Do Core Stability Exercise Classes Help Children With Cerebral Palsy Improve Their Balance

Introduction

The 'Core Muscles' are defined as '29 pairs of muscles that support the lumbo-pelvic hip complex in order to stabilize the spine, pelvis and kinetic chain during functional movement'.

Core stability refers to the control, co-ordination and synergism required by the core muscles for the maintenance of functional stability and balance. The role the core musculature plays in movement and postural control is long established. The understanding that our core muscles work in a feed-forward manner, laying the foundation of distal limb movement, formed the basis for studies into the use of core stability training programmes, such as pilates, core control training and spinal stability training, for improved postural control and balance.

Literature is replete with studies investigating the use of core stability programmes for varied populations from the adult population for chronic back pain to elite athletes for injury prevention and performance.

Studies investigating its use in adults with postural control impairment due to upper motor neuron lesions (UMN) from Multiple Sclerosis and Stroke showed positive effects on balance and mobility. The randomised controlled trial, by Chung et al, looked at the effects of a 4 week core stability exercise class on Dynamic Balance and Gait Function of 16 stroke patients. It showed a significant improvement of Timed-Up-And-Go (TUG) scores from 33.06 +-18.39sec to 27.64+- 13.73 sec (p=0.057) in the intervention group. Gait velocity (from 44.83+- 18.83 cm/s to 58.91 +- 18.21 ; p=0.024) and cadence ( from 74.55+- 13.85 steps/min to 84.07 +- 14.00 steps/min ; p=0.041) also showed significant improvement in the intervention group. To date there are no studies investigating the use or potential benefit of specific core stability intervention in the Cerebral Palsy (CP) population.

CP describes a group of permanent disorders of the development of movement and posture, causing activity limitation, that are attributed to non- progressive disturbances that occurred in the developing fetal or infant brain. It has been suggested that poor postural control may underlie delays and deviations in motor skill acquisition and development observed in children with CP. Therefore, it is important that treatment of children with CP tries to improve postural control and the evidence suggesting postural control mechanisms in school-age children with CP are modifiable signifies that this goal is achievable.

Young children with CP have been shown to use excessive, non-reciprocal trunk and hip muscle activation during walking. It has been hypothesized that one reason for this may be their need to compensate for poor control of their core deep stabilising muscles, thus limiting their ability to control changes in their body's centre of mass (COM) during dynamic movements. To understand this further we must look closer at the different functions of the core muscles.

The core muscles can be separated into large-lever, superficial global muscles, including the rectus abdominis and psoas major, that function as primary movers and smaller, deep, local muscles, including the Transverse Abdominis and Internal oblique, that function as primary stabilisers. It is postulated that if the deep stabilisers are not adequately functioning, then postural control is assisted by secondary compensatory activation of other muscles that typically function as primary movers like the hip flexors, knee flexors and spinal extensors. When a primary mover is being used to compensate for deep stabilisers, it becomes less efficient in its role in mobilizing and posturally adjusting.

An ineffective deep stabilizing system also limits the ability of the body to maintain the joints in a position where muscles are at a mechanical advantage. This can have an added 'weakening' effect on muscles that are essential for postural control, like the gluteus medius, as it reduces their force-generating capacity.

The objectives of the study are:

1. To measure changes in performance on a series of static, anticipatory and reactive balance tasks using three dimensional motion analysis in children who participate in core stability (intervention group) compared to children who continue their usual care (control group).
2. To compare changes in functional balance tests of the intervention group to the control group
3. To analyse qualitative data from a post intervention questionnaire to determine the broader effects of the 'Core stability' group intervention on the child's real life function, participation and quality of life.

Selection Criteria

The study aims to investigate the effects of a treatment intervention on children with Cerebral Palsy (CP). It is best research practice to choose a homogenous group of participants for meaningful results. It has been shown that in relation to balance of ambulatory children with spastic CP, a functional classification system (Gross motor Function Classification System-GMFCS level) can be used to group children more homogenously than traditional classification by diagnosis. On this basis, it was decided to include children with GMFCS levels I and II. Ambulatory children with a GMFCS classification level III were excluded as most studies showed a large gap in balance abilities between levels II to III. This would lead to a much greater variance in the participant sample.The Central Remedial Clinic (CRC) database of clients attending Clondalkin or Clontarf physiotherapy services will be used to generate a list of clients aged 7 to 17, with spastic CP diplegia or hemiplegia GMFCs level I or II for each centre.

The study inclusion/exclusion criteria will then be applied to this list. The clients not meeting the inclusion criteria or those meeting the exclusion criteria will be removed. The remaining clients will be invited to participate in the study and a list will be generated of participants who agree.

The resulting list will be split into 2 separate age groups (Age 7-12 years and Age 13-17 years) and unique identifying numbers will be assigned to each client on the day of their initial baseline assessment.

The clients will be assessed in groups of a minimum of 6 and maximum of 12 and will be randomised according to the procedure detailed below.

Sample Size

The sample size was calculated in Stata IC 13 (StataCorp, Texas, USA) using step length as the primary outcome measure. A previous study comparing gait in CP and typically developing children over level and uneven ground found a mean difference of 9cm (standard deviation 9cm) in step length between groups (Malone et al 2014, submitted for publication). With a power of 0.9 and significance level of 0.05, a sample size of 22 in each group was derived, giving a total of 44. To allow for a 10% drop out, it was decided to enroll 48 participants to the study.

Randomisation

A randomisation procedure will be carried out by an individual blinded to both the treatment and assessment procedure. The unique identifying number of the individual and their group will be in-putted into an electronic randomisation tool. Group assignment will be known to the treating therapists but not to the assessing therapist to ensure a single-blind design.

The participants will be allocated based on randomisation to either Intervention (I) or control (C).

Statistical analysis

The primary research question is whether core stability classes improve movement and function in the intervention group (I) compared to the control group (C). Data will be plotted graphically and described in the first instance using means, medians, standard deviations. Normality will be assessed using the Shapiro Wilk test. Groups will be inspected for baseline comparability. Quantitative parametric data from movement analysis assessment will be compared for (I) and (C) groups using analysis of co-variance including baseline levels of the outcome and adjusting for any baseline imbalances. Non-normally distributed data, e.g. Functional Walk Test, will be compared using Poisson regression.

Statistical analysis will be performed with Stata IC 13. Statistical assistance will be available from the Department of Epidemiology in RCSI.

Ethical Approval

Ethical approval has been obtained from the CRC Ethics committee

Informed Consent A written explanation of the study and core control group will be provided for the parent/guardian and participant. The information will be presented in a manner that is easy to understand and outline the risks and benefits of the study clearly. Each parent and participant will be given the opportunity to ask questions in writing or verbally and the parent/guardian will then sign a consent form. Refusal to participate in the study will not affect the client's general physiotherapy care from the CRC in any way.

Participants The control group will not work on focused balance specific core stability work in physiotherapy over the four-week control period. They will receive all other usual physiotherapy care during this period. Participants who are initially assigned to the control group will then be offered to participate in a Core Stability group after the control period assessments are completed. Therefore, all study participants (intervention and Control groups) will be given the opportunity to avail of the 'Core Stability' physiotherapy group programme. Each group will have to attend the same number of assessments (1 pre assessment and 1 post assessment)

Data Collection and Protection All data collected from the study will be restricted to the circumstances listed on the signed consent form. The procedures in place in relation to data storage and processing in the Gait Laboratory and the Physiotherapy Department in the CRC will be followed. Identifying information will only be stored in the CRC secure server.

Potential Risks During the Balance assessment in the gait laboratory, markers will be placed on the skin with adhesive tape. Taking these off may cause very slight discomfort. To alleviate this adhesive removal spray can be used.

The gait lab balance assessment is designed to be a measure of dynamic balance. Therefore, participants will be asked to do some tasks that may be challenging to them. They will be supervised at all times when carrying out the assessment by the independent assessor. Stand by assistance will be provided if required for safety.

The 'Core Stability' physiotherapy group intervention programme may be both mentally and physically challenging for the participants. It will involve concentration and repetition of activities. The group will be carried out under the supervision of two paediatric senior physiotherapists who work regularly with this CP population. These physiotherapists will have a strong knowledge base of this population's physical limitations. They are also experienced in how to encourage and motivate paediatric clients to carry out challenging activities.