Analysis of muscle activation in children and adolescents with severe cerebral palsy

Introduction: Children and adolescents with spastic quadriparesis have a worse selective motor control, and studies with this population are still very scarce. The same is true with scientific evidence of one of the methods most used as a physiotherapeutic treatment in this population, the Bobath Concept. Objective: To evaluate spine erector muscles activation, gluteus medius and gluteus maximus, through the handling of the Bobath Concept and the sustained kneeling posture in subjects with a diagnosis of severe cerebral palsy; and to compare muscle activation with a reference group, in order to increase the reliability of this study. Methods: A cross-sectional study was carried out with 38 children and adolescents with cerebral palsy, classified by GMFCS at levels IV and V, and 20 healthy participants, aged between 3 and 18 years. They were submitted to the handling of the Bobath Concept and to the sustained kneeling posture, with muscle activation obtained by electromyography. Results: We observed significant muscle activation during handling in side-sitting, with weight transfer and without the help of another therapist, and in the sustained kneeling posture, for the erector of the spine and gluteus medius. Conclusion: The evidence from this study suggests that both the handling in side-sitting and the sustained kneeling posture cause significant muscle activation in the erector of the spine and gluteus medius for severe quadriparesis subjects, GMFCS IV and V, which can contribute to the improvement of postural control and decision-making in physical therapy practice.


Introduction
Cerebral palsy (CP) is the most prevalent type of nonprogressive physical disability amongst children, resulted from injury in a developing brain. Such disability may vary in terms of timeframe, place, clinical implications and severity of the brain damage. 1,2 Its general prevalence is 2.1 per 1000 live births in developed countries and between 2.0 and 2.8 in developing countries. 3,4 In order to perform daily activities properly, many children spend the majority of their time sitting. The more severe cases (levels IV and V), classified by the Gross Motor Function Classification System (GMFCS), 5,6 demonstrate a lack of postural adjustment, not being able to sit independently. Factors such as spasticity, muscle weakness, excessive coactivation of agonist/antagonist muscles, decreased muscle coordination, and decreased response variability can contribute to this condition. 7 Therefore, it is possible to presume that children who lack a basic postural component will never learn to sit independently, even with extensive practice, 8 drastically limiting their functional mobility and daily life activities. 9 In the literature, evidence around physiotherapeutic approach employed in children with spastic quadriparesis CP type is very restricted. 10 The majority of studies focus on children in I, II and III GMFCS levels, since these have a higher capacity in having selective motor control.
Given that the focus in services related to secondary disabilities increases over time, more information from therapists would be useful to determine more efficient interventions, especially for children with reduced functional capacity. 11 The Bobath Concept, also known as neurodevelopmental therapy (NDT), is placed among the most commonly used approaches for motor intervention in CP [12][13][14] and is a strategy that aims to improve gross motor function and postural control, facilitating muscle activity through key control points assisted by the therapist. 15 The NDT emphasizes individualized therapeutic handling based on movement analysis, and therapeutic handling aims to enable participation in meaningful activities. 16 The Bobath Concept is inclusive and used with individuals of any age who have suffered damage to their central nervous system, regardless of the degree of severity. It is a facilitation via handling to enable the individual to have an experience of movement that is not passive, but one that they cannot yet do alone. 17 Clinical research that assesses muscular activation after the Bobath Concept handling facilitations in children and adolescents more severely affected, 18 and that quantifies the effects that such therapy model may offer to this select public are still scarce. 18   The sequence of handlings was randomized at every three participants, through opaque and sealed envelopes. The randomization was undertaken by an independent researcher who was not involved in the selection process and did not have access to the children's clinical information.

Data collection and processing
The EMG signal was collected following the guidelines of the International Society of Electrophysiology and Kinesiology (ISEK) and the SENIAM project (Surface ElectroMyoGraphy for the Non-Invasive Assessment of Muscles). The signal was captured using self-adhesive Ag/AgCl electrodes with a bipolar configuration and diameter 2.2 cm (from the 3M brand). The center-tocenter distance between the electrodes was 20 mm, as recommended by SENIAM. 28 To obtain data, the skin impedance was reduced through asepsis and mild abrasion with cotton soaked in 70% alcohol. The electrodes were positioned longitudinally to the muscle fibres, 29,30 on the right side of the body in erector of the spine, gluteus medius and gluteus maximus. The choice of one side of the body followed previous studies 18,20 and the fact that the handling is performed for the same side of muscle activation. 22 The reference electrode was placed in the tibial tuberosity, on the right side. 29 For the collection of the electromyographic signal,

Results
The general characteristics of the two participating groups are described in Table 1; the data reinforces the severity of children and adolescents diagnosed with CP in this study.

Side-sitting handling
During handling in side-sitting, Table 2  Handling of rolling from prone to lateral decubitus position During this handling, there was no statistically significant variation in muscle activation in relation to rest for any muscle in the CP group (Table 3). Only in the healthy group there was a significant difference for the erector muscle. Regarding variations in handling, there was also no significant difference for both groups.
In the handling of rolling, the superiority of the variation of muscle activation for the healthy group is confirmed in relation to the CP group, in all handling situations.

Sustained kneeling posture
During the sustained kneeling posture, muscle activation was statistically significant for the erector and gluteus medius, but with greater variation for the erector muscle in the CP group (    To promote muscle activation, the Bobath Concept was the treatment choice, as it is the most used for individuals with CP. 19 It is a model of holistic and interdisci- The muscle activation of the spine erector, verified in our study, was significantly greater in the sustained kneeling posture. In the study by Choi et al. 19 with ten diplegic children, there was also an increase in muscle activity of the erector both in the group that received Bobath therapy and in the group that received the taskoriented approach in order to improve the sitting posture.
For the sustained kneeling posture, the CP group in our study had a greater variation than the healthy group; a possible explanation for this would be that the CP group does not present adequate postural control, in addition to the lack of selective motor control, and therefore oscillated during the sustained posture even with the help of the therapist. In addition, during posture maintenance, we observed several times that children entered an extensor pattern, due to increased tone.
We are suggesting that the sustained kneeling posture is used for postural shifts in therapies or associated to a functional task when the patient collaborates or understands.
Regarding the handling of rolling, it seems that this was not enough to activate the analyzed muscles in a which may lead to variation in results. 32 In our study, the proper preparation of the skin, the use of filters for cleaning the signal, the adequacy of the environment, and the smoothing of data by the RMS were used to reduce external interferences.

Authors' contribution
FZ and FC were responsible for the study conceptualization and, along with TP, for the data analysis and interpretation. FZ was also responsible for the manuscript writing, and BTP, BF and CCL for data collection. All authors approved the final version.