Grand Valley State University
ScholarWorks@GVSU
Masters Theses
Graduate Research and Creative Practice
1997
Strength and Neuromuscular Characteristics of
Female and Male High School Basketball Players
Diane M. Beach
Grand Valley State University
Barbara J. Hoogenboom
Grand Valley State University
Lisa M. Rose
Grand Valley State University
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Beach, Diane M.; Hoogenboom, Barbara J.; and Rose, Lisa M., "Strength and Neuromuscular Characteristics of Female and Male High
School Basketball Players" (1997). Masters Theses. 325.
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strength and Neuromuscular Characteristics
of Female and Male High School Basketball Players
By
Diane M. Beach
Barbara J. H oogenboom
Lisa M. R ose
THESIS
Subm itted to th e D epartm ent of Physical Therapy and the Departm ent of Health
S cien ces a t G rand Valley S ta te University
Allendale, Michigan
in partial fulfillment of th e requirem ents for the deg ree of
Master of Science in Physical Therapy or
Master of Health Science
1997
Thesis Committee Approval:
i-2z - f 7
CXaM Jolene Bennett M S., P.T., OCS, A.T.,0
Date
Member Susan Allaben M.S.A., P.T.
Date
riSki M.S., OTR
Date
"—
strength and Neuromuscular Characteristics
of Female and Male High School Basketball Players
ABSTRACT
T he p u rp o se of this study w as to Identify possible differences In strength
ratios and neurom uscular perform ance betw een high school fem ale and male
basketball players, a s te sted by concentric Isokinetic testing using the Blodex®
Isokinetic sy stem . W e recruited high school basketball players, fem ales (N=26)
and m ales (N=27). All participants underw ent Isokinetic concentric testing of
bilateral ham strings an d quadriceps a t five s p e e d s (60, 180, 240, 300, 450
d e g re e s p er seco n d ). Fem ale subjects dem onstrated lower
ham strlng/quadrlceps ratios than m ales at 60 and 240 d e g re e s per second.
Com pared with m ale subjects, the fem ale subjects took significantly longer to
g en era te maximum ham string muscle torque during Isokinetic testing at all
s p e e d s ex cep t 450 d e g re e s per second. The results of this study suggest that
there are differences betw een ham strlng/quadrlceps ratios and time to peak
torque of th e ham strings by gender. The variable of strength should continue to
be Investigated In relationship to Injuries of th e ACL In th e fem ale athlete.
ACKNOWLEDGMENT
W e would like to thank S ain t Mary's Hospital and Rehabilitation
Professionals LLC of Grand R apids Michigan for the u se of their facility and
equipm ent. W e would also like to th an k th e Sports Physical T herapy Section of
th e American Physical Therapy A ssociation for grant support. A very special
thank you to Jolene Bennett, our chair, for her continued guidance an d statistical
expertise. Thank you also com m ittee m em bers S usan Allaben and Cynthia
Grapczynski for their feed b ack an d corrections.
Thank you to sp o u se s, family an d friends for their im m easurable support
and patience throughout our educational joumey. Thank you to S u sa n Naum for
original artwork included in text.
TABLE OF CONTENTS
Page
ABSTRACT................................................................................................................................i
ACKNOWLEDGMENT........................................................................................................... ii
LIST OF TABLES....................................................................................................................v
LIST OF FIGURES................................................................................................................ v
LIST OF GRAPHS.................................................................................................................. v
LIST OF APPEN D ICES........................................................................................................vi
DEFINITION OF TERM S.................................................................................................... vii
CHAPTER
1. INTRODUCTION..................................................................................................1
2. LITERATURE REVIEW......................................................................................4
Historical P erspective.................................................................................. 4
Factors th a t Contribute to ACL Injury......................................................5
A. Intrinsic F actors..........................................................................6
1. Ligament (joint) laxity................................................... 6
2. Limb Alignment.............................................................. 7
3. Notch Dim ensions (W idth/Shape)............................. 8
B. Extrinsic F actors......................................................................... 9
1. Motor Skill in Sport...................................................... 10
2. S h o e S urface Interface..............................................11
3. M uscular S trength....................................................... 11
4. Conditioning.................................................................. 13
M echanism s and ACL Injuries in Children........................................... 14
Isokinetics......................................................................................................14
A. Isokinetics- norm ative d ata for
ham string/quadriceps ratio.............................................. 16
B. Isokinetic testing .......................................................................16
1. P eak torque................................................................... 16
2. Time to peak to rq u e....................................................17
3. Testing s p e e d s ............................................................. 17
4. Stabilization................................................................... 18
5. W arm-up and rest intervals...................................... 18
6. Gravity correction........................................................ 19
Page
7. T e st repetitions.............................................................19
8. P atient testing position...............................................19
3. METHODS AND MATERIALS...................................................................... 21
S u b jects.........................................................................................................21
M aterials........................................................................................................21
P ro c ed u res................................................................................................... 22
D ata A nalysis............................................................................................... 23
4.
RESU LTS.................................................................................. 25
5.
DISCUSSION AND IMPLICATIONS......................................................... 30
C om parison to Previous S tu d ies............................................................30
A. C om parison to normative d ata for
ham string/quadriceps ratios........................................... 30
B. T rends in ham string/quadriceps ratios............................... 31
C. Specificity of sam p le............................................................... 32
D. T rends in time to p eak torque...............................................33
E. G en d er differences in time to p eak torque........................ 33
F. G en d er differences in ham string/quadriceps ratios
33
Limitations and R ecom m endations for Further Study......................34
C onclusio.................................................................................................... 36
REFER EN C ES........................................................................................................38
APPENDICES
A. C ontact Letter.......................................................................................43
B. P re-test Q uestionnaire....................................................................... 44
C. A ccep tan ce Criteria............................................................................ 45
D. C o n sen t Form ..................................................................................... 46
E. P a re n t Information Letter...................................................................48
F. Instruction for Isokinetic T esting...................................................... 49
G. H am string/quadriceps ratio a s p er Davies (1992)...................... 51
H. H am string/quadriceps ratio a s p er W yatt and Edwards,
(1981)............................................................................................... 52
I. Normative Isokinetic Data for Ham string/quadriceps ratios,
Moore an d W ade, (1989)............................................................ 53
IV
LIST OF TABLES
Page
4.1
D em ographic Sum m ary..............................................................................................25
4.2
Isokinetic D ata for H am string/quadriceps Ratio................................................... 27
4.3
Isokinetic D ata for Hamstring Tim es to P eak Torque..........................................28
4.4 Values for Mann-Whitney-U te st for H am string/quadriceps R atios
Isokinetic D ata......................................................................................................... 29
4.5 Values for T -tests for Independent sam p le for Time to P eak T orque
Isokinetic D ata...........................................................................................................29
LIST OF FIGURES
Page
2.1
Radiographic M easurem ent of NWI=A/B................................................................9
2.2
Classification of Notch S h a p e ..................................................................................10
LIST OF GRAPHS
P age
4.1
Distribution of Team Classification by G ender....................................................26
4.2
Distribution of School C lass by G en d er.................................................................26
LIST OF APPENDICES
Appendix
Page
A. Contact Letter.................................................................................................................43
B. Pre-test Q uestionnaire.................................................................................................4 4
C. A cceptance Criteria.......................................................................................................45
D. C onsent Form ................................................................................................................. 46
E. P arent Information Letter............................................................................................. 48
F. instruction for Isokinetic Testing................................................................................ 49
G. H am string/quadriceps ratios as per Davies, (1992).......................................... 51
H. Ham string/quadriceps ratios a s p er W yatt and Edw ards, (1981).....................52
I. Normative Isokinetic D ata for H am string/quadriceps ratios, Moore and
W ade, (1989)........................................................................................................... 53
VI
DEFINITION OF TERMS
ACL- anterior cruciate ligam ent
Blodex® S y ste m 2- a com pany nam e for an isokinetic system
C o n cen tric- a m uscle contraction resulting in shortening of th e m uscle
E c cen tric- a m uscle contraction resulting in lengthening of th e m uscle
H am strin g /Q u a d ric e p s ratio - a m athem atical calculation of ham string strength
divided by quadriceps strength, utilizing peak torque m easu rem en t
H ealthy- no m usculoskeletal injury to a foot, knee, hip, or back th at required
medical treatm ent or th a t kept the athlete out of practice for m ore than o n e w eek,
within the p a st one y ear
iso k in etic S y ste m - a p ie ce of equipm ent designed to m easu re strength. It
consists of a fixed s p e e d of m ovem ent with an accom m odating resistan ce
M edical T reatm en t- involved a visit to s e e a doctor
P e a k T orque- the single highest torque, m easured in foot pounds, produced by
a m uscle group through a range of motion
Tim e to p e a k to rq u e - th e am ount of time, m easured in milliseconds, it ta k e s the
m uscle to produce its p e a k torque during isokinetic testing
T orque- the m ovem ent of forces th at c a u s e s rotation or twisting
VII
CHAPTER 1
INTRODUCTION
W om en's participation in sports has in creased in recent years. With this
increase in participation, th e incidence of injuries to wom en h a s com e u n d er
review (H uston & Wojtys, 1996; Arendt & Dick, 1995; Hutchinson & Ireland,
1995; Ciullo,1993; Souryal & Freem an, 1993; Moore, & W ade 1989; D eH aven &
Lintner, 1986; Zelisko, Noble, & Porter, 1982; Clarke & Buckley, 1980;
W hiteside, 1980; Garrick & R equa,1978; Haycock & Gillette, 1976). At th e top of
the list is th e problem of injuries to th e anterior cruciate ligam ent (ACL). In
addition to th e athlete's physical pain, mental pain, and inability to participate in
her sport, so m e require surgery and extensive rehabilitation.
R ese arc h ers have noted an increased incidence of ACL injuries to fem ale
basketball players w hen com pared to m ale basketball players. This ratio h a s
b een reported to be a s high a s 8:1 (Malone, & S a n d ers, 1993) in the college
level fem ale basketball player. With th e growing num ber of fem ales participating
in athletics a t all levels, and the increasing o ccurrence of ACL injuries, research
into the c a u s e s is essential so preventative m e a su re s can b e em ployed. T he
fem ale ath letes' injury to th e ACL occurs primarily without contact (i.e. while
decelerating, landing from a jump, cutting, or k n ee hyperextension) and
secondarily with physical contact. Male athletes primarily injure their ACL's
through co n tact and secondarily without contact (Arendt & Dick, 1995; McBride,
M eade, & Ryan, 1993). Injuries in children and ad o le sc e n c e a re not a s prevalent
a s they a re in adults, but th e m echanism of injury, hyperextension involving a
twist, rem ains the sa m e for children and adults (L astihenos & Nicholas, 1996).
Many theories have been p resented a s to th e c a u s e s of ACL injuries in
fem ales, Including:
(1) in crease in Q-angle
(2) d e c re a se d size of the intercondylar notch
(3) w ider pelvis in fem ales than m ales
(4) d e c re a se d overall strength
(5) increased joint laxity
(6) interplay betw een fem ale horm ones and joint laxity
(7) altered neurom uscular perform ance
(8) sh o e surface interface
(9) in creased quickness of th e gam e a s imposed by a 30 seco n d shot
clock for wom en college basketball players vs. a 45 second sh o t for m ales
(10) inad eq u ate conditioning
Inadequate conditioning may be a primary factor contributing to the higher
injury rate in fem ale basketball players (Moore & W ad e,1989). Clinically, w e the
authors, have observed th at ath letes with a torn ACL have w eak ham strings in
relationship to th e quadriceps on th e uninjured leg, which may indicate that th e
injured leg may also have had a w eak n ess or m uscular im balance prior to th e
injury. Q uadriceps strength is n eed ed to allow the athlete to stay in th e bent
knee position while cutting and stopping. Hamstring strength is n ecessary to
a ssist in stabilizing the knee (Moore & W ade, 1989). Hamstring and quadriceps
peak torque are often com pared in th e form of a ratio. "Several authors have
su g g ested that screening of athletes to exam ine th ese ratios m ay identify
athletes who m ay b e at risk for injury due to their ratios being below th e se
reported norms" (Fleck & Falkel, 1986, p.66).
A problem exists in th e lack of normative strength and neurom uscular
d ata on the fem ale high school basketball player. It w as th e intent of this study
to determ ine if high school fem ale basketball players:
(a) have a d ec rea se d concentric ham string/quadriceps ratio, a s com pared
to high school male basketball players,
(b) have a d e crease d time to peak torque of th e ham strings a s com pared
to high school male basketball players.
T he authors hypothesized th at a difference existed in strength a s
m easu red by isokinetic concentric ham string/quadriceps ratio a t five different
sp e e d s w hen com pared betw een high school fem ale basketball players and high
school m ale basketball players. A seco n d hypothesis w as th a t differences
betw een g en d ers would also exist for hamstring time to p eak torque data, a
m easu re of neurom uscular perform ance, at five isokinetic s p e e d s .
T he study w as significant b e c a u s e it provided objective d a ta regarding
possible strength deficits, and d e c re a se d neurom uscular perform ance (as
m easured in time to p eak torque) in fem ale high school basketball players a s
com pared to m ale high school basketball players. This information will benefit
clinicians, co ach es, and athletes in th e planning of their strength program s.
gHAPIER.2
LITERATURE REVIEW
Hlgtprlgal Perspective
American fem ales had limited opportunities in athletics prior to World W ar
II. During th at time and in the post w ar era, girls participated in Girl's Athletic
A ssociations (GAA) in local high schools. T he GAA w as essentially an intramural
program . F em ales experienced their first m ajor break through in organized
sports participation in 1972 a s the result of th e p a s s a g e of Title IX of the
Educational Am endm ent. The project on th e S ta tu s and Education of W omen
states, "Sex discrimination is prohibited in any education program or activity
receiving Federal financial assistance" (as sta te d in Lutter, 1993, p.2). This
am en d m en t forced the general public to re-exam ine the role of fem ales in
society. Athletic achievem ent encouraged self-confidence, leadership, and
physical strength (Lutter, 1993). T h e se attributes w ere not considered a part of
a fem ale's traditional social role. A C onnecticut judge, in 1971, com m ented in
the project on the S tatus and Education of W om en,
"The p resen t generation of our younger m ale population h a s not becom e
so d e ca d en t that boys will experience a thrill in defeating girls in running
contests, w hether the girls be m em bers of their own team or an adversary
team ...A thletic competition builds c h aracter in our boys. W e do not need
th at kind of character in our girls, th e w om en of tomorrow" (as in Lutter,
1993, p.3).
T he Title IX Am endm ent h as unofficially b e e n identified a s th e starting
point for fem ale athletics. As with any new opportunity, "growing pains" are
experienced. Increased sports participation for fem ales instantly had
psychological, social, physical, and financial implication in the United S tates
(Lutter, 1993). "Problem s exist in th ree areas; social, competition, and illness
and injury" (Ireland, 1993). As participation in fem ale sp o rts in creases so have
the injuries.
"W hat problem s do fem ale athletes encounter? Lack of recognition and
support are th e m o st significant problems. This m e a n s less ink, less air
time, less a p p la u se , less fame and adulation. At th e professional level of
com petition, w o m en receive much less money. T h e fem ale athlete is
continually fa c e d with certain 'lacks' at m any levels. This includes lack of
e n c o u rag e m e n t to com pete, lack of family, peer, a n d financial support,
lack of recognition by fans and journalists, and lack of social acceptance"
(Ireland, p. 11).
R e se arc h ers b e g a n documenting injury rates in high school (Garrick &
Requa, 1978) girl's sp o rts an d college women sports a s early a s 1973 (Gillette,
1975). Gillette's 1975 d a ta show ed that college w om en h ad th e g re a te st am ount
of injuries in th e ankle an d k n ees followed by contusions, low back injuries, and
muscle pulls and strain s. T h e m ost common w om en's sp o rts producing injuries
were basketball, volleyball, field hockey, gym nastics, and track and field. As
injury d a ta h a s b e en g ath e re d on fem ales and m ales in sports, it h as shown
sport injuries to b e sp o rt specific, not g en d er specific (Ciullo,1993; Ireland, 1993;
Albohm, 1976). F e m a le s tend to have a g reater frequency of injuries but not
different types of injuries (Garrick & Requa, 1978; Albohm, 1976). However,
there is d ata th at s u g g e s ts th at fem ales have a g reater proportion of knee
disorders th at involve th e patellofemoral joint and ACL (Ireland, 1993).
Factnrs that Contribute to ACL Injury
R e se arc h ers h a v e su g g ested that there may be multiple factors that
contribute to ACL injuries in th e fem ale athlete. T h e se m ech an ism s of injury
have b een divided into categ o ries of intrinsic and extrinsic factors (Arendt & Dick,
1995; H utchinson & Ireland, 1995). Som e intrinsic factors h av e included: joint
laxity, limb alignm ent, notch dimension, and ligament size. Extrinsic factors have
included: body m ovem ent in sport, skill level, sh o e interface, and m uscular
strength (Arendt & Dick, 1995). Additional authors have added several oth er
possible physiological differences betw een m en and women including
endurance, m uscle recruitm ent order, and m uscle reaction time a s possible
causative factors (Huston & Wojtys, 1996).
A. Intrinsic Factors
1. Ligament Goint) Laxity
Fem ale athletes h av e le ss ligam ent laxity w hen com pared with non­
athlete fem ales (Jones, 1980). In 1985, Beck and Wildermuth and in 1995
Arendt and Dick su g g ested th a t this can be a function of conditioning or
genetics. R esults vary from study to study regarding knee laxity and injury.
Nicholas (1970) su g g ested th e re is an increase in knee ligament injury with
loose-jointed athletes (m ale o r fem ale). "G reater knee joint laxity and su b talar
pronation may be asso ciated with an increased risk of ACL injury." (WoodfordRogers, Cyphert, & D enegar, 1994, p. 345). O ther studies show ed no
correlation (G rana & Moretz, 1978). In their 1996 study, Huston and Wojtys
found knees of athletic fem ales to have g reater laxity than m ales with
statistically significant higher anterior translation of the tibia on th e femur.
However, in the sa m e study, both control groups (male and fem ale non-athletes)
had increased laxity a s com pared to their g en d er m atched elite athletes.
Nicholas (1970) studied 139 professional football players to determ ine
w hether there w as a relationship to knee joint laxity and stability in football
players relative to injury. His results were: 37 athletes out of 139 sustained
knee ligament rupture requiring surgery. Seventy-tw o percent of athletes th a t
had at least three indices of lo o se n e ss sustained ligament rupture.
G rana and Moretz (1978) tried to m ake a correlation betw een ligam ent
laxity and the occurrence or ty p e of injury. Their subjects w ere all m em bers of
varsity football and boys an d girls varsity basketball with a m ean a g e of 15.9
years. The testing included upper extremity rotation, lower extremity rotation,
palm s to th e floor, g en u recurvatum and th e lotus position. The testing occurred
over two s e a s o n s and included a control group of 167 boys and 223 girls, not
involved in interscholastic athletic competition. The results were: th e girl's
control group had more laxity than the boy's control group, there w as no
significant difference in th e m ale basketball players and football players when
com pared to the control group;
"...female athletes w ere dem onstrated to have looser joints than th e boys,
but they had tighter joints than girls not participating in sports
(P<.01). Fem ale basketball players sustaining sprains had significantly
looser joints than the fem ale athletes a s a group (P<.05), but th ere was
no significant difference in their laxity w hen com pared with th a t of the
non-participating girls" (G rana & Moretz, 1978, p. 1976).
The effects of cyclical horm ones in fem ales and their relationship to
ligam ent laxity h as b een being investigated (Liu, Ali-Shaikh, P anossian,
Finerman, & Lane, 1996) in basic science experim entation. In rabbit ACL
fibroblast (in culture), the p rese n c e of estrogen inhibited collagen synthesis and
proliferation of fibroblasts, in vitro. Clinically, th e se cellular and matrix alterations
m ay translate into a w eak er ACL during its constant exp o su re to changing
hormonal patterns. Further studies in vitro and in vivo a re needed to confirm the
significance of estrogen-collagen interaction a s a possible explanation for
ligam ent laxity, contributing to higher ACL injuries in fem ale athletes (Liu e t al.,
1996).
2. Limb Alignment
Fem ales have a variety of alignm ent and body composition issu e s that are
in direct contrast to m ost m ales. Fem ales have a wider pelvis, less m uscular
developm ent, increased flexibility, knee hyperextension, genu valgum, femoral
8
neck antéversion with a varus hip, external tibia! tubercle rotation, and pronation
of th e hind foot (Ciullo, 1993). Typically, limb alignm ent in fem ales includes an
increased Q -an g le-th e angle from th e anterior, superior iliac spine and the
patellar line to the tibial tubercle. T he Q -angle is reported to be an av erag e of
eight to ten deg rees for m ales and 12 to 16 d e g re e s for fem ales (Klafs & Lyon,
1978). Increased Q-angle c a u s e s (greater) lateral forces to be placed on the
quadriceps m echanism, (Hutchinson & Ireland, 1995) and excessive rotary limb
alignm ent (W oodford-Rogers e t al., 1994), which m ay correlate with increased
patellofemoral disorders, and altered m uscular dem ands. It has been su g g ested
that internal rotation of the tibia with a knee hyperextension and hyperpronation,
m ay predispose an athlete to an ACL injury (W oodford-Rogers e t al., 1994;
Moore & W ade 1989). "B ecause of th e anatom ical functions of the ACL,
prolonged pronation of th e foot and ankle com plex produces excessive internal
tibial rotation, and thus my produce a preloading effect on the ACL," (Beckett,
M assie, Bowers & Stoll, 1992, p. 60).
3. Notch Dimensions (Width/Shape)
T he ACL p a s se s betw een th e medial and lateral condyles of the femur,
a s it co n n ects the tibia to the femur. T he "tunnel" through which it p a s s e s is
called th e intercondylar notch. Notch width is a m easurem ent in millimeters
using an anterior view radiograph. A m easu rem en t of th e width of the
intercondylar notch related to total width of th e distal fem ur is referred to a s th e
notch width index (NWI), (Souryal, Moore, & Evans, 1988). R esearchers have
defined intercondylar notch sten o sis a s defined by a NWI equal to .20 or less in
m ales and .18 or less in fem ales a s a possible c a u s e for ACL rupture (Arendt &
Dick, 1995; Souryal & Freem an, 1993).
Figure 2.1 Radiographic Measurement of NWI = A/B
In 1993, Souryal and Freem an exam ined 902 fem ale and male athletes
from all sports In two high schools in Mesquite, T exas. T he authors m easured
thigh girth, height, and weight. A complete knee exam ination w as also
performed including th e Lachm an test, the pivot shift te st, varus-valgus stressing
at zero d e g re e s and 30 d e g re e s, and a reverse Lachm an test, and NWI w as
m easured radiographically a s described above. The au th o rs purpose w as to
determ ine if th ere w as an association betw een ACL injuries in athletes and NWI.
The results were:
(1) intercondylar NWI for men w as larger than th a t for wom en,
(2) ath letes [male and femal] sustaining non-contact ACL tears had
statistically significant intercondylar notch sten o sis,
(3) all w om en with non-contact ACL injuries had statistically significant
stenotic intercondylar notches,
(4) th o se ath letes who sustained contact Injuries had NWI
m easu rem en ts similar to the general population of athletes.
10
T he sh a p e of th e notch w as also exam ined and classified in three
categories:
1. Reverse U or
side Cishaped
ZU drshaped
3.i-A-sJiaped
Figure 2.2 Classifications of Notch Shape
Previous authors have also speculated that th e sh a p e of the notch m ay vary with
g en d er and contribute to injury. T he A -shaped notch may be a sign of a
congenitally sm aller ACL, placing th e fem ale ath lete at risk for a non-contact
ACL injury (Hutchinson & Ireland, 1995).
B. Extrinsic Factors
1. Motor Skill in Sport
Motor skill and skill level in sp o rt affect th e athlete's ability to perform.
Motor skills n e cessary for basketball include planting, starting and stopping,
cutting an d turning, and landing from a jump (deceleration). In a ten y ear study
of Division I fem ale basketball players, Griffis, Vequist, & Yearout (1989)
reported th ree major "no-hit" m echanism s of ACL injury; planting and cutting
(29%), straight knee landing (28%), o n e-step sto p landing with the knee
hyperextended (26%). All of th ese a re learned m otor skills which m ay be
prevalent in the fem ale basketball player.
Current research h as also b een conducted on possible neurom uscular
c a u s e s of alterations in motor perform ance. P ossible physiological
11
neurom uscular differences betw een fem ales and m ales w ere explored by Huston
and Wojtys (1996), Including m uscle recruitment order and m uscle reaction time.
The authors com pared elite fem ale athletes, elite m ale athletes, and non-athlete
g en d er m atched controls with isokinetic concentric testing. T h e authors found
time to peak to rq u e differences (p<0.001) in average knee flexion time to torque
at 60 and 240 d e g re e s per seco n d in fem ale and m ale ath letes. F em ales w ere
slow er th an th e m ales. They also found an altered pattern of m uscle recruitm ent
in re sp o n se to involuntary anterior tibial translation in fem ale ath letes a s
com pared to m ale athletes and controls. Fem ale athletes u sed th e order:
quadriceps-> ham strings-> gastrocnem ius.
Male ath letes an d controls u sed th e order:
ham strings->quadriceps-> gastrocnem ius.
In their article, Huston and Wojtys (1996) describe the fem ale order a s a
"quadriceps first" (p. 7) trend, which is exactly opposite of m ales and controls.
The authors indicated that training of fem ale athletes m ust b e critically reviewed
(Huston and W ohtys, 1996).
2. Shoe Surface Interface
Interface betw een the players sh o e and the playing su rface h a s been
su g g ested to h av e an effect on th e incidence of ACL injuries. A higher friction
rate of the sh o e surface interface m ay correlate with a higher incidence of ACL
injury (Arendt & Dick, 1995).
3. Muscular Strength
Dynamic stability of joints is accom plished with m uscle contraction
(Baratta, Solomonow, Ahou, Letson, Chuinard, & A'Mbrosia, 1988). W eakness
of the leg m uscles h as been investigated a s a possible c a u s e of ACL injury
(Arendt & Dick, 1995; Moore & W ade 1989). The "balance of power" betw een
quadriceps and hamstring m uscles is crucial to normal k nee function b e c a u se
12
the quadriceps m uscles can produce forces in e x cess of th o se need ed for
ligam ent rupture of th e ACL (Huston, 1996). T he role of th e hamstring m uscles
for joint stability m ay also b e key in prevention of ACL injuries by:
(1) Anatomical position within the k nee allowing dynamic m uscular
support to excessive anterior translation of tibia on the femur (B ackhouse
& Hutchings, 1986)
(2) Co-contraction/activation of ham strings with th e quadriceps resulting
in increased joint congruency (Baratta e t al., 1988)
(3) Forming thick medial and lateral m a ss e s to th e knee and giving
vital collateral support to th e k nee joint, while in flexion each
com ponent can give medial and lateral rotation or, rotary
stability (B ackhouse & Hutchings, 1986)
Previous studies have su g g ested th a t ham string/quadriceps strength ratios to b e
less in fem ale athletes than in m ale ath letes (Moore & W ade, 1989; Holmes &
Alderink, 1984; Dibrezzo, G ench, Hinson, & King, 1985). A study (Baratta e t al.,
1988) on th e role of antagonistic m usculature in maintaining knee stability w as
do n e using sim ultaneous EMG recordings from flexor and extensor m uscles of
the knee during maximal effort slow isokinetic contractions. This w as d o n e to
quantify th e coactivation pattern of k n ee flexor and ex ten so r m uscles. In
reviewing the study, it should be taken into consideration that the sam ple size of
th e su bjects and control group w ere small, g en d er mixed and included ath letes
from a variety of sports. T he control group included non-athletes. This control
group "dem onstrated that th e an tagonist exerts nearly constant opposing to rq u e
throughout joint range of motion" (Baratta e t al., 1988, p. 113). The ath letes who
routinely exercise their ham strings had results similar to th e control group.
A thletes with hypertrophied quadriceps "dem onstrated strong inhibitory effects
on th e ham strings coactivations" (B aratta e t al., 1988, p. 113). The authors
concluded that coactivation of antagonistic m uscles is n ecessary to aid
13
ligam ents in maintaining joint stability (B aratta e t al., 1988). Optimal
ham strlng/quadrlceps ratios w ere s u g g e ste d by Moore and W ade in their 1989
article. They suggested achieving th e ratios would assist in prevention of ACL
injuries. If an optimal ratio exists, a m uscle re-balancing conditioning program
for the lower extremity ap p ears to b e a rational first step for fem ale athletes
playing high risk sports (Huston & W ojtys, 1996).
4. Conditioning
Poor conditioning is related to an increased incidence of injury
(Hutchinson & Ireland, 1995). The b aselin e level of fem ale's conditioning h a s
b een significantly less than it h as b e e n for m en (Whiteside, 1980; Garrick &
Requa, 1978). Fem ale athletes are typically m ore prone to overuse syndrom es
than m ales (Malone & S anders, 1993). F itness program s need to be balanced
with m uscular strength, endurance an d flexibility in addition to aerobic fitness
(Malone & Sanders, 1993). In the H uston and Wojtys study (1996), the fem ale
ath letes who participated w ere in division I NCAA sports, w here training and
conditioning program s are sophisticated and am ong the b est available. High
school athletes receive training and conditioning th at is typically far less th an the
college athlete. If the problem is a deficit in early training, then the current
em p h asis on women's sports should correct this problem. If however, w om en
are substantially different than m ales physiologically, then male conditioning
program s may not be the answ er, an d further research may be needed to
a d d re ss th e se issues (Huston & Wojtys, 1996).
It is clear that both intrinsic an d extrinsic factors affect the frequency and
distribution of ACL injuries. W hat rem ains unclear is the relative contribution of
each factor and w hether alteration of an y given extrinsic factor can affect an
ath lete's potential for injury.
14
IVleglianigms.anri.ACL lni.uries.iaghildLea
L astihenos and Nicholas (1996) ad d ressed ACL injuries in children.
Although injuries to the ACL w ere not a s common in children a s they w ere in
adults, th ey m ay c a u s e chronic instability in adults. Stanitski (1993), studied 70
patients a g e d 18 years and younger with acute hem arthrosis injuries. The
results of th e study w ere a 63% incidence of ACL te a rs (as in L astihenos &
Nicholas, 1996). "The m ost common m echanism of injury is k n ee
hyperextension coupled with a twisting force, similar to the m echanism s e e n in
adults" (as in Lastihenos & Nicholas, 1996, p.61). It is clear th a t ACL injuries
occurred in th e ag e group of th e high school athlete and w hen they did occur
w ere a significant physical problem for the athlete.
isokineticg.
The co n cep t of isokinetics w as first introduced by J a m e s Perrine in the
late 1960's (Davies, 1992). The concept utilized a dynam ic p re -se t fixed sp e e d
with accom m odating resistan ce throughout the ran g e of motion.
Most sporting activities involve the use of closed-chain m ovem ents,
m eaning th e distal seg m en t of th e extremity is fixed, while th e proximal seg m e n t
m oves over th e fixed distal seg m en t (Fu, Woo, & Irrgang, 1992). Running,
jumping, squatting and walking are exam ples of closed chain activities. Testing
of isokinetic strength h a s traditionally been done in an open-chain fashion, d u e
to current equipm ent design for testing. In open-chain activities, th e distal
segm ent is free and the proximal seg m e n t is fixed a s with kicking a ball. "All
strength stu d ies to d ate have b een d o n e in an o p en chain fashion b e c a u s e of
our p resen t limitation in m uscle testing technique" (Arendt & Dick, 1995, p.695).
Valid and reliable closed chain testing equipm ent is not currently available.
15
Isokinetic testing can m e a su re concentric m uscle strength, eccentric
m uscle strength, or isometric strength, in an open-chain m anner (Biodex®,
1990). Predeterm ined s p e e d s are u se d with isokinetic testing a n d are m easu red
in d eg re es per second of m ovem ent around an axis of rotation. Torque
m easu red by th e dynam om eter varies in relation to m uscle-length tension
ch an g es, m om ent arm variation, fatigue, and pain during the motion (Biodex®,
1990).
Elftman, in 1966 described a predictable relationship betw een eccentrics,
isometrics, concentrics, an d force m uscle potential. He su g g ested eccentrics
had g reater force production than isom etrics and isometrics w ere greater than
concentric contractions (eccentrics>isom etrics>concentrics), (as in Davies,
1992). Data from num erous scientific studies of eccentric/concentric force
production show ed a range of 146% to 300% g re a te r eccentric torque than
concentric force production (Davies, 1992). B ased on normative d ata (Davies,
1992), m ales should be able to p roduce 100% torque to body w eight at 60
d eg re es per seco n d concentrically. T h e population being tested could potentially
overpow er the equipm ent available. S tudies reviewed for com parison (Davies,
1994; Moore and W ade, 1989; Dibrezzo e t al., 1985) all utilized concentric
testing. Additionally, eccentric contractions have a higher potential for
production of delayed o n set m uscle s o re n e s s (Albert, 1992).
M easurem ents of p eak torque, m ean p eak torque, a v erag e power, single
repetition work, total work and p e rc e n ta g e of p eak torque to body weight and
agonist to antagonist ratios have b een proven reliable from 60 d e g re e s per
second to 450 d eg rees p er seco n d (Fairing, Ellenbecker, & D ersheid, 1990;
Wilk, et al., 1988).
16
A. Isokinetics-normative data for hamstring/quadriceps ratios
Several authors h av e published normative d ata for ham string/quadriceps
ratios (Davies, 1992; M oore & W ade, 1989; Dibrezzo e t a!., 1985; W yatt &
Edw ards, 1981).
Davies (1992) original ham string/quadriceps ratio norms w ere described
for women and m en (age 15-40) and reported a s th e following:
S p ee d
Ham string/quadriceps ratio
60
180
240
300
60%-69%
70%-79%
80%-89%
85%-95%
d e g /se c
d e g /se c
d eg /se c
d eg /se c
In W yatt & Edw ards (1981) article, they reported th e following
ham string/quadriceps ratio sep a rated by gender:
S peed
Males
Fem ales
60 d e g /se c
180 d e g /se c
300 d e g /se c
72% (+/-11 %)
78% (+/-11%)
83%(+/-14%)
71 % (+/-11%)
79% (+/-11%)
85%(+/-16%)
They also stated that the ratios w ere similar for both sex es, even though there
w ere large differences in th e actual am ount of torque produced. In both m ales
and fem ales, th e ham string/quadriceps ratio moved closer to unity (p<0.01), a s
th e sp eed of th e exercise increased. It m ust be noted that th e ab o v e normative
d a ta w as collected without utilizing a gravity correction.
B. Isokinetic testing
1.
Peak torque: P e a k torque refers to th e single highest torque
produced by a m uscle group through a range of motion (Kannus & Y asuda,
1992).
There h a s been an "overshoot" phenom enon described in th e literature
w hen peak torque has b een used . T he "overshoot" phenom enon produces an
artificial spike in th e fast portion of a torque curve. (Perrin, 1993). T he
17
"overshoot" can be avoided by th e u se of av erag e torque or th e use of
"windowed data" (Biodex® 1990). "The term 'Isokinetic window' refers to filtering
out all data that have not b e e n obtained a t th e p reset Isokinetic sp eed or 95% of
th at speed," (Wllk, Arrlgo, & A ndrew s, 1992, p. 108). T he Biodex® com puter,
using windowed d ata records only torque production that occurs when the
testing sp eed m aintains 95% of desired sp e e d (Biodex®, 1990). Biodex® (1990)
claim s that using windowed d a ta n eg ates th e overshoot phenom ena.
Additionally, peak torque d a ta h a s been ch o sen to com pare to existing normative
data.
2. Tim e to p e a k to rq u e : Time to peak torque, m easured In milliseconds,
h a s been defined a s th e tim e tim e It takes for a m uscle to produce Its peak
torque during Isokinetic testing (Biodex®, 1990). Time to peak torque w as first
discu ssed In the literature by Huston and Wojtys In 1996. Huston and Wojtys
(1996) dem onstrated that fem ale athletes had slow er ham string time to peak
torque than m ale athletes a t two Isokinetic s p e e d s, 60 and 240 d eg re e s per
seco n d . No trends of time to p eak torque In relation to Isokinetic testing sp e e d s
w ere available In th e literature.
3. T e stin g s p e e d s : Isokinetic te st s p e e d s range from zero d e g re e s per
seco n d to 450 d e g re e s p er se c o n d depending on th e m anufacturer of the
m achine. The Biodex® com pany h a s recom m ended the u se of the following
testing sp ee d s for knee testing: 60, 180, and 240 d eg re e s per second for non­
ath letes and 300, 360, and 4 2 0 d eg rees p er second for ath letes (Biodex®,
1990). Recom m ended testing s p e e d s for knee flexion and extension a re 60 to
90, 180, and 300 d e g re e s p e r seco n d by D avies (1992). He further su g g ested
th at testing s p e e d s from 300 to 600 d eg rees per second would provide data
closer to sp ee d s at which functional activities w ere performed. The faster the
testing speed s, the less joint com pression and the less discomfort during testing.
18
Testing at s p e e d s below 60 d e g re e s per seco n d may c a u s e the patient
discom fort du e to high pateiiofemorai joint com pression forces (D avies, 1992).
R esearch has show n (Wilhite, C ohen, & Wilhite, 1992) th a t testing from th e
lowest sp e e d s to th e highest s p e e d s affected th e reliability of m uscle
perform ance d ata and su g g este d slow s p e e d s be introduced first before fast
sp e e d s. Timm an d Fyke’s (1993), te s t results on concentric isokinetic te st
s p e e d s se q u e n c e on knee ex ten so r m uscle groups concluded that; te s t sp e e d
order did not affect concentric p eak torque m easurem ents, there w ere specific
differences betw een te st s p e e d s, and that th e procedures afforded a high d e g re e
of m uscle perform ance m easu rem en t consistency.
4. S tab ilizatio n : In order to prevent unwanted m ovem ents from th e hip
and trunk, consistent position and stabilization of the patient is n e c e ssa ry
(N osse, 1982). D avies (1992) su g g ested proper stabilization be u se d to prevent
substitution of stro n g er m uscles for w eaker m uscles, and maintain reliability.
Biodex® (1990) recom m ended stabilization by straps around the thigh, w aist and
trunk with arm s folded acro ss the chest. M agnusson, Geism ar, Gleim, and
Nicholas (1993) found that maximum knee extension/flexion torque production
w as achieved with th e trunk strap p ed to th e back support and the h a n d s
grasping the seat.
5. W arm -up a n d r e s t in terv a ls: Utilization of warm -up s e s s io n s th at
include subm axim al and maximal repetitions a t each te s t sp e e d h av e b een
recom m ended by Perrin (1993) and Davies (1992). Joh n so n and S iegal (1978)
concluded that th re e subm axim al and three maximal w arm -ups m ust b e done
prior to testing for p eak torque m easu res to b e reliable and to becom e familiar
with th e isokinetic m achine. Perrin (1993) found three submaxim al an d th ree
maximal w as n ec e ssa ry for reliability p u rp o ses in testing total work, a v e ra g e
pow er and peak torque. A study by M awdsley and Croft (1982) show ed th at
19
warm -up did not effect the peak torque results, but som e subjects experienced
discom fort in th e group without warm -up. W arm -ups h av e b een used a s a safety
precaution. W hen multiple isokinetic sp e e d s a re being u sed for testing, rest
intervals a re a potential variable. It h a s been found that re st intervals result in
5% higher m ea su rem en ts with g re a te r reliability (Stratford, Bruulsema, Maxwell,
Black, & Harding, 1990). Perrin (1993) su g g ested intervals of 30 seco n d to one
minute following en d u ran ce testing but there w ere no recom m endations for rest
intervals betw een s p e e d s for te sts of peak torque.
The u s e of general body warm -up procedures h as b een traditional in
sports and h a s b een advocated by m any rehabilitation professionals a s the
m ean s of preparing th e body physiologically an d psychologically for exercise (as
in Arnheim & Prentice, 1993). The main purposes of warming up has b e e n to
raise both th e general body and th e d e e p m uscle tem p eratu res and to stretch
collagenous tissu e s to permit g reater flexibility. This red u ces th e possibility of
m uscle te a rs and ligam entous sp rains and helps to prevent m uscle so re n e s s
(Arnheim & Prentice, 1993).
6. Gravity correction; According to Nelson and D uncan (1983) and
Perrin (1993), gravity correction accounted for th e weight of th e isokinetic
dynam om eter lever arm and the limb being te ste d when th e m ovem ent w as in a
gravity d e p e n d e n t position. Error ranging from 26% to 43% for extension and
from 55% to 510% for knee flexion w ere dem onstrated in te s ts without gravity
corrections. (Winter, Wells, & Orr, 1981).
7. Test repetitions: The num ber of te st repetitions affects reliability.
Perrin (1993) su g g e ste d three to four repetitions to get reliable peak torque.
Davies (1992) recom m ended five te st repetitions.
8. Patient testing position: te st positions have varied am ongst
re search ers for hip angle and knee axis. Bohannon, Gajdosik, & LeVeau (1986)
20
determ ined that isokinetic k n e e ex ten so r torque w as not significantly g re a te r in a
sitting position w hen co m p ared to th e semi-reclined position. Brinks, DeLong, &
Stout (1995) also determ ined th at supine or sitting positions could b e u sed for
isokinetic testing. A study by Wilk and Andrews (1993) u sed a hip flexion angle
of 115 d eg rees, since that a p p e a re d to be optimal for quadriceps fem oris torque
generation (Currier, 1977).
T h e k n ee h a s a dynam ic axis of rotation. As a
result, Biodex® (1990) su g g e ste d th e b e st com prom ise w as placem ent of the
dynam om eter axis through an im aginary line drawn through the femoral
condyles, in the coronal plane.
In conclusion, th e review of literature show ed fem ale basketball players
have a higher rate of ACL injuries than m ale basketball players. T here w as a
similar m echanism of injury in children and adolescents a s com pared to adults.
Injuries that occur to th e ACL in children will have an im pact a s they e n te r
adulthood. Many factors, both intrinsic and extrinsic may contribute to ACL
injuries in fem ale athletes. T h e re a p p e a rs to b e special concern for basketball
players as a high risk group for sustaining ACL injuries (Arendt & Dick 1995;
Hutchinson & Ireland, 1995; De H aven & Litner, 1986; Zelisko et al., 1982; Clark
& Buckley, 1980; W hiteside, 1980).
More research w as n e e d e d on the role strength m ay play in ACL injuries
in the high school fem ale b asketball player. By looking a t strength ratios and
time to developm ent of p ea k torque in high school fem ale and male basketball
players, som e predisposing m u scular strength and balance factors m ay be
identified. This research m ay a s s is t co ach es, players, and trainers in designing
appropriate strength and conditioning program s and ultimately aid in ACL injury
prevention.
CHAPIER3
METHODS AND MATERIALS
Subjects
A convenience sam ple of 53 subjects was obtained by contacting athletic
directors, co ach es and/or athletic trainers, athletes (Appendix A), and by a
published solicitation In th e n ew sp ap er. Twenty-six fem ales and 27 m ales a g e s
13-18 years old, m et Inclusion criteria for participation In th e study. All subjects
w ere m em bers of a freshm an, junior varsity or varsity high school basketball
team .
The subjects w ere ch o sen from a convenience sam ple of C lass A, B, 0
and D high schools within 60 m iles of downtown Grand Rapids, Michigan.
Potential subjects filled out a p re-test questionnaire (Appendix B). All
participants accep ted for th e stu d y (se e Appendix C for ac c e p ta n c e criteria),
signed a consent form (Appendix D) before proceeding. Participants who w ere
minors (under 18 y ears old), had a parent read the parent Information letter
(Appendix E), sign th e pre-test questionnaire (Appendix B) and th e co n sen t form
(Appendix D). P aren ts w ere e n co u rag ed to attend th e testing session. In order
to maintain anonymity, each su b ject w as given an Identification num ber to be
u sed throughout th e study.
iVla.teriai§.
A Schwinn Alrdyne ex ercise bicycle w as used for w arm -up prior to testing.
The warm-up w as u sed to p rep are m usculature for maximal effort testing and
prevent after te st so ren ess.
A Biodex® System II Isokinetic dynam om eter w as u sed to te st the
subjects quadriceps and ham string concentric strength and tim e to peak torque.
Eccentric torque maximum Is 150 foot pounds on authors' available Isokinetic
21
22
equipm ent. Timm, Gennrick, Burns, & Fyke (1992), concluded that th e Biodex®
dem onstrated high levels of te st/retest reliability during m echanical and/or
physiological a s s e s s m e n ts of respective concentric, isokinetic functions. For
valid com parisons, prevention of delayed o n s e t m uscle s o re n e s s and equipm ent
reliability, concentric testing w as chosen for this study. Biodex® w as ch o sen for
this research over oth er isokinetic sy stem s d u e to its test-retest reliability and
face validity established in th e literature (Wilk, Johnson & Levine, 1988), a s well
as its' availability to th e research ers. H am string/quadriceps ratios and time to
p eak torque d ata of eac h limb w as collected a t five different testing sp e e d s.
D ata w as recorded and reduced, using th e Biodex® softw are version 3.2. All
data w as printed using Biodex® com prehensive report.
Procedures
The Biodex® system w as calibrated before each testing day per
Biodex® calibration protocol. O ne of two Biodex® m achines w as used
throughout the testing.
Subjects w ere w eighed in pounds and m easured in inches, in their street
clothing without sh o e s. T he subjects then perform ed a warm-up prior to strength
testing. For consistency, th e warm -up consisted of 10 m inutes on a Schwinn
Airdyne exercise cycle. T he s e a t height w as placed so there w as approximately
15 d e g re e s of flexion in th e knee th at w as extended toward the floor. The
intensity level w as 1.0 work load on th e airdyne gauge.
The isokinetic te st immediately followed warm -up on the bicycle. The
subject w as se a te d with 115 d e g re e s of hip flexion, m easured goniometrically
and stabilization stra p s w ere applied to the trunk, w aist and thigh per the
Biodex® (Biodex®, 1990) protocol. R ange of motion of the knee w as m easured
by the te ster with a goniom eter and s e t a t 110 d eg rees flexion and 0 d eg rees
23
extension. R an g e of motion sto p s were then s e t on th e Biodex®. The
dynam om eter p o w erh ead w as positioned so th e axis of motion corresponded to
an imaginary line through th e coronal plane of th e knee, from th e lateral to the
medial femoral condyles of th e knee. For consistency th e ankle pad was
positioned four inches superior to the distal tip of th e lateral malleolus. Subjects
were instructed to cro ss their arm s across their w aist during testing to prevent
u se of trunk and u p p er extrem ity musculature. T he isokinetic Biodex® testing
w as perform ed by any of th e th ree researchers for all subjects.
T he Biodex® isokinetic te st w as explained to th e subject (Appendix F).
After five repetitions at 60 d e g ree s per second to familiarize th e subject with the
machine, the subject perform ed three practice subm axim al repetitions followed
by three practice maximal repetitions prior to performing e a c h testing speed.
The subject then perform ed five maximal effort repetitions for concentric
quadriceps and ham strings a t 60, 180, 240, 300 a n d 450 d e g re e s per second.
W e have chosen s p e e d s of 6 0 ,1 8 0 , 240, 300 d e g re e s p e r second for
comparability with previous studies and 450 d e g re e s p er second to test the
fastest available isokinetic sp eed . Subjects com pleted their normal excursion of
knee flexion/extension ran g e of motion within th e s e t ran g es. The subject's legs
were tested in random o rd er determ ined by coin to ss . No attem pt w as m ade to
determ ine leg dom inance.
Data Analysis
Isokinetic d a ta from th e Biodex® software 3.2 p a c k a g e w as manually
entered by the re se a rc h e rs into S P S S for MS WINDOWS R elea se 6.1.
Descriptive statistics w ere com puted for the subject population,
ham strings/quadriceps ratios, and time to peak torque d a ta a t all sp eed s for all
subjects. Mann-Whitney-U te sts were used to determ ine th e difference betw een
24
fem ales and m ales ham string to quadriceps ratios. Paired t-tests w ere u sed to
determ ine the difference betw een fem ales and m ales tim e to peak torque.
Informal qualitative analysis betw een m ean s of d ata produced in this research
for ham string/quadriceps ratios and available norm ative d ata w as described.
ÇHAPTER-4
RESULTS
Concentric Isokinetic bilateral knee flexor and ex ten so r d ata w as obtained
from 26 fem ales and 27 m ales ranging in ag e from 13 to 18 years. Paired t-tests
for time to torque d ata (p<.05) and Wilcoxon M atched-Pairs Signed-R anks T est
for ham string/quadriceps ratio d a ta (p<.05) dem onstrated no difference betw een
tested limbs. As a result, to prevent a biased sam ple, only th e data from one of
the tested limbs (group A) w as u sed for d ata analysis. G roup A is com posed of
randomly assigned limbs by categ o ries of left or right and first or second tested
limb.
Table 4.1 sum m arizes, by gender, the m ean, standard deviation, and
range for subject's age, height and weight.
TABLE 4.1 DEMOGRAPHIC SUMMARY
Range
Variable
Mean
Standard deviation
Male (d=27)
Age
Height (in)
W eight (lbs)
15.52
71.41
159.19
1.05
2.71
19.48
14.00-18.00
66.00-78.00
15.00-205.00
Femaleio=26J
Age
Height (in)
W eight (lbs)
15.33
67.04
132.67
1.20
3.11
17.40
13.00-18.00
61.00-73.00
104.00-189.00
25
26
Descriptive d a ta for team level and school size classification are
sum m arized by g e n d e r in th e graphs below.
Graph 4.1 Distribution of Team Classification by Gender
12
10
'
8
TEAM
6
■ Mssing
4'
■
1.00
■
200
m
3.00
200
1.00
GENDER
Key for team
1= Varsity
2= Junior Varsity
Key for-geadei
1= F em ales
2= Males
3= Freshm en
Missing= Unavailable Data
Graph 4.2 Distribution of School Class by Gender
1.00
200
GENDER
Key for G ender
1= F em ales
2= Males
Key for School C lass
1= C lass A School Missing= Class C or
2= C lass B School
Unavailable D ata
27
T able 4.2 sum m arizes the m ean, standard deviation, and range for
ham string/quadriceps ratio isokinetic d a ta at 60, 180, 240, 300, and 450 d e g re e s
per seco n d . As isokinetic sp eed increased, m ean ham string/quadriceps ratio
increased until 450 d e g re e s per seco n d , w here th e ratio d e c re a s e d for both
genders.
Table 4.3 sum m arizes the m ean, standard deviation, and range for tim e to
peak torque isokinetic d ata at 6 0 ,1 8 0 , 240, 300, and 450 d e g re e s p er seco n d .
As isokinetic sp e ed increased m ean hamstring tim e to to rq u e d ec re a se d until
450 d e g re e s per second w here the tim e increased for both g en d ers.
Table 4.2 Isokinetic Data For Hamstring/quadriceps Ratios
Standard Deviation
Range
Variable
Mean
Males (11527)
HQ60
HQ180
HQ240
HQ300
HQ450
49.50
50.70
52.14
53.16
40.27
7.39
7.68
7.83
10.27
16.43
40.60-74.90
36.50-71.30
39.20-75.90
39.70-87.40
00.00-93.50
Females (n=26)
HQ60
HQ180
HQ240
HQ300
HQ450
44.40
47.31
47.62
48.31
36.90
9.03
11.09
12.10
11.82
16.91
29.30-69.60
32.40-72.20
28.90-82.50
27.2-78.00
00.00-79.40
HQ= hamstring/quadriceps ratio (%), for each speed listed in degrees per second
28
Table 4.3 Isokinetic Data For Hamstring Times to Peak Torque
Variable
Mean
Standard Deviation
Range
M ales (n=26)
TT60
TT180
TT240
TT300
TT450
452.96
236.04
171.73
156.19
177.81
104.66
81.78
46.28
39.82
53.64
260.00-664.00
100.00-410.00
110.00-270.00
98.00-270.00
00.00-320.00
Females (ri=2.6)
TT60
TT180
TT240
TT300
TT450
732.54
319.31
221.12
192.77
205.69
267.37
116.17
86.62
56.36
60.05
369.00-1410.00
115.00-560.00
115.00-420.00
120.00-340.00
00.00-300.00
TT= time to peak torque (msec) for each speed listed in degrees per second
Table 4 .4 sum m arizes results o f statistical analysis of data for
ham string/quadriceps ratios betw een g e n d e rs using Mann-Whitney-U analysis.
Statistically significant differences (p<0.05) w ere found at 60 and 240 d eg rees
per second. O ther tested s p e e d s w ere not statistically significant.
Table 4.5 sum m arizes results of statistical analysis of data for hamstring
time to peak torque values betw een g e n d e rs using a t-test for Independent
S am ples. Statistically significant differences (p<0.05) w ere found at 60, 180,
240, and 300 d eg ree s per second. D ifferences betw een th e m eans for m ales
and fem ales at 450 d eg re es p er seco n d w ere not statistically significant.
29
TABLE 4.4 Values for Mann-Whitney-U test for Hamstring/quadriceps Ratio
Isokinetic Data
Variable
2-Tailed P
HQ60
HQ180
HQ 240
HQ 300
HQ 450
*0.0313
0.2001
*0.0443
0.0944
0.6824
HQ= hamstring/quadriceps ratio (%), for eacti speed listed in degrees per second
'= statistical significance
Table 4.5 Values for T-tests for Independent Samples for Time to Peak
Torque Isokinetic Data
Variable
TT60
TT180
TT240
TT300
TT450
2-Tailed Significance
*0.000
*0.004
*0.014
*0.009
0.084
TT=time to peak torque (msec), for each speed in degrees per second
'= statistical significance
CHAPTER 5
DISCUSSION AND IMPLICATIONS
Clinically, we observed that ath letes with a tom ACL have w eak ham string
m uscles in relationship to th e q uadriceps m uscle on th e uninjured leg. Clinically
this is described a s a d ecrease d ham string/quadriceps ratio. W e believed th at
this m uscular ratio may b e different in fem ales than in m ales. This im balance
m ay b e a predisposing factor to the ACL te a r in th e fem ale basketball player.
Our results support this theory and offer d a ta related to other potential
contributing factors.
Compa rison .to previous, studies
A. Comparison to normative data for hamstring/quadriceps ratios
Davies (1992) published norm ative values for ham string/quadriceps ratios
for m ales and fem ales (reported together) a g e s 15-40 years old a t 6 0 ,1 8 0 , 240,
and 300 d e g re e s per second (se e A ppendix G for specific values). W yatt and
Edw ards (1981) reported ham string/quadriceps ratios for m ales and fem ales, but
s e p a ra te d them by gender (se e Appendix H for specific values). In their 1989
article Moore and W ade also published d a ta on high school basketball athletes'
ham string/quadriceps ratios se p a ra te d by g en d er (se e Appendix I for specific
values). In addition to published ham string/quadriceps ratios, M oore and W ad e
(1989) published the following "goals" for ham string/quadriceps ratios for
basketball athletes;
60 d eg rees p er second:
0.67- 0.77 (or 67-77%)
180 deg rees p er second:
0.80- 0.91 (or 80-91 %)
300 deg rees p er second:
0.95-1.11 (or 95-111 %)
30
31
Moore and W ade did not describe how they arrived a t th e values for goals, nor
did they s e p a ra te th e goals for gender. W e believe th a t it is inappropriate to
establish g o als b a se d on non-statistically analyzed d ata.
W hen values published in earlier studies w ere qualitatively com pared to
the results of our study, w e found our m ean ham string/quadriceps ratios were
significantly lower a t all te ste d sp eed s than th o se of previous authors' for both
g enders. T he differences m ay be attributed to the fact th a t our subjects were
te sted with gravity correction.
Gravity correction w a s shown to dramatically
d e c re a se th e overestim ation of torque production by th e ham strings (Perrin,
1993, W inter et al, 1981). Moore and W ade (1989) acknow ledged that their data
w as not gravity corrected and that gravity correction affected
ham string/quadriceps ratios.
Davies (1992) also did not utilize a gravity
correction. W e believe that it is important to utilize a gravity correction when
testing ham strings and quadriceps isokinetically. W e also believe the use of a
gravity correction in our study h as provided m ore a c c u ra te results than previous
published studies. As a result, it is inaccurate to co m p are our results with
previously published non-gravity corrected data. F u rth er studies a re needed to
establish gravity corrected ham string/quadriceps ratio goals.
B. Trends In hamstring/quadriceps ratios
H am string/quadriceps ratios increased (approaching 1.0 or 100%) as
isokinetic s p e e d increased in previous studies (Davies, 1992, M oore & Wade,
1989). D ata from our study supported a minimal in c re a se in m ean
ham string/quadriceps ratio a s test speed increased for th e subjects:
Males: 49.5% - 53.16% (60-300 d e g re e s p e r second)
Fem ales: 44.4% - 48.31% (60-300 d e g re e s per second)
32
a s com pared to the tre n d s published In the study by Wyatt an d Edwards (1981):
Males: 72% - 83%
Fem ales: 71% - 85%.
No previous research on ham string/quadriceps ratios w as available for
com parisons a t the 450 d e g re e p e r seco n d sp eed .
The trend of Increased ratios did not continue at the 450 degree per
second test sp eed .
O n e explanation for the ch an g e In trend w as that a t 450
d e g ree s per second th e subjects lacked the m otor control to m ove the lever arm
with a maximal effort, an d register torque. This w as dem onstrated by th ree
subjects w ho w ere u nable to move th e lever a t 450 d eg rees p e r second which,
resulted In a sco re of z ero for torque. A nother possible explanation may b e that
subjects dem onstrated a lack of concentration and/or fatigue a t higher s p e e d s
which may play a role In Inability to g e n e ra te maximal torque.
C. Specificity of sample
A nother source of variance betw een this study and previous studies w as
th e ag e ran g e and specificity of th e sam ple. T he subjects from our study w ere
all betw een th e a g es of 13 and 18 y e a rs old and w ere high school basketball
players. Davies' (1992) subjects u se d for normative data estim ates, ranged In
a g e from 15-40 years old. Specific Information ab o u t activity level and athletic
statu s of D avies' (1992) normative su b jects w as not available for com parison.
T he subjects used for rese arch by M oore and W ade (1989) m ore closely
resem bled th e subjects u se d In our study: high school boy and girl basketball
players (n=16 m ales, n=28 fem ales). Mean ham string/quadriceps ratios from
this study differed considerably from th e values obtained by M oore and W ade,
probably due to utilization of gravity correction.
33
D. Trends in time to peak torque
T here w ere no published descriptions of trends in tim e to p eak torque
data known to the authors. It w as hypothesized that a s th e isokinetic testing
speed increased, th e tim e to peak torque in milliseconds would d e c re a se , or
follow an inverse relationship. Data from our study supported the hypothesized
trend for s p e e d s 60 through 300 d e g re e s per second, for both m ales and
fem ales. However, a t 450 d e g re e s p er second th e m ean tim e to p eak torque
increased for both g e n d ers. This can be partially explained by fatigue. T he 450
degree per seco n d te s t sp e e d w as th e fifth an d final test sp e e d in th e te st series.
A nother potential explanation of the in crease in time to p eak torque a t 450
d eg rees per second would b e that th ere m ay b e a point at which torque sp e e d
no longer d e c re a se s. This phenom enon could b e referred to a s a ceiling effect.
We did not find p a st re se arc h that a d d re sse d a ceiling effect in tim e to p eak
torque. If a ceiling effect existed, and there w a s a point at which no d e c re a s e in
time to p eak torque took place, it m ay explain th e increase in time to p eak torque
at 450 d eg re e s per seco n d .
E. Gender difference in time to peak torque
Huston and W ojtys (1996) reported time to peak torque differences for the
knee flexors betw een elite fem ale athletes, elite m ale athletes, and non-athlete
gender m atched controls with isokinetic concentric testing. They found tim e to
peak torque differences (p<0.001) in knee flexion time to p eak torque a t 60 and
240 d eg ree s per seco n d . This study also dem onstrated significant differences
(p<0.05) for m ean tim e to peak torque values of th e ham strings a t 60, 180, 240,
and 300 d eg re e s per se co n d during concentric isokinetic testing. T here w a s no
significant difference a t 450 d e g re e s p er second.
34
F. Gender differences in hamstring/quadriceps ratios
Previous studies su g g ested th at ham string/quadriceps strength ratios
w ere lower in fem ales than in m ales (M oore & W ade, 1989; Dibrezzo e t al, 1985;
H olm es & Alderink, 1984). Our study dem onstrated statistically significant
differences in ham string/quadriceps ratios betw een m ales and fem ales a tte s t
s p e e d s of 60 and 240 d eg rees per seco n d . The authors w ere unclear a s to why
th e differences w ere significant a t th o se two s p e e d s an d were not significantly
different at the other tested sp e ed s. No apparent pattern w as identifiable.
B ased on clinical experience by the authors of this study, 60 d e g re e s per seco n d
h a s b een a sp e e d th at the majority of clients g en erate a consistent maximal
effort due to the slow speed.
The su bjects in this study perform ed five repetitions at 60 d e g re e s per
sec o n d to familiarize them selves with th e m achine. Prior to testing a t any sp e e d
th e subjects then performed three subm axim al efforts followed by three maximal
efforts to familiarize them selves with th e sp eed . The second te st sp eed , 180
d e g re e s p er second, required quicker m ovem ent of th e lever arm. Motor
learning may have occurred at the 180 d e g re e s per seco n d . This m ay have
allowed for a m ore consistent maximal effort at the next te st sp eed of 240
d e g re e s per second. Moore and W ade (1989) hypothesized a potential c a u se
for high sp e e d isokinetic differences (at 300 d eg re e s p e r second) betw een
g e n d e rs a s a d e c re a se in m uscular excitation or m uscular inhibition of the
ham strings by the quadriceps in fem ales. This theory would not account for lack
of difference at 300 and 450 d eg rees p er second in o u r study.
Limitations and recommendations for further study
We, the authors acknowledge th at th e correlation betw een concentric
isokinetic testing and function rem ains questionable. Reliable eccentric
35
isokinetic testing equipm ent w a s not available. An ideal im provem ent to this
study would be to perform eccentric testing of ham string/quadriceps ratios and
hamstring time to p eak torque and relate eccentric d ata to function.
Closed kinetic chain strength w as an asp ect th at w as not investigated in
this study. Reliable and acc essib le closed kinetic chain testing equipm ent w as
also not available. A nother future im provem ent to this study would b e to include
a closed kinetic chain m e asu re of strength, combined with eccentric function.
As with any sam ple of convenience, th e subject pool used in this study is
a potential source of limitation. It w as the intention of th e authors th a t all c la sse s
(Class A, B, C, and D) and team levels (freshman, junior varsity and varsity)
would have approximately eq u al representation within th e sam ple. T he sam ple
used in this study had minimal representation of class C, and no representation
of class D. It also had unequal representation of team levels.
Utilization of a
stratified random sam ple to ach iev e equality betw een c la s se s and team levels
may improve the subject population used in future studies and improve
generalizability.
Another potential so u rce of variation betw een g e n d e r sam p les w as that all
fem ale athletes te ste d resp o n d ed to an article published in the local p ap er
requesting volunteers. Many of th e m ale subjects had to be recruited specifically
through coaches, athletic trainers, and via personal contact. Ideally, all subjects
would have been recruited identically. Selection from a large sam ple of
volunteers (who m et inclusion criteria), drawn randomly, would provide greater
random ness of th e sam ple an d therefore g reater application to th e general
population. In this study all volunteers who m et inclusion criteria and presented
for testing were u sed a s part o f the sam ple.
Another suggestion for further research is to attem pt to correlate time to
peak torque data to function. It is unknown w hat differences in m ean time to
36
p ea k torque of th e ham strings betw een g e n d e rs m e a n s clinically. It w as also
unknown w hether time to p eak torque values will c h an g e with training, and w hat
ty p es of conditioning/training m ay optimally affect tim e to peak torque. Before
any recom m endations could b e m ade about training for ch an g e of this factor,
th e s e questions m ust b e a d d re ssed . The relationship betw een concentric time
to p e ak torque d ata and m echanism s of ACL injury h av e not been investigated.
Ideally, eccentric hamstring tim e to peak torque should be studied and related to
ACL injury. T he relationship betw een time to p eak to rq u e data and
proprioception also rem aine undefined, and m ay be a n important link to injury
prevention.
Since ham string/quadriceps ratio differences w ere se e n betw een genders
at two te st sp e e d s, it would se e m logical th a t fem ales could address this deficit
via conditioning. It is our hope that g en d er specific conditioning and prevention
program s may a d d re ss the surplus of ACL injuries in fem ales. Therefore,
an o th e r area of study m ay be th e relationship of g e n d e r specific conditioning on
ham string/quadriceps ratios. If conditioning can improve th e s e ratios, then
altering the ratios should m ake a long term difference in ACL injury prevention.
gonclHsi-on
The purpose of this study w as to determ ine if th e re w ere differences
betw een fem ale and m ale high school basketball players strength and
neurom uscular perform ance. Strength factors are believed to be a potential
extrinsic variable which m ay contribute to th e relative surplus of ACL injuries in
the fem ale athlete.
W hen teste d isokinetically the results w ere statistically significant for
differences betw een fem ales and m ales ham string/quadriceps ratios at 60 and
240 d e g re e s p er second, and ham string time to peak torque at 60, 180, 240, and
37
300 d e g re es per seco n d . As a result of th e s e differences found by g en d er, the
extrinsic factor of strength should continue to be investigated a s a potential
contributing factor in ACL injuries in th e fem ale athlete.
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for anterior cruciate ligam ent injury in high school and college athletes. Journal
Qf.Athlg.tlcTraining. 29(4), 343-346.
Wyatt, M., & Edw ards, A. (1981). C om parison of quadriceps and
hamstring torque values during isokinetic exercise. T he Journal oif O rthopedic
and-Sports Physical Thgiapy . ^(2), 48-56.
Zelisko, J. A., Noble, H. B., & Porter, M. (1982). A com parison of m en 's
and w om en's professional basketball injuries. T h e American Journal of Sports
Medicine. 10. 297-299.
APPENDIX A
CONTACT LETTER
D ear (Athletic director, coach, athletic trainer).
We are grad u ate stu d en ts In G rand Valley S tate University's M asters of
Physical Therapy program and are looking for volunteers of high school fem ale
and m ale basketball players.
Sports Illustrated recently highlighted the Incidence of anterior cruciate
ligam ent (ACL) Injuries In fem ale basketball players. There m ay be several
factors that contribute to th e knee Injury. Strength of leg m uscles and
neurom uscular conduction a re two a r e a s that have b een suggested.
The results of this study could h av e national Implications for prevention of
ACL Injuries In high school fem ale and m ale basketball players.
We n eed volunteers to test ham strlng/quadriceps strength ratios and
reaction time. They m ust b e a m em ber of a high school basketball team ,
freshm an, junior varsity or varsity. T he athletes will receive a free strength test
valued at approximately $125.00 In ex ch an g e for confidential Information to be
u sed In this study.
If any m em bers of your team a re Interested, p lease contact Saint Mary's
Sports Medicine departm ent main office at 752-6182 to receive th e n ecessary
co n sen t forms th e athletes n eed signed to be eligible for participation. Testing
will be performed In Saint Mary's Sports Medicine departm ent a t the downtown
location.
Thank You,
Diane Beach A.T.,C., S.P.T.
Certified Athletic Trainer
S tudent Physical Therapist
Barb Hoogenboom P.T., SCS, A.T.,C.
Physical Therapist,
Sports Clinical Specialist
Certified Athletic Trainer
Lisa R ose S.P.T.
S tudent Physical Therapist
43
APPENDIX B
PRE-TEST QUESTIONNAIRE
Subject's Name:_____________
Address:
Age:_________
Date of birth:
Sex: Male or fem ale (circle one)
Basketball team: freshm an, junior varsity, varsity (circle one)
1. H ave you injured any of th e following joints in th e p ast one year?
(circle y es or no)
a.
b.
c.
d.
knee
hip
ankle
foot
no
no
no
yes
yes
yes
no
your injury keep you out
a.
b.
c.
d.
knee
hip
ankle
foot
no
no
no
yes
yes
y es
no
3. Do you have any health restrictions?
No or Yes, p lease describe below
4. Did you p a s s your high school physical for the school y ear 1996-97?
Y es
or No
5. List an y m edications you currently tak e.________________________________
6. C heck here if you w ant a copy of th e research results.
subject signature
p aren t signature
44
APPENDIX C
ACCEPTANCE CRITERIA
1. The subject did not have an Injury to his/her knee, hip, ankle or foot, th at kept
him /her out of a practice or g a m e for m ore than o n e w eek in the past o n e
year.
2. The subject is not currently u n d er any health restrictions.
3. The subject p assed his/her high school physical for the school year 1996.
45
APPENDIX D
CONSENT FORM
I u n d erstand that I am participating in a study th at will m e a su re strength of the
ham string and quadriceps m uscles of the thigh (upper leg), using an isokinetic
testing m achine. Isokinetic testing is a way to m easu re strength. It consists of a
fixed sp e e d (s) with an accom m odating resistance. T he resistance is determ ined
by how hard the subject p u sh es during e ach testing s p e e d . I also understand
that th e know ledge gained from th e strength m easu rem en ts is expected to help
physical therapists, certified athletic trainers, co ach es, doctors, and ath letes to
better identify w here w e a k n e sse s exist.
I also u nderstand that:
1. I w as selected b e c a u se I have not had a knee injury in the p a s t one
y ear th at kept me out of practice or a gam e for more than one
week.
2. it is not anticipated that this testing/study will lead to physical risk to
myself.
3. th ere is potential for m uscle so re n e s s following th e testing procedure.
4. information I provide will b e kept strictly confidential and that th e data
will be coded so th at identification of individual participants will not
be possible.
5. a sum m ary of the results will be m ad e available to m e upon my
request.
6. I will "warm-up" on an exercise bicycle before testing on the Biodex
isokinetic m achine.
7. I will be given verbal and written instructions ab o u t th e testing
procedure before testing.
I acknow ledge that:
"I h av e been given an opportunity to a sk questions re: this research study
an d that th o se questions have been answ ered to my satisfaction."
"In giving my consent, I understand th a t my participation in this study is
voluntary and I m ay discontinue the study at any tim e during the testing."
46
47
"I hereby authorize th e Investigator(s) to re le a se information obtained in
this study to scientific literature. I understand that I will not be identified by
name."
"I have b e en given th e investigators nam es, Diane Beach, Lisa R ose, and
Barb Hoogenboom , p h o n e num bers, (616) 752-6182 so th at I m ay contact
them if I h av e questions."
"I acknow ledge th e I h av e read and understand th e above information and
that I a g re e to participate in the study."
If you h av e any questions concerning your hum an rights a s a participant
in this study, you may contact the Chair of Saint Mary's Institutional
Review Board at 752-6567.
Signature of athlete
Signature of p aren t (if athlete<18 years old)
Signature of w itness (must b e 18)
APPENDIX E
PARENT INFORMATION LETTER
D ear P aren ts,
W e are graduate stu d en ts in Grand Valley S tate University's M asters of
Physical Therapy and/or Health S cience program s and a re looking for volunteers
of high school fem ale and m ale basketball players.
S ports Illustrated recently highlighted th e incidence of anterior cruciate
ligam ent (ACL) injuries in fem ale basketball players. T here may b e several
factors th at contribute to the knee injury. Strength of leg m uscles and
neurom uscular conduction are two a reas th at have b e e n su g g ested .
T he results of this study could have national implications for prevention of
ACL injuries in high school fem ale and m ale basketball players.
W e need volunteers to te st quadriceps/ham string strength ratios and
reaction time. Your son/daughter h a s ex p ressed an interest in receiving a free
leg te st (normal cost is approximately $125.00) in ex ch an g e for u s e of numerical
confidential data. All testing will b e performed in Saint Mary's S ports Medicine
D epartm ent at the downtown location, 200 Jefferson, G rand Rapids, Ml. Parking
will be free.
If you are willing to allow your child to participate in this study, p lease call
(616) 752-6182 to s e t up an appointm ent for th e strength test. Your
so n /d au g h ter m ust have the attached consent form and pre-test questionnaire
signed and with them at th e appointm ent to be allowed to participate.
Thank You,
Diane B each A.T.,C.
Certified Athletic Trainer
S tudent Physical Therapist
Barb Hoogenboom P.T., SCS, A.T.,C.
Physical Therapist
Sports Clinical Specialist
Certified Athletic Trainer
Lisa R o se
S tudent Physical Therapist
48
APPENDIX F
INSTRUCTION FOR ISOKINETIC TESTING
You will be performing a strength te st on this m achine. The w ay this
m achine works is. th e harder you push on the leg bar, or th e faster you move the
leg bar, the more resistan ce the m achine will give you an d the higher your score.
You n eed to push with equal effort in both directions (up and down).
You will b e allowed to practice on each sp eed , three subm axim al efforts followed
by th ree maximal efforts. T here will be a 10 second rest, then begin th e test.
The te st will consists of five repetitions at each sp eed . You will be ask ed if you
are ready. If yes, you will be instructed in a com m and of ready, go! S tart the
test w hen you h ear th e word "go."
You will rep e at the sa m e procedure for each of th e next four testing
s p e e d s. Each sp e e d g ets progressively faster or "easier." W e ask th at you do
the b est th at you can. If you experience any discomfort or pain during th e test,
p le ase e a s e up or sto p during th e test. You are in full control of the resistance.
The m achine will respond to your effort.
TEST; "Do you h av e any questions before w e begin?...W e will now begin."
1. Set-up:
a. Check b alan ce on th e Biodex® dynam om eter
b. Position th e subject at 115 d eg rees hip flexion. (Adjust s e a t back
accordingly).
c. Line up th e knee axis of rotation with the coronal plane through the
knee axis. (Adjust s e a t back accordingly).
d. Stabilize subject with hip, thigh and shoulder strap s.
e. Pull strap s "snug." Tell subject "the strap s should feel snug, not tight."
49
50
2. S et ROM:
Instruct the subject: "P lease relax your leg while I adjust your ROM.
a. S e t the reference angle at 110 d eg rees flexion a s m easu red with a
goniom eter.
b. M easure 0 d e g re e s and s e t ROM buttons for knee extension and k n ee
flexion.
3. M easure the gravity effect:
"We n eed to weigh your leg now. Let me straighten your leg...now,
com pletely relax your leg."
"Now let me lower your leg down.
4. "You will now be given five repetitions to learn how to u se this m achine. W ait
until I s a y "ready?...go." ........... "R eady? (yes) go!"
5. "Does everything feel okay? Is anything too loose or too tight?"...
TEST at 60 d eg rees/seco n d :
a. Practice reps: "I w ant you to perform th ree subm axim al repetitions and
th ree maximal repetitions a s a warm-up. P le a se begin th e warm-up
after my com m and, ready?...go."
b. "R est 10 sec o n d s
c. "Now pull your leg all the w ay back in the starting position. You will do
five test repetitions a s hard a s you can. R eady? go."
R ep eat for contralateral limb and at all su b seq u en t te st sp eed s.
APPENDIX G
HAMSTRING/QUADRICEPS RATIOS PER DAVIES, (1992)
M ales and Fem ales a g e s 15-40 years.
S p eed
60 d e g /se c
H am string/quadriceps ratio
60% -69%
180 d eg /se c
70% -79%
240 d e g /se c
80% -89%
300 d e g /se c
85% -95%
51
APPENDIX H
HAMSTRING/QUADRICEPS RATIOS PER WYATT AND EDWARDS, (1981)
M ales
F em ales
60 d e g /se c
72%(+/-11%)
71% (+/-11% )
180 d e g /se c
78%(+/-11%)
79% (+/-11% )
300 d e g /se c
83%(+/-14%)
85%(+/-16% )
S p e ed
52
APPENDIX I
NORMATIVE ISOKINETIC DATA FOR HAMSTRING/QUADRICEPS RATIOS,
MOORE AND WADE, (1989)
Variable
Fem ales
Males
60 d eg rees/seco n d
.63 (63%)
.68 (68%)
180 d e g rees/seco n d
.80 (80%)
.85 (85%)
300 d e g rees/seco n d
.94 (94%)
.97 (97%)
53