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Updated: May 9, 2026
Procedures for Rat in situ Skeletal Muscle Contractile Properties
Published on: October 15, 2011
Maximal active force in skinned muscle fibres from children with cerebral palsy
Venus Joumaa1, Faizan Syed1, Jason J Howard2
1Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada.
Insights
Muscle weakness in children with cerebral palsy (CP) stems from compromised muscle fibers. Reduced sarcomeric proteins like actin and titin contribute to decreased force and stiffness in CP muscles.
Area of Science:
- Biomedical Engineering
- Muscle Physiology
- Pediatric Neuromuscular Disorders
Background:
- Cerebral palsy (CP) often leads to muscle weakness, impacting motor function.
- The precise origins of this muscle weakness at the cellular level remain incompletely understood.
Purpose of the Study:
- To investigate the intrinsic contractile properties of single muscle fibers from children with CP.
- To identify potential molecular contributors to muscle weakness in CP.
Main Methods:
- Single skinned muscle fibers were isolated from the adductor longus of children with CP and healthy adults.
- Maximal active stress, stiffness, and passive stress were measured at various sarcomere lengths.
- Myofibrillar protein content, including actin, titin, and nebulin, was quantified.
Main Results:
- Muscle fibers from children with CP exhibited significantly lower maximal active stress and stiffness compared to healthy adults.
- Content of actin, titin, and nebulin was reduced in CP muscle fibers.
- Passive stress was also diminished in CP muscle fibers at longer sarcomere lengths.
Conclusions:
- The contractile ability of muscles in children with CP is impaired at the single-fiber level.
- Reduced levels of key sarcomeric proteins, such as actin, titin, and nebulin, likely underlie this functional deficit.
Abstract:
The aim of this study was to gain insight into the origins of muscle weakness in children with cerebral palsy (CP) by investigating active force in single muscle fibres isolated from the adductor longus (AL) of children with CP. Single skinned muscle fibres (n = 43, from 11 children with CP) were isolated and tested for their maximal active stress, instantaneous stiffness, and the ratio of active stress to stiffness at a sarcomere length (SL) of 2.4 µm, and passive stress at SLs of 2.4, 2.6, 2.8, 3.0, 3.2, and 3.4 µm. The muscle biopsies were tested for their total myofibrillar protein content using a BCA assay, and myosin heavy chain, actin, titin and nebulin content using gel electrophoresis. Muscle biopsies from the vastus lateralis of healthy adults (HA; n = 19 fibres from 4 subjects) were used for comparison. The maximal active stress and the instantaneous stiffness, expressed as active elastic modulus, were lower in the CP fibres compared to the HA fibres (79 ± 4 vs. 170 ± 11 kPa, and 5479 ± 381 vs. 8943 ± 402 kPa, respectively). The maximal active stress to stiffness ratio was not different between CP and HA fibres (0.016 ± 0.001 vs. 0.020 ± 0.002). Actin, titin and nebulin content was reduced in the CP compared to the HA samples. Passive stress was also reduced in the CP fibres at SLs of 2.8, 3.0, 3.2 and 3.6 µm. These results suggest that the contractile ability of muscles from children with CP is compromised at the fibre level and this is likely the result of a decrease in sarcomeric proteins such as actin, titin and nebulin.
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