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Updated: Jul 12, 2025

Diagnosis of Musculus Gastrocnemius Tightness - Key Factors for the Clinical Examination
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Broader Estimates of Gastrocnemius Activity Generated a More Representative Cocontraction Index: A Study in Pediatric

Maria Vinti, Manob Jyoti Saikia, John Donoghue

    IEEE Transactions on Neural Systems and Rehabilitation Engineering : a Publication of the IEEE Engineering in Medicine and Biology Society
    |November 1, 2023
    PubMed

    Insights

    Electromyography (EMG) cocontraction index (CCI) estimates can be biased. Sampling the medial gastrocnemius muscle proximally and distally improves accuracy for cerebral palsy management.

    Area of Science:

    • Biomedical Engineering
    • Neuroscience
    • Rehabilitation Science

    Background:

    • The cocontraction index (CCI) quantifies spasticity in cerebral palsy using EMG.
    • Traditional EMG sensor placement may misestimate gastrocnemius muscle activity due to uneven electrical distribution.
    • This can lead to biased CCI estimates, impacting diagnosis and management.

    Purpose of the Study:

    • To investigate if dual-site EMG (proximal and distal) in the medial gastrocnemius (MG) improves CCI accuracy compared to single-site.
    • To assess differences in CCI estimates during isometric and dynamic conditions.

    Main Methods:

    • 10 healthy children (mean age 10) participated.
    • Surface EMG was recorded from proximal and distal bipolar electrodes on the MG.
    • Isometric dorsiflexion and swing phase of gait (using IMU sensors) were assessed.
    • CCI was calculated using conventional and broader MG region sampling.

    Main Results:

    • MG activity differed significantly between proximal and distal sites during both agonist (plantar flexion) and antagonist (dorsiflexion) actions.
    • CCI estimates using broader MG regions differed by ~36% from conventional single-site estimates.
    • This discrepancy was observed in all subjects during isometric tasks and in 2/10 during gait swing phase.

    Conclusions:

    • Dual-site EMG sampling of the MG reduces bias in CCI computation.
    • This approach provides a more representative and accurate cocontraction index.
    • Improved CCI accuracy is crucial for reliable comparisons in clinical populations like cerebral palsy.

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