Cruciate Ligament Forces Between Short and Long Step Forward Lunge

8/10/2019 Cruciate Ligament Forces Between Short and Long Step Forward Lunge

1/11

Cruciate

Ligament

Forces

between

Short-Step

and

Long-Step

Forward

Lunge

RAFAEL

F. ESCAMILLAt,

NAIQUAN

ZHENG

2

,

TORAN

D.

MACLEOD

3

,

RODNEY

IMAMURA

4

,

W.

BRENT

EDWARDS

5

, ALAN

HRELJAC

4

,

GLENN

S. FLEISIG

6

, KEVIN

E.

WILK7,

CLAUDE

T.

MOORMAN

III ,

LONNIE

PAULOS ,

and

JAMES

R.

ANDREWS

6

Andrews-Paulos

Research

andEducation

nstitute,

GulfBreeze,

FL;

2

Department

ofMechanical

Engineering

and

Engineering

Science,

The

Center

or Biomedical

Engineering,

University

ofNorth

Carolina

at Charlotte,

NC;

3

Department

ofPhysical

Therapy,

Center

or Biomedical

Engineering

Research,

University

ofDelaivare,

Newark,

DE;

4

Kinesiology

and

HealthScience

Department,

California

State

University

Sacramento,

CA;

5

Department

ofKinesiology

andNutrition,

University

of Illinois

at Chicago,

IL;

6

American

Sports

Medicine

Institute,

Birmingham,

AL;

7

Champion

Sports

Medicine,

Birmingham,

L

8

Duke University

MedicalCenter;

Durham,

NC

ABSTRACT

ESCAMILLA,

IL F.,N. ZHENG,

T.

D. MACLEOD,

R

IMAMURA,

W.

B.

EDWARDS,

A.

HRELJAC,

G.

S.

FLEISIG,

K. E.

WILK,

C.

T. MOORMAN

III,

L. PAULOS,

and

J. IR

ANDREWS.

Cmuciate Ligament

Forces

between

Short-Step

and

Long-Step

Forward

Lunge.

Med. Sci. Sports

Exerc. Vol. 42,

No.

10,

pp.

1932-1942,

2010. Purpose:

The

purpose

of this

study

was to

compare

cruciate ligament

forces

between

the

forward

lunge

with a

short step

(forward

lunge short)

and

the forward

lunge

with a

long

step (forward

lunge

long).

Methods:

Eighteen

subjects

used their

12-repetition

maximum

weight

while performing

the

forward

lunge

short and

long

with and

without a

stride.

EMG,

force,

and

kinematic

variables

were

input into a

biomechanical

model

using

optimization,

and

cruciate liga-

ment

forces

were

calculated

as

a

function

of knee

angle.

A

two-factor

repeated-measure

ANOVA

was

used

with

a

Bonferroni

adjustment

P

< 0.0025)

to assess

differences

in

cruciate forces

between

lunging

techniques.

Results:

Mean posterior

cruciate

ligament (PCL)

forces

(69-765

N

range)

were

significantly

greater

(P

< 0.001)

in the forward

lunge

long

compared

with

the forward

lunge

short

between

00 and

800

knee flexion

angles.

Mean

PCL

forces

(86-691

N

range)

were

significantly

greater

(P

< 0.001)

without

a stride

compared

with

those

with a

stride

between 00

and

20'

knee flexion

angles. Mean

anterior

cruciate

ligament

(ACL)

forces

were

generated

(0-50

N range

between 0

and

100 knee

flexion

angles)

only

in

the forward

lunge

short

with stride.

Conclusions:

All

lunge

variations

appear

appro-

priate and

safe during

ACL

rehabilitation

because

of

minimal

ACL

loading.

ACL loading

occurred

only in

the forward

lunge

short

with stride.

Clinicians

should

be cautious

in

prescribing

forward

lunge

exercises

during

early

phases

of

PCL

rehabilitation,

especially

at

higher

knee

flexion

angles

and during

the forward

lunge

long, which

generated

the

highest

PCL

forces.

Understanding

how

varying

lunging

techniques

affect

cruciate

ligament

loading

may

help clinicians

prescribe

lunging

exercises

in a

safe manner

during

ACL

and

PCL

rehabilitation.

Key

Words:

ACL, PCL, KNEE

KINETICS, REHABILITATION, CLOSED CHAIN

losed

chain

weight-bearing

exercises

such as

the

squat,

leg

press,

and

forward

lunge

are

commonly

used

in rehabilitation

settings,

such

as

after

anterior

cruciate

ligament

(ACL)

or

posterior

cruciate

ligament

(PCL)

reconstruction

surgery

(10,39).

These

exercises

can

be per-

formed

with technique

variations,

which

may

affect

ACL

and

PCL

loading.

Although

the

effects

of

exercise

technique

variations

on cruciate

ligament

loading

have

been

examined

while

performing

the squat

and

the leg press

(13,14),

there

are

Address

for correspondence:

Rafael

F.

Escamilla,

PILD.,

P.T.,

CSCS,

FACSM,

Director

of

Research,

Andrews-Paulos

Research

and

Education

Institute,

1020

Gulf

Breeze

Parkway,

Gulf

Breeze,

FL 32561;

E-mail:

[email protected].

Submitted

for

publication

November

2008.

Accepted

for publication

December

2009.

0195-9131/10/4210-1932/0

MEDICINE

&

SCIENCE

IN

SPORTS

&

EXERCISFO

Copyright

2010

by the

American

College of

Sports

Medicine

DOI:

10.12491MSS.0b013e3181d966d4

no studies

that have examined

the

effects of technique var-

iations

on

cruciate

ligament

loading

while

performing

the

forward

lunge.

Because

patients

use

the

forward

lunge

after

ACL

and PCL

reconstruction,

it

is

important

to

understand

how

the

cruciate

ligaments

are

loaded,

especially

during

the

early

phases

of

rehabilitation

when

the

goal

is

to

minimize

ACL

or

PCL

loading.

There

are

multiple

techniques

that individuals

can

use

during

the forward

lunge,

such

as

lunging

using

a sbort

step

length

or a

long

step

length.

Lunging

forward

using a

long

step

typically

results

in the

lead knee

being maintained over

the

lead

foot

throughout

the knee

range

of

motion,

whereas

lunging

forward

using a

short

step

length

lunge

typically

results in

the

lead knee

translating

beyond

the toes

throughout

much

of

the knee

range

of

motion.

Some

clinicians

believe

that

anterior

movement

of the

lead

knee

beyond

the toes

dur-

ing a

short step

forward

lunge

increases

cruciate ligament

loading,

although

there are very

limited

data

that support

this

belief

(2).

Moreover,

it

is

unclear

if

the

ACL

or

the

PCL

is

loaded

when

anterior

knee

movement

occurs.

1932


2/11

The

forward

lunge

can be performed

and progressed

using

varying

techniques. One technique involves

starting in

an

upright position,

stepping

forward

with the lead leg

and

flexing

the

lead knee until

the rear

knee

touches

the ground,

and then pushing

back

to the

starting

upright position. Be -

cause a stride

is

taken by the lead leg

during each repetition,

this

technique may

be called

a

forward

lunge with a stride.

Another

technique

involves

first stepping forward

with the

lead

leg

and starting with both

knees fully extended. From

this

position,

the individual

flexes the lead

knee until

the rear

knee touches

the

ground,

and then

both knees are

extended

back to

the

starting

position.

In this

technique,

which

has

been

previously

described

(16), both feet

remain stationary

as

the

individual lunges

up and down. Because this tech-

nique

does

not involve striding

forward

during each repeti-

tion, this technique

may be

called a

forward

lunge without a

stride. The lunge

with

a

stride can

be a

progression of the

lunge without

a

stride, with the lunge without a

stride being

a

beginning exercise and the

lunge with a stride being more

difficult

to

perform and advanced. The lunge with

a

stride

requires higher levels

of

lower

body strength

and

coordina-

tion

compared

with

the lunge without

a

stride.

Understanding

how

cruciate ligaments are loaded differ-

ently among these technique variations of the forward lunge

may allow clinicians to prescribe safer and more effective

knee rehabilitation treatment to

patients

during ACL

or PC L

rehabilitation. For example, during the forward

lunge,

if

ACL

loading occurs

when

using

a

short

step but not

when

using

a

long

step,

the forward

lunge

with

a long

step

may be

more appropriate for the patient

if

the

clinician's immediate

goal for the

patient

is

to

minimize

ACL

loading. Similarly,

during the forward lunge, if

PCL

loading occurs with a stride

but not without

a

stride, the forward lunge without

a

stride

may be more appropriate for the patient if the clinician's

immediate goal

for

the patient

is

to minimize

PCL

loading.

Our

purpose was

to

compare cruciate ligament tensile

forces

while

performing

the

forward

lunge with a

long step

(forward lunge long), with

a short

step

(forward

lunge short),

with a stride, and without a stride.

It

was

hypothesized

that

ACL tensile

forces

would

be greater

in

the forward

lunge

short compared

with the

forward

lunge long, PCL tensile

forces would

be

greater

in

the forward lunge long compared

with the forward lunge short,

and PCL

tensile forces would

be greater during the forward lunge with a stride compared

with

without a

stride.

Muscle

force

magnitudes in each

subject's

quadriceps and

hamstrings

will also

be

estimated

to

help

better understand ACL

and

PCL

force

magnitudes.

METHO S

Subjects.

Eighteen healthy

individuals (nine men and

nine

women) without

a history of

cruciate ligament pathol-

ogy participated with an average age, mass, and height of

29

t 7 yr, 77

9

kg,

and

177

6 cm, respectively,

for me n

and 25

2

yr,

60

4

kg,

and

164 6 cm, respectively, for

women. All subjects were required to perform the forward

lunge

exercises

pain free

and

with proper

form

and tech-

nique for 12 consecutive

repetitions using

their 12-repetition

maximum (12RM)

weight.

To control the EMG signal quality, this study was limited

to men and women who had average

or below

average

body

fat, which

was

assessed by

the

Baseline skinfold calipers

(Model

68900;

Country Technology,

Inc., Gays Mills, WI),

and appropriate

regression equations

and

body

fat standards

set

by the American

College

of Sports Medicine

(3).

Aver-

age

body

fat

was

12%

4%

for

men and

18%

1

for

women. The protocol used in

the current

study

was approved

by the institutional

review board

at the California

State Uni-

versity,

Sacramento, CA,

and

all

subjects

provided

written

informed

consent.

Exercise

description. Each subject performed

the

for-

ward lunge long

(Fig. 1) and

the

forward

lunge short

(Fig. 2)

with and without a stride. The starting and the ending posi-

tions

of

the forward

lunge long

with stride and forward lunge

short with stride were the same, which involved standing

upright

with

both feet

together and

the

knees

fully

extended

(full

knee extension

= knee

angle). From this

position, the

subject held

a

dumbbell weight

in each

hand

and lunged

forward with the right leg toward

a

force platform

at

ground

level. At right foot

contact, the

right

knee

flexed at

approxi-

mately

45.s-I

until

approximately

9001000

knee angle, at

which time the left knee made contact

with

the

ground. From

this position,

the

subject immediately pushed backward

the force platform

and returned to the upright standing posi-

tion with feet together.

During the forward lunge

long,

each

subject

used

a

long

step

length

that resulted in the

right leg

(tibia)

being

approxi-

mately vertical at the lowest position

of

the

lunge (Fig. 1), thus

maintaining

the knee

over

the

foot.

The

average

step

length

(measured from left toe to

right

heel)

for

the forward lunge

FIGURE 1-Fonvard

lunge

with a

long

step (forward

lunge long).

SHORT-STEP

AND LONG-STEP FORWARD LUNGE

Medicine Science in

Sports Exercisee

1933


3/11

11111:10 ,j

FIGURE

2-Forward

lunge

with a

short step forward

lunge

short).

long

was

89

+

4

cm

for

men

and

79 :

cm for

women.

Th e

step length

for

the forward

lunge

short

was

one half

the

dis-

tance of

he step

length

of

the

forward

lunge

long.

The

shorter

step

length

for

the

forward

lunge

short

caused

the

anterior

surface

of

the

knee to

translate

beyond

the

distal

end

of the

toes,

as

shown

in Figure

2.

The

forward

lunge

long

and

short

without

stride

was

performed

the same

as

the forward

lunge

long

and

short

with

stride,

with

the

exception

that

during

the

forward

lunge

long

and

short

without

stride

both

feet

remained

stationary

throughout

each repetition.

That

is,

from

the

lowest position

of

he forward

lunge

long

and

short

shown

in

Figures

1 and 2,

the subject

fully

extended

both

knees

and then

flexed

both

knees

returning

back

to

the

lowest

position

of

the lunge.

For

all

lunge

variations,

a

metronome

was

used

to help

ensure

the right

knee

flexed

and

extended

at

a normal

rate

of

ap-

proximately

45-s-

1.During

the

forward

lunge

long

and

short

with

and

without

a

stride,

maximum

forward

trunk

tilt

(which

occurred

near

maximum

lead

knee

flexion)

was

approxi-

mately

10'-20'

for

all

subjects.

Data collection.

Each

subject

came

in for

a

familiar-

ization

session

1 wk

before

the

testing

session.

The

experi-

mental

protocol was

reviewed, the

subject was

given the

opportunity

to practice

the

lunge

variations,

and

each

subject's

step

length for

the

forward

lunge

long

was

determined.

In

ad-

dition,

each

subject's

12RM

was

determined

while

performing

the

forward

lunge

with

stride

using

a

step

length

halfway

be-

tween

the

forward

lunge

long

and

the

forward

lunge

short.

Subjects

used

their

12RM

weight

for

the

four

lunge

variations

during

data

collection.

The

mean

total

dumbbell

mass

used

was

49:

11

kg

for

men

and

32

8 kg

for

women.

To

collect

EMG

data,

Blue

Sensor

(Ambu

Inc.,

Linthicum,

MD)

disposable

surface

electrodes

(type

M-00-S)

22 mm

wide

and

30 mm long were

positioned in a bipolar configuration

along

the

longitudinal

axis of

each

muscle,

with

a center-

to-center

distance

of

approximately

3

cm between

electrodes.

Before

applying

the

electrodes,

the skin

was

prepared

by

shaving,

abrading,

and

cleaning

with

isopropyl

alcohol

wipes

to reduce

skin

impedance.

Each

subject

had

electrode

pairs

positioned

on the

right

side

using

previously

described

locations

(4)

for

the

following

muscles:

a) rectus

femoris,

b) vastus

lateralis,

c)

vastus

medialis,

d)

medial

hamstrings

(semimembranosus

and

semitendinosus),

e) lateral

hamstrings

(biceps

femoris),

and

f)

gastrocnemius

(middle

portion

be-

tween

medial

and lateral

bellies).

Spherical

markers

(3.8

cm

in diameter)

covered

with

3MTM

reflective

tape were

attached

to adhesives

and

posi-

tioned

over

the

following

bony

landmarks:

a) third

meta-

tarsal head

of

he

right

foot,

b)

medial

and

lateral

malleoli

of

the

right

leg, c) upper

edges

of

the

medial

and

lateral

tibial

plateaus

of

the right

knee,

d) posterosuperior

greater

tro-

chanters

of

he

left

and

right

femurs,

and e)

lateral

acromion

of

the

right

shoulder.

After

the

subject

warmed

up

and

practiced

the exercises

as

needed,

data

collection commenced. A six-camera Peak

Performance

motion

analysis

system

(Vicon-Peak

Perfor-

mance

Technologies,

Inc., Englewood,

CO)

collected

60

Hz

of

video

data.

A force

platform

(Model

OR6-6-2000;

Advanced

Mechanical

Technologies,

Inc.,

Watertown,

MA)

collected

960

Hz

of

force

data,

while

a

Noraxon

EMG

system

(Noraxon

USA,

Inc.,

Scottsdale,

AZ)

collected

960

Hz

of

EMG

data.

The

EMG

amplifier

bandwidth

frequency

was

10-500

Hz

with an

input

impedance

of

20,000

k.M,

and

the

common-mode

rejection

ratio

was

130

dB.

Video,

EMG,

and force

data

were

electronically

synchronized

and collected

simultaneously

as

each subject

performed

one set

of

three

repetitions

using their

12RM

weight

of

the forward

lunge

long

with

stride,

forward

lunge

long

without

stride,

forward

FIGURE 3-Computer optimization

with input from measured

knee

torque

from

inverse

dynamics

and

predicted

knee

torque

from

muscle

model,

where

TK

=

resultant

knee

torque,

FK

=

resultant

knee

force,

I

= moment

of

inertia

about

leg center

of

mass, ax

angular

acceleration

of

leg,

=

mass

of

leg, a

- linear

acceleration

of

leg,

g =

gravitation

constant

9.80

mrs-

2

, Fe,t

= external

force acting

on

foot,

T.

external

torque

acting

on

foot,

FQ

=quadriceps

force,

Fp

= patellar

tendon

force,

Fu

=

hamstrings

force,

and

FG

= gastrocnemius

force.

Note-

to

simplify

the

drawing,

the

equal

and

opposite

forces

and

torques

acting

on

the

distal

leg

and

proximal

ankle

are

absent.

http://www.acsrn-msse.org

1934

Official

Journal

of the

American

College

of Sports

Medicine


4/11

FIGURE

4-Forces acting

on

the proximal tibia:

F

11

=

force

from

ham-

strings, FG

= force from gastrocnemius (note: this force does not act

directly on

proximal

tibia), Fpr = force

from

patellar tendon, FACL

force from ACL, FpcL

=

force from PCL, and FTF,= force from femur.

lunge

short with stride,

and

forward lunge short without stride,

assigned in

a

random order. Each subject

rested approximately

2-3 min between

lunge variations. Tape markers were used

to

help

each

subject

identify the

proper

stride length distance

between

their rear

and

lead foot for each

lunge variation.

After completing

all

lunge

variations,

each subject per-

formed

maximum voluntary isometric contractions (MVIC)

to

normalize the EMG

data

collected during each

lunge varia-

tion. The MVIC for the rectus femoris,

the vastus lateralis, and

the vastus medialis

were

collected

in a

seated

position at

90 '

knee

and

hip

flexion with

a

maximum effort knee

extension

(13). The MVIC for the

lateral

and medial hamstrings were

collected in

a seated

position at 900 knee

and

hip

flexion

with

a

maximum effort knee flexion (13), with the ankle main-

tained in

a

neutral

position. MVIC

for

the gastrocnemius

was collected

during a maximum effort standing one leg toe

raise

with

the

ankle

positioned

approximately halfway be-

tween neutral

and full plantarflexion (13). Two 5-s

trials

were

randomly collected for each MVIC, with 1-2 min of rest

given between

trials.

, Data

reduction.

Video

images for each reflective

marke r were tracked and digitized in -three-dime nsional

space

with Peak Performance software (version 5.0), using

the direct linear transformation calibration

method

(34).

An -

kle,

knee,

and hip

joint

centers from the link

segment model

were mathematically determined using the external markers

and appropriate equations

as previously

described

(7,13).

Testing of

the accuracy

of

the

calibration system

resulted

in

reflective markers that could be

located

in three-dimensional

space

within

our

laboratory

with an error less than 7 mm. The

raw position data

were

smoothed

with

a

double-pass

fourth-

order Butterworth low-pass filter

with

a

cutoff frequency

of 6 Flz

(13).

Joint angles, linear

and

angular

velocities,

and

linear and

angular

accelerations

were calculated

in

a

two-

dimensional sagittal

plane

of the

knee

using appropriate ki-

nematic equations

(13).

Raw EMG

signals were full-waved rectified,

smoothed

with

a

10-ms moving

average

window, linear enveloped

(5).

throughout the knee range of motion for each repetition, and

normalization

by expressing the data as

a percentage

of each

subject's

highest corresponding MVIC trial. The highest

EMG

signal

over

a

1-s

time

interval throughout

the 5-s

MVIC

was

determined to calculate

MVIC

trials. Normalized EMG

data

for

the

three

repetitions

(trials) were then averaged at

corresponding knee flexion angles between 0' and 90' and

were used

in

the biomechanical model described

below.

TABLE

1.

Mean

t

SD

cruciate ligament force

(N)

alues between forward lunge

step

length variations

and

between forward lunge

stride

variations.

ACL

forces represent

negative values

and

PCL

forces represent

positive values.

Step Length Varialions Stride Variations

Long Step

Short Step P Value

With Stride

Without

Stride P Value

Knee

angles for descent phase

0.

349

i

202

69 169


5/11

~ 800

S

0

E? 400

20 0

0

20

40

60

86

lbo

io

Knee

Flexing

(Descent)

Knee i

Knee Flexion

Angle

(deg)

Forward

Lunge

Long

Without

Stride

---

Forward

Lunge

Short

Without

Stride

FIGURE

5-AMean

(SD)

PCL

tensile

force

during

forward

lunge

long

and

short

without

stride.

Biomechanical

model.

As

previously

described

(13,41),

a

biomechanical

model

of

he

knee

(Figs.

3

and

4)

was

used

to

continuously

estimate

cruciate

ligament

forces

throughout

a

90*

knee

range

of

motion

during

the

knee flexing

(squat

de-

scent)

phase

(0o--90')

and

the

knee

extending

(squat

ascent)

phase

(90o0o--)

of

the

lunge.

Resultant

force

and

torque

equilibrium

equations

were

calculated

using

inverse

dynamics

and

the

biomechanical

knee

model

(13,41).

Anteroposterior

shear

forces

in the

knee

were

calculated

and

adjusted

to lig-

ament

orientations

to

estimate

ACL

or

PCL

forces,

while

moment

arms

of

muscle

forces

and

angles

for

the

line

of

ac-

tion

for

the muscles

and

cruciate

ligaments

were

expressed

as

polynomial

functions

of

knee

angle

(23).

Knee

torques

from

cruciate

and

collateral

ligament

forces

and

bony

contact

were

assumed

to be

negligible,

as were

forces

and

torques

out

of

the sagittal

plane.

Quadriceps,

hamstrings,

and

gastrocnemius

muscle

forces

were

estimated

an

EMG-driven

biomechanical

knee

model,

as

previously

described

(13,41).

Because

the

accuracy

of

estimating

muscle

forces

depends

on accurate

estimations

of

C

E

xtending Ascent)

a

muscle's

physiological

cross-sectional

area

(PCSA),

max-

imum

voluntary

contraction

force per

unit

PCSA,

and EMG-

force

relationship,

resultant

force

and

torque

equilibrium

equations may

not

be satisfied. Therefore, the modified

muscle

force

Fm(

equation

at

each

knee

angle

is

as follows:

F.

=

cik1krtA1orm .)

[EMG

1

MV1C

1

],

where

Ai

is

the

PCSA

of

the

ith muscle,

o-m()

is

the

MVIC

force

per

unit

PCSA

of

the

ith

muscle,

EMG

and

MVICi

are

the EMG

window

averages

of

the

ith

muscle

EMG

during

exercise

and MVIC

trials,

ci

is

a

weight

factor

(values

given

below)

adjusted

in

a computer

optimization

program

to

min-

imize

the

difference

between

the

resultant

torque

from

the

inverse

dynamics

(Tw,)

and

the

resultant

torque

calculation

from

the

biomechanical

model

Tin)

(Fig.

3), k l

represents

each

muscle's force-length

relationship

as

function

of hip

and

knee

flexion

angles

(on

the

basis

of

muscle

length,

fiber

length,

sarcomere

length,

pennation

angle,

and cross-sectional

area)

(36),

and

kv

represents

each

muscle's

force-velocity

relationship

on

the

basis

of

a Hill-type

model

for

eccentric

1000-

600

800

400

200

0

-200.

200

2'0 40

60

80

100

8'0

6'0

4 0

20

Knee

Flexing

(Descent)

Knee Extending

(Ascent)

Knee

Flexion

Angle

(deg)

Forward

Lunge

long

Nwith

Stride

-F--

Forward

Lunge

short with

Stride

FIGURE

6-Mean

(SD)

ACL

and

PCL

tensile

force

between

forward

lunge

long

and

short

with

stride.

http://www.acsm-msse.org

1936 Official

Journal

of

the

American

College

of Sports

Medicine


6/11

U

0i

Knee Flexing (Descent)

Knee

Extending

(Ascent)

Knee Flexion

Angle (deg)

- Forward

Lunge

Long

with Stride

-

Forward Lunge

Long

without Stride

FIGURE

7-Mean (SD)

PCL

tensile force

during

forward lunge long with

and without

stride.

and concentric

muscle

actions using

the following equations

from Zajac

(40)

and

Epstein

and

Herzog (12):

v =

b

- (a/Fo) ,)/(b

+ v)

concentric

k,. =

C- C- l) b+ a/Fo)v)/ b-

v) eccentric

with Fo representing

isometric

muscle force; lo, muscle

fiber

length at rest;

v, velocity;

a =

0.32

Fr

;

b = 3.210

per second;

and

C

=

1.8.

Ratios

of

PCSA

between muscle

groups (41)

were deter-

mined from the

PCSA data from

Wickiewicz

et al. (36).

According to Narici et

al. (29), the total PCSA

of the quad-

riceps

was

approximately

160 cm

2

for

a

75-kg man, and

the

total PCSA

of the quadriceps

was scaled up or

down by in-

dividual

body

mass

(41). Forces generated

by

the

knee flexors

and extensors at

MVIC

were assumed to

be

linearly pro-

portional to their

PCSA (41).

Muscle force per unit

PCSA

was

35

N.cm-

2

for

the hamstrings

and

gastrocnemius

and

40 N-cm-

2

for the quadriceps

(11,28,29,37).

The

objective function used

to determine each ith

mus-

cle's

coefficient

c,

was as follows:

-in

f

ci)

=

_ I

c 2

+X T.,

T.X

J=t

I-1

subject

to clow


7/11

TABLE

2. Mean

+

SD

quadriceps

and

hamstrings

force

values

during forward

lunge exercises.

Quadriceps

(N)

Hamstrings

(N)

Step

Length

Variations

Stride Variations

Step

Length

Variations

Stride

Variations

Long

Step

Short

Step

With

Stride

Without

Stride

Long

Step

Short

Step

With

Stride

Without

Stride

Knee

angles

for descent

phase

0. 87:

84

63

49

80 *

84 71

+ 49

47

121

29 15

22

15 54:20

10* 111

*

67

99:

76

116

89

94

t 55

64

38

28

18

34

30

57*

26

2

131

68

109:

74

135

90

105

t

51

66:

40

31

0

38

34

58:

26

300

179

80

126:

76

158 81

147

75

69 i

39

34

0

46

4

56

25

40*

227

117

157:

94

176

105

207 +

106

67:

39

38;

23

50

7

56 *

25

5

326

163

235

131

258

47

303 146

70:

36

41

27

58

8

53:

25

60*

435

86

344

187

354:

191

425

182

71

41 39 24 63 2 47

23

700

551

204

469

i

247

471 221

549

230

67 43

34

* 21

61

43

41

+ 23

o0o

560

157

527:

239

510

12

577

t

183

60

37

32t

2

51

4

41

:t

23

900

540:

172

599

219

563

196

577

195

57

33

36:

21

49

8

44* 26

Knee

angles

for

ascent

phase

90B

400

120

542

129

459

130

483:

120

1 1

48

99 51

102 49

98:

50

80

434

156

623

211

515

:L

08

542:

159

108

48

94

59

103

58

99

49

7

516

175

681

272

613

264

585 182

120

58

92

2

112

5

1 1

45

600

532

192

658 290

620

283

570:

199

128

3

90:

50

118

70

100

43

50

486:

188

577 278

571

73

492

193

134 64

87

49

122

71

99:

41

400

409

65

437t203

468

212

377

56

139:

71

82

45

122

5

100

41

300

336

i 144

349:

165

410

191

275:

118

143 4

84

42

125

75

102

1

2

268

19

257

24

338:

166

187

7

140

75

83 +

42

120

76

103

2

10*

206

05

183

1 1

269

49

119

57

142

80

81 41

119 81

104

0

0. 136 0 141

0 199

127

79 3,

121

t 84

70

6 88

4 103

36

variations

and

stride

variations)

repeated-measures

ANOVA.

To minimize

the

probability

of

type I

errors

secondary

to

the

use of

a

separate

ANOVA

for

each

knee

angle,

the

Bonferroni

adjustment

had

a

level of

significance

set

at P

Documents

Cruciate Ligament Forces Between Short and Long Step Forward Lunge