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Updated: Jan 24, 2026
Manual Muscle Testing: A Method of Measuring Extremity Muscle Strength Applied to Critically Ill Patients
Published on: April 12, 2011
Feasibility and Reliability of Muscle Strength Testing in Critically Ill Children
Kaitlyn Siu1, Samah Al-Harbi2, Heather Clark2
1Division of Pediatric Neurology, Department of Pediatrics, McMaster University, Hamilton, Ontario, Canada.
Insights
The Medical Research Council (MRC) score is not feasible for screening pediatric intensive care unit-acquired weakness (PICU-AW) in children. Further research is needed for a reliable pediatric screening tool for muscle weakness.
Area of Science:
- Pediatric Critical Care Medicine
- Neurology
- Rehabilitation Medicine
Background:
- Diagnosing pediatric intensive care unit-acquired weakness (PICU-AW) presents significant challenges.
- The Medical Research Council (MRC) score is a standard for assessing muscle weakness in adult critical care but its pediatric application is unproven.
Purpose of the Study:
- To evaluate the feasibility and interobserver reliability of using the MRC score for muscle strength assessment in critically ill children.
- To determine if the MRC score can be effectively implemented as an early screening tool for PICU-AW.
Main Methods:
- A prospective observational substudy involving critically ill children aged 1-17 years admitted to the PICU.
- Weekly MRC score assessments were conducted by two independent clinical raters for participants on bed rest within 48 hours of admission.
- Data on completion rates and inter-rater reliability (ICC and Cohen kappa) were analyzed.
Main Results:
- MRC exams were attempted on 33 children, but only 21 (64%) could be completed, with many only feasible post-PICU discharge.
- Over half (57%) of attempted MRC exams were not completed, primarily due to sedation, pain, or lack of cooperation.
- While inter-rater reliability for the MRC sum score was excellent (ICC: 0.87), it was only moderate for diagnosing PICU-AW (Cohen kappa: 0.48).
Conclusions:
- The MRC score is not a feasible early screening tool for muscle weakness in the majority of critically ill children.
- Current methods are insufficient for early PICU-AW detection, necessitating the development of new, validated screening tools for pediatric critical care.
Abstract:
Diagnosing pediatric intensive care unit-acquired weakness (PICU-AW) is challenging. The Medical Research Council (MRC) score is a widely used screening method for muscle weakness in critically ill adults; however, its utility in critically ill children has not been established. Our objective was to determine the feasibility and interobserver reliability of muscle strength testing using MRC score in critically ill children. A prospective observational substudy of critically ill children aged 1 to 17 years and limited to bed rest during the first 48 hours of PICU admission was evaluated with weekly MRC exams independently performed by two clinical raters. MRC exams were attempted on all 33 participants, but could be completed in only 21 (64%), 9 of who (43%) received at least one exam while in the PICU, and in the remaining 12 (57%), MRC exams could only be completed after PICU discharge. Of the 95 attempted MRC exams, 55 (57%) could not be conducted or completed, most commonly due to patient sedation, and inability to comply due to cognitive ability, pain, or noncooperation. The inter-rater reliability for MRC sum score was excellent (intraclass correlation coefficient: 0.87). However, the inter-rater reliability was only moderate when used to determine PICU-AW (Cohen kappa: 0.48). MRC testing in the PICU was not feasible as an early screening tool for muscle weakness in the majority of critically ill children in this study. Further research is needed to find an appropriate screening tool that is both feasible and predicts clinically relevant outcomes in children, such as function and recovery following critical illness.
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