relationships among strength, body composition, and ... · children with cerebral palsy (cp) are...

2151-805X/11/$35.00 © 2011 by Begell House, Inc. 15

Critical Reviews™ in Physical and Rehabilitation Medicine, 23(1–4), 15–29 (2011)

Relationships among Strength, Body Composition, and Measures of Activity in Ambulatory Children with Cerebral Palsy: A Cross-Sectional Study

Ann Flanagan,a,* Joseph Krzak,a Sahar Hassani,a Anita Bagley,b George Gorton,c Mark Romness,d Chester Tylkowski,e Mark Abel,d Barbara Johnson,f & Donna Oeffinger,e

aShriners Hospitals for Children–Chicago, Chicago, IL. bShriners Hospitals for Children–Northern California, Sacramento, CA. cShriners Hospitals for Children–Springfield, Springfield, MA. dUni-versity of Virginia, Charlottesville, VA. eShriners Hospitals for Children–Lexington, Lexington, KY. fShriners Hospitals for Children–Salt Lake City, Salt Lake City, UTAcknowledgment of Any Presentation of This Material: In part, this data was presented at American Academy of Cere-bral Palsy and Developmental Medicine (AACPDM) September 2010 in Washington DC; Gait & Clinical Movement Analysis Society (GCMAS), May 2010 Miami FL and at APTA – Combined Section Meeting in Chicago February 2012.

Financial Disclosure and Conflict of Interest: No commercial party having a direct financial interest in the results of the research supporting this paper has or will confer a benefit on the authors or on any organization with which the authors are associated.

*Address all correspondence to: Ann Flanagan, PT, PCS, Director of Rehabilitation Services/Research Outcomes Coordinator, Shriners Hospitals for Children – Chicago, 2211 N. Oak Park Avenue, Chicago, IL 60707; Tel.: 773-385-5575; Fax: 773-385-5459; [email protected]

ABSTRACT: The objective of this work was to quantitatively describe the relationships among overall lower extremity strength and body composition with measures of activity in ambulatory children with cerebral palsy (CP). The design was a prospective, multicenter cohort, cross-sectional study among seven pediatric orthopedic facilities. The participants included children ages eight to 18 years (n = 392; 249 male, 143 female), GMFCS levels I–III (I = 155; II = 160; III = 77) with diplegia (n = 280, mean age 12.9 ± 2.7 years) and hemi-plegia (n = 112, mean age 12.6 ± 2.9 years). Main outcome measures include lower extrem-ity strength, body composition, and activity. Quantitative relationships among variables were reported using Pearson correlation coefficients with p < 0.001. Results show strength had fair to moderate correlations with GMFM-66 and PODCI global function, sports and physical function, and transfer and basic mobility scores for children with diplegia. Chil-dren with hemiplegia demonstrated a fair correlation between strength and GMFM-66 score. For children with diplegia and hemiplegia, BMI was not correlated with measures of function or activity. Body fat percentage demonstrated a fair correlation with PODCI global function scores for children with hemiplegia. Body composition measures had a fair correlation to overall strength for both those with hemiplegia and diplegia. Stronger rela-tionships among measures were observed in higher functioning children. It is concluded that a positive relationship exists between lower extremity strength and measures of activity in ambulatory children with CP. There are multiple factors influencing activity in children with CP, and strength and body composition should not be ignored.

KEY WORDS: muscle strength, body composition, cerebral palsy, activity

ABBREVIATIONS: BIA: bioelectrical impedance analysis; BMI: body mass index; CP: cerebral palsy; GMFM: gross motor function measure; PODCI: pediatric outcomes data collection instrument

Critical Reviews™ in Physical and Rehabilitation Medicine

16 Flanagan et al.

I. INTRODUCTION

Children with cerebral palsy (CP) are known to have limitations in activity and func-tional abilities.1–3 Despite previous research, questions still remain regarding the role of strength and body composition related to activity limitations.The International Classification of Functioning, Disability, and Health is the World’s Health Organiza-tion’s framework for measuring health and disability at the individual and population levels. According to the ICF, body structure and function is defined as physiological functions of body systems and anatomical parts of the body that allow one to be ac-tive, whereas activity is defined as the execution of a task or action by an individual.4

Strength is an important component of body structure and function, and is a vital component of clinical management for children with CP. Children with CP are weaker compared to typically developing children.5,6 Factors contributing to weak-ness include incomplete muscle recruitment,6,7 increased coactivation of muscle groups,8,9 and spasticity.5 Sanger et al. identified strength as one of the foremost contributors in reduced functional ability in children.10 Weakness is a major fac-tor associated with deformity progression, referrals for therapy and orthotics, and postoperative reduction in function.11

Knowing the relationship between strength and activity limitations is important. Strength measurements have been associated with severity level and measures of activ-ity in children with CP.12 Eek and Bechung13 assessed 55 children with diplegia, stratified by gross motor function classification system (GMFCS)14 levels I–III, and found signifi-cant strength differences among levels. Additionally, they reported a moderate to high correlation between the gross motor function measure (GMFM-66)15 scores and muscle strength. The pediatric outcomes data collection instrument (PODCI)3,16 is also useful in clinical management. The PODCI provides parental perspective of overall function, sports and physical function, and transfers and mobility within the community as op-posed to a laboratory setting. To date, there are no previous studies that have evaluated the relationship between PODCI, strength, and body composition.

Body composition is another important measure of body structure and function that may be related to activity. Ambulatory children with CP have obesity rates similar to their typically developing peers.17 It has been suggested that changes in body com-position over time have an effect on levels of function and activity in individuals with CP.18 However, the associations among these measures have never been established. The prevalence of obesity in the CP population has risen over the last decade from 7.7 to 16.5%, similar to the increase seen in the general pediatric population.19 Obesity is associated with health risks and difficulties in walking and function in overweight children and adolescents who do not have other disabilities.20 The relationship be-tween body composition and activity has not been thoroughly examined for children with CP. High levels of body fat often impact major joints, which may lead to reduced mobility and inefficient body mechanics.21 In a study comparing overweight and non-overweight typically developing children.20 found that obese children self-reported greater difficulty in mobility than nonobese children.

Volume 23, Issue 1–4, 2011

Strength, Body Composition, and Measures of Activity in Children with Cerebral Palsy 17

The purpose of this study was to describe the relationships between strength and body composition and measures of activity for ambulatory children with CP. This study evaluated the relationships between activity measures of PODCI global function, sports and physical function, and transfers and basic mobility subscales, and the GMFM-66 score and lower extremity strength and body composition. How these associations are affected by severity level (GMFCS level) was then in-vestigated. Finally, the relationships between lower extremity strength and body composition were examined. The study hypotheses were (i) that strength and body composition would be moderately correlated with GMFM-66 scores and PODCI subscale scores, (ii) that the strength of these correlations would diminish with in-creasing GMFCS level, and (iii) strength and body composition would be strongly correlated. Determining how strength and body composition relate to function and activity will direct clinicians in choosing evaluations and developing interventions with the goals of preventing decline and improving function for children with CP.

II. METHODS

A. Participants

This study was part of a four-year prospective multicenter study. Participants were a convenience sample of eligible individuals from seven pediatric orthopedic fa-cilities including Shriners Hospitals for Children in Chicago, Illinois; Sacramento, California; Springfield, Massachussets; Lexington, Kentucky; Salt Lake City, Utah; the University of Virginia, Charlottesville; and Connecticut Children’s Medical Center. Institutional review board approval was obtained at each site and consent and Health Insurance Portability and Accountability Act forms were completed.

Inclusion criteria were individuals with a diagnosis of spastic CP, GMFCS levels I–III, ages eight to 18 years, who were able to complete an instrumented gait analysis with or without an assistive device. Children were considered hemiplegic if they had involvement of an upper and lower extremity on the same side of their body, and as diplegic if they had involvement of both lower extremities. Exclusion criteria included previous lower extremity orthopedic surgery within the prior year, botulinum toxin A injections in the prior four months, or a currently implanted and operating baclofen pump. These exclusion criteria were chosen so as not to include a participant in a period of recovery. A total of 748 individuals were screened; 338 did not meet inclusion crite-ria, and 80 declined participation. Demographic characteristics of individuals who did not participate were not different from those who did. Data from 18 participants were excluded for inconsistent or missing data, resulting in 392 in the final analysis.

B. Data Management

All coordinators attended a mandatory two-day training session to review and standardize administration of outcome tools and data collection processes prior to


18 Flanagan et al.

study initiation. All participant data were entered directly into a custom database designed for study management and data collection. Identifiable information was removed from the data and compiled for analysis. Data quality and consistency were ensured by the project manager and site coordinators.

C. Procedures

Each participant completed an assessment that included classification of GMFCS level by the study coordinator,9 height, weight, medical history questionnaire, and ad-ministration of the baseline PODCI (Version 2.0, AAOS 1997) to the parent,3,11 lower extremity strength, and GMFM15 dimensions D (standing) and E (walking, running, and jumping). The PODCI questionnaire is a validated measure for testing children with moderate to severe musculoskeletal issues that includes items that are a measure of activity and functional outcome in children.16,22 The GMFM was administered barefoot without assistive devices, and the GMFM-66 score was calculated using the gross motor activity estimator software.23 Body composition measures included body mass index (BMI) and body fat percentage estimated using bioelectrical impedance analyses. The above measures were all chosen because they are reliable and valid.

Lower extremity muscle strength of the hip flexors, extensors, abductors, and adduc-tors, knee flexors and extensors at 30 deg of knee flexion, and ankle plantar flexors and dorsiflexors were assessed with a handheld dynamometer (HHD) (JTECH PowerTrack II Commander, Salt Lake City, Utah) using a standardized protocol.6 The handheld dynamometry to assess isometric strength has shown good reliability in children with CP.24,25 All examiners received training on the standardized protocol, and reliability test-ing was completed. The strength score for each individual muscle was the maximum value of three trials. The overall strength score was calculated by averaging the indi-vidual strength scores for all muscles bilaterally. All strength scores were normalized to body weight and converted to z-scores to account for evaluator differences.

BMI values were calculated from height and weight measurements. Body fat percentage was measured using bioelectrical impedance analysis (BIA) with the Bodystat Quadscan 4000 (Bodystat Ltd, Isle of Man, British Isles). Data were cal-culated using the Quadscan software using the children regression equation within the software. Data were collected twice bilaterally and averaged to give an overall body fat percentage estimate.

D. Statistical Analysis

A priori power analysis using retrospective data from each participating site indicated that with 392 participants and an alpha level of 0.05, the power ranged from 70% to 95%, depending on test and tool selection. Bias analyses were completed on each of the studied measures using ANOVA with site or evaluator as the single factor. Pearson correlation coefficients (r) were calculated for all interval variables by GMFCS level. Analyses were performed separately for children with diplegia and hemiplegia because



previous research has shown that the functional profiles of these groups are different.26

Correlations between strength and activity measures, body composition and activity measures, and strength and body composition were investigated. Correla-tion analysis was chosen as the statistical technique because the a priori defined hypotheses were not predictive or causative, that is, there was no reason to assume that low strength causes decreased activity, versus the possibility that decreased activity for another reason causes decreased strength. Thus, the dependent vari-able is not known in advance. For children with hemiplegia, the involved side total strength z-scores were used to establish the investigated relationships. For children with diplegia, the average of the z-scores for the right and left sides was used. An r of 0.75–1.00 was considered good to excellent, 0.50–0.75 was considered moderate, 0.25–0.50 was fair, and 0.00–0.25 indicated little to no relationship.27

III. RESULTS

A. Study Population and Descriptive Statistics

Participant demographics for 392 ambulatory individuals with CP are reported in Table 1. The mean age was 12.7 ± 2.8 years, and 36% were female. Differences be-tween lower extremity strength scores were not observed between genders (males, 2.41 ± 1.00; females, 2.15 ± 1.03; p = 0.02). BMI was not different between genders overall (male, 19.65 ± 4.63; female. 20.82 ± 5.27; p = 0.02) or among GMFCS level. Females had a higher average body fat percentage than males (males, 23.79 ± 9.15; female, 30.80 ± 8.77; p < 0.0001) overall and at each GMFCS level.

Mean scores for the activity measures are reported in Table 1. Scores decrease with increasing severity level. Site bias analyses demonstrated no differences among sites for the study population or measures, with the exception of the strength data. Differences among evaluators were found in the weight-normalized strength scores; therefore, the scores were converted to z-scores for all further analyses.

B. Correlations among Children with Diplegia and Hemiplegia

Table 2 shows the correlations between measures of strength and body composition and GMFM and PODCI scores for participants with diplegia and hemiplegia. For those with diplegia, a moderate correlation was found between strength and GMFM-66 score. Fair correlations were found between lower extremity strength and PODCI global func-tion, sports and physical function and transfers and basic mobility domain scores, and BMI. There was a moderate correlation between BMI and body fat percentage.

For children with hemiplegia, fair correlations were seen between lower extrem-ity strength of the involved side and GMFM-66 score and BMI. The only significant correlation between body composition measures and activity was found between body fat percentage and PODCI global function. There was a moderate correlation between BMI and body fat percentage.


20 Flanagan et al.Ta

ble

1. D

emo

gra

ph

ics

and

mea

n v

alu

es o

f m

easu

res,

mea

n (

SD

)

Dem

ogra

phic

cat

egor

y

Dip

legi

aH

emip

legi

a

Tota

lG

MF

CS

le

vel I

GM

FC

S

leve

l II

GM

FC

S

leve

l III

Tota

lG

MF

CS

le

vel I

GM

FC

S

leve

l II

GM

FC

S le

vel,

n (%

)28

0 (7

1.4)

67 (

17.1

)13

6 (3

4.7)

77 (

19.6

)11

2 (2

8.6)

88 (

22.5

)24

(6.

1)

Mal

e, n

(%

)18

1 (4

6.2)

45 (

11.5

)93

(23

.7)

43 (

11.0

)68

(17

.4)

52 (

13.3

)16

(4.

1)

Fem

ale,

n (

%)

99 (

25.3

)22

(5.

6)43

(11

.0)

34 (

8.7)

44 (

11.2

)36

(9.

2)8

(2.

0)

Age

, mea

n (S

D)

12.9

(2.

7)13

.4 (

2.7)

12.8

(2.

7)12

.7 (

2.6)

12.6

(2.

9)12

.6 (

2.9)

12.6

(2.

9)

Mea

sure

BM

I20

.2 (

5.0)

19.7

(5.

0)20

.1 (

5.2)

20.8

(4.

7)19

.7 (

4.5)

19.7

(4.

2)19

.7 (

5.6)

Bod

y fa

t per

cent

age

26.2

(9.

6)24

.2 (

8.8)

26.3

(9.

6)28

.1 (

10.0

)26

.8 (

9.4)

27 (

9.0)

25.8

(11

.0)

Ove

rall

stre

ngth

z-s

core

-0.1

(1.

00)

0.5

(1.0

) -0

.1 (

0.8)

-0.8

(0.

8)0.

0 (0

.9)

0.2

(0.9

)-0

.5 (

0.6)

GM

FM

-66

69.3

(12

.9)

83.9

(8.

3)70

.9 (

6.5)

53.7

(6.

7)83

.3 (

8.1)

86.0

(6.

5)73

.3 (

5.1)

PO

DC

I—gl

obal

func

tion

71.5

(13

.7)

80.5

(10

.4)

72.7

(12

.6)

61.2

(11

.6)

81.1

(11

.5)

83.2

(10

.2)

73.0

(13

.1)

PO

DC

I—sp

orts

and

phy

sica

l fun

ctio

n50

.2 (

20.5

)65

.9 (

16.2

)51

.9 (

17.4

)33

.3 (

16.4

)68

.1 (

17.2

)72

.3 (

14.9

)52

.0 (

16.3

)

PO

DC

I—tra

nsfe

rs a

nd b

asic

mob

ility

78.6

(16

.7)

90.6

(8.

6)82

.0 (

12.2

)61

.7 (

16.1

)91

.8 (

8.3)

93.9

(6.

6)83

.9 (

9.4)



Tab

le 2

. Co

rrel

atio

n m

atri

x am

on

g s

tren

gth

an

d b

od

y co

mp

osi

tio

n s

core

s w

ith

mea

sure

s o

f fu

nct

ion

an

d a

ctiv

ity

Dip

legi

a

Mea

sure

GMFM-66

PODCI Global Func-tion

PODCI Sports and Physical function

PODCI Transfers and Basic mobility

BMI

Body fat %

Ove

rall

stre

ngth

sco

re0.

60*

0.39

*0.

43*

0.42

*–0

.37*

–0.2

4

BM

I–0

.12

–0.1

2–0

.13

–0.0

61.

000.

63*

Bod

y fa

t %–0

.18

–0.1

7–0

.13

–0.1

1 0

.63

1.00

Hem

iple

gia

Mea

sure

GMFM-66

PODCI Global Function

PODCI Sports and Physical Function

PODCI Transfers and Basic Mobil-ity

BMI

Body Fat%

Ove

rall

stre

ngth

sco

re (

invo

lved

sid

e)0.

44*

0.30

0.32

0.34

–0.4

4*–0

.24

BM

I–0

.13

–0.1

2–0

.14

–0.0

71.

00

0.61

*

Bod

y fa

t %–0

.15

–0.3

9*–0

.28

–0.2

5 0

.61*

1.0

0

* =

p

0.0

01


22 Flanagan et al.

C. Correlations among GMFCS Levels

Correlations for both groups were examined by GMFCS level to determine if sever-ity level impacted the strength of the relationships found between measures. These data are reported in Tables 3 (diplegia) and 4 (hemiplegia). Correlations reported for strength scores for individuals with hemiplegia are reported for the involved side only. Data were not analyzed at GMFCS level II for those with hemiplegia due to the small sample size (n = 24).

For individuals with diplegia, GMFCS level I, demonstrated a positive moder-ate correlation between lower extremity strength and GMFM-66 score, and a mod-erate, negative correlation between strength and BMI. Those children in GMFCS level II showed a fair positive correlation between overall strength and GMFM-66 score, and a fair negative correlation between overall strength and BMI. For GM-FCS level III, no significant correlations were identified between strength and other measures. However, there was a moderate positive correlation between BMI and body fat percentage for all three GMFCS levels.

For individuals with hemiplegia, there was a moderate negative correlation between overall strength and BMI at GMFCS level I. A fair negative correlation was shown between body fat percentage and PODCI global function. There was a positive moderate correlation between BMI and body fat percentage.

IV. DISCUSSION

In this study, we examined the relationships between strength, body composition, and measures of activity in ambulatory children with CP. The data was able to substantiate a positive correlation of strength and the GMFM measure for children with diplegia at a moderate level and the PODCI measure at a fair level. How-ever, there was no correlation between body composition and measures of activity for children with diplegia. In contrast, children with hemiplegia had a fair positive correlation between strength and GMFM scores, but not PODCI scores. Unlike children with diplegia, those with hemiplegia demonstrated that body fat percent-age had a fair, negative correlation to global function on the PODCI. The second hypothesis proved correct in that diminishing strength of these correlations with increasing motor involvement for children with diplegia was found. Our hypothesis that strength and body composition would be strongly correlated was partially sup-ported for children with CP, but at a fair level.

The findings from the current study are consistent with previous reports of the relationships between strength and measures of activity. Previous studies have established relationships between strength and walking abilities by demonstrating that improvements in lower extremity strength resulted in enhanced walking abili-ties and gross motor function in children with diplegic CP.13,28,29 In the current study, strength appears to play a larger role in activity level for those with diplegia than for those with hemiplegia. These findings are confirmed with work by Damiano



Tab

le 3

. Co

rrel

atio

ns

amo

ng

str

eng

th a

nd

bo

dy

com

po

siti

on

sco

res

wit

h m

easu

res

of

fun

ctio

n a

nd

act

ivit

y—

dip

leg

ia b

y G

MF

CS

Lev

els

GM

FC

S I

Mea

sure

GMFM 66

PODCI global function

PODCI sports and physical function

PODCI transfers and basic mobility

BMI

Body fat %

Ove

rall

stre

ngth

sco

re0.

54*

0.19

0.24

0.22

–0.5

4*–0

.34

BM

I–0

.07

–0.1

00.

04–0

.01

1.00

0.61

*B

ody

fat %

–0.1

0–0

.15

–0.0

1–0

.01

0.61

*1.

00

GM

FC

S II

Mea

sure

GMFM 66



PODCI transfers and basic mobility

BMI

Body fat %

Ove

rall

stre

ngth

sco

re0.

35*

0.19

0.21

0.15

–0.3

9*–0

.24

BM

I–0

.14

–0.1

0–0

.16

–0.0

21.

000.

69*

Bod

y fa

t %–0

.17

–0.1

2–0

.10

–0.0

40.

69*

1.00

GM

FC

S II

I

Mea

sure

GMFM 66



PODCI trans-fers and basic mobility

BMI

Body fat %

Ove

rall

stre

ngth

sco

re0.

220.

200.

150.

21–0

.15

–0.0

5B

MI

–0.1

0–0

.02

–0.1

2–0

.03

1.00

0.53

*B

ody

fat%

0.02

–0.1

2–0

.06

–0.0

60.

53*

1.00

* =

p

0.0

01


24 Flanagan et al.

et al., who showed that children with hemiplegia consistently performed better at gait tasks and lower extremity function than children with diplegia at the same GMFCS level.26 Perhaps this is because children with hemiplegia compensate with their stronger, uninvolved side.6

Correlation of strength to PODCI subscales has not been previously reported. This study provides unique information including descriptive measures of the vari-ous PODCI subscales for diplegia, hemiplegia, and GMFCS levels, as well as corre-lations of PODCI measures to strength measures. This information can continue to guide clinicians on the importance of strength as a factor in a child’s overall activity level as reported by parents.

Table 4. Correlations among strength and body composition scores with measures of function and activity—hemiplegia by GMFCS levels

GMFCS I

Strength measure

GM

FM

66

PO

DC

I glo

bal f

unct

ion

PO

DC

I spo

rts

and

phys

ical

func

tion

PO

DC

I tra

nsfe

rs a

nd b

asic

mob

ility

BM

I

Bod

y fa

t %

Overall strength score (involved side)

0.35 0.27 0.24 0.27 -0.53* -0.30

BMI -0.20 -0.23 -0.18 -0.22 1.00 0.57*

Body fat % -0.25 -0.43* -0.33 -0.36 0.57* 1.00

* = p 0.001



Stratification of children with diplegia by GMFCS levels allows clinicians and researchers to evaluate the impact of strength on activity levels relative to the child’s functional level. The current study demonstrated that the magnitude and number of significant correlations between strength scores and GMFM-66 scores decreased with increasing motor involvement. It can be postulated that this reduced associa-tion of strength and function in children with increasing motor involvement may result from the presence of additional impairments beyond weakness such as de-creased selective motor control, balance deficits, cognitive deficits, hypertonicity, pain, joint contractures, and bony deformities.

To our knowledge, the association between strength and body composition for children with CP has not been previously reported. The data in this study acknowl-edge an important relationship between higher strength scores and lower body composition scores. This relationship was stronger for the participants who walked without assistive devices. Lower BMI levels were more prevalent for children with diplegia and hemiplegia at GMFCS level I. Lower BMI levels may play a role in their higher activity levels and more advanced gross motor abilities such as running and jumping. For children with diplegia at GMFCS levels II and III, factors other than BMI may be more important for strength such as isolated muscle control, lower levels of spasticity, and muscle fiber composition. Further studies that assess whether strength training leads to improved BMI and body fat percentages and sub-sequently improved activity levels could help substantiate a relationship between these measures.

It is important to note that the positive moderate correlation between BMI and body fat percentage for all GMFCS levels indicates BMI is not a strong predictor of body fat percentage. This is not surprising based on previous literature indicating anthropometric methods tend to underestimate percentage of body fat in children with CP.30

The relationships found between body composition and lower extremity strength and measures of activity were fewer than expected by the investigators. It is often believed that the relationship between one’s body fat and strength will strongly in-fluence functional abilities. Perhaps these findings illustrate the indirect impact of measures at the level of body structure and function on more global measures such as function and activity. Function and activity measures encompass many factors beyond strength or body composition, including factors such as balance, spasticity, family resources, and parent and child motivation, that could influence the scores obtained on the tested measures of activity.

A. Study Limitations

This study improves on previous reports by having a large enough sample size to stratify by limb involvement (hemiplegia, diplegia) and by GMFCS levels.6,28,31 It also included measures of body composition not previously reported within the context of strength and activity. However, the study is not without limitations. The


26 Flanagan et al.

findings from this study are potentially limited by evaluator bias found in the HHD strength measures across assessors at different sites despite the onsite training. This was controlled by converting the weight-normalized strength scores to z-scores based on data from each individual examiner. An isokinetic dynamometer is the most reliable and objective measurement tool for strength. Due to lack of avail-able isokinetic equipment and the associated testing expenses, HHD was chosen as an alternative objective measure of strength. HHD is more objective and clinically applicable than a standard manual muscle test. While dual energy X-Ray absorpti-ometry (DXA) is a criterion standard for measuring body fat percentage, it is not easily accessible for application in the clinical setting and can be cost prohibitive. Therefore, to obtain an estimate of body fat percentage, BIA was used. This method is reliable and is more easily administered in clinical settings.32

This study used univariate analysis to quantify relationships among the mea-sures, and the analysis did not control for participant age. While there are only mild associations between strength and activity measures, a correlation statistic provides baseline information that is useful to the clinician. A directional relationship be-tween an individual’s strength and their performance on an activity measure may be assumed, but higher-level analysis is needed to help determine other factors that influence outcome. Future work will utilize these measures as a basis for multivari-ate statistical regression.

V. CONCLUSIONS

This study provides valuable information to clinicians working with this population regarding relationships of body structure and function measures to activity mea-sures in ambulatory children who have CP. Fair to moderate associations between strength, body composition, and activity measures were illustrated. The associations were weaker than expected, but provide information that could help guide clinical decision making and treatment plans. Clinicians should ensure a comprehensive physical therapy and recreational program that addresses more than just strength and body composition. Further studies that are underway will assess the impact of changes in strength and body composition on measures of activity.

ACKNOWLEDGMENTS

The Functional Assessment Research Group (FARG) acknowledge the funding of this work by Shriners Hospitals for Children Grant No. 9158; the contribution of statistical consultant Dick Kryscio, Ph.D., Department of Biostatistics at the Uni-versity of Kentucky; Sylvia Õunpuu, M.Sc., coinvestigator, Connecticut Children’s Medical Center; and the research coordinators and motion analysis laboratory staff at all participating facilities for their roles in data collection, as well as the partici-pants and their families.



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