Evaluation of Reflex- and Nonreflex- Induced Muscle Resistance to Stretch in Adults With Spinal Cord Injury Using Hand-held and Isokinetic Dynamometry

Transcription

1 Evaluation of Reflex and Nonreflex Induced Muscle Resistance to Stretc in Adults Wit Spinal Cord Injury Using Handeld and Isokinetic Dynamometry Background and Purpose. In tis study, we compared te intertrial reliability of resistive torque measurements obtained wit andeld and isokinetic dynamometers and examined te validity of te andeld dynamometer for te assessment of spastic ypertonia, defined as reflex and nonreflexinduced resistance to stretc. Subjects. Nine subjects (mean age=4.6 years) wit a cronic (15 years) spinal cord injury participated. Metods. Te plantar flexors were stretced at 5"/s (low velocity [LV]) and 18 /s (ig velocity [HV]) wit an isokinetic dynamometer wile te evaluator attempted to matc tese velocities wit a andeld dynamometer. Electromyograpic activity of te soleus and tibialis anterior muscles as well as ankle displacements were recorded. Resistive torque and velocity, measured at 5 degrees of dorsiflexion, were averaged (n = 4). Results. Hig intraclass correlation coefficients (ICCs) were found at LV and HV for bot te andeld (ICC=.93 and 34) and isokinetic (ICC=.99 and.93) dynamometers. Wit te andeld dynamometer, lower resistive torques were found at LV (.8 Nm) and HV (1. Nem), wereas iger velocities were attained at HV. Conclusion and Discussion. Te results indicate tat te reproducibility of resistive torques obtained wit andeld dynamometry compares wit tat obtained wit isokinetic dynamometry and allows testing of velocities tat can be adjusted to te specific level of resistance to stretc. Electromyograpy confirmed te validity of andeld dynamometry for assessing reflex and nonreflex components of SH. [Lamontagne A, Malouin F, Ricards CL, Dumas F. Evaluation of' reflex and nonreflexinduced muscle resistance to stretc in adults wit spinal cord injury using andeld and isokinetic dynamometry. Py.r Ter. 1998;78: Key Words: Handeld dynamometpr, Isokinetic dynamometer, Plantnrjkx~rs, Spasticity, Spinal cord iryury. Anouk Lamontap Francine Malouin Carol L Ricards Francine Dumas Pysical Terapy. Volume 78. Number 9. September 1998 on 3 June 18

2 S pastic ypertonia (SH), a syndrome common to upper motoneuron lesions, is defined as an increased resistance to stretc tat results from reflex yperexcitabilityl and also from canges in te pysiological properties of te muscle.'' Because te response to muscle stretcing is velocitydependent," applying muscle stretces at different velocities makes it possible to differentiate resistance tat originates from te reflex components from resistance tat originates from te nonreflex components. Te use of computerized dynamometers to assess reflex and nonreflex components of SH is costly and time consuming and requires muc space. Computerized dynamolmeters, terefore, are used mainly for researc purposrs. In a clinical setting, SH is usually assessed using scales suc as te Aswort scale%r te modified Asworr scalee7 Tese scales give a rating based on factors: (1) te presence of a sudden increase of resistance (catc) felt by te evaluator and () te angle at wic te catc is felt. Operational definitions for te 6level modified Aswort scale (from "normal resistance" to "unable to move te limb") were reported by Boannon and Smit.7 Tus, based on teir operational definitions, bot te Aswort scale and te modified Aswort scale assess te reflexinduced response to stretc. Tese scales, owever, are not appropriate for assessing nonreflexinduced muscle resistance to stretc associated wit muscle contractures or fibrosis tat develops after te spinal cord lesion. In ligt of recent findings about te canges in muscle and connective tissue properties after central nervous system (CNS) lesions and teir contribution to motor disability,'* we believe it is critical to separate te nonreflex components from te reflex components in te measurement of SH in order to select appropriate terapeutic interventions. Te assessment of te nonreflex components requires a quantitative measurement of te resistive torque during muscle stretces imposed at a velocity tat will not elicit a reflex suc as tat provided wit te andeld dynamometer metod."'"toug ordinal scales are easy to use and yield reliable measurement~,~ tey are expected to be less sensitive to cange1" compared wit quantitative and continuous types of measurement, suc as tat recorded wit force tranducers. Recently, te use of andeld dynamometers as been A Lamontagne, PT, is a doctoral student in neurobiology (reabilitation), Department of Reabilitation, Faculty of Medicine, Laval University, Quebec City, Quebec, Canada G1K 7P4. F Malouin, PD, PT, is Prof'essor. Department of Reabilitation, Faculty of Medicine, Laval University. Address all correspondence to Dr Malouin at Reabilitation Researc Group, Quebec Reabilitation Institute, 55, Blvd WilfridHamel, Bureau B77, Quebec, Quebec, Canada G1M S8 (fra~lcine.n~alouin@~~laval.ca). CL Ricards, PD, PT, ib Professor, Department of Reabilitation, Faculty of Medicine, Laval University. F Dumas. PT, is Researc Terapist, Department of' Reabilitation, Faculty of Medicine, Laval University. Tis study was part of a project supported by grants from Te Medical Researc Council of Canada and Healt Canada. Ms Lamontagne was te recipient of studentsips from te Rick Hansel1 Man in Motion Foundation and from Healt Canada. Tis studly was approved by te Resrarc Etics Board of Quebec Reabilitation Institute. Tis article was submitted Marc 1, 1997, und ruas accepted April 1, Pysical 'Terapy. Volume 78. Number 9. September 1998 Lamontagne et a on 3 June 18

3 proposed for measuring SH.8' Te purported advantage of tis metod is tat quantitative measurements of te resistive torque can be obtained during passive ~~love~nents, witout te disadvantages associated wit complex computerized dy~larnorneters (ie, time, cost, and space). Te testretest reproducibility of te resistive torque recorded by te andeld dynamometry metod as been repeatedly demonstrated for various muscle groups of te upper and lower extremities of adultss," and cildrenl%it CNS lesions. For instance, te resistive forces of te ankle plantar flexors and elbow flexors recorded wit a andeld dynamometer in 3 adults wit emiparesis by te same rater at 4our intewals (intrarater reliability) yielded intraclass correlation coefficients (ICCs) ranging from.89 to.9.h A comparable level of reproducibility (ICC=.8) was reported for te resistive forces measured wit a andeld dynamometer during passive ip abductions repeated at 3rninute intervals in 1 adults wit paraparesi~.~ In te study by Clautfe et al," te velocity during slow (18"/s) and faster (18"/s) passive ip movements was also found to be igly reproducible (I(:(:=.85 and.95, respectively). Comparisons between resistive forces recorded wit a andeld dynamometer and resistive forces recorded wit an isokinetic dynamometer in 1 cildren at Irno~it irlte~vals furter revealed a similar level of reproducibility (I(;(; =.85 and 34, respectively).lo Te andeld dynamometry metod as also been used recently, in a group of patients, to disclose a 39% increase in te nonreflex components of SH as early as monts after stroke.'* Te interrater reliability of measurements obtained wit te andeld dynamo~netry metod as been reported for studies.h.ii Te reproducibility of te resistive force measured in te elbow flexors of 3 adults wit emiparesis, by 3 raters, proved to be ig (ICC:=.X8) in contrast to tat obtaineci in te plantar flexors (I(X:=..i9). A variation ill te direction of force transmission at te ankle, a coniplex multijoint system, as beer1 suggested to explain te poor interrater reliability of tese measurements at tis joint. Te lower interrater reliability for te anklt. joint in te study by Malouin et alh disagrees wit te results of Dvir et al,i1 wo reported ig ICCs (>.89) for measurements taken by raters in te plantar flexors of cildren wit cerebral palsy. Tese contrasting results can likely be explained by differences in te way passive stretces were applied by Dvir et al." Indeed, te stretc end point of te passive dorsiflexions was maintained for 5 seconds. Te very ig force values obtained by tis metod (about twice as ig as tose norrnally obtained in cildren wit cerebral palsylo) may reflect te strengt of te evaluators rater tan te resistance provided by te muscles being tested. Tese results suggest tat measurements at te ankle joint require special attention and tat measurements obtained wit andeld dynanlometry sould be repeated by te same rater. To date, no study as examined te validity of te andeld dynamometer metod for te assessment of SH. For instance, altoug comparison of te reproducibility level between te metods (andeld dynamometry and isokinetic dynamometry) as been made,1 te resistive forces recorded by eac metod could not be compared. Te main reason te resistive forces could not be compared was tat bot te electromyograpic (EMG) activity and te ankle position were not monitored during andeld dynamometry testing, making te results difficult to interpret. Te present results originate from te baseline measures of an ongoing clinical trial in individuals wit spinal cord injuries. Measurements of SH obtained wit te Penny and Giles andeld dynamometer* and te KinCon1 dynamometert ave been compared. For bot metods, muscle activity and ankle position were monitored during passive movements at low and ig velocities. Te first objective of te present study was to examine te intertrial reproducibility of te resistive torque measured wit te metods. Te second objective was to validate te use of te andeld dynamometer as a measure of te reflex and nonreflex components of SH. Metod Subjects Nine adults wit spinal cord injuries (3 women, 6 men), aged 1 to 54 years (X=4.6, SD=1.5), consented to participate in tis study. Tey ad cronic lesions of te spinal cord (15 years' duration), eiter complete (n=7) or incomplete (n=), of traumatic (n=8) or iscemic (n=l) origin. All subjects ad increased resistance to passive stretc of te plantar flexors, as determined by a score of at least 1 on te modified Aswort scale.' Tis scale as 6 levels (, 1, 1 +,, 3, and 4), were a score of corresponds to normal tonus and a score of 4 corresponds to severe ypertonus. Exclusion criteria were fixed contractures or deformities of te lower limbs and istory of fracture or trotnboplebitis. Te subject caracteristics are given in Table 1. Te eval~rators were experienced pysical terapists and pysicians. Experimental Design Tis study took place in te Motor Evaluation L,aboratory of te Neurobiology Researc Center in Quebec City (Quebec, Canada), and eac subject was tested once. Te resistive torque of te plantar flexors was evaluated during passive ankle dor5iflexions. Passive * I.AM A~soriate~, 11 Sierra Blvd, Miwi~au~n, Ontario, Canada L4Y E3. Group Inc Adam\ Rd, PO Box 489, Hixron, TK (:t~nrtanoogn 966. Lamontagne et al Pysical Terapy. Volume 78. Number 9. September 1998 on 3 June 18

4 Table 1. Subiec~Caracteristics Subject No Age (Y) Sex Level of Injurya Time Since lniury (Y) M T5T6, C O M T7, C O M T5, C O M T5, C O M T5, INC T1, C O M C6, INC T8, C O M T1, C O M M F F M M M F M Aswo~ Scale (Plantar Flexors) Dorsiflexion Range of Motion" "Based or1 criteria from Inlnnationrrl Sfrrrzrlr~rdr for 1\'~u7olr~@'ralnrrd Funrlional Cln~~ijiralion of Spinal Cord Injury. Re\ ed. Cicago, 111: American Spinal Injury Alsocialion; COM=compIete lesior~.inc=i~lcompletelesion. movements were imposed first wit te andeld dynamometer and second wit te isokinetic dynamometer. Te igvelocity (18 /s) movements were evaluated first, followed by te lowvelocity (5"/s) movements. Te order of te tests was not randomized because of te context of te study. Te present study was part of a clinical trial involving a series of clinical and laboratory measures and a control group. Tis order was cosen for tecnical considerations and practical reasons pertaining to te clinical trial. Te testing procedures were performed by te same rater for all subjects, and testing was completed witin ours for eac subject. Procedure Te andeld dynamometer used in tis study was a Penny and C;iles dynamometer. Te experimental setup is sow11 in Figure 1. A plastic device was adapted at te distal end of te transducer to elp maintain te andeld dynamo~neterin contact wit te metatarsals during passive movements. Signals from te andeld dynamometer recording system were directed to a personal computer for continuous recording of te resistive torque measurements trougout te passive movements. Ankle displacement was measured using a custommade electrogoniometer consisting of flexible polystyrcne arms connected to a Spectrol potentiometer: (S6, 1 k a ), wic was aligned wit te ankle's center of rotation. Te proximal end was fixed to te lower leg, and te distal arm was attaced to te fift metatarsal (Fig. 1 ). Te accuracy of te potentiometer associated wit te linearity (.5%) and te numerical conversion is about.5 degrees according to te manufacturer and te laboratory engineer. Similar electrogonioineters ave been sown to yield reproducible angular position and velocity measurements of ip Experimental setup for te andeld dynamometry metod: (A) te Penny and Giles andelddynamometer adapted wit a plastic device at its distal end, [B) te arms of te ele~tro~oniometer, and (c) its potentiometer tat was aligned wit te ankle's center of rotation. abductionyand spinal flexion.14 Spectral Iilcctlonics Gorp. 177 E Calr A\.r, City of' Indusll), CA Pysical Terapy. Volume 78. Number 9. September 1998 on 3 June 18 Lamontagne et al. 967

5 A Handeld Dynamometer: Low Velocity B KinCom: Low Velocity g I V C,.. > 6 3 C, 4 W 1 z 8: V 6 $ 4; I :.L C,.i!V) 4.?, 4, a LO 8 efi L....*.*...*...* E 4 > a Figure. Soleus muscle electromyograpic (EMG) activity, resistive torque, and velocity as a function of ankle position recorded during a set of 5 passive ankle dorsiflexions imposed wit te andeld dynamometer (A and C) and wit te KinCorn dynamometer (B and D) for te same subiect (subiect ). Lowvelocity movements are illustrated in Figs. A and 8, and igvelocity movements are illustrated in Figs. C and D. Te EMG activity at low velocity is raw (negative signal not sown), wereas tat at ig velocity is processed. Arrows indicate te position at wic resistive torque and velocity measures were obtained (5" of dorsiflexion). Note tat te resistive torque rises as te ankle approaces full dorsiflexion. Te KinCorn records negative resistive torque values because of te correction for te gravitational force acting on te foot and te footplate. Note also tat te movement velocities imposed wit te andeld dynamometer and te KinCom dynamometer are similar and constant in a large part of te movement at low velocity. At ig velocity, te andeld dynamometer attains iger velocities (nearly 4Oo/s) and also includes acceleration and deceleration pases trougout te movements. Dased line represents first trial; solid lines represent trials troug 5. Te angular displacements were used to calculate te ankle position and te velocity of te passive movements during te use of te andeld dynamometer. Te isokinetic dynamometer used in tis study was a Kin Com dynamometer (model 54) modified by mecanically increasing te lengt of te load cell lever arm, using a stainless steel extension, to obtain a fold increase in sensitivity.15 Tis increased sensitivity provided a resolution of.5 N (about.15 Nm) and a precision of? N (about.6 Nem). Te KinCom delivered passive movements at preset velocities and, as for te andeld dynamometer, was connected to te computer. Disposable silversilver cloride surface electrodes (MediTrace pellet electrodes, model ECE 18lS), placed on te upper tird of te tibialis anterior muscle Grapic Controls Canada Ltd, 15 Herben, Gananoq~~e, Ontarlo, Canada KIG Y7. and on te soleus muscle (below te lateral gastrocnemius muscle, posterior to te tendons of te peroneus muscles), recorded EMG activity. For bot testing metods, subjects were evaluated wile seated on an adjustable cair wit te ip and te knee flexed at 7 and 3 degrees relative to te rectitude of te proximal and distal segments, respectively. Stabilization was provided wit belts at te cest and waist, and anoter strap just above te knee stabilized te lower leg during testing. For te KinCom metod, te foot was fixed to a footplate, wit its rotational axis aligned wit te ankle's center of rotation. Two adjustable straps, one located at te ankle and te oter at te metatarsal level, kept te eel in place during te passive movements. Subjects were asked to relax and to keep teir ead in midline during te testing. A set of 5 passive ankle 968. Lamontagne et a1 Pysical Terapy. Volume 78. Number 9. September 1998 on 3 June 18

6 C Handeld Dynamometer: Hig Velocity D KinCom: Hig Velocity 3 loo 8. $ c!l. E : a* a" +, 4 Ankle Position (O) b Ankle Position (O) dorsiflexion movements, ranging from 35 to 5 degrees of dorsiflexion, was imposed wit bot testing metods. Te selected preset velocities r te KinCon1 metod were 5"/s (low velocity) and 18 /s (ig velocity). A ig velocity of 1 8 /s was selected because te maximum velocity of te KinCom was 1 /s. For te andeld dynamometry metod, te evaluator manually imposed te passive movement wile olding te dynamometer. Te distal end of te dylramometer was eld perpendicular to te sole of te foot under te distal end of te melatarsals. Te velocity of te manuallv imposed movement was controlled by aving te evaluator count silently (ie, "one tousand one," "one tousand two," and so on) so tat te movement time for a 4.degree ankle displacement at 5'/s would take 8 seconds. In a previous study in our laboratory," we sowed tat tis metod of counting yields velocities of passive ~novementat are igly reproducible. Because some subjects did not sow a reflex response at 18Oo/s, we decided not to matc 18 /s wit te andeld dynamometry metod but instead to impose a velocity ig enoug to elicit a reflex response. Terefore, te evaluator ad to maintain a given cadence for successive trials, wic differed across subjects. A 1second pause separated eac passive movement and a rest period of 3 minutes, during wic te foot was taken off te footplate (for te KinCorn testing). Before eac series of rapid movements, subjects were asked to perform a Jendrassik maneuver, wic consisted of pulling apart, as strongly as possible, te ands tat were joined togeter at te cest level. Tis reinforcement maneuver was used to standardize events preceding muscle stretc and is tougt to promote comparable neuronal excitability levels from test to te~t.~,~() For bot te KinCom and andeld dynamometer testing, te sampling frequencies (torque, EMG, angle) were set at 1 Hz at low velocity and at 1, Hz at ig velocity. 'Te EMG signals were prearnplified and sent to te Grass polygrap (7P3 AC for initial bandpass filtering (57 Hz). For movements at ig velocity (for bot metods), because of a greater risk of movement artifacts and in an attempt to ensure te accuracy of EMG signals, te signals were sent to a personal computer and filtered (Hz, fourtorder, igpass filter), filllwave rectified, and ten smooted (5Hz, lowpass filter). Force and angle signals were also sent to te computer and stored for later analysis. Grass I~istrument Co, 11 Old Colony Avc, PO Box.il(i, Quiiicy, MA 169 Pysical Terapy. Volume 78. Number 9. September 1998 Lamontagne et al. 969 on 3 June 18

7 Data Analysis Using software developed in our laboratory, te resistive torque measurements obtained wit te KinCom dynamometer were corrected for te gravitational forces acting on te footplate and te foot. Tree measurements of gravitational forces were recorded at te beginning of te evaluation wile te subject was seated wit te ip and knee in te testing position described and wit te ankle positioned in 1 degrees of dorsiflexion. Online EMG monitoring during te measurements was used to confirm te relaxation of ankle plantarflexor and dorsiflexor muscles. Eac 3second recording (1 Hz) consisted of 3 measurements of gravitational forces, wic were averaged. Te last recording of te 3 identical (t.1 N) and consecutive recordings was retained for analysis. Corrections of resistive torque values for gravitational forces were performed a posteriori for eac ankle position during te stretces. Tis metod as been proven to yield igly reliable measurements in cildren wit cerebral palsy (n=1)i and adults wit meniscal tears (n= 19).I6 For te andeld dynamometry metod, resistive torque measurements were obtained by multiplying te force measurements by te lengt of a lever arm corresponding to te distance between te transducer and te ankle's center of rotation. Resistive torque measurements were obtained at 5 degrees of dorsiflexion, and 5 trials were averaged at eac velocity for 8 subjects for comparison between te KinCom and andeld dynamometry metods. In te remaining subject, only 3 trials were averaged for te andeld dynamometry metod at ig velocity because 5 degrees of dorsiflexion could not be obtained in te oter trials. As sown in Figure, for all conditions except igvelocity andeld dynamometry testing, 5 degrees of dorsiflexion occurred at a relatively constant velocity in a part of te movement tat was outside te impact range of acceleration or deceleration. Measurements of velocity were also analyzed at 5 degrees of dorsiflexion, except for andeld dynamometry tests at ig velocity. During igvelocity andeld dynamometric testing, because te position of 5 degrees of dorsiflexion often corresponded to te deceleration pase of te movement and because stretc reflex elicitation is, by definition, dependent on increasing velocity, te maximal velocity value was used in te analysis, as it was more representative of te stretc imposed on te plantar flexors during rapid movements. In te example illustrated in Figure C, te velocity at 5 degrees of dorsiflexion was lower tan te peak velocity attained earlier. Te presence of an EMG signal standard deviations larger tan te mean baseline level of EMG activity preceding te onset of te movement was used as a criterion to reject trials wit unwanted activation at low velocity and to identify reflex responses for igvelocity movements. None of te trials ad to be rejected because of reflex responses at low velocity. Typical EMG, resistive torque, and velocityangle curves recorded wit bot dynamometers at low and ig velocities are illustrated in Figure. Intraclass correlation coefficients (type,1)17 based on a 1way analysis of variance (ANOVA) for repeated measures and teir respective '35% confidence intervals1" were computed to determine te intertrial reliability of resistive torque measurements. Coefficients of variation (CVs) were computed for bot resistive torque and velocity values. Altoug te CV is not recognized as a probabilistic measure of reliability, we calculated CVs to allow comparison wit studies in wic it was used. Wilcoxon matcedpairs signedrank tests were used to compare resistive torque and velocity measurements between te andeld dynamometer and te KinCom. All statistical analyses were performed on GBSTAT 4. software,' and te level of significance was set at.5. Results lntertrial Reliability and Variability of Resistive Torque Measurements Mean resistive torque values for eac of te 5 trials recorded wit bot metods at low and ig velocities are illustrated in Figure 3. Te ICCs (and 95% confidence limit intervals) for resistive torque measurements are reported in Table. Wit te andeld dynamometer, te mean resistive torque values remained quite similar across te trials (Figs. 3A, 3C), and ICCs of.93 and.84 (Tab. ) indicate ig intertrial reliability for te andeld dynamometry measurements at low velocity and ig velocity, respectively. Wit te KinCom dynamometer, owever, te measurements obtained during te first trial were always iger tan te measurements obtained during te oter trials, particularly at ig velocity (Fig. D). Te ICCs indicate a lower level of reliability at ig velocity (ICC=.75) tan at low velocity (ICC=.83). To determine te effect of te first trial on te intertrial reliability, calculation of te ICCs was repeated witout te first trial. Te results (Tab. ) indicate tat removing te first trial markedly increases te reliability of te KinCom measurements at bot low velocity (ICC=.99) and ig velocity (ICC=.93), but not tat of te andeld dynamometry measurements. Intertrial variability for te last 4 trials was also estimated by calculation of CVs for resistive torque and velocity measurements. For te resistive torque measurements at low velocity, te intertrial variability was sligtly iger wit te andeld dynamometry metod, as sown in QOynanlic Microsystems, 133 Buccaneer Rd, Silver Spring, MD lamontagne el al Pysical Terapy. Volume 78. Number 9. September 1998 on 3 June 18

8 Table 3. At ig velocity, owever, te andeld dynamometer sowed greater variability (CV= %) tan did te KinCom (CV=6.43%). For te velocity measurements, as expected, te CVs were larger for te andeld dynamometry metod, particularly at low velocity (CV=4.43%). E Comparison of Velocity and Resistive Torque Measurements Between te. 9 : + Metods. Mean (n=8) velocity and resistive " I { torque measurements for te KinCom and andeld dynamometry metods at low and ig velocities are illustrated in Figure 4. As mentioned in te "Metod" section, te evaluator attempted to matc te velocity imposed wit te KinCom only for te lowvelocity condition wit te andeld dynamometer. Te mean velocity measured at 5 degrees of dorsiflexion wit te Kin Com was 4.5"/s, tus sligtly lower tan te preset velocity of 5"/s. Te mean velocity of te manually imposed movement was 3.3"/s, wic is about "/s lower tan tat expected wit te mental cadence. Bot testing metods allowed, at tis slow velocity, te evaluation of resistive torques tat were not reflex induced, as confirmed by EMG monitoring. At ig velocity, te velocity measurements obtained wit te KinCorn were again sligtly lower (177.4/~) tan te preset value (18/ ')' Te mean te manually imposed movement wit te ande1.d dynamometer was 311. lo/s (range= 187.3"393.5"/s), wic is more tan 13Oo/s iger tan te maximal velocity of te movement wit te KinCom metod. lntertrial Reliability at Low Velocity A Handeld Dynamometer ( ~=s ) B KinCorn ( n=8 ) 5: 5 z 4: 4 al 5 3{ 3 e lntertrial Reliability at Hig Velocity C Handeld Dynamometer ( ~=9 ) D KinCorn ( n=8 ) F z 6 6 V 5 5 " 4 4 a,. > 3.c. " Trial Trial Figure 3. Mean resistive torque values (1 SD) for te first 5 trials recorded wit te andeld dynamometer and te KinCom at low velocity (A and B) and at ig velocity (C and D). Note te similarity among te trials for te andeld dynamometry metod, especially at low velocity. For te KinCom metod, owever, te resistive torque values were iger for te first trial tan for te next 4 trials, contrast, clonus was not elicited in any subjects during te KinCom testing. Comparison of mean resistive torque measurements between te testing metods revealed tat te andeld dynamometry metod underestimated resistive torque values at bot low and ig velocities. Altoug te difference in resistive torque measurements at low velocity (.8 Nem) was significant (P<.5), it did not attain statistical significance (P>.5) at ig velocity (1. Nsm). Because of te iger velocities attained wit te andeld dynamometer ( "/s), more subjects (7 of te 8 subjects) displayed reflex responses in te soleus muscle, as compared wit te KinCom metod, wic elicited a reflex response in only 3 subjects. Moreover, clonus was elicited in 4 subjects wit te ande'ld dynamometer (Fig. 5) for all 5 trials. In Discussion Te results of our study sow tat, wen measuring resistance of te plantar flexors to passive movement at eiter low or ig velocity, te andeld dynamometer yielded reliable intertrial measurements of resistive torque, as sown by te ICCs of.93 and.84 computed for te low and igvelocity tests. Tese ig reliability values were greater tan tose computed for te Kin Com metod wen all 5 trials were considered. M'en te first trial was removed from te ICC calculation, owever, te KinCom resistive torque measurements sowed better reproducibility, wit ICCs of.99 and.93. Only Boiteau et allo ave also examined te reproducibility of force measurements recorded wit a andeld Pysical Terapy. Volume 78. Number 9. September 1998 Lamontagne et al. 971 on 3 June 18

9 Table. lntraclass Correlation Coefficients Computed for te Handeld Dynamometry and KinCom Metods for All Trials (n=5) and Witout te First Trial (n=4) Low Velocity Hig Velocity (SO/s) (18 "/~)~ No. of trials Handeld dynamometer.93 (.86)".94 (.86).84 (.7).81 (.63) KinCom dynamometer.83 (.6).99 (.96).75 (.54).93 (.84) " Lower I IIII~& of 95% confidence inlervdl\ \ow11 in parenteses. "1XO"/s or faster for te andeld clyndmomc.tcr. Table 3. Mean Intertrial Coefficients of Variation (Expressed as a Percentage) for Resistive Torque and Velocity Measurements Calculated for 4 Trials Handeld Dynamometer KinCorn Dynamometer Low Hig Low Hig Velocity Velocity Velocity Velocity Variable (SO/s) (18e/s)" (SO/s) (18"/s) Resistive torque Velocity " 18'/s or fastc~r for tr andeld dynarnornetes. dynamometer and te KinCom. Tey reported ICCs of.79 and.9 for force measurements obtained initially and after a 1mont interval wit te andeld dynamometer at low and ig velocities and of.84 for measurements obtained wit te Kin(;om at bot velocities. Tus, in te present study, as in tat of Boiteau et al,'" te reliability of resistive torque (or force) measurernents recorded wit te andeld dynamometer resembles tat of measurements recorded wit te Kin Com dynamometer. Moreover, te ICCs calculated for te andeld dynamometry values in te present study are in te same range as tose reported by Boiteau et al.") Te results also sow tat te first trials yielded larger resistive torque values tan did te subsequent 4 trials wit te KinCom dynamometer, but not wit te andeld dynamometer (Figs. 3B, 3D). Te larger resistive torque values obtained during te first trials ave a pysiological explanation, namely, ysteresis or muscle tixotropy. Wat some autors1"*(' called tixotropy is a beavior tat canges muscle stiffness, depending on te muscle's istory of lengtening or contraction. Tixotropy is tougt to be related to te residual crossbridges in te resting muscle." According to Proske et al," in a review of te effect of muscle tixotropy, te residual crossbridges bind witin a few seconds at te lengt at wic te muscle is left undisturbed and can be detaced by a large stretc. Te fact tat te testing order was not randomized cannot account for our findings, because a similar penomenon (larger resistive torque values in te first trials) was also reported even wen te testing order was rai~domized.~~ Tis finding was demonstrated in 18 subjects, were passive ankle dorsiflexions, applied at 6 different velocities ranging from 5" to 18Oo/s, resulted consistently in a first resistive torque tat was larger tan te following responses. We can question, owever, weter te nonrandomization of te testing order (andeld dynamometry testing preceding KinCom testing) could be responsible for not observing te penomenon of tixotropy wit andeld dynamometry testing? We believe tis possibility is unlikely because te time separating eac series (3 minutes) was similar for bot testing metods. Te factor tat could explain wy te resistance for te first trial was not greater tan te resistance for next trial ould be a sorter duration of te period during wic te muscle was left undi~turbed,'"~',~ wic was not te case ere. One alternative explatlation for our findings wit te andeld dynamometry metod is te difference in te way muscle stretces were elicited by te testing metods. Constant stimuli from trial to trial, suc as tose delivered by an isokinetic device, are required for te expression of tixotropy. Manually applied passive movements (Fig. C) do not appear to ave yielded consistent acceleration and deceleration from trial to trial, wic niay ave contributed to masking te tixotropic element during testing wit te andeld dynamometer. At bot low and ig velocities, te resistive torque values obtained wit te andeld dynamometer were lower tan te values obtained wit te KinCom. At low velocity, bot te resistive torque values and te velocity were lower wit te andeld dynamometry metod tan wit te KinCom metod. Altoug te nonreflex muscle response to stretc is velocitysensiti~e~'.':~.~~ due to te viscoelastic properties of skeletal muscle, it cannot account for te difference in resistive torque between te metods at low velocity. Te difference in movement velocity between te testing metods was very small (1."/s). In addition, Hufscmidt and Mauritzs reported tat no velocitysensitive beavior was present for te plantar flexors at movement velocities ranging from " to /s in eiter subjects wit or witout CNS damage. At ig velocity, te resistive torque values tended to be lower wit te andeld dynamometer, despite te fact tat te mean maximal velocity was larger tan 18 /s. Higer resistive torques would ave been expected because of te iger velocities attained and because of te larger incidence of reflex responses wit te andeld dynamometry metod. An underestimation of resistive torque wit te and 97. Lamontagne et a1 Pysical Terapy. Volume 78. Number 9. September 1998 on 3 June 18

10 eld dynamometer at bot low and ig velocities may, in part, be explained by te ankle position measurement. Because te distal end of te electrogoniometer was fixed at te level of te ead of te fift metatarsal, te angles measured were influenced by forefoot movements taking place in te sagittal and frontal planes. Wit te andeld dynamometer being applied iinder te forefoot, te occurrence of forefoot movements could ave resulted in an overestimation of te ankle dorsiflexion position. Tus, te position of 5 degrees of dorsiflexion may ame corresponded to a less dorsiflexed plosition, and, as resistive torque increase~d wit dorsiflexion (Fig. ), it may ave yielded lower resistive torque values. R4alouin et al,8 in a study using te andeld dynamometer at te ankle, suggested tat te transmission of forces; may be affected by te multijoint system at te ankle and may, in part, explain te lower interrater reliability ccbmputed for te plantar flexors as compared wit te elbow flexors. Wit KinCom testing, owever, te effect of forefoot movements were eliminated by te rigid footplate and E A a, e P 3; Passive Ankle Dorsiflexion at Low Velocity (n=8) Myometer KinCorn Myometer KinCorn I Passive Ankle Dorsiflexion at Hig Velocity (n=8) a, * E 1 Handeld Dynamometer KinCorn Handeld Dynamometer KinCom fixation system. Tus, because it is not Figure 4. possible to ascertain tat resistive Mean resistive torque and velocity values [ ~ SE) recorded wit te andeld dynamometer and te KinCom dynamometer at low velocity (A) and at ig velocity (B). Note tat te torque values were measured at te standard error of te velocity measurements recorded wit te KinCom dynamometer is too same ankle position, our data cannot small to be seen in Fig, be used to confirm te concurrent validity of te resistive torque measurements obtained wit te andeld dynamometry and Anoter observation associated wit te andeld dyna KinCorn1 metods. Te monitoring of EMG signals during low and igvelocity passive movements sowed an absence of reflex responses at low velocity for bot te andeld dynamometry and KinCom metods. Tus, bot metods can be used to assess te nonreflex components of SH. Altoug only 3 subjects displayed reflex responses (based on EMG data) in te soleus muscle wit te KinCorn testing at ig velocity, passive movements wit te ancleld dynamometer elicited reflex responses in all subjects except one. Tis larger incidence of reflex responses is likely related to te iger velocities (187" 394"/s) applied wit te andeld dynamometer. Tis observation indicates one advantage of te andeld dynamornetry metod: it allows te velocity of te manually imposed movements to be increased in order to reac te tresold of te reflex responses. mometry metod was te occurrence of clonic responses, consisting of bursts or more, in 5% of te subjects. During tese clonic responses, bot te velocity and angular position curves sowed oscillations near te end of te dorsiflexion movement (Fig. 5). For instance, during te fastest movement, tere was a sudden drop in velocity at 1 degrees of dorsiflexion, and a cange of direction of te movement followed te reflex activation of te soleus muscle. Tis drop in velocity and te cange of movement direction are likely due to te inability of te evaluator to matc te sudden increase in resistive torque resulting from te soleus muscle activation. Burke as stated tat te ease of elicitation of clonus depends on factors: "First, a critical degree of muscle stretc must be maintained so tat muscle relaxation can trigger a syncronized spindle discarge. Second, te reflex patway must be in a ig state of excitability."'(ptoq) Tus, features of te manual stretc, namely, te large acceleration pases and te ig peaks Pysical Terapy. Volume 78. Number 9. September 1998 Lamontagne et a on 3 June 18

11 5 6 z 5 = 4 e I 3. C.I? 1 a 5 15 L '15 e.. * c 1 a Clonic Responses 3 Y Time (s) Figure 5. Soleus muscle electromyograpic (EMG) activity, resistive torque, velociiv. and ankle ~osition as a function of time recorded durina clonic r. responses e~icitkd wit rapid movements (n=4) imposed durini andeld dynamometry testing (subject 6). Te EMG bursts in te soleus muscle induced increases in te resistive torque and also oscillations in bot te ankle position and te velocity of te movement. of velocity, as it induced reflex responses, may set te reflex loop at a ig excitability level. Furtermore, te fact tat te evaluator attempted to reac te end position and te muscle relaxed after te reflex contraction may ave resulted in successive muscle stretces tat were likely to induce repeated EMG bursts in te soleus muscle. Te KinCom dynamometer, owever, moves at a lower velocity (177.4"/s) and at a constant rate tat does not always reac te reflex tresold. Te KinCom also does not allow oscillating movements at te ankle. Tus, te repetition of te stimuli cannot occur, reducing te likeliood of eliciting clonus. For tese reasons, clonic responses may ave not been elicited wit te use of te EnCom. Malouin et a1,8 in teir study of adults wit emiparesis, also observed clonic responses in te plantar flexors wen imposing rapid dorsiflexions wit a andeld dynamometer. Tey recorded peak resistive force values, and, even if te final position (") of te stretc was controlled wit a visual marker, tis did not affect teir intrarater reliability (ICC=.89.go). Finally, examination of te CVs revealed tat te intertrial variability of resistive torque was similar between te testing metods at low velocity, wereas at ig velocity tat of te andeld dynamometer was 1% iger (Tab. 3). Tis iger variability likely as pysiological and metodological explanations. First, andeld dynamometer testing elicited reflex responses more frequently tan te KinCom testing did. Second, at ig velocity, it is more difficult to maintain te andeld dynamometer perpendicular to te forefoot trougout te muscle stretcing. Lastly, te lower resistive torque values (37%) recorded wit te dynamo~neter (Fig. 4) can also contribute to te larger (X. For te velocity values, as expected, at bot low and ig velocities, te intertrial variability was lower for te KinCom tan for te andeld dynanlorneter. Despite te fact, owever, tat te evaluator applied a wide range of velocities ( J/s) across te subjects to elicit reflex responses at ig velocity, te intertrial variability for velocity measures was less tan 13%. Tis relatively low intertrial variability is consistant wit te reproducibility of resistive torque measurements at ig velocity (lcc=.84) obtained wit te myometer metod. It is also consistent wit te results of Claude et al,!' wo found ig intrasubject reliability of movement velocity measurements, at a 3minute inte~val, wen assessing SH of ip adductors wit te andeld dynamometer metod. Tus, our results indicate tat wen using a standardized protocol, an evaluator is able to manually impose reproducible velocities of stretc to measure reproducible resistive torque values wit a andeld dynamometer. Conclusion Witin te limits of tis study (eg, small sample size), we demonstrated tat a andeld dynanlorneter, wen used in a standardized protocol, yields intertrial resistive torque measures as reliable as tose obtairled wit a cornputerized device suc as te KinCom dynamometer, for eiter low or igvelocity movements. At low velocity, EMG recordings validate te use of te andeld dynamometer for te evaluation of te nonreflex components of SH because, based on EMG data, no 974. Lamontogne et 1 Pysical Terapy. Volume 78. Number 9. September 1998 on 3 June 18

12 reflexinduced muscle activation occurred. At ig vclocity, as te velocity of movement wit te andeld dynamometer as a iger upper limit tan te Kin Com dynamometer, reflex responses could be elicited in most individuals. Tus, te andeld dynatnometer appears to be potentially useful for assessing te reflex components of SH in persons wit a spinal cord injury ccause tey can ave a wide range of reflex excitability. Te appropriate velocity for a given individual can be selected by te evaluator based on te catc felt during te passive movement. Te andeld dynamomrtry mrtod, terefore, provides a measure of resistive torque tat reflects not only te reflex components but also te nonreflex components of SH, wic is not possible wit te Aswort scale. Moreover, because andeld dynamometry provides a reliable and easily available measure, we believe tat it can be used by cliniciar~s as an outcome measure. Te results also indicate tat resistivr torque measurements at a given ankle position were underestimated wit te andeld dynamometer, possibly due to forefoot movements. Because muscles wit increased SH often ave contractures, controlling forefoot movements during andeld dynamometry testing is important as resistance from tarsal joints may interfere wit te measurement of muscle resistance. Tese measures migt be improved by using a ligt, but rigid, footplate fixed to te foot to control tarsal movements during te ankle displacements. Acknowledgments We tank Nicole Roger, PT, and Ricard Beaupri., MD, (Institut de Readaptation en Deficience Pysique de Quebec, Quebec City, Canada) for te screening of te patients, as well as Fran~ois Comeau and Daniel Tardif for tecnical assistance. References 1 Burke I3 Spasticity as all adaptation to pyramidal tract i~!ju~y. Adu Npvrol. 1988;47:4143. Diet[ V, Quintern J, Rerger M'. Elect~~opysiological stutlirs of gait in spasticity ;u~d rigidity: evidence tat altered mecanical properties of' ~nusclr contribute to ypertonia. Bruin. 1981;14: Hufscrnidt A. Mauritz KH. Cronic transformation of muscle in spasticity: a periperal contribulion to increased tone. J Neurol Nrurosurg P,i'yc~c~try. 1985;48: Tiln~ar~n AF, Fellows SJ, Ross HF. Biomecaniral canges at te anklr joint after strokr. J N~urol ivpurosurg Pyic~tq ;54: RIIIkr L), Gillies Jl), 1.anrr JW. Te quadriceps stretc reflex in ~unan spastirity.,j.vru,vl Neurosurg Psyriatq. 197;33: Aswort D. Prelimina~\. trial of carisoprodal in multiple sclerosis. Pmrtilion~;,. 19(i4;19: Boaunon RM', Smit lr. Interrater reliability of a modified Aswort scale of musrlr spasticiq. Pyc 7Ytpr. 1987;67:67. B Malouin F, Boiteau M, Bonneau (:, et al. Use of a ar~tleld dynamometer for te evaluation of spasticity in a clinical setting: a reliability study. P,ysio/era@ Canada. 1989;41: Claude S, Malouin F, Ricards CL. Utilisation de la dynamometric n~anuelle pour mesurer la spasticite des muscles adducteurs de la ance. Annnles de Riadaplation en Midecin~ Pysiqu~. 199;35: Boiteau M, Malouin F, Ricards CL. Use of a andeld dynamometer and a Kin(;om dynamometer for evaluat~ng spastic ypertonia in cildren: a reliability study. Pys Ter. 1995;7.5: Dvir, Arbel N, BarHaim S. Te use of andeld dynamometry for measuring te effect of sortleg tone reducing casts on te passive compliance of calf ~nuscles in cildren wit cerebral palsy. J Npurol Keabil. 1991;5: Malouin F, Bonneau C, Picard L, Corriveau D. Nonreflex mediated canges in plantarflexor muscles early after stroke. ScundJRenbil AIed. 1997;9: Ricards CL, Malouin F, Dumas F, Tardif D. Gait velocity as an outcome measure of locomotor ~rrcove~y after stroke. In: Craik RI., Oatis RL, eds. Gait Anolyrir: Tlr~or? nnd Application. St Louis, Mo: Mosby; 1995: Paquet N, Malouin F, Ricards CL., et al. Validity and reliability of a new electrogoniometer for te measurement of sagittal dorsolumbar movements. Spine. 1991;16: Lamontagne A. Malouin F, Ricards CL, Dumas F. lmpaired viscoelastic eavior of spastic plantarflexors during passive stretc at different velocities. Clinicnl Biom~canic.~. 199'7;1: Durand A, Malollin F. Ricards CL, Bravo G. lntertrial reliability of work measurements recorded during concentric isokinetic knee extension and flexion in subjects lt and witout meniscal tears. Pys Ter. 1991;71: Srout PE, Fleiss Jl,. lntraclass correlations: uses in assessing rater reliability. Psyco1 Bull. 1979;86: Fleiss JL, Srout PE. Approximate intelval rstilnatio~~ for a certain intraclass correlation coefficient. Psycomelrikn. 1978;43: Hagbart KE, Hagglund JV, Nordin M, Wallin EU. Tixotropic beaviour of uman finger flexor muscles wit accon~panying canges in spindle and reflex respollses to stretc. J Ppiol (Lond). 1983;368: anke MT, Proske U, Str~~ppler A. Measurements of 11111scle stiffness: te electromyogram and activity in single muscle spindles of uman flexor muscles following conditioning bv passive stretc or contraction. Brazn Res. 1989;493: Hill DK. Tension due to interaction etween te sliding filan~euts in resting striated muscle: te effect of stimulation. J Plrysiol (Lord). 1968: 199: Proske U, lorgan DL., Grego~y JE. Tixotropy in skeletal rnuscle and in muscle spilldies: a review. Prog 'nrtubiol. 39'33;41: Lamontagne A, Malouin F, Ricards CL. Viscoelastic beavior of plantar flexor muscletendon unit at rest.,i filq'~ Sports Pys Ter. 19!)7:6: Tixotropic beavior of te plantarflexor muscles in normal individuals. Soci~ty for N~trroscienre. 1994;: L.emann JF, Price R, de1,ateur BJ, et al. Spasticity: quantitative measurements as a basis for assessing effectiveness of terapelltic i~itewention. Arc I'ligs bled Reabil. 1989;7:61.5. Pysical Terapy. Volume 78. Number 9. September 1998 Lamontagne et al. 975 on 3 June 18