Evaluation of a method to scale muscle strength for gait simulations of children with cerebral palsy

Amy K. Hegarty, Trey V. Hulbert, Max J Kurz, Wayne Allan Stuberg, Anne K. Silverman

Research output: Contribution to journalArticle

Abstract

Cerebral palsy (CP) is a neurological disorder that results in life-long mobility impairments. Musculoskeletal models used to investigate mobility deficits for children with CP often lack subject-specific characteristics such as altered muscle strength, despite a high prevalence of muscle weakness in this population. We hypothesized that incorporating subject-specific strength scaling within musculoskeletal models of children with CP would improve accuracy of muscle excitation predictions in walking simulations. Ten children (13.5 ± 3.3 years; GMFCS level II) with spastic CP participated in a gait analysis session where lower-limb kinematics, ground reaction forces, and bilateral electromyography (EMG) of five lower-limb muscles were collected. Isometric strength was measured for each child using handheld dynamometry. Three musculoskeletal models were generated for each child including a ‘Default’ model with the generic musculoskeletal model's muscle strength, a ‘Uniform’ model with muscle strength scaled allometrically, and a ‘Custom’ model with muscle strength scaled based on handheld dynamometry strength measures. Muscle-driven gait simulations were generated using each model for each child. Simulation accuracy was evaluated by comparing predicted muscle excitations and measured EMG signals, both in the duration of muscle activity and the root-mean-square difference (RMSD) between signals. Improved agreement with EMG were found in both the ‘Custom’ and ‘Uniform’ models compared to the ‘Default’ model indicated by improvement in RMSD summed across all muscles, as well as RMSD and duration of activity for individual muscles. Incorporating strength scaling into musculoskeletal models can improve the accuracy of walking simulations for children with CP.

Original languageEnglish (US)
Pages (from-to)165-173
Number of pages9
JournalJournal of Biomechanics
Volume83
DOIs
StatePublished - Jan 23 2019

Fingerprint

Muscle Strength
Cerebral Palsy
Gait
Muscle
Muscles
Electromyography
Walking
Lower Extremity
Muscle Weakness
Nervous System Diseases
Biomechanical Phenomena
Gait analysis
Kinematics
Population

Keywords

  • Biomechanics
  • Muscle strength
  • Musculoskeletal modeling
  • Pathological gait
  • Strength scaling

ASJC Scopus subject areas

  • Biophysics
  • Orthopedics and Sports Medicine
  • Biomedical Engineering
  • Rehabilitation

Cite this

Evaluation of a method to scale muscle strength for gait simulations of children with cerebral palsy. / Hegarty, Amy K.; Hulbert, Trey V.; Kurz, Max J; Stuberg, Wayne Allan; Silverman, Anne K.

In: Journal of Biomechanics, Vol. 83, 23.01.2019, p. 165-173.

Research output: Contribution to journalArticle

@article{0ec633ea73984ac6b2b5ca92f2189c9e,
title = "Evaluation of a method to scale muscle strength for gait simulations of children with cerebral palsy",
abstract = "Cerebral palsy (CP) is a neurological disorder that results in life-long mobility impairments. Musculoskeletal models used to investigate mobility deficits for children with CP often lack subject-specific characteristics such as altered muscle strength, despite a high prevalence of muscle weakness in this population. We hypothesized that incorporating subject-specific strength scaling within musculoskeletal models of children with CP would improve accuracy of muscle excitation predictions in walking simulations. Ten children (13.5 ± 3.3 years; GMFCS level II) with spastic CP participated in a gait analysis session where lower-limb kinematics, ground reaction forces, and bilateral electromyography (EMG) of five lower-limb muscles were collected. Isometric strength was measured for each child using handheld dynamometry. Three musculoskeletal models were generated for each child including a ‘Default’ model with the generic musculoskeletal model's muscle strength, a ‘Uniform’ model with muscle strength scaled allometrically, and a ‘Custom’ model with muscle strength scaled based on handheld dynamometry strength measures. Muscle-driven gait simulations were generated using each model for each child. Simulation accuracy was evaluated by comparing predicted muscle excitations and measured EMG signals, both in the duration of muscle activity and the root-mean-square difference (RMSD) between signals. Improved agreement with EMG were found in both the ‘Custom’ and ‘Uniform’ models compared to the ‘Default’ model indicated by improvement in RMSD summed across all muscles, as well as RMSD and duration of activity for individual muscles. Incorporating strength scaling into musculoskeletal models can improve the accuracy of walking simulations for children with CP.",
keywords = "Biomechanics, Muscle strength, Musculoskeletal modeling, Pathological gait, Strength scaling",
author = "Hegarty, {Amy K.} and Hulbert, {Trey V.} and Kurz, {Max J} and Stuberg, {Wayne Allan} and Silverman, {Anne K.}",
year = "2019",
month = "1",
day = "23",
doi = "10.1016/j.jbiomech.2018.11.037",
language = "English (US)",
volume = "83",
pages = "165--173",
journal = "Journal of Biomechanics",
issn = "0021-9290",
publisher = "Elsevier Limited",

}

TY - JOUR

T1 - Evaluation of a method to scale muscle strength for gait simulations of children with cerebral palsy

AU - Hegarty, Amy K.

AU - Hulbert, Trey V.

AU - Kurz, Max J

AU - Stuberg, Wayne Allan

AU - Silverman, Anne K.

PY - 2019/1/23

Y1 - 2019/1/23

N2 - Cerebral palsy (CP) is a neurological disorder that results in life-long mobility impairments. Musculoskeletal models used to investigate mobility deficits for children with CP often lack subject-specific characteristics such as altered muscle strength, despite a high prevalence of muscle weakness in this population. We hypothesized that incorporating subject-specific strength scaling within musculoskeletal models of children with CP would improve accuracy of muscle excitation predictions in walking simulations. Ten children (13.5 ± 3.3 years; GMFCS level II) with spastic CP participated in a gait analysis session where lower-limb kinematics, ground reaction forces, and bilateral electromyography (EMG) of five lower-limb muscles were collected. Isometric strength was measured for each child using handheld dynamometry. Three musculoskeletal models were generated for each child including a ‘Default’ model with the generic musculoskeletal model's muscle strength, a ‘Uniform’ model with muscle strength scaled allometrically, and a ‘Custom’ model with muscle strength scaled based on handheld dynamometry strength measures. Muscle-driven gait simulations were generated using each model for each child. Simulation accuracy was evaluated by comparing predicted muscle excitations and measured EMG signals, both in the duration of muscle activity and the root-mean-square difference (RMSD) between signals. Improved agreement with EMG were found in both the ‘Custom’ and ‘Uniform’ models compared to the ‘Default’ model indicated by improvement in RMSD summed across all muscles, as well as RMSD and duration of activity for individual muscles. Incorporating strength scaling into musculoskeletal models can improve the accuracy of walking simulations for children with CP.

AB - Cerebral palsy (CP) is a neurological disorder that results in life-long mobility impairments. Musculoskeletal models used to investigate mobility deficits for children with CP often lack subject-specific characteristics such as altered muscle strength, despite a high prevalence of muscle weakness in this population. We hypothesized that incorporating subject-specific strength scaling within musculoskeletal models of children with CP would improve accuracy of muscle excitation predictions in walking simulations. Ten children (13.5 ± 3.3 years; GMFCS level II) with spastic CP participated in a gait analysis session where lower-limb kinematics, ground reaction forces, and bilateral electromyography (EMG) of five lower-limb muscles were collected. Isometric strength was measured for each child using handheld dynamometry. Three musculoskeletal models were generated for each child including a ‘Default’ model with the generic musculoskeletal model's muscle strength, a ‘Uniform’ model with muscle strength scaled allometrically, and a ‘Custom’ model with muscle strength scaled based on handheld dynamometry strength measures. Muscle-driven gait simulations were generated using each model for each child. Simulation accuracy was evaluated by comparing predicted muscle excitations and measured EMG signals, both in the duration of muscle activity and the root-mean-square difference (RMSD) between signals. Improved agreement with EMG were found in both the ‘Custom’ and ‘Uniform’ models compared to the ‘Default’ model indicated by improvement in RMSD summed across all muscles, as well as RMSD and duration of activity for individual muscles. Incorporating strength scaling into musculoskeletal models can improve the accuracy of walking simulations for children with CP.

KW - Biomechanics

KW - Muscle strength

KW - Musculoskeletal modeling

KW - Pathological gait

KW - Strength scaling

UR - http://www.scopus.com/inward/record.url?scp=85057973372&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85057973372&partnerID=8YFLogxK

U2 - 10.1016/j.jbiomech.2018.11.037

DO - 10.1016/j.jbiomech.2018.11.037

M3 - Article

C2 - 30545605

AN - SCOPUS:85057973372

VL - 83

SP - 165

EP - 173

JO - Journal of Biomechanics

JF - Journal of Biomechanics

SN - 0021-9290

ER -