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Published on: February 12, 2018
Instrumented strength assessment in typically developing children and children with a neural or neuromuscular
Ineke Verreydt1, Ines Vandekerckhove1, Elze Stoop1,2
1Department of Rehabilitation Sciences, KU Leuven, Leuven, Belgium.
Insights
This study validated an instrumented strength assessment for children, finding it reliable for assessing strength in typically developing children, those with cerebral palsy (CP), and Duchenne muscular dystrophy (DMD). The assessment effectively detected strength improvements in CP patients post-intervention.
Area of Science:
- Pediatric Rehabilitation
- Neuromuscular Disorders
- Biomedical Engineering
Background:
- Accurate strength assessment is crucial for children with neuromuscular conditions like cerebral palsy (CP) and Duchenne muscular dystrophy (DMD).
- Instrumented strength testing offers objective measurement of force, torque, and normalized torque, but its clinimetric properties require validation in pediatric populations.
Purpose of the Study:
- To evaluate the reliability, validity, and responsiveness of an instrumented strength assessment in typically developing (TD) children, and children with CP and DMD.
- To establish the measurement error (SEM, MDC) and assess the ability of the instrument to detect changes in strength over time and between groups.
Main Methods:
- Maximal voluntary isometric contractions (MVICs) of lower limb muscles were measured using an instrumented device.
- Intra-rater, inter-rater, and inter-session reliability were assessed using Intraclass Correlation Coefficients (ICC) in TD children, CP, and DMD cohorts.
- Construct validity was determined by comparing strength measures between TD children and those with CP and DMD. Responsiveness was evaluated through post-intervention changes in CP and longitudinal follow-up in DMD.
Main Results:
- The instrumented assessment demonstrated good to excellent intra-rater reliability across all groups, with slightly lower inter-rater reliability in TD children.
- Children with CP and DMD exhibited significantly lower strength (p < 0.001) compared to TD children, with differences exceeding minimal detectable change (MDC).
- Strength significantly improved in children with CP post-intervention, with changes surpassing the standard error of measurement (SEM). Limited strength decline was observed in DMD over time.
Conclusions:
- The instrumented strength assessment is reliable and valid for differentiating strength between TD children and those with CP and DMD.
- The assessment is responsive to strength changes following intervention in children with CP.
- Further research is needed to confirm the responsiveness of this assessment for tracking the natural strength decline in children with DMD.
Abstract:
The aim of this study was to determine the clinimetric properties, i.e., reliability, validity and responsiveness of an instrumented strength assessment in typically developing (TD) children and children with cerebral palsy (CP) and Duchenne muscular dystrophy (DMD). Force (N), torque (Nm) and normalized torque (Nm/kg) were defined for maximal voluntary isometric contractions (MVICs) of the lower limb muscles using a pre-established protocol. Intraclass correlation coefficient (ICC), standard error of measurement (SEM) and minimal detectable change (MDC) of TD children (n = 14), children with CP (n = 11) and DMD (n = 11) were used to evaluate intra-rater reliability for the three cohorts and the inter-rater intersession as well as inter-rater intrasession reliability for TD children. Construct validity was assessed by comparing MVICs in TD children (n = 28) to children with CP (n = 26) and to children with DMD (n = 30), using the Kruskal Wallis and post-hoc Mann-Whitney U tests. Responsiveness was investigated by assessing changes in MVICs following a strength intervention in CP (n = 26) and a 1 and 2 year follow-up study in DMD (n = 13 and n = 6, respectively), using the Wilcoxon Signed-Rank test. The overall intra-rater reliability, was classified as good to excellent for 65.1%, moderate for 27.0% and poor for 7.9% of the measures (47.6%, 76.2%, and 66.7% good-excellent; 28.6%, 23.8%, and 33.7% moderate; 23.8%, 0%, and 0% poor in TD, CP, and DMD, respectively), while ICC values for TD children were slightly lower for inter-rater intrasession reliability (38.1% good-excellent, 33.3% moderate and 26.6% poor) and for inter-rater intersession reliability (47.6% good-excellent, 23.8% moderate and 28.6% poor). Children with CP and DMD were significantly weaker than TD children (p < 0.001) and the majority of these strength differences exceeded the MDC. Children with CP significantly improved strength after training, with changes that exceeded the SEMs, whereas only limited strength decreases over time were observed in the DMD cohort. In conclusion, the investigated instrumented strength assessment was sufficiently reliable to confirm known-group validity for both cohorts and could detect the responsiveness of children with CP after a strength intervention. However, more research is necessary to determine the responsiveness of this assessment in children with DMD regarding their natural decline.
