Ki Hyuk Sung, MD

Relationship between isometric muscle strength, gait parameters, and gross

motor function

Seoul National University Bundang Hospital

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Introduction

• Muscle weakness is a common impairment in patients with cerebral palsy

• Lower limb muscle strength is reduced by 6%-59% compared with peers with typical development

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Introduction

• Muscle strength had a significant association with gross motor function

• Muscle strengthening exercise could result in functional improvements

• Recent studies showed no improvement of functional activity after muscle strengthening training

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Introduction

• No single study which investigates the

relationship between muscle strength

and gross motor function, gait

kinematics, and gait kinetics in patients

with CP

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Purpose of the study

• To the correlation between isometric

muscle strength and gross motor

function, gait kinematics and kinetics in

ambulatory patients with spastic CP

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Materials and Methods

• Prospective design

• Inclusion

– consecutive ambulatory patients with spastic CP

– patients who planned for single event multilevel

surgery including DHL

– preoperative 3D gait analysis and gross motor

function measure (GMFM) scoring

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Measuring isometric muscle strength

• Handheld dynamometer

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Measuring isometric muscle strength

• Hip flexor muscle

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Measuring isometric muscle strength

• Hip extensor muscle

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Measuring isometric muscle strength

• Knee flexor muscle

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Measuring isometric muscle strength

• Knee extensor muscle

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• Gross motor function measure (GMFM)

– 88 items within five dimension

– Dimension D(standing) and E(walking,

running, jumping) scoring

• 3D gait analysis

– Kinematic, kinetic and temporal parameters

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Reliability of strength measurement

• Intra-session reliability, 3 trial

• ICC (intraclass correlation coefficient)

& 95% confidence interval

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Statistical analysis

• Correlation between peak isometric strength and GMFM, gait kinematics and gait kinetics– Pearson’s correlation coefficient

• Difference in peak isometric muscle strength according to GMFCS level– One-way analysis of variance (ANOVA)

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Results

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Demographics, GMFM, and peak isometric strength of patients

Muscle group Peak isometric strength

Age (year) 11.5±7.7 (range 5.3 -30.5) Hip flexor (N) 8.71±6.53

Gender (M / F) 13 / 12 Hip flexor (N/kg) 0.26±0.12

Type (hemi/di/quadri) 7/ 17/ 1 Hip extensor (N) 15.46±12.30

GMFCS level (I/ II/ III) 7/ 13/ 5 Hip extensor (N/kg) 0.51±0.36

Height (cm) 130.6±20.9 Knee flexor (N) 6.60±5.47

Weight (kg) 33.9±18.6 Knee flexor (N/kg) 0.21±0.14

GMFM-D (%) 85.1±33.9 Knee extensor (N) 10.26±5.30

GMFM-E (%) 73.9±20.7 Knee extensor (N/kg) 0.34±0.20

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Intra-session reliability of measurements of peak isometric muscle strength

Muscle groups ICC 95% CI

Hip flexor 0.975 0.951 to 0.988

Hip extensor 0.973 0.948 to 0.987

Knee flexor 0.984 0.970 to 0.992

Knee extensor 0.973 0.949 to 0.987

ICC, intraclass correlation coefficient; CI, confidence interval

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Correlations between peak isometric muscle strength and GMFM

Muscle groupsGMFM-D GMFM-E

r p r p

Hip flexor 0.014 0.950 0.225 0.290

Hip extensor -0.266 0.209 0.042 0.847

Knee flexor -0.057 0.785 0.183 0.381

Knee extensor -0.255 0.219 -0.115 0.584

GMFM, gross motor function measure

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Peak isometric muscle strength according to GMFCS levels

Muscle groups GMFCS I GMFCS II GMFCS III p

Hip flexor (N/kg) 0.27±0.09 0.29±0.15 0.19±0.06 0.338

Hip extensor (N/kg) 0.53±0.27 0.59±0.41 0.21±0.11 0.172

Knee flexor (N/kg) 0.24±0.14 0.22±0.16 0.12±0.10 0.352

Knee extensor (N/kg) 0.36±0.21 0.36±0.22 0.24±0.06 0.478

Data are presented as mean ± SD. GMFCS, gross motor function classification system

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ParametersHip flexor Hip extensor Knee flexor Knee extensor

r p r p r p r p

Stride length -0.077 0.719 -0.080 0.711 0.120 0.568 -0.029 0.891

Cadence -0.110 0.610 0.000 0.999 -0.080 0.704 -0.022 0.919

Walking speed -0.114 0.596 -0.092 0.669 -0.016 0.939 -0.160 0.444

Maximum pelvic tilt

-0.178 0.405 -0.552 0.005 -0.103 0.626 -0.377 0.063

Mean pelvic tilt -0.202 0.344 -0.581 0.003 -0.138 0.511 -0.420 0.037

Maximum pelvic obliquity

-0.218 0.306 -0.463 0.023 -0.217 0.297 -0.433 0.031

Mean pelvic obliquity

0.030 0.890 -0.209 0.328 -0.023 0.912 -0.276 0.181

Minimum hip flexion

-0.099 0.646 -0.314 0.135 -0.004 0.986 -0.059 0.778

Maximum hip flexion in stance

-0.206 0.334 -0.375 0.071 -0.029 0.889 -0.106 0.615

Maximum hip flexion in swing

-0.352 0.092 -0.543 0.006 -0.241 0.247 -0.263 0.203

Knee flexion at initial contact

0.026 0.904 0.321 0.127 0.126 0.549 0.496 0.012

Minimum knee flexion in stance

0.101 0.639 0.395 0.056 0.119 0.572 0.449 0.025

Peak knee flexion in swing

-0.369 0.076 -0.223 0.295 -0.306 0.137 -0.132 0.528

Knee flexion at terminal swing

0.032 0.880 0.300 0.154 0.116 0.579 0.468 0.018

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Correlations between peak isometric muscle strength and gait kinetics

Kinetic parametersHip flexor Hip extensor Knee flexor Knee extensor

r p r p r p r p

Hip Flexion/Extension Moment

Peak Extensor in early stance 0.162 0.451 -0.125 0.559 0.160 0.440 -0.188 0.367

Peak Flexor in stance -0.101 0.639 0.015 0.946 -0.041 0.846 0.117 0.578

Peak Extensor in swing 0.008 0.970 -0.212 0.321 -0.073 0.728 -0.334 0.102

Hip Flexion/Extension Power

Peak generation in early stance 0.098 0.648 -0.144 0.501 0.135 0.521 -0.106 0.614

Peak absorption in mid-stance 0.283 0.180 0.237 0.265 0.168 0.422 0.215 0.301

Peak generation in terminal stance -0.236 0.267 -0.283 0.180 -0.186 0.374 -0.274 0.185

Knee Flexion/Extension Moment

Peak extensor in early stance 0.162 0.450 0.378 0.068 0.298 0.148 0.430 0.032

Peak Flexor in mid-stance 0.179 0.403 0.311 0.139 0.144 0.493 0.327 0.111

Peak extensor in terminal stance 0.108 0.616 0.297 0.159 0.192 0.357 0.416 0.038

Peak flexor in swing 0.150 0.485 0.165 0.442 0.117 0.577 0.269 0.193

Knee Flexion/Extension Power

Peak absorption in early stance 0.340 0.104 0.067 0.755 0.185 0.377 0.015 0.943

Peak generation during stance 0.154 0.472 0.302 0.152 0.286 0.166 0.312 0.130

Peak absorption in terminal stance -0.201 0.346 -0.198 0.353 -0.140 0.505 -0.195 0.350

Peak absorption in terminal swing 0.440 0.031 0.447 0.029 0.474 0.017 0.435 0.030

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Conclusions

• There is no correlation between muscle

strength and gross motor function.

• However, higher muscle strength,

especially extensor muscle group of hip

and knee joint, stabilizes the pelvic motion

and makes walking more energy-efficient

in flexed knee gait.

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Thank you !