t ",~i """c>
lOS
171
'.Jld "-,,,ei,,,, Se'enc.:c II (2003) 17 1- 119
Prc~'
Closed kinetic chain (linear) isokinetic
testing: Relationships to functional testing
Robert C. Manske,,·b,., Barbara S. Sm ith ", Michael E. Rogers C and Frank B. Wyand
" Depal1lnem of Physical Therapy. Widlita 5tllle Ullireniry. Wichita. K567260. USA
b v,o Christi 5ports and Orthopedic Physical Therap); Wichita, K5 67212. U5A
C Deparfmellt of Kinesiology ami 5porr 5l11dies. Wichita 5/(lle Ull il·ersil): lIIichita. K5 67260. U5A
d Depal1lllem of Hea/th. HUlIIall Pelfonnallce. alld Recrearioll. Bay/or University. \\hco. 7X 76798. U5A
Abslrac t . S/lidy (Ies/gll: A corrcJ;;llion slUdy 10 delcmline Ihe relati onship of the results of linear isokinctk Icsti ng and various
fUllctionultests.
Objeclil·cs: To detenni ne the relationshi p of scores on a linear isokiuetic test 10 scores on a ' ·<lriCI), of lowe r extremity functional
tests.
Background: Both isokinetic testing aud functional tests arc commonly used during the rehabilitation of individuals wilh sports
<l nd orthopedic injuries. Limi ted inforll1ation exists regarding the re1<1tionships of scores on a linear isokinetk lesl and scores on
functionallesls.
M ethods all(/ measures: Twenty-nine hC<ll1hy subjccts perfonned a n:locity spectrum linear isokinetic test consisting of 3 sets in
<I bilateral rec ipmc<ll Illode. followed by three scl~ in a bilateml coupled mode. Testing ,·elocities were 25A. 50.8 <lml 76.2 cm per
second. Six Ill<l.\im<ll volitionul1inear isokinetic repetitions were perfonlled at e:lch testing velocity. Following linear isokinetic
testing. su bjects perfonned 5 funct ional tests: bilateral leg ,·ertical jump. unilateral leg venic:lI jump. double legjump for distance.
si ngle.leg hop for distance. an d single.leg limed 6·meter hop. Functional testing ent:likd 3 lI1<1xilll<ll volitional attempts of the
5 procedures for both the dominant and non·dominant lower extremity. The me<ln of the 3 al1empl~ was used for c:llculmions.
Memls and sl:lnd:lrd devimions of the func tion:!1 test scores :lnd isokinelic lesl scores were detemlined us ing sl:lndard st<lliSlic<l1
procedures. PC<lTSon product moment cOTTei<Jtion cocfficiems were used to detemline the rel:ltiollship between the mean scores
onlhc linc<lr isokinctic test scorcs <lnd funct ion<llteSls for both Ihe dominam ami non-dominant limbs.
Re.\JI/ts: Twellly-Ihree OUI of 36 cOTTel<llion cocfficielll!; were significant at the p < 0.01 level. whi Ie 12 OUI of 36 were significant
at the p < 0.05 lel'el. Onl y l out of 36 was non-significant whe n co mparing bilateral rcci proc<ll scores 10 single.leg functional
te, 1 scores. The bilater<ll reciproc<ll cOTTelation coefficients ranged from -0.36 to 0 .65. Six OUI of 12 bilmer.J1 coupled correlation
coefficienlS were s ignificant at p < 0.0 1. while 3 out of 12 were signific:lnl al ~he JJ <: 0_05 1.,,·.,1 and only 3 were cOll,idered
non-significant. The bilmeral coupled cOTTelation coefficicnts rang.,d from 0 .11 100.64.
COllell/siolls: Results from this slUdy indicate :! signific:l1II rel:ltionship exists belween the resullS of linear iso kinetic !esting <lnd
various function:lllesis. Despite the signific<llll rel <ltionshi p. Ihe m<ljorit)' of Pearson Product mome nt correl:ltion coefficienlS
were in the low to moder<lte range. Thcrefore. Ihe usc of either a line:lr isokinetic test or a functional test in isolation 10 deteml ine
strength :llld perform:lnce is strongly discouraged. LinC<lr isokinelic testing should be used for testing lower e"trem ity slrength.
while functi on<ll tests should be used to dete mline pc rfoml<lncc le,·els. The authors recoJllmend lIIilizing both testing m~thods
since Slrengl h docs nOi <llwa)'$ cOTTelate strongly with ph)'sieal perfonnance.
Keyword,: Muscubr strength. perfonnance tests. isokinetics
. Addre~s for corre~pondcnce: Roben e. Manske. MPT. MEd.
SCS. ATe. CSCS . ."-,siSlanl Professor. Depanmem of Physical
ehila. KS 67160·00B. USA. Fax: +1 316978 3025; E-m:til:
Ther;Jpy.
robcrt.ntansk~ @\\' ichi~a .edu.
\\~chita
Siale Uni'·ersiIY. I 8~5 North Fairmount Wi·
ISSN {)959-30201031S8.00 © 2003 - lOS P..... ss. All right> ..... sened
171
R.C. ,\IullSk~ ellll.1 C/useJ kinelic elw;" ( lillear) isokill<'lic I<,sling: Re/nriomhips to fimcliorU/l l"slin.~
1. Intr oduction
More stringent demands are being placed on spons
and onhopedic clinicians 10 document functional outcomes. Clinicians must continue to find measuremems
that are objective. and reliable when evaluating these
outcomes . Due to reimbursement issues and shoner
coverage fo r rehabilitation. the need to accurately and
effectively assess knee function during in itial evaluation and upon subsequent re-examination has become
paramount. Traditionall y, the evaluation performed
following a lowerextre lll.it~' injury has focused on physical characteristics such as measurements of joint effusion, knee ligament laxity, range of motion. muscle
strength. and endurance [25.27.28}.
Iso kinetic dynamometf}' has become a standard 1001
fo r evaluation of and follow-up testing of muscular strength of the lower extremi ty due 10 the benefits of range of motion control , accommodating resislance. varying movement velocity. and reliability [2.6.12.20.30}. One of Ihe newer modes of isokinetic dynamometers is the Lido Linea Closed Kinet ic
Chain Isok.inetic Dynamomeler (Loredan Biomechanieal, West Sacramento, CA). Thi s dynamometer has
been developed at a time when clinicians have come 10
rely on closed kinetic chain exercises as a key componelll in spons and onhopedic rehabilitatioll. For purposes of this study, closed kinetic chain isokinetie tesiing will be operationally defined as utilizing a linear
isokinetic pattern, while open kinetic chain isokinelic
test ing will be operat ionally defined as utilizing an angular pattern.
Until recently. most isokinetic systems llIilized an angular pattern of testing in which the distal ponion of the
extremity tested was free to move. Previous isokinet ic
smdies that have investigated linear strength parameters used a modified dynamometer that provided resistance to a movement through an angular arc of motion
similar to the open chain methods [5, 17]. With newer
isokinetic devices. measures of strength and power can
be obtained in a linear paHem with Ihe distal extremity
fi xed to the apparatus [6. 14]. In addition to the Lido
Line[l. the Closed Kinetic Chain Rider (MeHler Electronics, Anaheim. CAl . and the Cybex Li fta sk (Cybex
Division of Lumex, Inc .. Ronkonkoma, NY) are several
other examples of isok.inetic devices that utilize a linear
pattem for strength assessment. To date. only 2 studies
have been performed examining the relationships between results of linear isokinetic testing and func tional
tests r13, 181.
Another common means of assessing lower extremity strength is through the performance of funct ional
tesls. Functional tests are activities that can be objectively measured th[ll closely simulate spons or recreation[ll activity. In addition to muscular strenglh these
functional tests also assess neuromuscular control.
speed of muscle contraction. lower extremity power.
joint function and joint range of mot ion. These tests
are numerous and a paniall ists includes single-leg tests
such as the one-legged hop lest fo r distance [3.8.9.1 9}.
the timed one-legged hop tesl over a distance of 6 meters [3J, the one-legged ven ical jump [3]. lhe crossover
triple hop [19]. and the leap [3. 11J. In addition 10
these tests. two-legged tests are available: the fi gureof-eight-test [29] the stair-running tesl [29 J. the carioca
test [ IS}, the shuttle run [ 16], the semic ircular test and
the vertical jump test [ 15] .
Many studies have assessed the relationship between
results of isokinetic tests and func tional tests. ironically, each of Ihese studies compared an angular pattem of isokinetic testing with closed kinet ic chain functional test [1,3,4.7,1 5,21 ,23.26,3 1]. The n[lture of the
two different tesling procedures, (i.e .. using funct ional
tests that are closed kinetic chained and isokinetic tests
that are angular) would suggesl that rclationships may
be low. Only a few slUdies have assessed relat ionships
between linear isokinetic testing and functional performance testi ng [ 13. IS}.
Negrete and Brophy [ 18} compared results of angular and linear isokinetic testing with se"eral funct ional
tests. Using a group of 60 volunteers, results of isokinetic knee extension, leg press. and single-leg squat
strength were correlated with functional test scores of
single-leg hop, wnical jump and a speed/agi lit)' les\.
Isokinetic leg press strength eval uated at 76.2 cmis
demonstrated moderate to high correlations (r = 0.67
to 0.76) with 2 unilateral perfonn3nce tests: the singleleg hop for distance and the single-leg vertical jump.
More recently, Kovaleski et al. [ 13J utilized both angular and linear isokinetic tesling to detennine their relationships to funct ional performance. In their study.
30 uninjured men and wo men were tested to determine relationships between low-speed isokinetic testing and perfomlanee on func tional tasks such as jumping. hopping. and speed agil ity. Ne ither lower-limb linear nor angular isok inetie strength measurement s correlated highly (r = 0.26 to 0.62) with the functional
test results.
1l1erefore, the primary purpose of this study was to
assess the relationship between linear concentric isokinetic tesl scores on the Lido Linea and scores on a series
I7l
R.C. Mmu/;t' 1'1 Ill. / Clos.'" ki"l'lic elwill ( lim·or) i50/;j""lic ,,,s,i,,g: RdmiOllsllips 10 fimclimllllll'Slillg
of closed kinetic chain fu nctional tests. The research
hypothesis guiding this study was that linear concentric isokinetic testing scores obtained on the Lido Linea
would have a positive association with jumping and
hoping closed kinetic chain lower extremity functional
test scores. and have a negat i \"(~ association with results
of the 6-meter single-leg timed hop.
Tabl~ 1
,t:mdard dC'·iati on. and range of subjects' (n = 29) agc.
height. and weight
M~:m.
Age (years)
H ~ight (enl)
Weight (kg)
~Ican
SO
Range
26.7
5.1
lOA
l-t 8
19-37
157.5-193.0
·H.3- 106.2
175.3
75. 1
2.1. Pmcedures
2. Methods
A sample of 29 healthy panicipams aged 19-33
years (mean = 26.7 +/- 5.2) with no history of prior
knee surgery or recent acute knee injury were recruited
through a university physical therapy department and
through a local spons and orthopedic physical therapy
outpat iem cli nic. Sixteen of the participams were men .
while 13 were female . Means. standard dc"iations and
range of particip:1ms weight and height can be seen
in Table I. Participallls were evaluated for lower extremity pathology through a self-reponed heallh history questionnaire and through a physical examination
by the principal author to assess any instability in the
knees or ankles. A manual physical examination including the Lachman's Test. posterior drawer. varus
and valgus stress to the knee were all perfonned prior
to testing. In addition. ankle joi nt amerior drawer. and
varus/valgus stress testing were also perfonned to rule
out instabil ity at the knee or ankle as a possible cause of
low corrclations during our study. Any participant with
a recem knee or ankle inju!)' (within past 9 months).
past surgical procedure(s) to one or both knees. ligamentous instabi lity. or loss of balance found on examination was e;.;cluded from the study. Participant's balance was assessed via a single leg stance tes!. Thi s test
had to be held fo r a minimum of 30 seconds wuhout
loss of balance for the participant to be included in out
study. No participant demonstrmed a loss of balance.
which would havc excluded them from the study. A
health histol)' questionnaire detertnined if the partie·
ipants ever had an upper extremity inju!)' that would
hinder their ability to reach during the vertical jumping.
No subjects reponed a prior history of upper or lower
extremity injury or surgel)'. All 29 subjects staned and
finished our study. Leg dominance was determined by
asking participants with which leg they would be most
comfortable kicking a ball. Prior to testing each participant received an explanation of the risks. benefit s.
procedures and signed a consent fonn approved by the
university's and medical center"s lnstillllional Rcvicw
Boards.
Participants perionned the tests begin ni ng with a
brief wann-up fo llowed by isokinet ic testing and fi nally the performancc of four funct ional tests. followed
by a brief cool-dowll. The surface on which the functional testing was perfonned was a low-pile carpet
glued m·er a concretc floor. FUllclionaltests were chosen due to their prevalence in the orthopedic and sports
medicine literature. All testing was perfonned in a
non-randomized order beginning with isokinetic tests
firs!. foll owcd by the fUlictional tests. This was done
purposefull y to more closely simulate actllal rehabi litation clinical conditions itt which fu nctional testing is
usually preceded with isokinctic testing. All fun ctional
tests were performed itt a systematic manner beginning
with bilateral leg tests progressing to unilateral leg testing. Functional tests progressed from those with the
least stress applied to the lowcr extremities, c.g .. bilateral venical jump. to those with the most stress appl ied to the lower extrem ities, e.g .. 6-111 timed singleleg hop. Three practicing spons and onhopedic physicaltherapists. all with a minimum of 6 years of cli nical experience. perfonned all testing. All of the testing procedures were perfonned on the sattle day. The
entire (esting session lasted approximately 40 minutes
for each panicipant. Due therapist perfonned all of the
isokinetic tests. while the other 2 lherapists perfonned
the fun ctional tests.
2.2.
/IISrl"lllllelll(ll;Oll
The Lido Linea Closed Kinetic Chain lsokinetic Dynamometer was used to measure strength and power
pcrfomlance during concentric linear isokinetic leg
press testing in both bilateral reciprocal pattern and bilateral coupled p<luern. A bilateral reciprocal repetition
on the Linea is ddined as a compkte leg press stroke
from the fl exed knec position to the extended knee p0sition for each limb in direct succession (each pedal
mo\·ed independent or unlocked). A bilateral coupled
leg press on thc Linea is defined as a complete leg
press stroke from the flexed position to the extended
position with both extremities in unison (pedals moved
'"
R.C MUllsk"
0"
at / Closf'J kinetic' chain (/i" ..ar) iso~i""Iic' IUI;ng: NI"/mio,uiJips WfimCfiQl!(l/ ,('sling
together or locked), The l ido Linea has been shown
be reliable [6]. Measurements of peak force were
recorded for each limb by the system's soft ware. Stat ic
calibration was perfomlt:d per in struction manual and
has been previously described [6].
Panicipants performed a standardized warm-up prior
to each tesling ~e<:<:. i n n . Th.. sl:mdard ized w::mn-up
consisted of fiye mimlles of cardiovascular and musculoskeletal exercise on a stationary bicycle at a selfselected. submaximnl inte ns ity.
Participants were positioned semi rccumbem in the
Linea's leg press chair and stabilized by a lap bell.
Panicipants were placed in the Lido Linea with their
knees fully extended. and with their hi ps in approx i ~
mately 70" of ncx ion. TIlis position was standardized
to ensure that thc length of the trunk. thigh and legs
could not be a c;\Usc of mO\'emelll error during testing .
A li near rangc of mot ion was established so that the
knees mo\'ed from approximately 90 ° of knee flexion
to 5° of flexi on during the complete leg press stroke.
A popliteal pad was placed behind the knees to pre~
"em knee hyperextension. Panici pants were allowed
10 grasp the system 's handgrips duri ng testing.
Prior 10 each test. partic ipants performed an linear
isokinetic waml-up of three gradient. submaximal repetitions plus one maximal repetition at each test velocity. The suhmaximal ,,' ann~up repetitions progressed
from 25-50....75% of"oli tional effon. Panicipants pc r~
formed the bilateral coupled lesl followed by the bilateral rec iprocal leg press test molion .
Testing consisted of a velocit), spectrum of linear
isokinetic leg press exercises performed in the concen~
tric mode at slow (25.4 c m!s). medium (50.8 cmfs),
and fast (76.2 cmfs) velocities. For each test velocity.
six successi,·c maximal "olitional concentric isokinetic
repetitions were pcrfomled. An isokinetic test velocity
o n the Lido Li ne:1 refers to a constant change ill the
linear shaft ovcr time. Strong vcrbal encouragement
was provided in a consistent manner to elici t maximal
effon from the panicipant. Panicipants were provided
visual feedback of the perfomlance. A one~minu te rest
period separatcd testing at each ,·elocit)'. The testing
sequence progressed from slow 10 medium to fast velocities. which is common in clinical isokinetic strength
testing.
At the conclusion of Lido Linea isokinetic testing.
panicipants perfomled light lowerextremilY stretching
at thei r discretion. These stretches generally consisted
of quadriceps :lnd hamstring stretching exercises for
up to 3 minutes. Isokinelic testing preceded functional
tcsting.
\0
Following the wann-up. isokinetic stre ngth tests . and
stretching. each participant perfonned the follow ing
func tional tests: the bilateral venical jump test. singleleg vcrtical jump. 2-leggcd j um p test. single-leg ho p
test. and the timed 6-m single-leg hop test. These tests
wcre chosen for this study due to their ease o f use in a
clinical selling :lnd Ihe ability to perform them in our
clinic. T hree wamH tp trials fo r each f1.lnclional test
were allowed for familiarit), wilh the actions required
and to ensurc competence and understanding wilh instnlctions for thc testing proccdures. Part icipants perfonned 3 attcmpts of each test and were asked to give
maximal effort for each attempt. A one-minute rest
period was allowed betwecn lests. Upper extremity
movement was restricted as much as possible whcn appropriate. At completion of functionaltesli ng. pani c~
ipants perfonned a cool down by riding a stationary
bicycle and or stretching.
2.3. \'erricaf jllmp tesr
Sargent [22] and Semenick [24] prc\'iouslydescribcd
the stand ing venicaljump lest. It is gelleral1y accepted
that using tradilional chalk or tape methods of assessing vcnical jump can generale a large amoum of e r~
ror. so the Venec jump apparatus (Spons Impons. Inc ..
Columbus, Ohio) was used. A standing basel ine reach
measurement was initia\1y perfonl1ed with panicipants
standing fl at foot ed and reaching as high as possible
wit h both the right. then the left upper cxt remity. Par~
ticipants then jumped as high as possible with both
legs. the dominant leg. and with the Ilon-dom inamleg.
Three trials were completed with both legs together and
with each single leg. Participants were asked 10 jump
as high as possible and to reach with Ihe opposite upper
e.~ tre mity to displace a movable plastic vane ofO.5-inch
increments. Counte r movcmcnts with the upper extremities werc utilized during this lest because reaching
is a pan oftile testing procedure. The standing basel ine
reach was subtracted from the total venical j ump score
to obtain the distance jumped.
The 2~ l egged j ump lest and thl! single· leg hop test
were perfonned in a similar fashio n to each other. The
Stand ing Long Jum p Mat (5 BP. Toronto. Canada) composed of a durable rubber material was used fo r mea~
suring j um ps and hops. This mat has a standardized
starting position and is able 10 measure jumps of 50
to 320 cm. Panicipants were asked to stand with the
front of their shoes al the starting maJk . Pall idp;mls
stood with the front of the ir shoes behind the staning
!Hark with hands on hi ps and knees bent. Panic ipants
H_C. .Ilwuk(' ('I al.1 e lM.,,! kill('/ir drain ( lill.'ar) i.·o killl'lic l<'fliIlS: R('lmiollS/,ips
jumped or hopped (2-legged or single-leg hop) as far
horizonlal1 y as possible. landing with belli knee(s) 10
help decrease risk of injury. During perfonnanceofthe
2-kgged jump for dislance the participant jump from
both feet and landed on both feet. During the singleleg hop for distance_ the pan icipant hopped from a single leg and landed on that same leg from which they
hopped off of. TIle spot where the heel of thc more
posterior shoe lnnded was marked and used as jump
distance. To qualify for a legitimate jump. participants
had to land withom fall ing down or taking a step. After
landing. thi s position had to be held for at least 2 seconds. A fa iled jump included loss of balance. touching floor with the contr:tlatcrallowe r extremity (during
single-leg hop). the upper extremities. or an addi tional
hop aft er landing. The distance of 3 maximal attempts
for each test wa.." recorded.
When testing the single-leg hop. panicipnnts hopped
using the non-dominant leg first followcd by the dominant leg . Once again . as with the 2-legged jump test.
panicip:l.I1ts hands were held at the hips to decrease
gaining momentum with the anns. Participams bent
their knees and hopped as far horizontal1y as possible.
this time landing on the same ex tremit y. The distance
from the starting mark to thc heel of the landing leg was
measured. Participants had to land without losing balance and without relying on the other lower extremity
to aid in landing.
Barber ct al. [3} have described the single-leg 6-m
timed hop. The single-leg timed 6-m hop began at
a mark of siandard athletic tape pl aced on the floor.
The single-leg timed 6-m hop was pcrfonned using
large forceful single-leg hopping motions across the
noor. A standard manu.,\ slOpwmeh was used 10 time
each trial to the nearest 11100 second. Three trials
were performed for each lower extremity with the nondominallileg tested first. foll owed by the dominant leg.
IIJ jimcliOlm/I<'5Iiug
175
3. Results
A total of 29 subjects ( 19- 33 years of age) agreed
to complete the research study. All 29 subjects started
and ended the testing procedures. Table 2 shows mean.
standard deviations and ranges of the functional test
scores fo r each variable meas ured.
Data from the bilateral reciprocal concentric isokinet ic pe:Lk force scor;><; <;howerl rel:u ionships 10 singlcleg fuuctional test scores ranging from - 0. 36 to 0.65
(Table 3). Ncgati\'e correlations are due to the two differen t measurement methods. For isokinetic testing.
the relative scores increase numericall y as the person
obtains a higher score. Thus. a greater peak force generat ion will resull in a greater isokinetic score. In pcrfonnan ce of the single-leg 6-m timed hop. the greater
amount of time taken to hop 6-m results in a WONe or
lower score. A subject with a higher or better score is
able 10 perfonn the test in a shoner lime. Therefore. a
negative correlation c.x ists.
With the exception of one comparison. all of Ihe
functional test scores demonstrJ.ted signifi cant correlations (p ~ 0.05) with each linear testing parameter. The
test not showi ng significance was between the singleleg hop and the bilateral rec iprocal mode. dominant leg
at 76.2 cm. per second (p = 0.059). An interpretation
of the coefficients of determination (r2) for these tests
indicates that the single-leg hop tests account for only
15% to 42% of the variation in the isok inetic measures.
Relationships between bilateral coupled concentric
isokinetic peak force scores and double-leg function al
lest scores demonstrated positi"e eorrelmion coefficients ranging from 0. 11 to O.M (Table 4). The scores
for Ihe 2-legged hop tests account for onl y I Sb 10 4 1%
of the variation in the isokinet ic measures.
4. Discussion
2.4. Doro (ll1alys i_f
Mean and standard deviations for isokinetic scores
and scores on functional tests were ca\culmed using
standard statistical procedures. Pearson product moment correlation coeffi cients were Ilsed to detemline the
relationship between the mean scores on the functional
tests and the mean scores of semi recumbent lcg extension peak force (ft-Ib) isokinctic linear strength measurements for the dominant and non-domin:mt limbs.
An alpha le\·el was set at p ~ 0.05. Statistical anal ysis was perfonned using Statistical Pack:lge for Social
Sciences (SPSS. V. 9.0. Chicago. IL).
No study to date has compnred velocit)' spectrum lin·
e·ar concentric isokinetic testing scores with fun ctional
performance tests. The results of this study show low
10 moderate. yet statistically significant relationships.
between strength on a linear concentric isokinetic leg
press and the perfonnance of functional tests such as
the bilateral vertical jump test. single- leg vertical jump.
double-leg jump fo r di stance. single-leg hop test and
the timed 6-meter sing le-leg hop test. ~·lost correlations were significant at the p ~ 0.05. In addition . most
tests demonstrated correlations in the low to moderate
le\·els with r-values ill most cases greater than 0.25 . A
116
R.C. MalISki' <'I 01. / CIOl~" killetie chain (fill"ar) iloki,rel;c /CJting' RelatiQIIships IQ june/imla/te5Iing
~lcan.
Table 2
standard dC\"'al;oll. and ran!;/: of fu nclional tCSt S(Cores
2·kgged j ump B (em)
Single-leg hop DL (e m)
Single-leg hop NOL (em)
Vcnical jump - B (em)
V~ "ic:ol
jump - DL (tnl)
" ('nical jump - NOL (em)
Single-leg limed 6 III bop DL (se<;)
Sin£le-l~8 timed 6 m hop NOL (sec)
B _ Bi]Jlcro]: DL _ Dominant Lower
Lm\ er E.\I",mil)'.
Mean
SD
R ~nge
162. 1
126.5
127.8
26.7
21.6
110.5-224.0
28-2
88. 1- 185...\
86...1-1 88.0
42.7
27-"'
ms
27.2--6--'.8
SA
17.0--44.5
JU
2.1
2. '
10...\
0 .36
17.8-51.7
1.7-2.9
1...\9-3.33
E"t~mj[)';
0.41
NOL _ Non-duminant
Table j
COrrdalion co,:,flicienlS for bilalcml reciprocal concentric isokinctic peak force and single-kg
functionil
SL HD
SLHN
VJD
VJN
STHD
STHN
1<'>1 SCO~'i
BR·DL lO
BR-NDLJO
BR·DL10
BR-;'1DL20
BR·DL30
BR .. NDL30
0 51 "
O·W039'
OAO'
-051-'
-0..18"
0.51 ' ,
0.55- ,
0.380.39 '
-0.48 "
-0.52' ,
OA5 OAs-O.+!' ,
0...\5' ,
- OAS" '
- 0.39-
0.550.650..190.55-0.53"
-0..58"
0.44 '
0..15'
OA7"
OA S'
- 0.-'6 '
- 0.36
0..19 ' .
0.57" .
0.52 ' •
0.5-" 0.50' .
-0.50"
,
.
,
,
Note: •• p < 0.01 len'l (2-t:lited); • p < 0 .05Ie,·el {2· tai led)_
BR-DL 10 = Bilateral reciprocal dominant leg 100/so:"C.
BR-N DL 10 = Bilateral reeiproc:lI non-dnm inant leg 100/sec.
BR-DL20 = Bilateral reciprocal domin:uu I~£ UNsee.
BR-N DUO = Bil ateral reciprocal non-domioant leg 2(J'/~(c_
BR-DUO = Bilateral reciprocal domin:mlleg 30'/5«.
BR-ND UO = Bibteral reciprocal non-domin:mt leg 3(J'lscc.
SLHD = SinEI~-I(£ hop for dist:lnce domin:mt les.
SLiI N = Sin~le·I(1! hop for distance noo·dominam le~ .
VJD = Venieal jump unilJter.1l domin aOl leg.
VJN = Venical jump unilateral non-dominant leg.
STH D :: Singl~- kJ! limed Gill hop domin:mt lel!.
SHI N = Sinf!e-Ieg timed 6m hop nnn-dominant leg.
correl:lIion coeffi ciem of 0.90 to 1.00 is inlerpreled as
a \'ery high correlation. a 0.70 to 0.89 is imcrpreted as
a high correlation. 0.50 10 0.69 is considered a moderate correlation. while 0.26 10 0.49 is considered a low
corrchllion [IOj .
Negrete and Brophy (1 81 found significant correlations between functional test scores and linear concentric isokinetic test scorcs. The si ngle-leg hop and the
bilateral reciprocal leg press mOlion were correlated
at 0.73. while the isokinetic single-leg squat and the
single-leg hop were co rrelated at 0. 73 . with each signifka m at the p < 0.00 1 leveL The corrcl:ttion between
the single-leg \·enical jump and the bil:lIeral leg press
was O.5S. while with the isokinetic single-leg squat correlated at 0.57. again. both signifi cant at the p < 0.001
level.
One potential difference between resullS of Negrete
nnd Brophy [ 18J and those of the present study i_~ the
position that panici pants were placed in the isokinetic
machine. The present study lIsed a semi recumbent
posit ion. similar to that used by Davies and Heiderscheit [6] during their study 10 determi ne reliabililY of
the Lido Linea_ The Negrete and Brophy [ ISJ study
used a true supine posilion. Theoretically Ihis supine
position could h:J.\-e altered the biomechanics of the hip
and knee and ankle enough 10 more truly simulate fu nctional testing. The full supine position would place the
hip and knee eXlensors in better length-tension relationships to allow g reater torque production. TIle present
study, with subjects placed in a semi recumbent position. may not have allowed full torque produclion of
the hip and knee extensor muscles or the ankle planlar
fl exor muscles. This could have slightly reduced the
coefficicnls seen in thi s siudy.
The low to moderate correlations fou nd in this and
the slluJy loy NC~ JC: t ~ alii.! Brophy [ 18J could have im-
R.C. Mmlskl/'
t'r
al.1 C/Qud kiM/ic chain (Iinf'lIr) imki/If/ic ff'f1ing: Hf!miolfsllips 10 illlfcliorral /f's/inS
In
T:lble J
CO/Telation coefficients for bil:J.ter.J1cou pled cuncent ric isokinetic peak force and two- legged
function:J.i test scores
TU
VJB
BC-DLI O
BC-NDLI O
0. 1]
0.1 6
0.-16 '
OA 7
BC-DUO
BC-NDL20
BC 030
BC-I'. .'DUO
038 '
0.-18 - -
0.59- •
0 .-13"
0.59' -
O.(H--
0.53' .
0.61--
Note: • • p < 0.0 1 Ie>-d (2·tailed): • p < 0.05 ]e,·(1 ( 2-t:ll!cd).
BC-DlI O = Bi13ter.l1 coupled dominant leg lli'ls.:c.
BC-N DLIO = Bilateral coupled non·dominant leg 10'/,<'C.
Be DL20 ~ Bi] .. t~ rul coupled d(m,in~nt leg 20' 1.",:.
BC-NDUO = Billte",1 coupled non-dominant le£ 2fI'/scc .
BC· DUO = Bilateral coupled domin:uu leg 3fJ'/s«.
BC-N DUO = Bilateral coupled non·dominant leg 3(}'/~
TIJ = Two-legged jump for di stance.
V1 B = Venical jump bilJtcral.
ponant clin ical appl ic3lions. Although generalizalions
to a injured population are d ifficult to make from our
sludy of normal panicipanls. we feel Ihat the present
stud y demonstrates that one single test whelher it be
an isokinetic test or a func tional test. may not be sufficient 10 emirely de tennine a panic ipams slTength and
ultimate functional level or safe ability 10 participate in
sporting activilies. A lthough test ing was done in a linear fashion . low to moderate correlations suggest that
the Lido Linea still does 110110tally e mulate a fun clional
[cst. llle linear motion of Ihe Lido Linea funclions at
a preset \-clocir)' with a constrained range of motion
during knee extension and flexion . Therefore. \·ams.
valgus. and rotary forces at the hip. knee and ankle are
non-existent. This is in direct contrast to a fu nclional
test in which the participant nas to deal with gravilY.
balance. proprioception. kinesthesia. vams. \'algus and
rotary fo rces at the knee. hip. and an kle. In addition.
velocity. range of motion. and eccentric deceleration
forces are nOllim ited by functional testing. Therefore.
even though each method i.e .. isokinetic and fun ctional.
is perfonned 1ft a closed chain manner, thc), are quile
differenl . The low to moderate correlalions between
Ihc functional tests and linear isokinetic tesling may
suggesl thai these functional tests may be influenced
by other factors such as tmnk strength. upper extrcmilY
strength. balance and proprioception. Therefore. we
fee l thai linear isokinclic testing should be utilized 10
detennine on ly Ihe s[rength or muscle perfonnance of
the enlire lower extremity chain. During linear [esting
it musl be emphasized thai a decrease in strength of any
single join t along the kinet ic c hain may becompensaled
for by another joint in that chain_ For inslance. weakness of the quadriceps muscle may be hidden in the
linear isokinetic test if the panicipants' hip and ankle
eXlensors nave increased in sirength as a compens:lIory
pallern . For testing muscular strength of a single joint.
an angular method of isokinelic tcsling would be most
appropriate. Furthennore. funct ional testing should be
used 10 assess true --funClion·· of Ihe lower extremity.
Again it must be stressed lhal ··function·· does not always correlate strongl y wilh ··slrength--. Our recommcndalion is [0 utilize both fornls of isokinetic testing
if avai lable. Linear isokinet ic res[ing wi ll giye the clin idan tme object iye measures of the cumulative s[rcngth
of the entire kinetic chain musculat ure. while angular
isokinetic testing can assess m uscular slrcnglh at each
ind ividualjoinl. If Ihe participant being tesling demonstrates fa\-orablc scores on linear isokinetic (eSls. functionaltesting could be [he nexi progression. Functional
testing can also gi,'e objecth-e measures regarding ones
physical perfonnance le,·el.
Correlat ions between linear isokinel ic lesling wiln
the non-dominan! leg and functional testing are higher
than correlations using scorcs from the dom inant leg.
This smdy used the standard lechnique ofUlilizing the
leg [hat olle would use to kick a ball to delennine dominance. The finding that the non-dominant leg demonslr:lIed higher correlalions between lincar isokinelic
strenglh scores and funclional test scores than the dominanlleg may be imponanllo the field of rehabilitation
and physical therapy. Should dominance bcdetennined
with respect 10 which mode of strength tesling is ulitiled? The s[andard method of detennining dominance
by having the participants kick a ball may be very appropriate for angular lesling. since kicking a ball is an
open chain :lctivit}'. BUlthe present sludy used a linear
isokinetic lesting apparalus. and functional testi ng is a
closcd chai n activily. When using the standard rne[hod
or de termining dominance. lhe non-dominant leg is the
leg most used in a closed kinetic chain fas hion during
kicking a b:lll . This could explain why. when [esting
in a linear manner. lhe scores o n Ihe non-dominant.
i.e .. closcd chain leg. dcmonstrated higher correlations
mentioned above.
118
R.C. Mallsk"
1!1
uL I Claud tinnic chain ( linear) isoki/ln;r tellilrg: H.-Im/onships If} f lllletiunal f('Sling
5. Conclusions
The single-leg and 2-1egged fun ctional tests used in
the prc'>cnl sfUdy are both clinical tests thai provide
quaiilati\'c and quam ilal ivc d;lIa regarding the physical
fUllction of the knee. Furthermore. each of these tests
can be perfonned easily in a clinical sc ttim~ withoU!
expensive isokinetic le~li ng devices such as~lhe Lido
Linea. Despite this, the present study showed Ihat
1101
111 1
[12[
[13[
the correl :lIions between these tests and closed kinetic
chain isokinetic test scores are in the low to moderate
ronge. Neither functional testing nor isokinetic tests
should be used in isolation when 3ncmpling 10 determine bmh muscle perfo nnancc and physical function
o f the knee and lower extre mity.
1]-11
[151
n,..,
Acknowledgments
The authors gratefully than M ark Needham. Julie
Oler-i\'lanske. and Kim Yearout for their assistance during Ihis projec t.
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