Com paris on of Kine tic V ariable s and M u s c le A c tiv ity of A nkle Joint D urin g W alkin g in S ubje c t s W ith and W ithout D iabetic P lant ar U lc e rs

Com p ari s o n o f Kin e t ic V ari able s an d M u s c le A c t iv ity o f A nk le Jo in t D urin g W alk in g

in S ubj e c t s W ith an d W ith o ut D i ab e t ic P lant ar U lc e rs

K w o n Oh - y u n , P h .D., P .T .

Dept . of Reh abilitation T her apy , College of Health S cience In stitut e of Health S cience, Yon sei Univ er sity

C h o i K y u - h w a n , M .P .H . , P .T . Dept . of Phy sical T her apy , An san 1 College

국 문 요 약

보 행 시 정 상 인 과 당 뇨 병 성 족 부 궤 양 환 자 의 족 관 절 운 동 역 학 적 변 수 와 근 활 성 도 비 교

권오윤

연세대학교 보건과학대학 재활학과 및 보건과학연구소 최규환

안산1대학 물리치료과

본 연구는 보행주기 동안 정상인과 당뇨병성 족부궤양 환자의 족관절 운동역학적 변수 와 족관절 근육들의 근활성도에 차이가 있는지 알아보기 위하여 실시하였다. 본 연구의 대상자는 당뇨병성 족부궤양이 있는 환자 9명(남자: 6명, 여자: 3명)과 성, 연령, 체중으로 짝짓기(matching)시킨 대조군 9명이었다. 3차원 동작분석기, 힘판, 표면 근전도를 이용하 여, 보행주기 동안 족관절의 관절가동범위, 모멘트(moment ), 일률(power ), 그리고 내측 가자미근, 전경골근, 비복근의 근수축 개시시간(onset time)과 종료시간(cessation time)을 측정하였다. 정상군과 비교하여 당뇨병성 족부궤양군의 보행속도는 느렸고, 입각기 기간 이 길었으며, 족관절의 가동범위가 적었고, 족관절 최대 족저굴곡 모멘트와 일률이 정상 군에서보다 유의하게 낮았다. 보행주기에서 당뇨병성 족부궤양군에서 내측 가자미근과 비 복근의 근수축 개시시간은 유의하게 빨랐으며, 전경골근과 비복근의 근수축 종료시간은

유의하게 지연되었다. 당뇨병성 족부궤양 환자군의 족관절 근육에서 동시수축

(co- contr action )이 증가되고, 보행속도가 느리며, 입각기 기간이 증가하였다. 이러한 보행 특성의 차이는 족부 감각손실에 따른 보행의 안정성을 유지하기 위한 보행전략 때문으로 판단된다. 앞으로 이러한 비정상적인 보행특성이 당뇨병성 족부궤양에서 발생하는 비정상 적인 족저부 압력분포과 족부궤양 발생과 어떤 관계가 있는지 알아보는 연구가 필요할 것이다.

핵심단어 : 근전도; 당뇨병성 신경증; 당뇨병성 족부궤양; 보행분석.

In t r o d u c t i o n

Mor e than 50% of the 120,000 non - tr aum atic, low er ex tr emity amput ation in the United States each y ear r esult fr om complication s of diabet es (Pecor ar o et al, 1990). T he most common type of neur opathy in diabet es is a distal symmetric polyneur o- pathy , w hich is m ainly char act erized by sen sory and aut onomic manifest ation s (T homas, 1992). In diabetes mellitus, neur o- pathy can appear as a sen sory , aut onomic, or m ot or disor der that is irr ev er sible (Pfeffer et al, 1997). Dist al m ot or neur o- pathy r esult s in w eakness of foot and ankle mu scles (Ander sen et al, 1996).

Diabetic n eur opathy m ay disrupt both affer ent and effer ent pathw ay s of the low er extr emity necessary for th e m aint enance of postur e an d norm al gait (Cav anagh et al, 1992). Neur opathy may lead t o a disturban ce of foot mechanics as ex pr essed in specific gait par am et er s (Kat oulis et al, 1997).

W eakness of foot and ankle mu scles contributes t o deformity and causes abnormal weightbearing distribution (Edm ond, 1998).

Sever al studies have analyzed gait patt ern s in patient s w ith diab etic n eu r op at h y (Court em anche et al, 1996; Kat oulis et al, 1997; Mueller et al, 1994). Mueller and colleagues (1994) r eported that subject s with diabetic neur opathy and a hist ory of plant ar ulcer s had less ankle m obility , peak ankle plant ar mom ent an d pow er , w alkin g v elocity , and stride length than contr ol subject s . Kat oulis and colleagues (1997) r eport ed that subject s in their ex perim ent al gr oup with diabet es and a hist ory of foot ulcer ation had slow er w alking speed an d

sm aller m ax imum knee joint angle in the sagittal plane compared with healthy subject s, and with subj ect s in the diabetic gr oup without foot ulcer ation . Court em anche and colleagues (1996) r eported that patient s with diabetic neur opathy had sm aller cycle amplitude, cy cle speed, and per cent age time spent in sin gle support ph ase than contr ol subject s .

T he fun dam ental inform ation u sed in the analy sis of hum an gait con sist s of motion , ground reaction forces, and electr omyogr aphy (S elikt ar an d Bo, 1995). In pr eviou s studies (Kat oulis et al, 1997; Mueller et al, 1994), kinem atic and kin etic par am et er s w er e u sed t o compar e gait char acteristics of subject s with an d without diabetic neur opathy . T he joint mom ent calculat ed fr om an inv er se dynamics analy sis is a n et mom ent , the algebr aic sum of all mu scle mom ent s acting about that joint. When co- contr action t akes place at a j oint , analy sis yields only th e net effect of both the agonist and antagonist mu scles (Wint er , 1990). Inv er se dyn amics does not differentiate between co- contr action of agonist s and ant agonist s, or pr ovides isolat ed activity of a sin gle mu scle gr oup (Zaj ac, 1993). Electr omyogr aphic dat a ar e essential t o under stand timing of mu scle function , an d t o in dicat e the contribution of activ e mu scle gr oup s t o net mu scle tor qu es durin g a g ait cy cle (Br an dell, 1977).

Alth ough pr eviou s studies (Court em anch e

et al, 1996; Kat oulis et al, 1997; Mueller et

al, 1994) quantify t empor al, kinem atic, and

kinetic parameter s during walking in subject s

with diabetic neur opathy, no studies describe

EMG activity r elat ed to joint mom ent s

durin g w alkin g in subj ect s with diabet es,

peripher al neur opathy , an d a hist ory of diabetic plant ar ulcer s (DPU ). T he study of electr omyography may be useful for the interpret ation and clarification of the kinetic chan ges and biomechanical mechanism of ankle j oint during w alking in patient s with DPU . T he purposes of this study w er e t o ex amine mu scle activity of the ankle joint , and t o compar e joint m om ent s and pow er of the ankle joint during walking bet ween subject s with DPU and m at ched contr ol subject s .

M e t h o d s

S ubje c t s

Nine subject s with DPU w er e r ecruit ed fr om the Diabetic F oot Clinic an d Reh abili- t ation an d F itness Cent er , both at Barnes Jewish Christian Health Sy st em , in St . Louis, MO. T h e selection crit eria of DPU subject s in cluded diagn osis of diabet es m ellitu s and periph er al neur opathy , hist ory of diabetic plant ar ulcer s, ability t o w alk independently without an as sistiv e device, and mental alertness. Subjects with dem entia , an amput ation , or a significant neur ological or orthopedic problem were excluded. Subject s unable t o sen se th e 5.07 m on ofilam ent on any portion of their foot w er e con sider ed t o hav e peripher al neur opathy (Mu eller et al, 1989). Hist ory of a plant ar neur opathic ulcer w as u sed t o v erify the diagnosis of peripher al n eur opathy . Nin e age, sex , an d w eight - m at ched contr ol subj ect s w er e r e- cruit ed from the st affs at W ashington Univ er sity an d the community . Crit eria for contr ol subject selection w er e no hist ory of diabet es m ellitu s, ability t o w alk inde-

pendently without an assistiv e device, and no hist ory of mental, neur ological or ortho- pedic pr oblem s .

P ro c e dure s

T he principal inv estigat or ex plained all pr ocedur es t o the subj ect s, and all subject s signed an informed con sent form appr ov ed by the W ashingt on Univ er sity School of Medicin e Hum an Studies Committee befor e t esting . Each subject w as ev aluat ed in the Movement Science Laboratory of the Phy sical T her apy Pr ogr am at the W ashin gt on Univ er sity S chool of Medicin e.

Inform ation obt ained fr om each subject , included respon ses to a questionnaire, clinical m ea sur em ent s , sur face elect r om y gr aphic (EMG) dat a, kin em atic, and kin etic dat a. A brief questionn air e w a s u sed t o obt ain each subject s m edical hist ory . Subj ect s with DPU w er e question ed r eg ar din g the hist ory of their disease, type of diabet es, dur ation of diabetes , and the sit e of plantar ulcer s.

Clinical mea sur em ent s in cluded ankle j oint range of motion, and the Semmens W ein st ein m onofilam ent t est . Ankle j oint r ang e of m otion for ankle dor siflexion with knee ext ended (DFE ), dor siflexion with knee flex ed (DF F ), inv er sion , and ev er sion w as m easur ed with a univ er sal goniom et er . Reliability of these m easur es h as been established in this group of patient s (Diam ond et al, 1989). Dem ogr aphic dat a in cludin g sex , dat e of birth , w eight , and height w er e r ecor ded.

All subject s had their gait assessed using videography

and surface electromyogr aphic

1. Motion Analysis Co. 3617 Westw ind Blv d,

Sant a Rosa, CA 95403

r ecor ding s

. All in strum ent s w er e calibrated before data collection. The subj ect s in short s exposed th eir low er extr emities for the att achm ent of r eflectiv e m arker s and EMG electrodes. And then each subj ect w or e their own low - heeled (less than 2 centimet er s) shoes during gait trials. Retr or eflectiv e m arker s w er e placed ov er th e fibular head, dist al lat er al m alleolu s , head of the fifth m etatar sal, lat er al calcaneu s, and supra- navicular . In addition, t wo m arker s w er e att ached on the leg at mid- thigh lev el and mid- shank lev el.

EMG sign als durin g w alking w er e tr an s - mitt ed by a thr ee- ch annel cabling unit . Raw EMG signals w er e collect ed fr om pr e- amplified (nomin al 35v/ v gain ) surface electrodes (33×17×10 ㎜). Skin pr epar ation con sist ed of a light scrubbing w ith alcohol befor e application of the EMG electr odes.

Double- sided adhesiv e w ash er s

w er e u sed t o secur e electr odes t o the skin . Electr odes w er e placed on the belly of the mu scle of int er est , with the long ax is of the electr ode positioned par allel t o the mu scle fiber s.

Anatomical guidelin es by Per otto (1994) w er e u sed t o position electr odes. T hr ee muscles, soleus, medial gastrocnemius, and tibialis ant erior of the ulcer at ed low er limb w er e ch osen for this EMG study . T hese mu scles w er e select ed becau se of their agonist/ antagonist r elation ship , an d their m onoarticular/ biarticular syner gistic r ole. A r efer ence electr ode w as placed on the m edial malleolu s. A foot swit ch w as taped

2. T herapeutics Unlimited, Model #67, 2835 Friendship Street , Iow a cit y , IA 52240 3. Converters, Inc. 1617 Republic Rd. Huntingdon

Valley , PA 19006

under the subject s heel. F or ce platform dat a w er e u sed t o det ermin e initial heel- strike (HS ) and t oe- off (T O) tim e. F oot swit ch dat a w er e u sed to det ermine th e time of the next heel strike.

P articipant s w er e asked t o w alk n orm ally along a 6 m w alkw ay at a fr eely chosen comfort able w alkin g speed. Prior t o dat a collection , subj ect s w er e allow ed t o pr actice trials t o en sur e that th ey could st ep onto the for ce platform successfully w ith th e foot t o be m easur ed. W alking speed (㎧) w as m easur ed u sing a st opw atch .

T wo camer as wer e used t o capture marker trajectories as the subject pr ogr essed along the w alkw ay . Gr ound r eaction for ces and ext ernal moment s during gait were r ecor ded by a for ce platform embedded in th e w alkw ay . Simult aneou s dat a sampling fr om the EMG electr odes at 1200 ㎐, and cam er as, a foot swit ch an d for ce platform w as perform ed at 60 ㎐ during gait trials.

After gait trials, m aximum v olunt ary

contr action (MVC) t est s w er e isom etrically

performed to pr ovide a level for normalizing

EMG data collect ed during g ait trials. T w o

m aximum effort s w er e perform ed in each

position and held for a three second r ecor ding

period, with a 60 second r est betw een each

contr action . T h e MVC v alue of the soleu s

w as obt ain ed by havin g subject s perform a

m aximum heel rise with knee joint flexion

at 50 degr ees , while the subj ect h eld th e

ex aminer s h ands t o m aintain balance. T he

MVC v alue of th e m edial gastr ocn emiu s

w as obt ain ed by havin g subject s perform a

heel rise t o maximum plant ar flexion w ith

the knee extended. The maximum voluntary

contr action t est for the tibialis anterior w as

performed isometrically in mid- range position while seat ed. Maximum r esist an ce w as applied at th e dist al end of the dist al limb segm ent by the ex aminer .

D at a re du c tion

Dat a fr om the cam er as, a for ce platform , a foot swit ch , and EMG w er e r educed u sing the Kintr ack soft w ar e sy st em

. T o define the gait cycle v ariables, dur ation of swing and st ance ph ases, the foot swit ch and force platform signals were in dividually identified and adju st ed by Kintr ak soft w ar e so that dat a for all subject s w er e int er - polat ed t o 100 per cent of a gait cy cle.

Kinem atic dat a w er e u sed t o calculat e joint angle at ankle. Kinetic dat a w er e u sed t o calculat e m om ent s. Kinem atic and kinetic gr ound r eaction for ce dat a an d anthr opom etric v ariables w er e combined with standard link - segment kinetic equation s t o calculat e m om ent at ankle. T he av er ag e of thr ee trials for each subject w a s taken . Mom ent s an d pow er w er e normalized by body weight in Newt on met er s per kilogr am (Nm/ ㎏) an d W/ ㎏, r espectiv ely , and all m om ent and pow er dat a w er e r eport ed with r espect to per cent age of the g ait cy cle (%GC, wher e HS =0% and next HS of sam e low er ex tr emity =100%). En semble averaged moment and power data, norm alized by body w eight , w er e plotted ov er th e gait cy cle for both DPU and contr ol gr oups.

Raw EMG signals r ecor ded during gait were bandpass- filt ered u sing a fourth - or der filt er at 40～300 ㎐ and full- w av e r ectified (P erry , 1996). Dat a w er e sampled at 1200

4. Motion Analysis Corporation, 3617 W estw ind Blv d, Sant a Rosa , CA 95403

㎐. EMG analy sis determined onset and cessation tim es of all mu scles activity thr ough out the entir e gait cy cle. On set and cessation times were determined aut om atically by the Kintr ak soft w ar e sy stem based on select ed thr eshold v alues. A thr eshold of thr ee st andar d deviation s above the quiet est portion of th e EMG r ecor d w as u sed t o identify mu scle firin g on set and cessation time (Di F abio, 1987). All EMG activity on set and cessation tim es w er e r eport ed a s a percentage of the gait cycle (%GC). T he aver age of thr ee trials for each subj ect w a s t aken .

T o quantify mu scular activity and t o compar e the activity bet w een differ ent mu scles and bet w een differ ent subject s, EMG dat a w er e normalized. T o det ermine the r efer en ce v alu e for norm alizin g EMG dat a, signals r ecor ded during MVC t est s w er e filt er ed and r ectified in the sam e fashion as for the EMG dat a for the gait cy cle. One hundr ed per cent MVC w as defined as th e m ean r ectified EMG for th e highest one second of dat a for the t w o contr action s performed durin g the MVC t est .

Ankle joint range of motions, joint m om ent dat a, on set and cessation tim es of mu scle activity , pow er , and t empor al par am et er s were compared statistically between subject s with DPU and contr ol subject s u sing a pair ed t - t est .

R e s u l t s

S ubje c t s

T able 1 describes the subject s. Nine

subject s (3 fem ale, 6 m ale) with DUP an d

T able 1 . Descriptiv e charact eristics of the subj ect s

Char act eristic Gr oup

DPU (n =9) Contr ol (n =9) ov er all (N =18) A ge (yr )

Mean (SD) 59.2 (11.2) 59.2 (12.6) 59.2 (12.6)

Rang e 39～79 35～76 35～79

Gender

F em ale (%) 3 (33.3) 3 (33.3) 6 (33.3)

Male (% ) 6 (66.7) 6 (66.7) 12 (66.7)

W eight (㎏)

Mean (SD) 105.4 (10.5) 106.6 (10.9) 106.0 (11.1)

Rang e 74～161 85～180 74～180

Height (㎝)

Mean (SD) 177.0 (10.1) 176.4 (11.3) 176.7 (10.4)

Rang e 155～187 156～193 155～193

F oot deformity

Hamm er toe (%) 4 (44.4) 3 (33.3)

Hallux v algu s (%) 3 (33.3)

Hamm er toe ＋ Hallux v algu s (% ) 2 (22.2) Dur ation of DM

Mean (SD) 19.3 (7.2)

Rang e 2.0～35.0

T ype of DM

IDDM (%) 2 (22.2)

NIDDM (%) 7 (77.8)

Number of ulcer s

1 tim e (%) 2 (22.2)

2 tim es (%) 5 (55.6)

4 tim es (%) 2 (22.2)

Side of ulcer

Right (% ) 5 (55.6)

Left (%) 4 (44.4)

Sit e of ulcer

1st and 2nd MT P j oint (%) 5 (55.6) 3r d an d 4th MT P joint (% ) 2 (22.2)

Gr eat t oe (%) 2 (22.2)

No significant difference betw een gr oups (p> .05) in age, w eight , height (pair ed t - t est )

Abbr eviation : DM , diabet es m ellitus ; IDDM , insulin - dependent diabet es m ellitus ; NIDDM ,

non - in sulin - depen dent diabet es m ellitus ; MT P , m et at arsophalangeal

a m ean age of 59.2 year s (SD =11.2, r an ge

=39～79) w er e designat ed as the DPU gr oup . Nine ag e, sex , and w eight - matched subject s (3 female, 6 male) without diabet es and peripher al n eur opathy had a m ean age of 59.2 year s (SD =12.6, r ange=35～76) and were designated as the contr ol gr oup. T he av er age w eight of subject s with DPU and contr ol subj ect s w er e 105.4 ㎏ and 106.6 ㎏, r espectiv ely , and th e av er age height w er e 177.0 ㎝ an d 176.4 ㎝, r espectiv ely . T h er e w er e no significant differences in age, weight , or height bet w een subject s w ith DPU and contr ol subject s (p> .05).

F our subj ect s (44.4%) in the gr oup with DPU and thr ee subject s (33.3%) in contr ol gr oup had a hamm er toe deformity . T hr ee subject s (33.3%) in the gr oup with DPU had a hallux valgus deformity. T wo subj ect s (22.2%) in the gr oup with DPU had both hamm er t oe and h allux v algu s deformities.

T he m ean dur ation of diabetes in the subject s with DPU w as 19.3 y ear s (SD=

7.2, r ange=2.0～35.0). T he subject s with DPU in cluded tw o (22.2% ) with in sulin - depen dent diabet es m ellitu s (T ype I) an d

sev en (77.8%) with n on - in sulin - depen dent diabet es m ellitu s (T ype II). F iv e subject s (55.6%) had a hist ory of plantar ulcer s under the fir st and second m et at ar sal heads. T w o subject s (22.2%) had a history of plant ar ulcer s under the thir d an d fourth m etatar sal h eads, and t w o subj ect s (22.2% ) had a hist ory of plant ar ulcer s under the gr eat toe.

A nkle ran g e of m ot ion

Mean v alues and st andar d deviation s of ankle r ange of m otion , m easur ed by a goniom et er , for subject s w ith DPU and contr ol subj ect s ar e shown in t able 2.

Subject s with DPU sh ow ed decr eased dor siflex ion compar ed with contr ol subject s (- 0.6±2.5 v s 4.8±4.8 , p< .05 for DF E ; 5.8

±3.8 vs 10.9±4.0 , p< .05 for DFF ). Subjects with DPU showed decreased subt alar joint motion compared with control subject s (22.0

±5.7 vs 29.0±5.7 , p< .01 for inver sion ; 2.0

±3.0 v s 8.9±5.9 , p< .01 for ever sion).

On s e t an d c e s s ation tim e s

T able 3 pr esent s the m ean v alues an d

T able 2 . Comparis on of ankle ran ge of m otion (degree) betw een subject s w ith DPU and cont rol subj ect s

Motion

Gr oup

t DPU (n =9) Contr ol (n =9)

DF E - 0.6±2.5 4.8±4.8 2.90

DF F 5.8±3.8 10.9±4.0 2.84

Inv er sion 22.0±5.7 29.0±5.7 5.14

Ev er sion 2.0±3.0 8.9±5.9 3.56

Mean±SD

Abbreviations : DF E , dor siflexion w ith knee ext ended, DF F , dorsiflexion w ith knee flex ed

*

p< .05,

p< .01

T able 3 . Comparis on of onset t ime and cessation t im e (% of gait cycle) betw ee subj ect s w ith DPU and control subj ect s

Mu scle

On set T im e Cessation T im e

DPU Contr ol DPU Contr ol

Soleu s 2.5±2.3 11.5±2.6

58.9±6.6 56.4±5.7

Medial

gastr ocnemiu s 3.9±2.8 14.1±2.4

59.7±6.1 57.1±5.3

T ibialis

anterior 58.4±3.5 59.1±4.0 30.4±8.9 13.8±1.5

Mean±SD

*

p< .05,

p< .01

F i g 1 . Ensemble- averaged EMG profiles of soleus, medial

gast rocnem ius , tibialis ant erior muscle for subj ect s w ith DPU

(n =9) and contr ol subj ect s (n =9). T he ordin at e present s

inform ation in percent of an MV C. T he abscissa pr esent s

inform ation in percent of a gait cycle (0%=heel cont act ,

100%=n ext heel cont act ).

standar d deviation of the onset and cessation times (%GC). Comparing on set tim e (%

GC) of mu scle activity during w alking bet w een subject s with DPU and contr ol subject s , activ ation w as significantly earlier in DPU subj ect s than in contr ol subject s for th e soleu s (2.5±2.3% v s 11.5±2.6% , p< .01), and medial gostr ocnemiu s (3.9±

2.8% v s 14.1±2.4%, p< .05). Cessation tim es for the soleu s (58.9±6.6% v s 56.4±5.7%, p< .01), and tibialis ant erior (30.4±8.9% v s 13.8±1.5%, p< .01) occurred lat er in subject s with DPU .

F igur e 1 pr esent s m ean amplitude (%

MVC) curv es during w alking in subject s with DPU an d contr ol subject s (en semble av er aged curv e, n =9 for each gr oup ). T her e ar e differ ences in the shape and amplitude of mu scle activity (%MVC). Mu scle activity of soleu s , tibialis ant erior had a longer dur ation in subject s with DPU when compar ed t o contr ol subject s. Activities of the soleu s an d m edial gastr ocnemiu s mu scle began earlier durin g the initial st ance pha se in the contr ol subject s.

T e m poral , kin em ati c s , m om ent an d po w er dat a

Differ ences in temporal parameter s bet - ween the two groups are pr esented in table 4. Comfort able walking speed was signi- ficantly slower in subject s with DPU than in control subject s (.70±.19 ㎧ v s .90±.17 ㎧, p< .01). T he stance phase (%GC) was significantly longer in subject s with DPU (66.92%±3.58 v s 63.33±1.15%, p< .05). During walking subject s with DPU showed lower mean values of peak ankle dor siflexion moment (.04±.05 Nm/ ㎏ v s .10±.03 Nm/ ㎏, p< .01) and peak ankle plantar flexion moment (1.18±.19 Nm/ ㎏ v s 1.54±.16 Nm/ ㎏, p< .05).

During walking subject s with DPU showed significantly lower mean values of peak ankle plantar flexion power (.62±.52 W/ ㎏ v s 1.85

±.51 W/ ㎏, p< .01). T he subjects with DPU showed lesser peak ankle dor siflexion range of motion (6.10±3.69 v s 8.66±2.95, p< .05) during walking.

Ensemble- averaged ankle dor siflexion range of motion, joint moment , and power profiles (n =9 for each group) of subject s with DPU and control subject s are shown in Figure 2.

T able 4 . Comparis on of t emporal and j oint m om ent , pow er , and ran ge of m otion dat a betw een subj ect s w ith DPU an d contr ol subj ect s

P ar amet er DPU (n =9) Contr ol (n =9)

W alkin g speed (㎧) .70±.19 .90±.17

St ance ph ase (% of gait cy cle) 66.92±3.58 63.33±1.15

P eak dor siflexion m oment (Nm/ ㎏) .04±.05 .10±.03

P eak plantar flexion mom ent (Nm/ ㎏) 1.18±.19 1.54±.16

P eak dor siflexion (degr ee) 6.10±3.69 8.66±2.95

P eak plantar flexion pow er (W/ ㎏) .62±.52 1.85±.51

Mean±SD

*

p< .05,

p< .01

D i s c u s s i o n

Alth ough pr eviou s studies (Court em anch e et al, 1996; Kat oulis et al, 1997; Mueller et al, 1994) hav e described v ariou s t empor al, kinem atic, an d kinetic attribut es of subj ect s with DPU , the pr esent study described fir st EMG activities r elat ed to joint m om ent s and pow er of ankle j oint during w alking . Ankle j oint m otion in subj ect s with DPU

w as differ ent fr om th at in the contr ol subject s , as m easur ed with a g oniomet er . In th e pr esent stu dy , ankle m obility of subject s with DPU w a s less than that of contr ol subject s durin g w alkin g . Ankle m otion v alues in this study w er e similar t o those r eport ed by Mueller an d colleagues (1989) an d Salsich an d colleagues (Salsich , 2000).

Comfort able w alking speed is best likely F i g 2 . Ensemble- av eraged m om ent , pow er , and range of m ot ion profiles

for subj ect s w ith DPU (n =9) and cont rol subj ect s (n =9). T he or dinat e present s inform ation in norm alized r ange of m otion , m om ent (Nm/ ㎏), and P ow er (W/ ㎏). T he abscis sa pres ent s inform ation in percent of a gait cycle. (0% = heel cont act , 100% = next heel cont act ).

Abbreviations : Ext , ex t ension ; Plant a, plant ar flexion ; Dorsi, dorsiflexion

t o r epr esent ov er all w alking perform ance (F riedm an et al, 1988). Alth ough w alkin g trials in the pr esent study w er e condu ct ed at a self - selected comfort able walking speed, the g ait of subj ect s with DPU w as ch ar a - ct erized by slow er w alking speeds than those of contr ol subject s . T his is con sist ent with the r eport of Mueller and colleagues (1994) who reported that patient s with DPU had slow er w alking speeds than subj ect s without diabet es and neur opathy . Kat oulis and colleagues (1997) also r eport ed that the w alking speed of subject s with diabet es, neuropathy , and a history of foot ulcer ation , w as significantly low er th an that of subject s with diabet es and n eur opathy an d norm al h ealthy contr ol subject s. W alking speeds of both gr oup s in the pr esent study w as slow er than those r eported in the pr eviou s stu dies (Kat oulis et al, 1997;

Mueller et al, 1994; Ostr osky et al, 1994).

T hese differ ences m ay be a r esult fr om the dem ogr aphic fact or s such a s age and body w eight , as the subject s in pr esent stu dy w er e older and heavier th an those in the pr eviou s stu dies (Kat oulis et al, 1997;

Mueller et al, 1994; Ostr osky et al, 1994).

S ev er e disturban ces of balance and gait can occur in proprioceptive affer ent disor der s (Bergin et al, 1995). Patient s with periph er al neur opathy feel less safe while w alking and standing than do control subjects (Cav anagh et al, 1992). F urtherm or e, a fear of fallin g and a lack of confiden ce ar e con sider ed t o be import ant fact or s that influence postur al contr ol and gait behavior (Alex ander , 1994).

In the present study , slower walking speeds in subject s with DPU m ay hav e been a result of pr oprioceptive and somatic feedback

sensory deficits which are present in patient s with peripher al n eur opathy . Court emanche and colleagu es (1996) r eport ed that patient s with diabetic neur opathy spend les s time in single support phase than contr ol subject s . In our study , th e av er age tim e spent in th e st ance pha se in subject s with DPU and contr ol subject s w er e 66.92% an d 63.33%

of a gait cycle, respectively (p<.05). Decr eased w alking speed an d in cr eased pr oportion of time spent in st an ce phase in subj ect s w ith DPU m ay be a r esult of decr ea sed st ability durin g w alking .

At the ankle j oint , at lea st thr ee major

mu scles contribut e significantly t o joint

m om ent s during gait . T he tibialis ant erior

mu scle contributes t o ankle dor siflex ion ,

while the soleu s and gastrocnemius mu scles

w ork as plant ar flex or s . At heel strike,

ther e is a sm all dor siflexion m om ent as the

pr etibial mu scle gr oup low er s the foot to

the floor (Wint er , 1983). In th e pr esent

study , subject s with DPU pr esent ed with a

low er peak ankle dor siflex ion m om ent at

initial cont act than contr ol subject s . T his

m ay be r elat ed t o pr em atur e activ ation of

the soleu s and medial gastrocnemius mu scles

in the subj ect s with DPU. T he av er age

on set tim e (%GC) of soleu s an d m edial

gastr ocnemiu s in the subj ect s with DPU

w as 2.5%, an d 3.9%, r espectiv ely . Pr eviou s

studies (Dubo et al, 1976; Milner et al,

1971; Sutherland, 1966) r eported that activity

of the ga str ocnemiu s and soleu s mu scles in

norm al population s begin s at appr oxim at ely

10% of the gait cycle. In the present study ,

the av er age on set tim e of the soleu s and

gastr ocnemiu s in the contr ol subj ect s w as

11.5%, an d 14.1%, r espectiv ely .

As indicated previously, the tibialis ant erior mu scle is activ e in pr oducin g a net dor si- flex ion m oment at heel strike, contr acting eccentrically to prevent the foot from slapping down (Milner , 1971). After heel strike and until flat foot , the tibialis ant erior mu scle activity domin at es plant ar flex or mu scles (soleu s an d gastr ocnemiu s) activity . In subject s with DPU, how ev er , the soleu s and gastr ocnemiu s mu scles w er e activ at ed early , an d co- contr acted with the tibialis ant erior . T his co- contr action may hav e contributed t o the decr eased peak ankle dor siflex ion m om ent in subj ect s w ith DPU.

In addition , ankle passive dor siflexion r ang e of motion (- .6±2.5 v s 4.8±4.8 , p< .05, p< .01, p< .05) of subject s with DPU w as less than that of contr ol subj ect s, which m ay hav e also contributed t o decr ea sed peak ankle dor siflex ion m om ent .

A ccor ding t o Kam ey am a and colleagues (1990), th e r epr esent ativ e pattern of the tibialis anterior is a double peak , with one peak occurring ar ound t oe- off, and the other before heel strike. Ericson and colleagues (1986) also reported that the tibialis ant erior mu scle pr esent s t w o peak s : one at the time of heel strike (5%GC) and one at th e beginning of acceler ation in the sw ing phase (70%GC). In the pr esent study , en semble- av er aged EMG pr ofiles of th e tibialis ant erior in contr ol subject s w er e similar t o those of other studies (Ericson et al, 1986; Kam eyam a et al, 1990). T he activity of the tibialis ant erior mu scle in the subject s with DPU , how ev er , w as significantly prolonged. T his activity patt ern demonstrated co- contraction with the ga str o- cnemius and soleu s muscle. Co- contr action

m ay contribut e t o the st abilization of the ankle joint upon h eel strike an d the impr ov em ent of foot st ability during early st ance pha se.

Pr eviou s r esear cher s (Ericson et al, 1986;

P edotti, 1977; Wint er and Yack , 1987) r eport ed that the activity of the tricep s sur ae has a single bur st patt ern . Ericson and colleagues (1986) r eported that the peak activity of gastrocnemiu s and soleus mu scles occur s at 40～45% of the gait cy cle at the beginning of the pu sh - off phase. Accor ding to Wint er and Yack (1987), the plantarflexor s (medial and lat er al gastr ocnemiu s, soleu s, per on eu s lon gu s) all hav e peak s at pu sh - off (50% GC). P edotti (1977) r eport ed that the peak of gastr ocnemiu s and soleu s mu scle activity coincides with the peak plantar flexor m oment of for ce. Dubo and colleagues (1976) also confirm ed that the peak activity of the gastr ocn emiu s EMG occur s at pu sh - off.

T her e ar e sev er al possible r eason s why

subject s with DPU had a low er peak ankle

plant ar flexion m om ent an d pow er than

did subject s in control group. A compen sat ory

adaptiv e str at egy m ay be employ ed t o

m aint ain balance during w alking . Winter

and colleagues (1990) r eport ed that healthy

elderly subj ect s h av e a shorter st ep len gth ,

incr eased double- support st ance period,

decr ea sed pu sh - off pow er , and a m or e

flat - footed lan ding compar ed w ith y oung

adult s. T he author s (1990) suggest ed that

all of these differ ences ar e r elat ed t o a

safer (less destabilizing) gait stride. Kerrigan

and colleagues (1998) r eport ed that healthy

elderly subject s pr esent w ith r educed ankle

plant ar flexion during w alking compar ed t o

young adult s. T he author s (1998) st at ed that ankle plant ar flex ion is purposely r educed in elderly subject s t o maint ain greater foot - floor cont act at t erminal st ance t o br oaden the base of support . Subject s with DPU hav e a deficit of som at osen sory and pr oprioceptiv e per ception at th e ankle, cau sin g the joint feel less st able, and they will purposely r educe ankle plant ar flex ion m otion during pu sh - off phase to impr ov e balance. T his adaptive strat egy is a possible explan ation for why subj ect s with DPU hav e a low er peak ankle plant ar flex ion m om ent and pow er th an contr ol subject s.

S alsich an d colleagues (2000) r eport ed that subject s with diabet es m ellitu s and peripheral neuropathy had appr oximately 36%

less concentric plant ar peak t orque compar ed with subject s in the contr ol gr oup. Mueller and colleagu es (1994) r eport ed that the subject s with diabetes mellitus and periph er al neur opathy also dem on str ate les s ankle m obility , ankle mom ent , ankle pow er , and w alking speed than age- m at ched contr ols.

T he author s (1994) pr oposed that decr eased plant ar flex or str ength m ay ex plain the diminished ability of the plant ar flex or mu scles t o pu sh - off during t erminal st ance.

Decreased plant ar flexor strength in subject s with DPU m ay be another r ea son for th e decr ea se in peak ankle plant ar flex ion m om ent and pow er .

Differ ences in w alkin g speed m ay be anoth er r eason why subject s w ith DPU hav e a low er peak ankle plant ar flex ion m om ent an d pow er compar ed t o contr ol subject s . In the pr esent stu dy , subject s with DPU had slow er w alking speeds than did contr ol subject s. It is r easonable t o

expect that m om ent and pow er dat a v ary with w alking speed. Wint er an d colleagues (1995) dem on str ated that plant ar flexion moment and power increased pr oportionat ely with walking speed. Kerrigan and colleagues (1998), how ev er , r eport ed that , in elderly subject s , peak ankle plantar flexion m om ent do n ot in cr ease significantly with incr ea sed speed.

A ccor ding t o Sutherland (1966), soleu s activ ity cea ses b efor e h eel- off . In th e present study , soleus muscle activity ceased significantly lat er in subject s with DPU than did contr ol subj ect s. T his m ay be associat ed with differ ences in th e dur ation of the st ance phase, with the DPU subject s spending a gr eater am ount of time in the st ance pha se.

In the pr esent study , ther e w er e pr o-

nounced differences in muscle activity pattern s

bet w een subject s with DPU and contr ol

subject s . It is possible that the differ en ces

in EMG activity patt ern s w er e associat ed

with differ en ces in w alkin g speed. In the

present study, the walking speed of subject s

with DPU w as significantly slow er than

that of control subjects. Lyons and colleagu es

(1983) r eport ed that the on set of activity

occur s earlier in fa st w alkin g . Adler an d

colleagues (1983) r eport ed that the on set of

vastus medialis activity during fast w alking

begin s thr ee per cent earlier in the gait

cy cle on av er age. Conv er sely , Yang and

Wint er (1985) dem on str ated that th e timing

of EMG activity is closely r elated t o the

normalized stride time and remained inv ariant

at differ ent w alkin g speeds. In the pr esent

study , how ev er , the activity of th e soleu s

and medial gastr ocnemiu s mu scles of

subject s with DPU who w alked at slow er speeds than contr ol subj ect s began earlier than th at of contr ol subject s. T hese r esult s suggest that differ ences bet w een subject s with DPU and contr ol subj ect s in timing of mu scle activity an d shape of en semble- av er aged pr ofile curv es ar e not r elat ed t o differ ences in w alkin g speed.

Subj ect s with diabet es m ellitu s and peripher al neur opathy dem on str ate loss in t ouch - pr essur e per ception (Mueller et al, 1989; Sim on eau et al, 1996), decr eased vibr ation per ception (Ber gin , 1995), an d diminished m ov em ent per ception at the ankle joint (Sim oneau et al, 1996).

Courtemanche and colleagues (1996) r eport ed that a lack of pr oprioception fr om the leg s affect s gait contr ol in diabetic n eur opathic patient s. In addition , Ber gin an d colleagues (1995) r eport ed that the un st eadin ess of patient s with peripher al polyneuopathy is corr elat ed with vibr ation per ception , but not with mu scle str ength . Sin ce subject s with DPU have a deficit of somatosen sory and pr oprioceptiv e per ception at the ankle joint , they feel less safe and steady . In the pr esent stu dy , co- contr action of agonist and ant agonist mu scles t ook place at the ankle in subject s with DPU during st ance phase. T hese co- contr action s ar e pr obably r elat ed t o an adaptiv e w alkin g str at egy that compen sat es for the diminished sensory inform ation fr om the ankle and foot .

Human w alking is a complex skill in which motor , sensory, and cognitive v ariables continuou sly int er act t o contr ol the lar ge number of anatomical and phy siological degr ees of fr eedom within the body as w ell as the t ask con str aint s imposed (de Visser

et al, 1998). Differ ences in EMG activity patt ern s an d joint mom ent s and pow er at ankle j oint durin g w alkin g in subject with DPU may be explain ed by sev er al fact or s including loss of sen sory perception, decreased plantar flexor con centric strength, decreased ankle mobility , and slow w alking speed. It is difficult t o identify w hich fact or m ost influenced finding s of this study . It is not clear whether the observed ch anges in EMG activity ar e the dir ect r esult of one single fact or or a combination of all of these fact or s . F ur th er st u dies ar e n eeded t o identify which specific fact or s ar e r elated to changed EMG activity patterns in subject s with DPU .

C o n c l u s i o n

T he EMG activity patt ern s at ankle j oint in subject s with DPU w er e foun d t o be differ ent fr om those of contr ol subj ect s.

When comparing the av er age on set and cessation tim es (%GC) of ankle j oint mu scles activity , the soleu s and m edial gastrocnemius muscles were activated signi- ficantly earlier in subj ect s w ith DPU. T he aver age cessation time of soleu s and tibialis ant erior mu scles w as significantly lat er in subject s with DPU.

Co- contractions of agonist and antagonist mu scles took place at the ankle j oint in subject s with DPU during st ance pha se.

T hese mu scle activity pattern s virtually

coin cided w ith j oint m om ent and pow er

dat a for the ankle for subject s with DPU .

T hese co- contr action s during st an ce phase

are probably r elat ed t o the fact that subj ect s

with DPU employ a safer , m or e st able gait

patt ern t o accomm odat e for the diminish ed sen sory inform ation fr om the ankle and foot . Other fact or s, how ev er , such as decr ea sed ankle plant ar flex or str ength , w alking speed, and decr eased ankle m otion , m ay be contributin g fact or s.

A c k n o w l e d g m e n t s

I w ould like to ex pr ess thank s t o Dr . Mueller , Dr . Minor an d Dr . Klaesner for their t echnical assist an ce and Katrina Maluf, PT , MS , Hasting s Mary , PT , MS , and Jennifer Henry, BS, for their assist ance in r ecruitin g subject s. I also expr ess a special thank s t o all of subject s.

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