Muscle Activation Patterns When Passively Stretching Spastic Lower Limb Muscles of Children with Cerebral Palsy

PLoS ONE, 2014 · DOI: 10.1371/journal.pone.0091759 · Published: March 20, 2014

Simple Explanation

This study investigates how muscles in the lower limbs of children with cerebral palsy (CP) activate when passively stretched. The research team aimed to identify different patterns of muscle activation and develop methods to quantify these patterns. Researchers used inertial sensors and electromyography (EMG) to record muscle activity and joint motion in the adductors, medial hamstrings, rectus femoris, and gastrocnemius muscles as they stretched these muscles at different speeds. The study found that muscle activation patterns varied among individuals and specific muscles, suggesting that spasticity in children with CP is complex and can manifest differently depending on the muscle and the person.

Study Duration

Not specified

Participants

54 children with spastic CP

Evidence Level

Not specified

Key Findings

1
Muscle activation patterns were found to be both muscle- and subject-specific, indicating variability in how spasticity manifests in different muscles and individuals.
2
Comparing RMS-EMG between incremental position zones during low velocity stretches was found to be the most sensitive in categorizing muscles into activation patterns.
3
All patterns were dominated by high velocity-dependent muscle activation, but in more than half, low velocity-dependent activation was also observed.

Research Summary

The study aimed to quantify different muscle activation patterns in the lower limbs of children with CP using an instrumented assessment. Fifty-four children with CP were included, and their muscle activity was recorded during passive stretches at varying velocities. The researchers categorized muscle activation patterns and defined quantitative parameters using stretch-reflex thresholds and normalized RMS-EMG. These parameters were compared between muscles with different activation patterns. The study found that muscle activation patterns were both muscle- and subject-specific, and that low velocity stretches were most sensitive in categorizing these patterns. The intra-rater reliability of the quantitative parameters was moderate to good.

Practical Implications

Targeted Treatment

Identifying muscle-specific patterns may help in the development of more targeted treatment modalities.

Treatment Variability

Understanding different activation patterns may explain the variability in treatment response among children with CP.

Improved Spasticity Assessment

Instrumented measurements can provide more detailed information on muscle activation patterns compared to clinical spasticity assessments.

Study Limitations

1
Visual determination of EMG onset in 10% of the stretch repetitions introduces subjectivity.
2
Limited number of subjects used to assess reliability, especially for the TSRT.
3
Manual stretches result in inconsistencies in velocity.

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