Cerebral palsy (CP) describes a group of nonprogressive lesions or anomalies of the brain arising in the early stages of its development, causing secondary motor impairment syndromes.1 The lesions or anomalies of the brain are static, but the physical representation of the symptoms is variable with time.2 Features of this neurological disorder may include spasticity, secondary changes in the musculoskeletal system such as decreased muscle strength, tightness or contractures around joints, and abnormalities in bony structures and eventually deterioration in the mobility of the individuals.3
Static weight-bearing (SWB) exercises are widely used for children with CP.4 For the lower extremities (LEs), SWB is commonly achieved by positioning the individuals with support in a standing frame.5 For the upper extremities (UEs), usually weight is born directly through the hands or forearms in various positions, such as prone with arms in extension or side sitting with support on an extended arm.6 SWB is assumed to prevent tightness or contracture of soft tissues and restore the length of muscles by prolonged stretching.7 SWB is believed to reduce spasticity by inhibiting motor neuron excitability through prolonged stretch and compression on the muscle spindles, Golgi tendon organs, cutaneous receptors, and joint receptors.8,9 There also are claims that SWB exercises improve bone growth and mineral density.10,11 Particularly for those children with limited mobility, the exercises are said to stimulate antigravity muscle strength and endurance,5 prevent hip dislocation,12 improve self-esteem,13,14 and improve breathing and general circulation of the blood, which in turn may assist feeding15 and bowel and urinary functions.5,13 SWB through the UEs is thought to reduce muscle tone in the affected hand16 and improve hand function.17 Although SWB exercise has been widely used in children with CP, its effectiveness, except for an increase in bone mineral density in healthy subjects,10 has not been thoroughly investigated. Clinicians need to have research-based evidence to justify their clinical decisions in the management of children with permanent disability. This review aimed to investigate the research evidence concerning the use of SWB exercises in children with CP.
The clinical question of this review was “Does weight-bearing in both UEs and LEs improve the following functions more effectively in children with CP than no weight-bearing?” The effects of WB may be to increase bone mineral density, reduce or prevent hip dysplasia, improve passive joint range of movement, reduce spasticity, improve bowel and urinary functions, improve self-esteem, improve communication, improve hand function, and improve feeding.
SWB is defined as loading full or partial body weight through the LEs in an upright position with or without support through the hands or forearms of the UEs. The prime focus of the review was on studies with intervention consisting of activities mainly involving static body weight bearing through the LEs or UEs.
The inclusion criteria for this review were (1) studies of children with a diagnosis of CP regardless of the type, severity, or the child’s ambulatory status; (2) research studies; (3) studies involving subjects younger than 18 years of age; (4) studies consisting of SWB exercise as the intervention and reporting findings analyzing its effectiveness; and (5) studies published in English in peer-reviewed journals. Studies that compared SWB exercises with the effects of medications, surgery, or serial casting were excluded.
Electronic databases including MEDLINE, CINAHL, PsycINFO, Embase, full Cochrane Library, and PEDro were searched from the earliest possible date until October 2006 by using the following keywords: child, cerebral palsy, weight bearing, bone density, hip dysplasia, contracture, range of movement, stretching, muscle spasticity, bowel and urinary function, morale, communication, hand function and feeding. Subject headings, truncations, and a thesaurus were used whenever possible. The details of the search strategy are available from the author on request. Reference lists from relevant studies and review articles also were examined. The titles and abstracts of articles identified in the final search were first screened by the author against the inclusion and exclusion criteria. When the title and abstract did not indicate clearly if an article should be included, the complete article was read to determine its suitability.
Quality Assessment of Methodology
All the included studies were scored on their methodological rigor with the PEDro scale.18 The PEDro scale examines 11 aspects of the quality of methodology including: (1) specification of eligibility of subjects, (2) randomization of subjects, (3) allocation concealment of subjects, (4) comparability of subject groups at baseline, (5) blinding of subjects, (6) blinding of therapists, (7) blinding of assessors, (8) more than 85% follow-up of subjects in at least one of key outcomes, (9) “intention-to-treat” analysis, (10) between group statistical analysis of at least one of the key outcomes, (11) point estimate of at least one of the key outcomes. According to the PEDro guidelines, a positive answer to each of the criteria 2 to 11 will yield one point, obtaining a PEDro score between 0 and 10.18 The details of the scoring criteria can be found in the web link http://www.pedro.fhs.usyd.edu.au/criteria.html. The PEDro scale has been shown to have moderate interrater reliability with the intraclass coefficient for the total score of 0.56, and a 95% confidence interval (95% CI) of 0.47 to 0.65.19
The American Academy of Cerebral Palsy and Developmental Medicine (AACPDM) evidence table of internal validity was used to grade the levels of evidence of each selected study.20 This classification of levels of evidence is a modification of Sackett’s hierarchy of levels of evidence,21 but it includes and grades single subject research designs, which are increasingly common in research in the developmental disability domain.20 The AACPDM evidence table was used to judge the internal validity of the study based on its study design.20
Data from all the included studies were summarized in the format as suggested by the AACPDM.20 The format includes the following headings: subjects’ characteristics, including numbers in each group, target population, diagnosis, numbers and ages in each diagnostic subgroup; intervention used; controls used; research design and level of evidence for the study; and outcomes of interest.
Effect sizes with 95% CIs were calculated if raw data were available for the calculation in the published report of the studies.22 The effect sizes provide an easy understanding of how large the treatment effect is. The clinical significance or relevance of these statistically significant treatment effects can then be justified according to an individual patient’s situation. The effect size was the difference between the means of outcome measures of the subject and control groups. If there was no control group, the difference of the pre- and post-treatment means was used as the subjects were acting as their own controls. The 95% CI was approximated by the following formula:
where SD = standard deviation and N = number of subjects in the study. The averages of the standard deviations of the group means and the numbers of subjects were used if there were experimental and control groups.22 This formula for calculating the effect size with a 95% CI was chosen as it has been deliberately devised for clinicians who are not experienced in complicated statistical calculations.22
An electronic search on various databases and hand searching reference lists identified 648 articles, of which 17 studies met the inclusion criteria. The full text of these 17 studies was reviewed, and seven studies were further excluded because of the following reasons. One study was an expert opinion on the topic of interest,10 in which the author quoted two of his studies on the effect of a standing program in children with CP without listing the study design and raw data on the outcome measures in details. The original two studies were not published in a peer-reviewed journal. One study23 was a critical review of a study15 on the effect of positioning on the hand function of boys with CP. The original study15 was included in this review. One study included subjects with diagnosis of spina bifida, muscular dystrophy, or spinal cancer.24 No data were available to allow separate analysis of children with CP. The WB program of one study included positions other than standing,12 and it was not possible to differentiate the effects from standing from other positioning such as lying prone or supine. All subjects in one study were older than 18 years of age.25 One study described a new type of stander,26 and another described a new body-shaped orthosis.14 Neither of these two studies included data collection on children with CP while using the new equipment.
The intervention in the study by Chad and colleagues27 was a physical activity program with no detail provided about the exercises (whether static or dynamic WB exercises). The authors emphasized that WB was the main focus in their intervention and two-thirds of the subjects in the intervention group were non-ambulatory or ambulatory with assistance. It was likely that static WB exercises were included. Thus, this study was included in this review. Therefore this report analyzed the results from ten research studies on the effects of WB exercises in children with CP. Five of these studies investigated the effects of the WB exercises on the UEs and five studies were focused on the LEs.
The PEDro scoring of each study is listed in Table 1. The median score of the 10 studies was five (interquartile range three to six) with four studies equal to or more than six of 10. According to the AACPDM evidence table, seven studies15,27–32 should be classified as level I randomized controlled trials (RCTs; see Table 2). However, one study29 did not use statistical analysis of the results and therefore was downgraded to a Level II RCT. The PEDro scores indicated that most of the studies did not have concealed allocation of subjects (criterion three) and blinding of subjects, therapists, or assessors (criteria five to seven; see Table 1). Hence, although all these seven studies are of level I or II evidence, their methodological quality is moderately poor. Most of the 10 studies fulfilled PEDro criteria eight to 11, showing that most of the subjects undertook the designated WB programs and their outcomes were reported, together with the statistical comparisons of both point measures and measures of variability (see Table 1). Table 3 summarizes the outcomes of interest of these 10 studies. The outcomes of interest in these studies were mainly at the levels of impairment or functional limitation/activity.
Three studies investigated the change in muscle tone in the affected hand,16,17,33 in which the contact area of the hand was measured before and after WB. Two studies16,17 reported an increase in the hand contact area after WB. The relationship between the hand contact area and the muscle tone of the hand was not discussed in these reports. The average effect size from one study was approximately 2 cm2 (Table 3), and the increase was not sustained after some prehension activities.17 Thus, the present evidence from the two single-subject studies to support WB exercises on UE in children with CP in decreasing muscle tone in the affected hand is consistent despite the low levels of evidence of the studies, but of poor clinical significance because the effect is not sustained. One may argue that the increase in the hand surface area post-SWB exercises would be clinically worthwhile from the point of hand hygiene and prevention of skin breakdown, as was also shown by an increase in passive ranges of thumb abduction and extension in the study by Smelt.16 As the minimal increase in hand area was achieved by a regular program in the presence of a therapist, the cost-effectiveness of this program was questionable. Perhaps alternatives such as home-based programs of splinting with or without WB exercises should be considered. These questions should be verified with studies employing more stringent research design, more rigorous methodological quality and a larger sample size.
In hand function such as reaching, grasping, and releasing an object, three studies15–17 showed positive outcomes after WB or negative outcomes after stopping WB. No raw data were provided for the calculation of the effect size of the outcome measure from the study by Chakerian and Larson.17 Smelt16 did not analyze the outcome measure statistically in her Level IV study. Noronha and colleagues15 in their Level I study did not use a statistical method to analyze the quality of the grasp during the standardized hand function test. On the other hand, the report of the Level IV study by Kinghorn and Roberts33 did not show any difference in hand function with WB. It appears that the present evidence in supporting improvement in hand function in children with CP after SWB remains inconclusive because the studies with positive outcomes were either of low levels of evidence or of less rigorous methodological quality (PEDro scores between three and five). Estimation of the effect size is not possible and thus it is difficult to judge whether the improvements were clinically significant.
Noronha and colleagues15 reported that the children showed significantly faster speed in simulated feeding in a prone-standing position (7.33 seconds faster) when compared with supported sitting as a result of their Level I study (see Table 3). The children showed faster times in picking up small objects in supported sitting than in the prone-standing position (6.91 seconds faster). There is some evidence showing that the WB position can enhance feeding in terms of speed of finishing the task. The effect size was small and the authors did not discuss the clinical significance of the increase in speed in simulated feeding.
In the report of the Level I study by Miedaner and Finuf,30 only one subject used a prone-stander/side-lyer in comparison with supported sitting. There was no difference in scores in this child’s cognitive test in these two positions. The evidence is limited as to whether WB can enhance performance in the cognitive test as only one study with one subject investigating this outcome has been reported (Table 2).
Two studies, both of Level I evidence,27,28 reported that WB exercises or activities could result in significant increase in bone mineral density (BMD) in the lumbar spine (6% mean increase in the volumetric BMD28) or femur (5.6% increase in the volumetric BMD27). Although their findings were positive, Gudjonsdottir and Mercer (Level II study)29 did not analyze their results statistically. The authors of the two Level I studies27,28 believed the increase was clinically significant in reducing the susceptibility of fractures. SWB exercises or activities can apparently increase BMD in the lumbar spine or femur in children with CP as the studies with positive outcomes were of high level of evidence and rigorous methodological quality (PEDro score six and seven). Hence, SWB in a standing frame is a simple but effective way to increase bone density in children with CP. The actual association between increase in BMD and reduced incidence in fractures in this population needs to be further verified with longitudinal population-based studies with larger sample sizes.
Two studies31,32 used SWB exercises as a method of prolonged muscle stretching to reduce muscle tone in children with CP. Surface electromyography (EMG) of the ankle muscles was used to measure spasticity of the muscles in both studies. Richards and colleagues31 demonstrated a significant reduction in the surface EMG pre/post ratio of the tibialis anterior muscles at the initial gait cycle after standing on a tilt-table for 30 minutes. The difference in the pre/post ratio between the treatment and control groups was 0.25. No 95% CI was reported. The authors considered this reduction to be clinically nonsignificant, as the reduction was not demonstrated in the other outcome measure used in the study (Spastic Locomotion Disorder Index; see Table 3). Tremblay and colleagues32 reported a significant reduction in resistance (effect sizes ranging from −0.28 to −0.67) and in the surface EMG pre/post ratio during passive movements in the ankle (effect sizes ranging from −0.2 to −0.42 for triceps surae and −0.33 to −0.48 for tibialis anterior muscles) after standing on a tilt-table for 30 minutes and the effect lasted up to 35 minutes afterwards (see Table 3). Both findings indicated significant reduction in spasticity in the ankle muscles after WB. Although there was an increase in EMG activation, ie, more muscle recruitment, during static plantarflexion of the ankle after the SWB exercises, the authors did not further investigate whether there was any other functional change such as during walking. Hence, there is some evidence to suggest that SWB used as prolonged stretch can temporarily reduce spasticity in children with CP as both studies provided Level I evidence and had more rigorous methodology (both PEDro scores of six). The effect sizes were however, fairly small and the clinical significance was questionable.
SWB exercises through the UEs or LEs have been widely used for children with CP, particularly for those with greater mobility restrictions, as a result of the belief that WB can increase bone mineral density and so reduce risk of fractures, reduce or prevent hip dysplasia, improve passive joint ranges of movement, reduce spasticity, improve bowel and urinary functions, improve self-esteem and communication as in a more upright position, improve hand function and improve feeding. It is interesting to find that there was no yield in the literature search in various electronic databases (with some search dated back to 1966) in this review in the areas of improving bowel and urinary functions, improving self-esteem and communication. The only study found that investigated the effects of WB exercises on hip dysplasia had a combined program of different static positions other than solely in a standing frame. It appears that some commonly claimed benefits of WB remain anecdotal.
A limiting factor of this review is that the selection of studies and methodological quality assessment was performed by one person. Two or more reviewers should reduce the risk of selection bias. Another limitation of this body of evidence is the small number of subjects in each study and their heterogeneity, which has already been identified as a major barrier in research, particularly in children with CP.34 None of the studies in this review had more than 15 subjects. Only one study28 reported that the power of the sample size was calculated a priori, but the sample size did not reach the ideal number of subjects required. Because the power of these studies was unknown, it is suggested that the statistically nonsignificant results are inconclusive, rather than indicative of there being no effect from WB exercises.20
More than half of the studies achieved less than the middle range in the total PEDro score. There is a need to conduct more rigorous trials for evaluation of the effects of both UE and LE SWB exercises for children with CP. Because of the limitations in the methodology of these studies and lack of studies investigating the claimed benefits of SWB exercises, it is difficult to make definite recommendations regarding the current clinical practice for children with CP. Clinicians should be skeptical about their rationale in using SWB exercises in children with CP.
There are a few conclusions that can be drawn from the existing evidence: (1) there is good evidence favoring WB exercises through the LEs for increasing bone mineral density in the spine or femur in children with CP; (2) there is some favorable evidence indicating that SWB exercises through the LE may temporarily reduce spasticity as prolonged stretch in children with CP although the effect size is small and the clinical value is questionable; (3) the evidence for SWB exercises in reducing spasticity and improving hand function in the UE in children with CP is limited and requires further studies to verify the effects of SWB for these outcomes; and (4) there is no research evidence to support the use of SWB exercises to reduce or prevent hip dysplasia, improve bowel and urinary functions, improve self esteem, or improve communication in children with CP.
Implications for Research and Clinical Practice
The findings of this review prompt clinicians to rethink their rationale for using standing frames or direct SWB through the UEs in their clinical practice. Clinicians should be confident to claim the benefits of SWB exercises based on research evidence in children with CP, but should avoid exaggerating those benefits for which there is not much research evidence. At the present time, SWB has been shown to be beneficial in improving bone mineral density of the spine or femur, thus reducing the susceptibility of fractures, so it is clinically worthwhile to use standing frames for children with CP, particularly in those with poor mobility. Other potential benefits of SWB exercises through the UEs and LEs need to be verified by studies of more rigorous methodological quality, of larger sample size, and also in terms of functional limitation/activity and participation level. Studies that aim to investigate the optimal forms, duration and frequency of SWB to obtain the desirable clinical changes in children are also necessary.
The author would like to sincerely thank Associate Professor Dinah Reddihough, Ms. Sue Reid (both from Royal Children’s Hospital, Melbourne, Australia), and Professor Mary Galea (University of Melbourne, Victoria, Australia) for their assistance in preparing the manuscript for publication.
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