 2) of the tilting of the platform. -  Mean inversion speed: ratio of total inversion time to total angular displacement(being 50 8 ). -  Maximum inversion speed ( 8 /s): maximum inversion speed (in m/s)  57.3/0.157 m with 57.3 being the conversion factor from radials into degrees and0.157 m being the distance from the accelerometer position to the axis of platform rotation (nr. 5, Fig. 2). -  Timeofonsetoffirstdeceleration:timebetweenstartofthetiltingofplatform(A,Fig.2)andfirstupwarddeflectionofthevelocitygraph(C,Fig.2).Incontrasttothe total angular end position of the sudden ankle inversion, which is identical to alltested subjects, total inversion times differ between subjects. Therefore, the timeof onset of first deceleration was also expressed as a percentage of the totalinversion time assessed during the same ankle inversion. -  The angular position of onset of first deceleration, corresponding to the time of onset of first deceleration can be read simultaneously from the electrogonio-metric curve. -  Time of onset of second deceleration: time interval between start of the tilting of the platform and second upward deflection of the velocity graph (D, Fig. 2). Also,thetimeofonsetofseconddecelerationwasexpressedasapercentageofthetotalinversion time assessed during the same ankle inversion. -  Theangularpositionofonsetofseconddeceleration,correspondingtothetimeof onset of second deceleration can also simultaneously be read from theelectrogoniometric curve. -  Electromechanical delay of the peroneus longus muscle was assessed in aseparatetestpriortotheperturbationtestandisidenticaltothetestprocedureasdescribed in Eechaute et al. [18]: time between start of EMG and the start of movement of the foot into eversion, read from the accelerometric curve. -  Motor response time of the peroneus longus muscle: sum of the peroneal latencytime and its electromechanical delay.  2.3. Statistical analysis Resultsof the dataof six inversionswere averaged for eachvariable andused forfurther statistical analysis. Data of all variables were normally distributed(Kolmogorow–Smirnow goodness-of-fit test,  p > .05). Reliability coefficients, usinganintra-classcorrelationmodel(3,1)followingrepeatedmeasuresANOVAwiththesignificance level set at  p < .05, were calculated as well as standard errors of themeasurements (SEM).Student  t  -tests for independent samples were used for the between-groupdifferences. Thesignificancelevel wassetat  p < .05.Further on,statisticalpowerof the results was calculated.Finally, correlational analyses (Pearsons’  r  ) were conducted to study therelationship between the patients’ characteristics (body height, body weight andtalar tilt) and the ankle inversion measurements. Fig. 1.  Starting position and end position of the sudden ankle inversion. C. Eechaute et al./Gait & Posture 30 (2009) 82–86   83  3. Results  3.1. Test–retest reliability of sudden ankle inversion measurements ICCs ranged from .20 to .98, representing poor to excellentagreement between test results (Table 1). Both the electromecha-nical delay (ICC = .98; SEM = 0.5 ms) and the latency time of theperoneus longus muscle (ICC= .88; SEM = 4.7 ms) demonstrate thehighestreliabilitycoefficients.The angularpositionofonsetofboththe first (ICC= .51; SEM = 2.4 8 ) and second deceleration (ICC = .20;SEM= 2.6 8 ) demonstrate the lowest reliability coefficients.  3.2. Validity of sudden ankle inversion measurements Significant between-group differences were only observed fortheelectromechanicaldelayoftheperoneuslongusmuscleandthetime of onset of the second deceleration (Table 2).The electromechanical delay of the peroneus longus muscle inhealthy subjects (19.8 ms) is significantly shorter than in patients(23.6 ms,  p  = .001; 95% CI:   5.4 to   2.2 ms).The time of onset of the second deceleration in patients(96.1 ms) occurred significantly earlier than in healthy subjects(101.4 ms;  p  = .040; 95% CI: .26–10.3 ms). Fig.2. Variablesofthe suddeninversion inthestandingposition inpatientswithCAI.Adownwardcourseof thevelocitygraph implicates anincreaseof inversion speed andan upward course a decrease of inversion speed. A = start of the sudden inversion, B = end of the sudden inversion, C = onset of first deceleration, D = onset of seconddeceleration, E = start of first EMG in the peroneus longus muscle, 1 = total inversion time (ms), 2 = time value of onset of first deceleration (ms), 3 = time value of onset of second deceleration (ms), 4 = latency time of the peroneus longus muscle (ms), and 5 = maximum inversion speed (m/s).  Table 1 Reliability results of the sudden ankle inversion measurements in patients with CAI ( n  = 15).Variable Test Retest ICC SEM Range of measurements (95% CI)  1.96  SEM Mean Sd. Mean Sd.Lat (ms) 61.7 13.5 60.6 11.8 .88 4.7 51.4–70.9Tit (ms) 105.0 8.5 106.9 5.4 .81 3.7 97.7–114.2Mis ( 8 /s) 469.8 24.1 479.6 38.8 .80 17.4 435.7–513.7Maxis ( 8 /s) 552.7 80.2 544.1 88.9 .61 55.5 435.1–661.7Emd (ms) 22.8 3.3 22.8 3.8 .98 0.5 21.8–23.8Mr (ms) 78.3 12.8 81.7 14.4 .83 5.9 66.7–93.3Dect1 (ms) 36.0 5.1 33.3 6.7 .63 4.1 25.3–44.0Deca1 ( 8 ) 14.6 2.8 13.6 3.4 .51 2.4 8.9–19.3Dect2 (ms) 103.6 6.7 100.7 10.0 .75 5.0 90.9–113.4Deca2 ( 8 ) 45.2 2.9 45.2 2.3 .20 2.6 40.1–50.3Lat,latencytimeoftheperoneuslongusmuscle;Tit,totalinversiontime;Mis,meaninversionspeed;Maxis,maximuminversionspeed;Emd,electromechanicaldelayoftheperoneuslongusmuscle;Mr,motorresponsetimeoftheperoneuslongusmuscle;Dect1,timeoftheonsetofthefirstdeceleration;Deca1,angularpositionoftheonsetofthefirstdeceleration;Dect2,timeoftheonsetoftheseconddeceleration;Deca2,angularpositionoftheonsetoftheseconddeceleration;Sd.,standarddeviation;ICC,intra-classcorrelation coefficient; SEM, standard error of measurement; CI, confidence interval. C. Eechaute et al./Gait & Posture 30 (2009) 82–86  84  For the other variables, no significant between-group differ-ences were observed (  p > .05).The statistical power of these non-significant differences rangebetween 3% (for the maximum inversion speed) and 78% (for thepercentage time of onset of the second deceleration).Thecorrelationoftalartiltvalues(Pearsons’ r  between  .03and.26), body height ( r   between   .01 and .21) and body weight ( r  between   .03 and .25) with the variables was insignificant(  p > .05). 4. Discussion 4.1. Test–retest reliability of sudden ankle inversion measurements In patients and in healthy subjects, the latency time and motorresponse time of the peroneus longus muscle, the total inversiontime and the mean inversion speed demonstrate good to excellentreliability and show also rather small SEMs. Therefore, thesemeasurements are useful to detect possible deficits in the controlof sudden ankle inversions in patients with CAI.The maximum inversion speed values in patients are con-siderably less consistent (ICC = .61) and less accurate (SEM= 55 8 /s)when compared with healthy subjects [18] (ICCs between .82 and.89; SEMs between 31 and 34  8 /s). Based upon its SEM, we are 95%confident that maximum inversion speed values in patients willvary between 435 and 662 8 /s. This wide range jeopardizes thecapacity of this variable to discriminate between healthy subjectsand patients with CAI.Like in healthy subjects, the angular position of the onsets of both decelerations represent poor to moderate reliability inpatients. This makes the validity of these variables questionable. 4.2. Discriminative validity of sudden ankle inversion measurements4.2.1. General Reporting confidence intervals and the statistical power of theobserved differences is important for a correct interpretation of   p -values.Statisticalpowerisrelatedthesamplesizeandsmallsamplesincreasetheprobabilityoftype2errors(i.e.incorrectlyacceptingthenullhypothesis)[17,19].Baseduponthelowpowervaluesobservedinourstudy,onemayconcludethatthepresentsamplesizewastoosmallto drawconclusionsfromit and thatmore subjectsshould bestudied. However, the current sample size was apparently largeenough to demonstrate a high statistical power for two variables(theelectromechanicaldelayoftheperoneuslongusmuscleandthetime of onset of the second deceleration).Furthermore, based uponthe observed small between-group differences,a very highnumberofsubjectswouldbeneededtoobtainsignificantdifferenceswithastatistical power of 80% for a  p -value of .05. For example, withrespect to the total inversion time, although a measure with a highICCcoefficientandalowSEM,asamplesizeof500subjectswouldbeneeded to prove the observed difference to be significant at the .05level [19]. With respect to the other variables, many more subjectswould be needed.The observed between-group difference of the total inversiontime (and also for most other variables) is smaller than its SEM(Table1).Themeantotalinversiontimevaluesofthepatientgrouplie within 1 SEM (between 5.4 and 5.9 ms) of those of the healthygroup. This indicates that, with respect to this variable, patientswith CAI ‘‘behave’’ like healthy subjects and that the between-group difference is merely the result of measurement error.One can assume that the difference in the ratio of males tofemalesbetweenbothgroupsmightbeaconfoundingfactorfortheobserved results. However, when comparing test results of malepatients with those of the male healthy subjects or comparingfemale patients with female healthy subjects, the same resultswere obtained as those that are srcinally presented. 4.2.2. Latency time and motor response time If CAI is related to a delay in the peroneal reaction time, wewould expect a significantly lengthened latency time and motorresponse time of the peroneus longus muscle in patients. This wasnot the case in the present study. Our findings agree with somestudies [5–10] but conflict with other [11–15]. This may be due to differences in test protocols, patient populations being studied,equipment or techniques to detect the first electromyographicsignal. However, the lack of knowing how reliable and precise themeasurements of these studies are, also impedes the interpreta-tion of their test results. 4.2.3. Inversion time, inversion speed and onset of decelerations Very highinversion speed values wereobserved inboth healthysubjects and patients. This indicates that during the test procedureankle joint tissue is substantially stressed. One can assume that inpatients with CAI the mechanical properties of the ligaments and joint capsule of repetitively sprained ankles are deteriorated overtime.Ifso,wewouldhaveobservedasignificantlyshorterinversiontime and a significantly higher inversion speed in patients aselements of an impaired ankle joint stabilization during suddeninversionstress.However,thiswasnotthecaseinthepresentstudy.The mechanical behaviour of ankle joint tissue during highinversion speed seems notto bethe same as during slow inversion  Table 2 Results of the sudden ankle inversion measurements in healthy subjects ( n  = 30) and in patients with CAI ( n  = 40).Variable Healthy Patients  P  ( F  )  P  ( t  ) 95% CI 1- b Mean Sd. Mean Sd.Lat (ms) 62.5 13.3 59.4 13.3 .561 .334   3.3/9.5 28%Tit (ms) 109.8 9.9 107.9 7.6 .025 .386   2.5/6.3 25%Mis ( 8 /s) 458.7 42.4 460.6 36.9 .090 .845   20.8/17.1 5%Maxis ( 8 /s) 528.1 59.3 527.5 73.1 .433 .977   42.9/44.2 3%Emd (ms) 19.8 2.7 23.6 3.9 .140 .001   5.4/  2.2 100%Mr (ms) 82.3 13.3 81.9 13.0 .648 .903   6.0/6.7 4%Dect1 (ms) 30.8 5.2 29.9 6.6 .246 .518   2.0/3.9 16%Dect1p (%) 28.4 5.8 27.8 6.6 .511 .743   2.5/3.5 7%Deca1 ( 8 ) 14.5 3.3 14.9 2.9 .705 .585   1.9/1.1 12%Dect2 (ms) 101.4 9.5 96.1 10.8 .235 .040 .26/10.3 86%Dect2 (%) 92.1 5.4 88.6 9.1 .001 .053   .05/7.0 78%Deca2 ( 8 ) 45.3 2.6 44.8 2.7 .735 .476   8.3/1.7 18%Lat,latencytimeoftheperoneuslongusmuscle;Tit,totalinversiontime;Mis,meaninversionspeed;Maxis,maximuminversionspeed;Emd,electromechanicaldelayoftheperoneuslongusmuscle;Mr,motorresponsetimeoftheperoneuslongusmuscle;Dect1,timeofonsetofthefirstdeceleration;Deca1,angularpositionoftheonsetofthefirstdeceleration; Dect2, time of theonset of the seconddeceleration; Deca2, angular position of theonset of the seconddeceleration; Sd., standard deviation;  P  ( F  ), probabilityof  F  max in testing homogeneity of variance;  P  ( t  ), probability of   t   for independent groups; CI, confidence interval of the between-group differences.; 1- b , statistical power. C. Eechaute et al./Gait & Posture 30 (2009) 82–86   85  stress because, in our study, the degree of mechanical ankleinstability correlated poorly with the sudden ankle inversionmeasurements. For instance, the correlation between talar tiltvalues and the mean and maximum inversion speed values arerespectively   .18 (  p  = .314) and   .10 (  p  = .572). This confirmssomehow the strain rate dependency of ligaments [20,21] andmuscle tendon units [22].With respect to the time of onset of the first deceleration, wefound no significant differences between tested samples which isin contrast with the study of Vaes et al. [10]. However, statisticalsignificanceisnotthesameasclinicalsignificance.Ifthecontrolof inversion speed during sudden ankle inversions is impaired inpatients, the onset of the decrease of inversion speed in patientsshouldoccurlaterintimewhencomparedtohealthysubjects(andnot earlier). Moreover, between-group differences of percentagesof times of onset of both decelerations (times related to its totalinversion time) did not reach statistical significance. The clinicalsignificance of the observed onsets of decelerations becomesquestionable. 5. Conclusions The latency time and motor response time of the peroneuslongus muscle, the total inversion time and the mean inversionspeed have acceptable reliability in both healthy subjects andpatientswithCAI.Thelatencytimeandmotorresponsetimeoftheperoneus longus muscle is not delayed in patients with CAI. Ankleinversion measurements are not discriminative for CAI.  Acknowledgements ThecollectionofdatawasfundedbytheResearchCounciloftheVrije Universiteit Brussel (OZR 880).We want to express our deepest respect to Prof. Dr. WilliamDuquet, who unfortunately deceased on February 4th 2008, andthank him for his substantial contribution to the development of this paper. Also special regards to Prof. Dr. Romain Meeusen andMr. Jannes Pockele for the development of the injury registrationfile of the Human Physiology and Sports Medicine Department.Lastly, many thanks to Mr. Geert Vermeulen for his technicalassistance to the construction of the inversion platform. Conflict of interest None declared. References [1] YeungM,ChanK,SoC,YuanW.Anepidemiologicalsurveyonanklesprain.Brit J Sports Med 1994;28:112–6.[2] Braun B. Effect of an ankle sprain in a generic clinical population 6 to 18months after medical evaluation. Arch Fam Med 1999;8:143–8.[3] VerhagenR,deKeizerG,VanDyckC.Long-termfollow-upofinversiontraumaof the ankle. Arch Orthop Traum Surg 1995;114:92–6.[4] Gerber J, Williams G, Scoville C, Arciero R, Taylor D. Persistent disabilityassociated with ankle sprains. Foot Ankle Int 1998;19:653–60.[5] Isakov E, Mizrahi J, Solzi P, Susak L, Lotem L. Response of the peroneal musclesto sudden inversion of the ankle during standing. 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