Athletic participation r esult s in a r elativ ely high risk of injury t o the ankle joint . Ankle spr ain s ar e the m ost fr equently

In t r o d u c t i o n

Athletic participation r esult s in a r elativ ely high risk of injury t o the ankle joint . Ankle spr ain s ar e the m ost fr equently

r eport ed injury in sport . T h e sport with the highest pr ev alence of ankle injuries is basketball, with over 50% of player s having ankle joint pr oblem s that hav e r esult ed fr om ligam ent injuries (Brynn on and

A nk le T apin g an d V e rt ic al D ro p L an din g

Y i Ch u n g - h w i, 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

국 문 요 약

발 목 관 절 의 테 이 핑 과 수 직 착 지 동 작

이충휘

연세대학교 보건과학대학 재활학과 및 보건과학연구소

발목에 대한 유착성 테이핑의 적용은 물리치료 분야와 운동 트레이닝 분야에서의 일반 적인 치료 접근 방법이라 할 수 있다. 즉 발목 염좌 같은 손상을 예방하기 위한 방법과 재활의 부가적인 치료 형태로 이용될 수 있는 것이다. 본 연구는 발목의 테이핑과 트레드 밀에서의 30분간 보행이 수직 착지 동작 동안 하지의 운동 역학적 요소들에 어떠한 영향 을 주는지 알아보기 위해 시행되었다. 14명의 신체 건강한 대상자들 (남:10, 여:4)이 본 연구에 참여하였다. 한발로 서있는 동안 40 ㎝의 높이로 뛰게 하였다. 가자미근, 전경골근, 안쪽넓은근, 넙다리 두갈래근에 근전도 전극이 부착되었다. 테이핑된 신체 부위로 착지하 는 동안 근전도와 힘판(force plate) 자료가 500 ㎐의 주파수로 수집되었다. 대상자들의 우세쪽 하지 발목에 테이핑을 하였고, 대상자는 한발로 뛰어 내리는 동작을 반복하였다.

트레드밀에서 30분 동안 발목에 테이핑을 한 채로 보행하였고 이후 한발로 뛰어 내리는 동작을 반복하여 수행하였다. 테이핑을 적용한 상태와 테이핑한 채로 30분 동안 트레드밀 에서 걷기 운동을 한 조건에서 수직 지면 반발력의 통계학적으로 유의미한 증가가 있었 다. 착지 동안에 네 가지 상황에서의 최대 내측 가속도의 유의한 차이가 있었고, 그 차이 는 테이핑 전과 테이핑을 한 채로의 운동 조건에서 유의한 차이가 있었다. 테이핑한 상태 에서 가자미근은 접촉되는 착지 순간부터 최대 수직 지면 반발력이 나타나는 동안의 평 균 근전도의 수치에 있어서 유의한 감소가 있었다. 반면에 다른 근육들에서는 아무런 변 화를 보이지 않았다. 비록 발목 테이핑이 발목 손상의 위험을 줄이는데 효과적이라고 일 반적으로 인식되고 있으나 이번 실험의 결과는 30분 동안의 트레드밀에서의 보행 후 테 이핑은 발목의 움직임을 제한하는 효과는 있지만 한편으로는 가자미근의 활동을 감소시 키는 것을 보여주었다. 따라서 이 연구의 결과는 테이핑을 하면 점프와 착지로 이어지는 동작 중에 발목관절 손상 위험을 증가시킬 가능성이 있음을 보여주었다.

핵심단어 : 발목 테이핑; 운동역학적 분석; 착지.

Ren str om , 1991). Later al ligam ent s of the ankle ar e the m ost comm on sit e of injury in netball (Hopper , 1986; Hopper et al, 1999). A study ha s shown th at 90～95%

ar e inv er sion injuries cau sing partial or complet e ruptur e of the ant erior t alofibular ligament and occasionally the calcaneofibular ligam ent (Garr ack an d Requ a, 1988). Due t o the high incidence of acut e ankle spr ain and spr ain r eoccurr en ce, m any phy sician s, phy sical th er apist s, and athletic tr ainer s att empt t o pr ev ent ankle injuries thr ough the use of various taping/ strapping t echniques or ankle orthoses. S ev er al studies hav e examined the effect s of prophylactic br acing/

t aping on the incidence of ankle spr ain s in basketball (Garrick , 1977; MacKean et al, 1995; Miller and Her genr oeder , 1990). T o decr ea se the risk of an inv er sion spr ain , tr adition al ankle t aping or v ariou s comm er - cially av ailable ankle st abilizer s hav e been u sed t o pr ovide function al stabilization t o the joint . Ankle t apin g has become the principal mean s of pr ev enting ankle spr ain s in sport (Bullar d et al, 1989). Wher eas t aping w as on ce thought t o st abilize the ankle m echanically , this seem s unlikely considering report s that show no mea sur able st abilizin g effect of t ape aft er as little a s 20 minut es of ex er cise (Perlm an et al, 1987). Accor dingly , ankle t apin g is now thought t o pr ev ent ankle injury m ainly thr ough impr ovin g the u ser s judgment of position and orient ation of the plant ar surface with r espect t o the leg . T his foot position aw ar eness , in the domain of pr oprioception , is u sually r eferr ed t o as kinaesthetic sense (Karlsson and Andr easson , 1992). Pr esum ably hum an s u se kinaesthetic

sen se inform ation in anticipation of foot contact with a surface either t o position the plant ar surface befor e the support phase t o attenuat e for ces cau sing inv er sion , or to command mu scle support t o su st ain these for ces, ther eby pr ev enting ligam ent loading , or both . By this r easoning , ankle spr ains are cau sed by impair ed foot position aw ar en ess r esulting in in adequat e u se of these anticipatory maneuver s under condition s such as sport s, when ther e is in sufficient time t o r espon d t o the actu al loadin g ev ent (Robbin s et al, 1995).

Ankle taping is commonly used by athletic tr ainer s or sport s phy sical ther apist s t o pr ot ect the ankle and t o m ax imize it s function durin g sportin g activities (Cerney , 1972; Firer , 1990). Nevertheless, r ecomm end - ation s for or again st th e u se of t apin g ar e som etim es confu sing and n ot so clear , r angin g fr om pr ophylactic ext ernal stabili- zation of both ankle joint s during all ex er cise, to r efu sal due t o the assumed risk or adv er se effect of ankle injury cau sed by r estriction of joint m ov ement (Hume an d Gerr ar d, 1998). T he positiv e effect of t apin g , th er efor e, is not so con clu siv e and th e effect on low er limb kinetics an d kinem atics aft er ex er cise w ith ankle t apin g has n ot been widely studied (Heit et al, 1996; Shapir o et al, 1994).

A v ertical or v ertical- horizont al fall and the collision of the human body with gr ound is a frequent occurrence in human locom otion (Kov acs et al, 1999). Landing fr om a jump is a t ask that is important t o m any sport s.

Pr eviou s studies hav e ex amined the effect s

of landing surfaces (Gr oss and Bunch ,

1989), the m anipulation of stiffn ess (DeVita

and Skelly , 1992; Dufek and Bates , 1990;

Gr os s and Nelson , 1988; Mizar ahi and Su sak , 1982), or ela stic ener gy st or age an d utilization an d coor dination (Dufek an d Bat es, 1990) on low er ex tr emity j oint kinetics. Bobbert et al (1986, 1987) r eport ed gr oun d r eaction for ce data and low er extr emity joint m ov em ent s and pow er s by applying count erm ov em ent and boun ce type dr op jumps falling fr om sev er al height s.

T hey ob serv ed ankle joint domin ance in pow er pr oduction for bounce dr op jump in contr a st with count erm ov em ent dr op jump wher e knee j oint domin ance w as ob serv ed.

These studies showed that all lower extr emity joint s participat ed in ener gy ab sorption an d gener ation in landing s an d jump s u sing for efoot lan ding str at egy , and as landing height incr eased the r ole of the ankle mu sculatur e incr ea sed (Kov acs et al, 1999).

T he purpose of this study , ther efor e, w as t o det ermine the effect of ankle taping an d the combined effect of ankle t aping plu s 30 minut es of a tr eadmill w alking on ankle st abilization during lan ding fr om a jump.

Su ch inform ation is of int er est not only for athlet es t o impr ov e tr aining ex er cises but also for clinician s including phy sical ther apist s becau se of th e w ide application of ankle t aping in differ ent types of sport s and the dearth of study on landin g impact t o ankle with t aping . T he r esult s of this study will pr ovide u seful inform ation for phy sical ther apist s, athletic tr ain er s, and other pr ofessionals r elat ed t o sport s t o judge the injury pr ev ention effect of ankle t aping .

M e t h o d s

S ubje c t s

F ourt een healthy adult s (10 fem ale, 4 male) volunteer ed for this study . All subj ect s signed inform ed con sent form s appr ov ed by the Univ er sity In stitutional Review Boar d prior t o their participation .

In s trum e nt atio n

Mat erials utilized for th e taping w er e one and one half inch tape

, foam prewrap

, and adher ent spr ay

.

Surface electr odes w er e applied to th e cent er of the mu scle bellies of the tibialis ant erior , soleu s, v astu s m edialis and biceps femoris mu scles of the dominant limb . Con ductiv e pa st e w as fir st applied t o the electr odes , which w er e held in place by adh esiv e t ape. Each r ecor ding electr ode con sist ed of t w o silv er - silv er chloride 1- ㎝ diam et er electr odes embedded in an epox y - m ounted pr eamplifier sy stem (x35) whose center s w er e spaced 2 ㎝ apart . A r efer ence electr ode w as att ach ed t o the m edial aspect of the tibia on the non - domin ant side. T he EMG signals ar e band - pass filt er ed (20 ㎐ t o 4 ㎑) (T her a - peutics Unlimit ed, Iow a City , Iow a ) and full- wave rectified on - line. Final ampli- fication w a s 2 k . On e for ce plat e, embedded in a lev el w alkw ay (10 in length and 1.22 m in width ), m easur ed gr oun d reaction forces. Processed EMG and amplified for ce platform signals w er e sampled on -

1. Johnson & John son Product s , Inc.

2. Johnson & John son Product s , Inc.

3. T uf- skin , Cram er Pr oduct s , Inc. Gar dner ,

Kan sas 55030

line at a r at e of 500 ㎐ for 5 secon ds

. All gr oun d r eaction for ces w er e n orm alized t o body w eight .

P ro c e dure s

Subj ect s w er e asked t o complet e four t ask s on one occasion . F ir st , subject s st ood on their dominant limb on a 40 ㎝ high platform that w as placed 20 ㎝ fr om the edge of the for ce plat e. T he for ce plat e t o measur e ground r eaction forces was situ at ed wher e the subj ect w ould land fr om a hop.

Subject s w er e asked t o hop dow n su ch that they landed safely without the need t o readjust the landing leg. Subject s complet ed 3 pr actice trials follow ed by 3 ex perim ent al trials (PT : Pr et ape trials ). T he arm s w er e not con str ained during the landing s an d 4. BIOPA C Syst em s , Golet a, CA

w er e g ener ally held up and in fr ont of th e subject s for balance. T he ankle of the domin ant limb w as then taped by a certified athletic trainer . T he taping configu - r ation inv olv ed t w o cir cumfer ential anchor strips of tape applied at th e for e- foot r egion and pr oxim ally at the low er 1/ 3 part of tibia. T hr ee stirrups w er e applied in a basket w eav e configur ation . Cir cular s w er e applied t o fill in gaps , follow ed by t w o heel lock s. T he taping m ethods w er e applied with the ankle in neutr al inv er sion - ev er sion and dor siflexion . T h e subj ect r epeat ed 3 hopping trials (T : T aped trials).

T he subj ect then w alked for 30 minut es on a tr eadmill at comfort able self- select ed speed. F ollowin g a 5 minut e r est , th e subject again r epeat ed the 3 hoppin g trials (T W : T ape and w alk trials). Aft er r em ov al F ig 1 . F orceplat e r ecord and EMG of S oleus . F y :

m ediolat eral accelerat ion , F z : v ertical ground reaction force,

a : 100 ㎳ prior t o landing , b : landing , c : peak Fz on t oe

impact , d : peak ㎐ on heel impact .

of ankle taping , 3 hopping trials w er e perform ed (RT : Rem ov al of the t ape trials ).

D at a an aly s i s

T he EMG depen dent v ariables w er e av er age amplitu de of iEMG 100 m s prior t o lan ding and av er age amplitude of four mu scles fr om impact t o peak v ertical r eaction for ce. F or ce platform m easur es include timing and amplitude of the m edial- lat er al (F y ), and v ertical (F z) gr ound r eaction for ces un der th e dominant limb (F ig 1).

S t ati s tic al an aly s i s

One- w ay analy sis of v ariance (ANOVA ) with r epeat ed m easur es w as u sed t o ex amine the differ ences bet w een th e independent (initial hopping , T , T W , and RT ) and the dependent v ariables of EMG activity and kin etic v ariables. In cases wher e the on e- w ay analy sis of v arian ce with r epeated m easur es demon str at ed a differ ence (p< .05), a post hoc within - subject analy sis w as perform ed. A Bonferr oni type adju stm ent w as m ade t o account for the possibility of T ype I err or occurring with multiple comparison s .

R e s u l t s

Groun d re a c tio n f orc e s

T w o peak s w er e ob serv ed in th e v ertical gr oun d r eaction for ce- tim e curv es an d show ed peak for ces at the tim e of t oe t ouch - down an d heel cont act in that or der (F ig 1). T he fir st peak w as alw ay s significantly low er compar ed with th e secon d peak . T h e v ertical for ce incr ea sed sharply fr om the in st ant of heel contact and r each ed abov e 500% of body w eight acr os s 4 condition s (T able 1). T her e w er e st atistically significant incr eases in VGRF s for the t aped condition and ex er cise with t aping con dition compar ed with th at in pr et aped an d unt aped con dition s (T able 1).

How ev er , th er e w er e n o significant differ ences bet w een th e t aped con dition an d the ex er cise w ith t apin g condition . During landing , th er e w as a significant differ ence in th e peak m edial acceler ation acr oss 4 con dition s an d ther e w a s a st atistically significant differ ence bet w een pr et aped an d ex er cise w ith taping condition s u sing Bonferr oni adju stm ent . How ev er , in the peak lat er al acceler ation , n o significant differ ence w as foun d acr oss condition s (T able 2).

T able 1. P eak v ert ical ground react ion force (% body w eight ) across conditions

Con dit on s Mean SD

p

Pr e- t aped 1) 503.42 34.23

T aped 2) 549.51 45.04 .002

Ex er cise with T apin g3) 550.70 47.83

Unt aped 4) 512.41 33.71

*

SD : st andard deviation

T here w ere st atistically significant differ ences in 1) v s 2), 1) v s 3), 2) v s 4), and 3)

v s 4).

At the m om ent of toe impact , th e tim e t o peak gr ound r eaction for ce w as the short est in th e t aped condition and at th e m om ent of heel impact , the time t o peak gr oun d r eaction for ce of the t aped condition w as the short est t oo (T able 3).

E M G a c tiv it y

T o identify the muscle preparation during landing , 100 ㎳ int egr al EMG dat a prior t o impact w er e an alyzed. T her e w as no significant differ ence acr os s condition s (T able 4).

T he soleu s mu scle show ed th e least activ ation t aken fr om impact t o v ertical gr oun d r eaction un der th e t aped an d ex er cise with t aping condition (T able 5).

D i s c u s s i o n

Jump landing activities can be seen in m any sport s dealing w ith a ball or with phy sical tr aining cour ses. T w o peak s in v ertical gr ound r eaction for ce w er e shown in the curr ent study (Fig 1 c and d). T he fir st peak w a s alw ay s significantly low er T able 2 . P eak m edial (pronation ) and lat eral (supin ation ) acceler ation forces (% body w eight ) across condit ions

Medial Acceler ation Lat er al Acceler ation

Condition Mean SD

p Mean SD p

Pr et aped 1) 201.40 43.33

.048

- 40.36 17.54

T aped 2) 218.88 27.61 - 44.82 15.74 .588

Ex er cise with T aping 3) 228.81 46.54 - 43.81 22.32

Unt aped 4) 217.35 41.15 - 47.57 26.10

*

SD : st andard deviation

Bonferroni adjustm ent in m edial acceleration show ed t hat t here w as a significant difference at the .05 in 1) v s 3).

T abl e 3 . T im e (㎳) t o peak vertical gr ound reaction force of t oe and heel across condition s

T oe Heel

Con dition Mean SD

p Mean SD p

Pr etaped 1) 11.71 2.66

.002

41.57 4.33

T aped 2) 9.76 2.04 36.29 2.96 .000

Ex er cise with T apin g 3) 10.71 1.72 37.67 2.98

Untaped 4) 11.94 2.73 40.72 4.24

*

SD : st andar d deviation

Bonferroni adjustm ent in t oe show ed t here w ere significant differences at the .05 in 1) v s 2), and 2) vs 3).

Bonferroni adjustm ent in heel show ed there w ere significant differences at the .05 in 1)

v s 2), 1) v s 3), 2) v s 4), and 3) v s 4).

compar ed w ith the secon d peak w hich m ean s a t oe- heel str at egy w as u sed by all subject s at landing .

In this study , aft er landing , w e asked the subject s t o keep their position for 2～3 secon ds, and n ot t o t ake ev en one st ep con dition s, it is no w on der that r apid deceler ation of the body mu st occur . Accor din g to St eele and Milburn s r eport

(1989) applied t o netball play er s, VGRF s on landing w er e 6.8 tim es body w eight . In our study , w e had similar r esult s as the peak VGRF s r an ged fr om 503.42% t o 550.70%

body w eight acr oss 4 con dition s (T able 1).

F r om pr eviou s studies on landing , the m agnitude of these VGRF s v aried fr om 3.12 t o 3.37 times body w eight (Hopper et al, 1999) in single leg for w ar d jump , 4.4 T able 4 . IEMG (㎷) 100 ㎳ pre- impact across muscles and condition s

Pr e- t aped T aped Ex er cise with

T aping Untaped

Mu scles Mean SD

Mean SD Mean SD Mean SD p

S oleu s 1.32×10

0.45×10

1.23×10

0.55×10

1.09×10

0.41×10

1.12×10

0.56×10

.063 T ibialis

Ant erior 1.32×10

0.39×10

0.69×10

0.51×10

0.68×10

0.48×10

0.71×10

0.54×10

.956 Bicep s

F em oris 1.32×10

0.48×10

0.66×10

0.45×10

0.60×10

0.31×10

0.62×10

0.34×10

.253 Vastu s

Medialis 1.32×10

0.49×10

1.07×10

0.41×10

0.96×10

0.43×10

0.92×10

0.38×10

.096

*

SD : st andard deviation

T able 5 . IEMG (㎷) from impact t o peak v ertical ground reaction force (% body w eight )

Pr e- t aped T aped Ex er cise with

T aping Untaped

Mu scles Mean SD

Mean SD Mean SD Mean SD p

S oleu s 0.53×10

0.20×10

0.37×10

0.18×10

0.38×10

0.14×10

0.48×10

0.19×10

.011 T ibialis

Ant erior 0.37×10

0.22×10

0.35×10

0.24×10

0.34×10

0.20×10

0.35×10

0.22×10

.333 Bicep s

F em oris 0.39×10

0.29×10

0.34×10

0.23×10

0.35×10

0.32×10

0.37×10

0.28×10

.064 Vastu s

Medialis 0.77×10

0.34×10

0.71×10

0.36×10

0.63×10

0.36×10

0.71×10

0.48×10

.265

*

SD : st andard deviation

Of the 4 muscles , only soleus muscle show ed significant decreas e across condit ioins .

times body w eight (Numm ela et al, 1994) durin g fast running , 7 t o 12 tim es body w eight (Ram ey an d William s, 1985) in a triple jump, t o 8.8 t o 14.4 tim es body w eight for v ault lan ding s in gymnastics (P an zer et al, 1987). Variation s in th e v elocity at which the subject appr oaches the for ce plate, the subj ect s lan ding t echnique, th e court surface, the position of the foot at the tim e of landing , th e dr opping height , and foot w ear et c. may hav e been the car din al fact or s influ encing the m agnitu de of the VGRF s. W e should be especially cautiou s in int erpr eting these findings since the court surfaces are differ ent fr om those of the for ce plate. T hese previous studies indicated that if the landing movement happens from a dynamic st arting position such as a jog or sprint , VGRF s w er e higher than those r ecor ded fr om the stationary starting position as in the pr esent study .

A possible ex planation for the incr eased VGRF s in the tape condition s , is that as t aping r estrict s the am ount of m otion at the ankle an d subt alar j oint s. T he r educed ankle r an ge of m otion during landin g m ay r esult in less ener gy being ab sorbed by th e soft tis sues contr ollin g ankle motion , especially by the eccentric action of the post erior ankle mu sculatur e (McCaw an d Cerullo, 1999). Lindenber ger et al (1985) r eport ed that t aping ha s a significant pr ophylactic effect again st lat er al ligam ent injuries. In addition , taping offer ed the m ost support for limitin g dor siflex ion r ang e of m otion , but it could in duce incr ea ses in the m agnitude of the peak VGRF s in the low er ex tr emity at landin g (Cor dov a et al,

2000). Con sequently this finding su ggest ed that the r estriction of ankle ROM u sin g ankle t aping m ay be harmful t o ankle, knee, an d hip joint s. F ukuda et al (1987) found that knee an d hip j oint s play an import ant r ole in sh ock att enu ation . S o ther e is a possibility that shock on lan ding might be tr an sferr ed mor e t o the knee or hip j oint than t o the ankle in the ankle t aped con dition than in n orm al lan ding . How ev er , the r esult s of this study ar e not sufficient t o pr ov e wh eth er knee an d hip joint kinem atics ar e alt er ed when ankle t aping is u sed.

Wh en t apin g m at erial str et ches, or the limb sw eat s during ex er cise, t apin g is know n t o loosen (Hum e and Gerr ad, 1998).

Ex er cise periods commonly r anged fr om 5

t o 20 minut es but th e am ount s of activities

with t apin g is differ ent fr om each studies

(Hume and Gerr ar d, 1998). Although , in the

pr esent stu dy , the ankle ROM befor e and

aft er 30 minutes of walking on the tr eadmill

with t aping w a s not m easur ed, con siderin g

the m agnitude of the peak VGRF s in

ex er cise with t apin g , it is evident that th e

t ape did not lose it s r estrictiv e ability t o a

significant ext ent ev en with 30 minut es of

w alking . It seem s that the m ain r eason for

this is that the w alkin g ex er cise w as not

str enuou s en ough t o cau se the t ape t o lose

it s t en sion . T he r esult s indicat e that ankle

t aping affect s the kin etics of landing , likely

thr ough r estricting r ange of m otion , and

affect the soleu s, possibly thr ough the

sam e mechanism . And the changes seen in

pr e- and post - ex er cise condition s in dicate

that 30 minut es of moder at e activity does

not significantly affect th e support pr ovided

by the t ape.

On the oth er han d, t ape u se has been r eport ed t o significantly limit inv er sion befor e and aft er ex er cise but t o lose con sider able am ount s of r estriction aft er ex er cise compar ed with the pr e- ex er cise con dition (Bauer , 1988). Oth er stu dies hav e r eport ed that although the r estriction in ROM w as r educed with ex er cise, the r estriction w as still significantly gr eat er than without any t ape support (Gr os s et al, 1991). T o det ermine the effect of ankle taping, the type of tape, application t echnique, and length of time the t ape is in u se, all need t o be con sider ed. In addition , the adh er ence of t ape t o th e skin , and the t en sion of th e t ape strip s need t o be ex amined (Hum e and Gerr ar d, 1998).

P eak pr onation r eaction for ce incr eased about 2 times body w eight at t ouch down (T able 2). Glick et al (1976) st at ed that t ape w ould fail t o support th e ankle m echanically (ie. as a mean s of ext ernal support ) aft er 20 minut es of ex er cise, and that an ankle with an incr eased talar tilt m ay be m or e pr one t o injury than on e with a norm al t alar tilt . T he con struction style and quality of m at erials could affect all of the abov e su ggest ed m ech anism s.

T he t en sile str ength of t ape is low er than the str ength of the ant erior t alofibular ligam ent (Hum e and Gerr ar d, 1998). If an ext ernal support is t o pr ovide m echanical support to a ligam ent it should ex ceed the str ength of the ligament . And Bauer (1988) con cluded that athletic t ape w ould fail t o support the ankle effectiv ely during and aft er ex er cise. In th e pr esent study , it seem s th at the pr on ation r eaction for ce at

landing w as str onger than the pr ot ection ability of taping in relation to talar m ov em ent . T he possibility of a cancelin g out effect , contr ary t o r eport s that ankle t apin g is effectiv e limiting ankle m otion , of inv er sion and ev er sion mu st be con sider ed.

With r espect t o tim e t o peak v ertical gr oun d r eaction for ce of the t oe, m ean differ ences acr os s con dition s w er e about 2

㎳ and these differences were statistically significant (T able 3). Although th er e w as a st atistically significant differ ence, w e can not ex clu de the possibility of m easur em ent err or . Becau se w e sampled at a r at e of 500

㎐ in the acquisition of EMG signal, a 2 ㎳ difference may have occurred due to m easur e- m ent err or . And although ther e w er e significant differ en ces in peak VGRF , these differ ences w er e v ery small an d pr obably not m eanin gful. F or ex ample, ther e w as a 2.18 ㎳ differ en ce betw een t aped an d untaped post - exercise which was statistically significant (T able 3).

With r egar ds t o tim e to th e peak v ertical

gr oun d r eaction for ce of heel, significant

m ean differ ences acr oss con dition s w er e

found. This means that in the taped con dition

and ex er cise w ith t apin g condition , the

ankle joint had the short est tim e t o ab sorb

the r eaction for ce fr om th e gr ound. T his

findin g is con sist ent with the r eport of

Hopper et al (1999) who r eported th at

ther e w a s a tr end t o a short er tim e to

peak v ertical for ce when subject s w er e

br aced, an d th at m ay be w orthy of further

inv estigation . A r edu ction in tim e t o peak

v ertical gr ound r eaction for ce of h eel could

r eflect a decr ease in ener gy ab sorption and

suggest s that this m ay incr ease the risk of

ankle injury .

T o identify the muscle preparation during landing , 100 ㎳ pr e- impact iEMG acr oss con dition s w er e analy zed (T able 4). T her e was no significant difference across con dition s in soleu s, tibialis ant erior , biceps fem oris , and v astu s m edialis. Which m ean s, during landing , ther e is no mu scle pr epar ation in the abov e mentioned 4 mu scles. Surv e et al (1994) suggest ed that the m ain effect of an orthosis w a s t o impr ov e pr oprioceptiv e function of the pr eviou sly injur ed, r ather than to pr ovide m ech anical support alone.

Hume and Gerrard (1998) who had r eview ed the lit er atur e r elat ed t o mu scle activ ation , r eport ed that the magnitude, dur ation or timin g of mu scle activ ation patt ern s may or m ay n ot ch ange with u se of ex tern al support su ch as br acing . Becau se r elativ ely few studies hav e inv estigat ed mu scle pr e- par ation of th e low er extr emity at landing , little inform ation is av ailable on whether the mu scle pr epar ation at landing ex ist s or not .

Concerning the iEMG fr om impact t o peak VGRF s (T able 5), when subj ect s w er e t aped, only soleu s iEMG of the 4 low er ex tr emity mu scles w as decr eased.

McKanna and F inch (1991) suggest ed that a decr ease in ankle soleu s , per oneu s longu s and ant erior tibialis mu scle activity may hav e been due to th e r estriction of m ov e- m ent by t ape application or the mu scles r elyin g on the t ape for support . Hopper et al (1999) r eport ed that g astr ocn emiu s EMG activity decr ea sed when u sing a br ace or t aping . Ev en though w e m easur ed soleu s EMG in st ead of gastr ocnemiu s, significantly decreased soleus iEMG activities were found

acr oss conditions. T his in dicates that the plant ar flex or s ar e important in reducing the VGRF s associat ed with landing (McNitt - Gr ay , 1991). In this study , it is impossible t o explain clearly w hy the only soleu s EMG decr ea sed w hen subject s w er e taped.

T aping or br acin g m ay diminish mu scle activ ation amplitude and inhibit the natur al injury pr ev ention m otion of the ankle j oint by r estricting r ange of m otion (F er gu son , 1973; Hum e and Gerr ar d, 1998).

In this study , t o ex clu de the influen ce by shoe type, all subject s w er e in struct ed t o w ear low - top sneaker s m ade by the sam e company wh en they performed the landin g activity . Garrick and Requa (1988) concluded that the u se of pr ev entiv e ankle t aping , in addition to decr easing th e likelih ood of r e- injury , offer ed som e pr ot ection for the ankles of pr eviou sly uninjur ed player s although this w as only ob serv ed for th ose w earing high - t op shoes. T he injury r at e for the low - t op shoes with t ape condition w as low er than the r ate for the high - t op shoes and no- t ape condition indicating that t ape possibly had mor e of an effect than shoe type.

Limit ation s of this study w er e the sm all subject sample size, an d due to u sing within - subj ect design , a possible carry - ov er effect or learning effect occurring durin g the perform an ce of landing . Addi- tionally , m easur es t o ex clude the or der effect s could n ot be applied in this study . T hu s, claim s based on this stu dy sh ould be int erpr et ed with caution .

In conclu sion , ev en thou gh it has been

widely believ ed th at the benefit s of ankle

t aping in r educing the risk of ankle injury ,

our r esult s suggested th at t ape can pr ovide enou gh m echanical r estriction t o ankle m otion ev en aft er 30 minut es of w alking on the tr eadmill t o diminish th e magnitude of iEMG of soleu s th at w ould r esult in incr easing the risk of an ankle injury at landing fr om a 40 ㎝ height .

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