Author Manuscript NIH Public Access 2, and Chang S. Nam ......age group. A commercial dynamometer...

Leg Strength Comparison between Younger and Middle-ageAdults

Sukwon Kim1, Thurmon Lockhart2, and Chang S. Nam31 Human Factors and Ergonomics Laboratory, Department of Industrial Engineering andTechnology, Texas A&M University-Commerce, Commerce TX 754282 Locomotion Research Laboratory, Department of Industrial and Systems Engineering, VirginiaTech, Blacksburg VA 240613 Department of Industrial Engineering, University of Arkansas, Fayetteville AR 72701

AbstractAlthough a risk of occupational musculoskeletal diseases has been identified with age-relatedstrength degradation, strength measures from working group are somewhat sparse. This is especiallytrue for the lower extremity strength measures in dynamic conditions (i.e., isokinetic). The objectiveof this study was to quantify the lower extremity muscle strength characteristics of three age groups(young, middle, and the elderly). Total of 42 subjects participated in the study: 14 subjects for eachage group. A commercial dynamometer was used to evaluate isokinetic and isometric strength atankle and knee joints. 2 × 2 (Age group (younger, middle-age, and older adult groups) × Gender(male and female)) between-subject design and Post-hoc analysis were performed to evaluatestrength differences among three age groups. Post-hoc analysis indicated that, overall, middle-ageworkers’ leg strengths (i.e. ankle and knee muscles) were significantly different from younger adultswhile middle-age workers’ leg strengths were virtually identical to older adults’ leg strengths. Theseresults suggested that, overall, 14 middle-age workers in the present study could be at a higher riskof musculoskeletal injuries. Future studies looking at the likelihood of musculoskeletal injuries atdifferent work places and from different working postures at various age levels should be requiredto validate the current findings. The future study would be a valuable asset in finding interventionstrategies such that middle-age workers could stay healthier longer.

Keywordsmiddle age workers; dynamic leg strength; risk of musculoskeletal disorder

1. IntroductionAge-related strength degradation has been identified as a risk factor for occupationalmusculoskeletal disorders (MSDs) because its dreadful impacts on a fundamental role ofmuscle strength in functional capabilities or performances in many work-related settings(Hoogendorn et al., 1999; Johnson and Nussbaum, 2003; Kallman et al., 1990; Kim andLockhart, 2008; Kumar et al., 1994; National Research Council, 2001; Sjøgaard and Sjøgaard,1998; Sprince et al., 2007; Yip, 2004).

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NIH Public AccessAuthor ManuscriptInt J Ind Ergon. Author manuscript; available in PMC 2011 May 1.

Published in final edited form as:Int J Ind Ergon. 2010 May 1; 40(3): 315–320. doi:10.1016/j.ergon.2009.11.003.

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Overexertion, rapid work pace and repetitive motion patterns, intensive static effort or forcefulexertions, and insufficient recovery time significantly contributed to the increases in thelikelihood of MSDs (Butler and Kozey, 2003; Jensen et al., 1996; Jensen 2008; Kee and Seo,2007; Malchaire et al., 2001; McMillan and Nichols, 2005; Newell and Kuman, 2004; Sjøgaardand Sjøgaard, 1998; Thorn et al, 2002; Viikari-Juntura and Silverstein, 1999; Water, 2004).Additionally, risk of work-related musculoskeletal disorders (MSDs) increased as theoccupational tasks required a larger fraction of a worker’s physical capability (Cooper et al.,1994; Felson et al., 1991; Jenson 2008; Johnson and Nussbaum, 2003; Kumar, 1994). In thatregard, simple strength measures have been used to predict risk of the injuries at various work-settings (Frievalds, 1996; Pheasant and Scriven, 1983; Seth et all, 1999).

In 2004, Center for Disease Control (CDC) reported that workers age between 35 and 54accounted for 50% of MSDs whereas workers age over 54 accounted for only 10% of MSDssuggesting the importance of understanding the injury characteristics of this worker population(i.e., middle aged group age between 35–54 years). More importantly, leg strength measuresfrom this working group are somewhat sparse. This is especially true for the lower extremitystrength measures in dynamic conditions (i.e., isokinetic) although among occupationalmusculoskeletal injuries and disabilities, the knee is one of the most common sites ofoccurrence (Gagnon et al., 2002; Gallos, 2006; Jin et al., 2009; Sulsky et al., 2002). Theobjective of this study was to quantify the lower extremity muscle strength characteristics oftwo age groups (young and middle adults). Additionally, the strengths of older adults (over 65years-old, retired) were measured to compare with that of the two age groups; authors thoughtthat comparing the strengths between middle-age adults and older adults would accentuate thesignificance of understanding the risk of injury of middle-age workers. The present studyhypothesized that middle-age adult’s strength would not be statistically different from youngeradults’ strength. More importantly, the present study hypothesized that leg strengths in middle-age adults would not be different from that in older adults; the study expected to see leg strengthdifferences between younger adults and middle-age adults, but, not between middle-age adultsand older adults (over 65 years old). The major goal of this evaluation was to compare overallleg strengths between younger adults and middle-age adults; the evaluation in this study wasnot performed to identify the individual’s ability to perform certain manual material handlingtasks such as lifting, pushing, pulling or carrying.

2. Methods2.1. Subject

Fourteen young (18–34 years old) individuals (7 male and 7 female), 14 middle age (35–54years old) individuals (7 male and 7 female) and 14 elderly (65 and older) individuals (7 maleand 7 female) participated in this experiment (Table 1). The young adults were recruited fromgeneral student population at Virginia Tech, and the middle age adults and older adults wererecruited from the local community. All the middle age adults were working full time and allthe older adults were independently living. All participants were compensated for their timeand effort. Each participant completed an inform consent procedure approved by the VirginiaTech Internal Review Board (IRB). Participants were excluded from the study if they indicatedany physical problems (i.e. hip, knee, ankle problems). A questionnaire was used as an initialscreening tool.

2.2. Apparatus, Testing, and RecordingParticipants were instructed to avoid physical activity for at least 24 hours before testing. Acommercial dynamometer (Biodex System 3; Biodex Medical Systems, Shirley, NY) was usedto test ankle plantar- and dorsi-flexor muscle functions and knee extensor and flexor musclefunctions. This commercial dynamometer was found to be acceptable in measuring valid and

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reliable joint torques and positions (Drouin et al., 2004). Participants were seated in theadjustable Biodex chair and were strapped by two diagonal straps across the chest and by aseatbelt applied over the hips to minimize extraneous movements during the contractions. Thecommercial dynamometer (Biodex System 3) used in the present study was reported to haveacceptable reliability and validity for measuring torque (Drouin et al., 2004). Visual inspectionswere performed to properly align the axis of rotation of the ankle and knee with the axis ofrotation of the dynamometer before each trial. Isokinetic and isometric strength measures wereused to test the lower limb strength in the present study although isotonic, isovelocity, etc.strength measures can be used to find their impacts on work performance and safety. Thetorques measured by the dynamometer were synchronously recorded and stored in a laboratorycomputer by LabView at a sampling rate of 1024 Hz. The data from the dynamometer werelow-pass filtered using a computer program developed using LabView (Butterworth, zerophase-lag, 4th order, 6 Hz cut-off).

Ankle Strength Testing—For ankle isokinetic strength tests (Figure 1 and 2), the footplatewas adjusted at 40 degrees for the total range of motion at the ankle joint axis: 10 degrees ifdorsiflexion (flexion) and 30 degrees of plantarflexion (extension). Participants were instructedto push down against the footplate and pull back up “as hard as you can” continuously for 5seconds after a spoken cue. Participants were allowed to practice two to three trials beforecollecting measurement data and asked to apply three dynamic maximum exertions at each ofthree levels randomly (30, 60, and 120 degrees per second). The rest periods of 45–60 secondswere given after each exertion. The highest plantarflexion and dorsiflexion torques of the threetrials in each testing level was used for statistical testing. For isometric strength evaluation,participants were asked to apply their maximum exertion at each of three fixed angles randomly(0, 15, and 30 plantar-flexed angles, see Figure 2b) and the best of them were used forevaluation. The each individual’s ankle strengths were normalized by his/her body mass (N·m/kg)

Knee Strength Testing—Peak isokinetic knee strengths at 30, 60, and 120 degrees/second,and isometric knee flexion strengths at 0, 15, and 30 degree extension were evaluated.Participants were instructed to sit with their right ankle strapped to a knee attachment fixed toa commercial dynamometer. They were instructed to exert their maximum efforts as instructedsimilar to ankle strength test. The each individual’s knee strengths were normalized by his/herbody mass (N·m/kg)

Statistical Analysis—Descriptive and inferential statistical analyses were performed byutilizing the JMP statistical packages (SAS Institute Inc. Cary, NC, USA). 2 × 2 (Age group(younger, middle-age, and older adult groups) × Gender (male and female)) between-subjectdesign was used to test main effect (Age) and interaction effect (Age × Gender). In addition,Post-hoc analysis among three different age groups’ strength data was performed pairwisecomparisons among the groups. The results were considered as statistically significant whenp≤0.05.

3. Results3.1. Ankle Strength

Overall, isokinetic and isometric ankle strengths among three age groups were statisticallydifferent although a few measures such as IK 120 RE and IM 0 LE indicated no significant ageeffect (Table 2). Most importantly, the results by Post-hoc analysis (Table 3) indicated that,overall, ankle strengths in middle-age adults were not different from that in older adults (Figure3). In Table 3, the same letter such as B in both middle age group and older age group suggestedthat middle age group’s ankle strength was almost same as older group’s ankle strength. In

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other words, older adults’ strengths and middle-age adults’ strengths were significant lowerthan younger adults.

3.2. Knee StrengthOverall, isokinetic and isometric knee strength was different among three age groups (Table4, Figure 4). Post hoc analysis (Student’s t, Table 5) suggested that younger adults statisticallyexhibited stronger isokinetic and isometric knee strength. Additionally, Post hoc analysissuggested that, overall, middle age adults’ strengths were statistically not different from olderage adult’s strength. Particularly, strengths of knee flexor muscle in middle-age groupsdemonstrated almost identical to older adults. In Table 5, the same letter such as B in bothmiddle age group and older age group suggested that middle age group’s knee strength wasequivalent as older age group’s knee strength.

4. DiscussionThe main objective of the study was to examine three different age groups’ leg strengths, and,particularly, the study was interested in identifying differences in leg strength between a middleage adult group and a younger adult group. Additionally, leg strength of an older adult groupwas evaluated in order to emphasize the values in leg strength found in the middle-age group;the author thought that comparing older adults’ leg strengths with middle-age group’s legstrength would draw attention to the risk of injuries of middle-age workers.

Overall, in disagreement with previous literature (Lindle et al., 1997), leg strengths in middleage adults were not statistically different from older adults in the present study. In the previousstudy (Lindle et al., 1997), muscle strength comparisons were performed on 654 women andmen aged between 20–93 years old, whereas, the present study evaluated muscle strengths of42 healthy adults; Statistical Power analysis and Sample Size Estimation were performed inthe present study. The previous study suggested that isokinetic strengths degraded withadvancing age. The different outcomes between the present study and the previous study maybe resulted by the fact that the previous studies did not normalize the torque by individualweights. It is very important to normalize the individual torque measures when presenting datasince a person with more mass is likely to produce more torque at their joints. So, it may havebeen the weight differences between older adults and middle-age adults that have contributedto different outcomes although the data from the Lindle et al. (1997) showed very similaraverage weights between two age groups. A study by Frontera et al., (1991) suggested thatmuscular strength was significantly lower in the 65- to 78-yr-old adults than in the 45- to 54-yr-old adults, but, when strength was normalized for muscle mass, the age-related differenceswere not significant in most of the muscle groups. Additionally, in the present study, it wasinteresting to see more degradation in flexor muscles than extensor muscles in middle-ageadults when compared to younger adults.

Zhang and Buhr (2002) stated “Naturally, degradation of muscular strength leads to reducedfunctional capabilities and possibly elevated risk of injury…” As an intervention for reducingrisks of injuries, strength improvement was proposed by researchers (Campbell et al., 1997;Hainaut and Duchateau, 1989; Kuruganti et al., 2006; Müller, 1965) because strengthimprovement enhanced not only strength but also muscular resistance to fatigue which was akey contributing factor to risks of injuries. In the present study, the attenuation of musclestrength in both middle age group and older adult group was almost identical when comparingto younger adult group. Studies (Keran et al., 1994; Shin et al., 2006; Vollestad, 1997;Westerblad et al., 1998) suggested that reductions in muscle strength were found to bepositively related to muscle fatigue which was a key precursor for musculoskeletal injury.These results from the current study could suggest that not only older adult group was exposedto higher likelihood of MSDs, but also middle-age group was exposed to higher likelihood of

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MSDs such as knee injuries (Gagnon et al., 2002; Gallos, 2006; Jin et al., 2009; Sulsky et al.,2002). The previous study (Sulsky et al., 2002) suggested that the risk of disability dischargedue to knee injuries among women in the US army increased following the age of 33 years.

The results in the present study indicated a significant trend in strength degradation;degradations in knee flexor muscle were more dominant in comparison to knee extensor musclein middle-age adults. Knee flexor muscles play a dominant role in decelerating forward legmomentum while walking. Older adults were reported to be at higher risk of slip-induced fallsbecause inability to properly decrease forward leg momentum at heel contact was suggested(Lockhart et al., 2005), suggesting that the middle-age adults could be at as much risk of slipsand falls as older adults although a complex of many factors were responsible for slip inducedfalls for older adults. The knee flexors also function as dynamic stabilizers at the knee joint.This prevents tibial anterior displacement and sustains the function of the ligaments at the kneejoint. While pushing, pulling, and carrying a load, significant lower leg strengths are requiredto stabilize the knee joints as much as to perform tasks. Knee joint injuries at work werecommon (Gagnon et al., 2002; Gallos, 2006; Jin et al., 2009; Sulsky et al., 2002) and exampleswere torn meniscus of the knee, anterior cruciate ligament injuries, medial and lateral collateralligament injuries, and patella femoral pain syndrome. Knee osteoarthrosis (all degrees) wascommonly found among workers with heavy physical work such as kneeling or squatting work(Jensen and Eenberg, 1996). For example, carpet fitters and floor layers were in higher risk ofknee injuries because the recent popularity of fitted floor covering (Cooper et al., 1994;McMillan and Nichols, 2005). Meniscus tears were often caused by sudden rotation orabduction on the semi-flexed knee joint and the miner was opt to meniscus tears because oftheir working posture such as the kneeling or crowling (McMillan and Nichols, 2005).Meniscus injury could facilitate the injured knee to develop knee osteoarthrosis with advancingage. In fact, this suggested that middle-age workers who experience knee injuries would belikely to develop osteoarthrosis as they got older. Frequent or heavy lifting, pushing, pulling,or carrying heavy objects were the potential risk factors for these injuries because such activitiescould involve bodily reaction and exertion which accounted for 40% of total nonfataloccupational injuries and illnesses with days away from work in 2004, and could contribute tosprains, strains, and tears which accounted for 76% of total musculoskeletal disorders withdays away from work in 2001 (CDC, 2004).

Overall, the study suggests that middle-age work forces’ health should be administered withelevated concerns although the present only studied 14 middle age workers who resided inBlacksburg, Virginia. Future studies looking at the likelihood of musculoskeletal injuries atdifferent work places and from different working postures at various age levels should berequired to validate the current findings. The future study would be a valuable asset in findingintervention strategies such that middle-age workers could stay healthier longer.

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Figure 1.Biodex dynamomter setup and position for ankle strength test

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Figure 2.Range of motion for a) isokinetic and b) isometric strength tests.

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Figure 3.Mean and ±1SD for ankle a) Isokinetic 60 Left Extension, and b) Isometric 30 Left Extension

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Figure 4.Mean and ±1SD for Knee a) Isokinetic 60 Right Extension, and b) Isometric 30 Right Flexion

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Tabl

e 1

Des

crip

tive

stat

istic

s for

hei

ght a

nd w

eigh

t of e

ach

grou

p.

You

nger

Mid

dle-

age

Old

er

Mea

nS.

DM

ean

S.D

Mea

nS.

Dp-

valu

e

Age

(yrs

)25

.34

2.98

41.0

13.

2470

.20

3.46

0.00

Hei

ght (

cm)

172.

4110

.93

170.

97.

2016

8.50

9.09

0.53

Bod

y M

ass (

kg)

71.5

912

.14

72.5

816

.30

82.6

021

.13

0.18


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Kim et al.

Tabl

e 2

Des

crip

tive

Stat

istic

of I

soki

netic

and

Isom

etric

Ank

le S

treng

th b

y A

ge a

nd A

NO

VA

Sum

mar

y Ta

ble

Lev

elY

oung

erM

iddl

e-ag

eO

lder

Age

Effe

ctA

ge x

Gen

der

Mea

nS.

DM

ean

S.D

Mea

nS.

Dp-

valu

ep-

valu

e

IK 3

0 R

E0.

940.

290.

620.

170.

650.

200.

0000

9*0.

62

IK 3

0 R

F0.

360.

090.

300.

090.

270.

070.

03*

0.56

IK 6

0 R

E0.

680.

220.

550.

190.

450.

050.

02*

0.21

IK 6

0 R

F0.

280.

060.

220.

060.

210.

050.

04*

0.99

IK 1

20 R

E0.

460.

130.

400.

140.

370.

170.

200.

56

IK 1

20 R

F0.

220.

060.

180.

040.

180.

040.

02*

0.68

IK 3

0 L

E0.

840.

360.

640.

210.

680.

210.

100.

80

IK 3

0 L

F0.

350.

090.

330.

10.

270.

080.

070.

68

IK 6

0 L

E0.

670.

280.

510.

210.

540.

200.

200.

75

IK 6

0 L

F0.

280.

070.

250.

080.

200.

090.

05*

0.41

IK 1

20 L

E0.

500.

230.

370.

160.

420.

160.

150.

99

IK 1

20 L

F0.

230.

060.

190.

050.

180.

050.

090.

62

IM 0

R E

1.05

0.38

0.75

0.18

0.86

0.33

0.05

*0.

66

IM 1

5 R

E0.

740.

270.

540.

150.

550.

230.

04*

0.50

IM 3

0 R

E0.

530.

170.

340.

110.

330.

150.

001*

0.43

IM 0

L E

1.01

0.56

0.76

0.25

0.91

0.38

0.28

0.89

IM 1

5 L

E0.

750.

380.

550.

166

0.64

0.23

0.16

0.85

IM 3

0 L

E0.

510.

260.

350.

100.

340.

150.

04*

0.83

* indi

cate

s sta

tistic

al si

gnifi

canc

es, p

< 0

.05

Stre

ngth

val

ues a

re d

ispl

ayed

in N

·m/k

g

Leve

l is e

xpre

ssed

in a

bbre

viat

ions

; IK

= Is

okin

etic

stre

ngth

, IM

= Is

omet

ric st

reng

th, R

= rig

ht, L

= le

ft, E

= pl

anta

rfle

xion

, F=

dors

iflex

ion

30 re

pres

ent e

ither

30°

/sec

ond

for I

K te

st o

r 30°

for I

M te

st


NIH


NIH


NIH


Kim et al.

Tabl

e 3

Pairw

ise

Com

paris

ons (

Post

hoc

Stu

dent

’s t)

of A

nkle

Stre

ngth

for A

ge G

roup

s, (A

ge g

roup

s not

con

nect

ed w

ith sa

me

lette

r ind

icat

e si

gnifi

cant

diff

eren

ce,

for e

xam

ple

in IK

60

RF,

mid

dle

age

grou

p’s s

treng

th (B

) was

not

diff

eren

t fro

m o

lder

gro

up’s

stre

ngth

(B) w

here

as b

oth

mid

dle

age

and

olde

r adu

lts’

stre

ngth

s (B

s) w

ere

diff

eren

t fro

m y

oung

er a

dults

(A))

Lev

elY

oung

erM

iddl

e ag

eO

lder

p-va

lue

IK 3

0 R

EA

BB

0.00

009*

IK 3

0 R

FA

A, B

B0.

03*

IK 6

0 R

EA

A, B

B0.

02*

IK 6

0 R

FA

BB

0.04

*

IK 1

20 R

FA

BB

0.02

*

IK 6

0 L

FA

A, B

B0.

05*

IM 0

R E

AB

B0.

05*

IM 1

5 R

EA

BB

0.04

*

IM 3

0 R

EA

BB

0.00

1*

IM 3

0 L

EA

BB

0.04

*


NIH


NIH


NIH


Kim et al.

Tabl

e 4

Des

crip

tive

Stat

istic

on

Kne

e St

reng

th b

y A

ge.

Lev

elY

oung

erM

iddl

e-ag

eO

lder

Age

Effe

ctA

ge x

Gen

der

Mea

nS.

DM

ean

S.D

Mea

nS.

Dp-

valu

ep-

valu

e

IK 3

0 R

E2.

020.

481.

660.

430.

350.

340.

0007

*0.

63

IK 3

0 R

F1.

130.

210.

970.

250.

810.

210.

003*

0.25

IK 6

0 R

E1.

680.

461.

350.

311.

110.

300.

0008

*0.

45

IK 6

0 R

F1.

010.

220.

810.

210.

710.

240.

005*

0.77

IK 1

20 R

E1.

210.

501.

060.

090.

800.

090.

02*

0.88

IK 1

20 R

F0.

820.

270.

700.

260.

600.

210.

070.

37

IK 3

0 L

E1.

940.

651.

550.

411.

270.

330.

003*

0.80

IK 3

0 L

F1.

150.

220.

980.

231.

010.

310.

180.

91

IK 6

0 L

E1.

580.

521.

210.

371.

030.

280.

004*

0.43

IK 6

0 L

F1.

070.

210.

870.

210.

890.

230.

03*

0.86

IK 1

20 L

E1.

130.

430.

930.

320.

740.

230.

01*

0.97

IK 1

20 L

F0.

900.

190.

750.

210.

700.

230.

04*

0.73

IM 0

R E

2.15

0.72

1.73

0.46

1.52

0.55

0.02

*0.

96

IM 0

R F

0.91

0.28

0.67

0.22

0.59

0.17

0.00

2*0.

99

IM 1

5 R

E2.

100.

741.

780.

431.

520.

380.

02*

0.75

IM 1

5 R

F1.

050.

330.

790.

240.

700.

170.

002*

0.99

IM 3

0 R

E1.

800.

611.

480.

391.

320.

240.

02*

0.88

IM 3

0 R

F1.

130.

370.

810.

250.

790.

200.

004*

0.82

IM 0

L E

2.19

0.80

1.46

0.46

1.46

0.44

0.00

2*0.

76

IM 0

L F

0.99

0.29

0.74

0.22

0.66

0.14

0.00

1*0.

91

IM 1

5 L

E2.

020.

741.

590.

511.

430.

350.

02*

0.93

IM 1

5 L

F1.

070.

310.

850.

200.

770.

170.

004*

0.97

IM 3

0 L

E1.

710.

511.

420.

451.

170.

300.

008*

0.65


NIH


NIH


NIH


Kim et al.

Lev

elY

oung

erM

iddl

e-ag

eO

lder

Age

Effe

ctA

ge x

Gen

der

Mea

nS.

DM

ean

S.D

Mea

nS.

Dp-

valu

ep-

valu

e

IM 3

0 L

F1.

170.

340.

880.

190.

890.

150.

006*

0.95

* indi

cate

s sta

tistic

al si

gnifi

canc

es, p

< 0

.05

Stre

ngth

val

ues a

re d

ispl

ayed

in N

·m/k

g

Leve

l is e

xpre

ssed

in a

bbre

viat

ions

; IK

= Is

okin

etic

stre

ngth

, IM

= Is

omet

ric st

reng

th, R

= rig

ht, L

= le

ft, E

= ex

tens

ion

(mov

emen

t aw

ay fr

om b

ody,

F=

Flex

ion

(mov

emen

t tow

ard

body

)

30 re

pres

ent e

ither

30°

/sec

ond

for I

K te

st o

r 30°

for I

M te

st


NIH


NIH


NIH


Kim et al.

Tabl

e 5

Pairw

ise

Com

paris

ons (

Post

hoc

Stu

dent

’s t)

of K

nee

Stre

ngth

for A

ge G

roup

s.

You

nger

Mid

dle-

age

Old

erp-

valu

e

IK 3

0 R

EA

BB

0.00

07*

IK 3

0 R

FA

A, B

B0.

003*

IK 6

0 R

EA

BB

0.00

08*

IK 6

0 R

FA

BB

0.00

5*

IK 1

20 R

EA

A, B

B0.

02*

IK 3

0 L

EA

BB

0.00

3*

IK 6

0 L

EA

BB

0.00

4*

IK 6

0 L

FA

BB

0.03

*

IK 1

20 L

EA

A, B

B0.

01*

IK 1

20 L

FA

BB

0.04

*

IM 0

R E

AA

, BB

0.02

*

IM 0

R F

AB

B0.

002*

IM 1

5 R

EA

A, B

B0.

02*

IM 1

5 R

FA

BB

0.00

2*

IM 3

0 R

EA

A, B

B0.

02*

IM 3

0 R

FA

BB

0.00

4*

IM 0

L E

AB

B0.

002*

IM 0

L F

AB

B0.

001*

IM 1

5 L

EA

A, B

B0.

02*

IM 1

5 L

FA

BB

0.00

4*

IM 3

0 L

EA

A, B

B0.

008*

IM 3

0 L

FA

BB

0.00

6*

Age

gro

ups n

ot c

onne

cted

with

sam

e le

tter i

ndic

ate

sign

ifica

nt d

iffer

ence

, for

exa

mpl

e in

IK 3

0 LE

, mid

dle

age

grou

p’s s

treng

th (B

) was

not

diff

eren

t fro

m o

lder

gro

up’s

stre

ngth

(B) w

here

as b

oth

mid

dle

age

and

olde

r adu

lts’ s

treng

ths (

Bs)

wer

e di

ffer

ent f

rom

you

nger

adu

lts (A

)


Author Manuscript NIH Public Access 2, and Chang S. Nam ......age group. A commercial dynamometer...

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Transcript of Author Manuscript NIH Public Access 2, and Chang S. Nam ......age group. A commercial dynamometer...