What is the evidence of the effectiveness of strengthening for children with cerebral palsy aged 4-18 years?

Keeping Current. © Adrienne Harvey & Dianne Russell, 2009

This study was completed in part for the International Society for Prosthetics and Orthotics (ISPO) Conference, Wolfson College, Oxford, September 2008

Why is This Topic Important?

Muscle weakness is commonly seen in children with cerebral palsy (CP) and can impact on their activities and participation in daily life situations. Muscle strengthening as a treatment intervention has gained in popularity in the past 10 years since earlier concerns that strengthening would increase spasticity and produce abnormal movement patterns appear unfounded. This review critically analyses the current literature to determine the evidence of the effectiveness of muscle strengthening in children with CP.

How was the Literature Review Done?

An electronic search was performed in May 2008 of the following databases: MEDLINE, Embase, CINAHL, PubMed, Database of Reviews of Effectiveness (DARE), the Physiotherapy Evidence Database (PEDro), and Cochrane Database of Systematic Reviews. Keywords used in the search included 'cerebral palsy', 'treatment outcome', 'physical therapy (specialty)/or physical therapy modalities/ or physiotherapy.mp'. Targeted hand searching was also employed by searching reference lists in key studies and review articles. To focus the research question studies were included if they involved children with CP aged 4-18 years, were published from 1995 onwards and were full text papers in peer reviewed journals. Studies were excluded if they were reviews, were single case studies, focused on the upper limb only or were abstracts and conference proceedings. Two reviewers independently extracted the data and assessed the quality of the studies using an individualized data extraction form. The Oxford Centre for Evidence-based Medicine Levels of Evidence (May 2001) were used to assign a level of evidence for each study (see table below for relevant categories).

Table 1:Oxford Centre for Evidence-based Medicine Levels of Evidence (May 2001)

Level Therapy/prevention, Aetiology/Harm
1b Individual RCT (with narrow confidence interval)
2b Individual cohort study (including low quality RCT.e.g. <80% follow-up)
3b Individual Case-Control Study
4 Case-Series (and poor quality cohort and case-control studies)
5 Expert opinion without explicit critical appraisal, or based on physiology, bench research or "first principles"

RCT:randomised controlled/clinical trial; categories 1a, 2a and 3a all systematic reviews Produced by Bob Phillips, Chris Ball, Dave Sackett, Doug Badenoch, Sharon Straus, Brian Haynes, Martin Dawes since November 1998 (http://www.cebm.net/index.aspx?o=1025)

What Do We Know About This Topic?

Eighteen studies were included in the review. There were 8 randomized controlled trials (RCT) and 10 case series. Based on the Oxford guidelines, three of the RCTs were level 1b evidence and five were level 2b. The 10 case series were level 4 evidence, that is, lower levels of evidence. See Table 2 for studies included in the review.

The treatment programs in the studies often consisted of 2-3 sessions per week for 6 weeks. Progressive resisted strength training (PRST) programs usually consisted of 4-5 reps, 3 times weekly for 6-8 weeks, starting at 65% maximum isometric strength. Functional based programs used a number of exercise stations for 1 hour, twice weekly for 4-6 weeks. The post-operative strength studies used a set of exercises, 3 times weekly for 6 weeks in one study and 9 months in the other two. Other studies included a 6 week program of loaded sit-stand, general strengthening or exercise bike. The population of children investigated in the studies was primarily those classified in GMFCS levels I-III.

The Gross Motor Function Measure (GMFM) and dynamometry were the most commonly used outcome measures. The GMFM was used in 10 studies with scores showing trends for improvements in a few studies but only two reached statistical significance. Using dynamometry, strength was improved in selected targeted muscle groups following PRST in a number of studies. The three studies with higher levels of evidence comparing post-operative strengthening and loaded sit-to stand with standard treatment showed that both groups tended to improve with no significant differences between the groups. There were no significant changes on gait parameters seen, however endurance was increased significantly in 2 studies. Strengthening did not increase spasticity.

There have been previous reviews of strengthening. One performed in 1997 by Darrah et al found only 7 studies, 6 of which had very low levels of evidence (level 5). A more recent review by Dodd et al in 2002 included 11 studies and concluded that although strength increases were reported in 8 studies, only one of those was an RCT and more rigorous studies were required. This current review indicates that since then more RCT's have been reported with some evidence of increased strength in targeted muscles for children with CP as measured by dynamometry. These improvements were seen at the body functions and structure level and carryover into improvements at the activity and participation level are less clear. It is possible that the treatment dosages used in the studies were ineffective (most were only 6 week periods) and that longer treatment periods are required before benefits are carried over into activities and participation.

There were a number of confounders seen in the studies in this review. The most common was the impact of children having "usual" or "standard" physiotherapy either as a control or in conjunction with the intervention in question. It was often not clearly stated what and how much this was, whether both groups received similar baseline treatments or the potential impact on the results. Many of the studies also had small sample sizes.

What are the Implications for Clinical Practice?

The current evidence for strengthening suggests that targeted strength training can improve the strength of particular muscle groups for children with CP in GMFCS levels I-III as measured at the body function and structure level without provoking increases in spasticity. There is evidence of more improvements in muscle strength than gait or functional parameters. Carryover effects into activity and participation has not been shown using the treatment regimes employed in the studies in this review. Some of the studies did consider the effect of the environmental setting such as home programs or group based programs with no significant differences, however many children subjectively stated that they enjoyed the group experience.

Where Do We Go From Here?

It is reassuring to see that in more recent years there has been an increase in the quality of studies performed to examine the effects of strengthening in children with CP. However, the effects seen so far remain at the body functions and structure level. One possible explanation is ineffective dosages used in studies to date. It is yet to be determined what the most effective treatment regime (dosage and frequency) actually is for strengthening in children with CP. Further evidence of benefits at the activities and participation level are required before these interventions can be stated to impact positively on the daily functioning of children with CP.

Update written by:

Adrienne Harvey, PT, PhD, McMaster Child Health Research Institute Post-Doctoral Fellow

Want to know more? Contact:

Adrienne Harvey

  • Click here for list of references

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