Related Experiment Video
Updated: Apr 27, 2026
Muscle Imbalances: Testing and Training Functional Eccentric Hamstring Strength in Athletic Populations
Published on: May 1, 2018
Does muscle size matter? The relationship between muscle size and strength in children with cerebral palsy
Siobhán L Reid1, Christian A Pitcher, Sîan A Williams
1School of Sport Science, Exercise and Health, The University of Western Australia , Perth , Australia .
Insights
Children with spastic cerebral palsy (CP) have smaller, weaker muscles than typically developing peers, but muscle size doesn't fully explain their reduced strength. Muscle volume is a better strength predictor in CP.
Area of Science:
- Neurology
- Pediatrics
- Rehabilitation Medicine
Background:
- Children with spastic cerebral palsy (CP) often exhibit impaired motor function, including reduced muscle strength.
- Understanding the relationship between muscle size and strength is crucial for developing effective interventions in pediatric CP.
Purpose of the Study:
- To compare the muscle size-strength relationship of knee flexors and extensors in children with spastic CP versus typically developing (TD) children.
- To identify the best muscle size predictor of strength in children with CP.
Main Methods:
- Magnetic Resonance Imaging (MRI) was used to measure muscle volume (MV) and anatomical cross-sectional area (aCSA).
- Biodex dynamometry assessed peak torque (PT) and work isometrically and isokinetically, normalized to body mass (Bm).
- Eighteen children with spastic Diplegia (GMFCS I-III) and 19 TD children participated.
Main Results:
- Children with CP demonstrated significantly lower torque across all measures compared to TD children (p < 0.05).
- Both MV and aCSA of knee flexors and extensors were smaller in children with CP (p < 0.003).
- The muscle size-strength relationship was weaker in children with CP than in TD children.
Conclusions:
- Children with CP have smaller, weaker muscles, with muscle size only partially explaining their reduced torque capacity.
- Muscle volume (MV) is a better predictor of muscle work in children with CP compared to aCSA.
- Assessing muscle capacity in CP should prioritize total muscle volume and isokinetic strength measurements.
Purpose:
To investigate the muscle size-strength relationship of the knee flexors and extensors in children with spastic cerebral palsy (CP) in relation to typically developing children (TD).
Methods:
Eighteen children with spastic Diplegia, Gross Motor Function Classification System I-III (mean 7 y 5 mo SD 1 y 7 mo) and 19 TD children (mean 7 y 6 mo SD 1 y 9 mo) participated. Muscle volume (MV) and anatomical cross-sectional area (aCSA) were assessed using MRI. Measures of peak torque (PT) and work of the knee flexors and extensors were assessed isometrically and isokinetically using a Biodex dynamometer, and normalised to bodymass (Bm).
Results:
Children with CP were weaker than their TD peers across all torque variables (p < 0.05). MV and aCSA of the knee flexors (MV: p = 0.002; aCSA: p = 0.000) and extensors (MV: p = 0.003; aCSA: p < 0.0001) were smaller in children with CP. The relationship between muscle size and strength in children with CP was weaker than the TD children. The strongest relationship was between MV and isometric PT/Bm for TD children (r = 0.77-0.84), and between MV and isokinetic work (r = 0.70-0.72) for children with CP.
Conclusions:
Children with CP have smaller, weaker muscles than their TD peers. However, muscle size may only partially explain their decreased torque capacity. MV appears to be a better predictor of muscle work in children with CP than aCSA. This is an important area of research particularly in regard to treatment(s) that target muscle and strength in children with CP. Implications for Rehabilitation This research adds to the evidence that children with CP have smaller, weaker knee flexor and extensor muscles than their TD peers. However, unlike their TD peers, muscle size does not necessarily relate to muscle strength. The weak correlation between MRI-derived muscle volume and isometric peak torque suggests children with CP are underpowered relative to their muscle size. For children with CP, muscle volume appears to be the best predictor of isokinetic muscle torque output. Therefore, when assessing the capacity of a muscle, it appears preferable to measure total muscle volume and torque development through a range of motion (isokinetic strength).
More Related Videos
Related Concept Videos
01:12Alterations in Muscle Tone ll
01:27Exercise and Muscle Performance
Endurance exercises
Endurance exercises involve running, swimming, or cycling, which require repetitive movements with low force output. When a person engages in endurance exercise, a few noticeable changes occur in their skeletal muscles. For instance, the number of capillaries...
02:36Cells Coordinate Growth and Proliferation
01:28Disorders of the Skeletal Muscle
Musculoskeletal disorders
Musculoskeletal disorders involve injuries and conditions affecting the skeletal muscles and associated connective tissues. These disorders can arise from acute biomechanical stresses or chronic overuse and can occur across different age groups. Common injuries include sprains, fractures, and muscular strains, often resulting from...
01:11Alterations in Muscle Tone lll
01:20Motor Unit Stimulation
The latent period of contraction marks the onset of excitation-contraction coupling, when the action potential propagates across the sarcolemma, preparing the muscle fibers for contraction. As the fibers enter the contraction phase, the...