Effectiveness of exercise therapy for chronic non-specific low back pain

Chapter

|15 |

Effectiveness of exercise therapy for chronic nonspecific low back pain Marienke van Middelkoop*, Sidney M. Rubinstein†, Arianne Verhagen*, Raymond Ostelo†‡, Bart W. Koes* and Maurits van Tulder†‡

*Department of General Practice, Erasmus Medical Centre, Rotterdam, The Netherlands, †Department of Epidemiology and Biostatistics and EMGO Institute for Health and Care Research, VU University Medical Centre, Amsterdam, The Netherlands and ‡Department of Health Sciences and EMGO Institute for Health and Care Research, VU University, Amsterdam, The Netherlands

CHAPTER CONTENTS Background Methods Literature search, inclusion criteria and study selection Assessment of methodological quality and quality of evidence Data extraction and analysis Results of the review Description of studies Effectiveness of exercise therapy

BACKGROUND 171 172 172 173 173 173 173 176

Exercise therapy vs. waiting list controls/no treatment

176

Exercise therapy vs. usual care/advice to stay active

176

Exercise therapy vs. back school/education

176

Exercise therapy vs. behavioural treatment

176

Exercise therapy vs. TENS/laser therapy/ultrasound/massage

178

Exercise therapy vs. manual therapy/manipulation

179

Exercise therapy vs. psychotherapy

179

Exercise therapy vs. other forms of exercise therapy

179

Motor control exercise Discussion of results The effectiveness of exercise therapy Evidence-based practice Implications for practice References

179 180 180 180 181 181

Low back pain is usually defined as pain, muscle tension, or stiffness localized below the costal margin and above the inferior gluteal folds, with or without leg pain (sciatica). Low back pain is typically classified as being ‘specific’ or ‘non-specific’. Specific low back pain refers to symptoms caused by a specific pathophysiologic mechanism, such as hernia nucleus pulposus (HNP), infection, inflammation, osteoporosis, rheumatoid arthritis, fracture or tumour. Specific underlying diseases can be identified only in about 10% of the patients (Deyo et al. 1992). The vast majority of patients (up to 90%) are labelled as having non-specific low back pain, which is defined as symptoms without clear specific cause, i.e. low back pain of unknown origin. Spinal abnormalities on radiographs and MRI are not strongly associated with non-specific low back pain, because many people without any symptoms also show these abnormalities (van Tulder et al. 1997). Non-specific low back pain is usually classified according to duration as acute (less than 6 weeks), subacute (between 6 weeks and 3 months) or chronic (longer than 3 months) low back pain. In general, prognosis is good and most patients with an episode of non-specific low back pain will recover within a couple of weeks. However, back pain among primary care patients is often a recurrent problem with fluctuating symptoms. The majority of back pain patients will have experienced a previous episode and acute exacerbations of chronic low back pain are common. Low back pain (LBP) is not only a tremendous medical problem, but also a huge socioeconomic problem in Western countries due to high rates of disability and work absenteeism (Andersson 1999). It is important to provide effective and cost-effective interventions to improve

171

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Clinical evidence of control approach

patient outcomes and get maximum benefits within available health care budgets. Evidence-based medicine has become increasingly more important over the past decade. The management of low back pain has been positively affected by the availability of more scientific research and better use of critical appraisal techniques to evaluate and apply research findings (Chou 2005). The randomized controlled trial remains the gold standard of evidence on effectiveness of therapeutic interventions, but, there are many other sources and types of evidence relevant to clinical practice. A large number of systematic reviews are available within and outside the framework of the Cochrane Back Review Group that have evaluated the therapeutic interventions for low back pain by critically appraising and summarizing randomized trials (Bombardier et al. 1997; Bouter et al. 2003). This large body of evidence has greatly improved our understanding of what does and does not work for low back pain. The evidence from trials and reviews have formed the basis for clinical practice guidelines on the management of low back pain that have been developed in various countries around the world. Two recent papers summarized the quality and content of 25 international clinical guidelines on the management of low back pain (Koes et al. 2001; Bouwmeester et al. 2009). There seems to be consensus about the optimal management for acute low back pain. Recommendations for treatment of acute low back pain were rather consistent among the various international guidelines:

• Reassure patients on the favourable prognosis, if available provide printed patient information.

• Advise patients to stay active. • Discourage bed rest. • Prescribe medication if necessary (preferably

time-contingent):   paracetamol/acetaminophen   non-steroidal anti-inflammatory drugs. • If patients do not improve, spinal manipulation is an option for pain relief. Exercise therapy was not recommended for acute low back pain in any of the guidelines. However, all guidelines recommended exercise therapy for patients with chronic nonspecific low back pain. Exercise therapy is probably the most widely used type of conservative treatment worldwide. A systematic Cochrane review published in 2005 found that exercise therapy significantly reduces pain and improves function in adults with chronic low back pain, particularly in patients visiting primary care providers because of back pain (Alexandre et al. 2001). Since the publication of the Cochrane review, new studies have been published investigating various types of exercise interventions for chronic low back pain. The present chapter provides an update of the evidence on exercise therapy compared to other

172

interventions, but also on the comparison of different types of exercise in patients with chronic low back pain.

METHODS Literature search, inclusion criteria and study selection A literature search was performed using the following electronic databases: MEDLINE, EMBASE, CINAHL, CENTRAL and PEDro (up to 22 December 2008). References from the relevant studies were screened in order to identify any additional studies. The language was limited to English, Dutch and German. The search strategy outlined by the Cochrane Back Review Group (CBRG) was perused. Two reviewers working independently from each other conducted the electronic searches. The inclusion criteria were as follows:

• Randomized controlled trials of two or more interventions.

• The study population should consist of adults, older than 18 years, with non-specific chronic low back pain that persisted for 12 weeks or more. • RCTs studying any type of exercise therapy. Exercise therapy was defined as ‘a series of specific movements with the aim of training or developing the body by a routine practice or physical training to promote good physical health’ (Bendix et al. 1995). Additional treatments were allowed provided that the intervention of interest was the main contrast between the intervention groups included in the study. • RCTs including subjects with specific low back pain caused by pathological entities, such as vertebral spinal stenosis, ankylosing spondylitis, scoliosis, coccydynia, were excluded. The diagnosis for these specific entities had to be confirmed by means of an MRI or another diagnostic tool. Trials on post-partum low back pain or pelvic pain due to pregnancy were also excluded as well as postoperative studies and prevention studies. • The following self-reported outcome measures were assessed in this review: pain intensity (e.g. visual analogue scale (VAS), McGill pain questionnaire), back-specific disability (e.g. Roland Morris, Oswestry Disability Index), perceived recovery (e.g. overall improvement), return to work (e.g. return to work status, sick leave days) and side effects. The primary outcomes for this overview were pain and physical functional status. Studies with a follow-up less than one day were excluded. Two authors independently screened the abstracts and titles retrieved by the search strategy and applied the

Effectiveness of exercise therapy for chronic non-specific low back pain inclusion criteria. The full text of the article was obtained if the abstract seemed to fulfil the inclusion criteria or if eligibility of the study was unclear. All full text articles were compiled and screened on inclusion criteria by the two authors, independently. Any disagreements between the authors were resolved by discussion and consensus. A third author was consulted if disagreements persisted.

Assessment of methodological quality and quality of evidence Two reviewers conducted the risk of bias assessment, independently. Risk of bias of the individual studies was assessed using the criteria list advised by the CBRG, which consists of 11 items. Items were scored as positive if they did fulfil the criteria and negative when there was a clear risk of bias, and marked as inconclusive if there was insufficient information. Differences in assessment were discussed during a consensus meeting. A total score was computed, and high quality was defined as fulfilling six or more (more than 50%) of the internal validity criteria (range 0 to 11). GRADE (Grades of Recommendation, Assessment, Development and Evaluation) was used to evaluate the overall quality of evidence and the strength of the recommendations (Chatzitheodorou et al. 2007). Quality of evidence of a specific outcome was based upon the following principal measures:

• Limitations (due to for example, study design) • Consistency of results • Indirectness (e.g. generalizability of the findings) • Precision (e.g. sufficient data) • Other considerations, such as reporting bias. The overall quality was considered to be high when RCTs with a low risk of bias provided consistent, sufficient and precise results for a particular outcome; however, the quality of the evidence was downgraded by one level when one of the factors described above was not met. The following grades of evidence were applied: High quality: Further research is very unlikely to change our confidence in the estimate of effect. Moderate quality: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate. Low quality: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate. Very low quality: We are very uncertain about the estimate.

Data extraction and analysis The same two review authors who performed the risk of bias assessment conducted the data extraction,

Chapter | 15 |

independently from one another. Data were extracted onto a standardized web-based form. Comparison therapies were combined into main clusters of presumed effectiveness (no treatment/waiting list controls, other interventions). Separate analyses were planned for each type of exercise therapy, each type of control, each main outcome measure, and time of follow-up (post-treatment: short-term = closest to 3 months, intermediate = closest to 6 months and long-term = closest to 12 months). If trials reported outcomes only as graphs, the means scores and standard deviations were estimated from these graphs. For continuous data, results are presented as weighted mean differences (WMD). All scales were converted to 100-point scales. For dichotomous data, a relative risk (RR) was calculated, and the event was defined as the number of subjects recovered. A test for heterogeneity was calculated using the Q-test (Chi-square) and I2. Confidence intervals (95% CI) were calculated for each effect. A random effects model was used and funnel plots were examined for publication bias. If standard deviations were not reported, we calculated it using reported values of confidence intervals if possible. If the standard deviation of the baseline score was reported, this score was forwarded. Finally, if none of these data were reported, an estimation of the standard deviation was based on study data (population and score) of other studies. In order to correct for bias introduced by ‘doublecounting’ of subjects of trials that had two control groups in the same meta-analyses, the number of subjects of these trials was divided by two.

RESULTS OF THE REVIEW Description of studies Thirty-seven studies (3957 patients) were included (see Table 15.1). Multiple publications were found for Bendix et al. (1995, 1996, 1998), Gudavalli et al. (Cambron et al. 2006a, 2006b; Gudavalli et al. 2006), Niemistö et al. (2003, 2005), and Smeets et al. (2006, 2008). Information from all publications was used for assessment of risk of bias and data extraction, but only the first or most prominent publication was used for citation of these studies. The results of the risk of bias assessment are shown in Table 15.1. All studies were described as randomized, however the method of randomization was only explicit in 75.7% (N = 28) of the studies. Only 15 studies (40.5%) met six or more of the criteria, which was our preset threshold for low risk of bias. Only the criteria regarding the baseline characteristics, timing of outcome measures and description of dropouts were met by 50% or more of the included randomized trials.

173

174 concealed?

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Alexandre et al. 2001

Bendix et al. 1995

Chatzitheodorou et al. 2007*

Chown et al. 2008

Critchley et al. 2007*

Deyo et al. 1990

Donzelli et al. 2006*

Elnaggar et al. 1991

Ferreira et al. 2007*

Frost et al. 1995 (1998)

Galantino et al. 2004

Gladwell et al. 2006*

Goldby et al. 2006*

Gudavalli et al. 2006*

Gur et al. 2003

Harts et al. 2008

Hildebrandt et al. 2000

Johannsen et al. 1995

Allocation

Randomization

First-named

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Table 15.1  Risk of bias of studies investigating exercise therapy for chronic low back pain

Part | 4 | Clinical evidence of control approach

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+, Fulfils criteria; − did not fulfil criteria; ?, unclear whether this item fulfils criteria. *New studies (not included in Cochrane reviews).

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Smeets et al. 2006* (2008)

Yelland et al. 2004

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Williams et al. 2005*

+

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Risch et al. 1993

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Turner et al. 1990

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Tekur et al. 2008

concealed?

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Effectiveness of exercise therapy for chronic non-specific low back pain

Chapter | 15 |

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Part | 4 |

Clinical evidence of control approach

Effectiveness of exercise therapy (Table 15.2) Exercise therapy vs. waiting list controls/no treatment Eight studies were identified as comparing some type of exercise therapy to waiting list controls or no treatment (Turner et al. 1990; Risch et al. 1993; Alexandre et al. 2001; Galantino et al. 2004; Sjögren et al. 2005; Gladwell et al. 2006; Smeets et al. 2006; Harts et al. 2008). Five studies reported post-treatment data only, because after the treatment period the waiting list controls also received the treatment. Only two studies (Alexandre et al. 2001; Smeets et al. 2006) had intermediate or long-term follow-up. All studies reported data that could be used in the statistical pooling. The pooled mean difference of the five studies reporting post-treatment pain intensity was not statistically significant (−4.51 (95% CI −9.49, 0.47)). The WMD for post-treatment improvement in disability was −3.63 (95% CI −8.89, 1.63). The pooled mean WMD for pain intensity at intermediate follow-up was −16.46 (95% CI −44.48, 11.57). Only one study (102 people) reported intermediate outcomes for disability and long-term outcomes for pain intensity and disability. There were no differences between the group receiving exercise therapy and the waiting list control group (Smeets et al. 2006). Therefore, there is low quality evidence (serious limitations, imprecision) that there is no statistically significant difference in pain reduction and improvement of disability between exercise therapy and no treatment/waiting list controls.

Exercise therapy vs. usual care/advice to stay active A total of six studies (Hildebrandt et al. 2000; Niemistö et al. 2003; Frost et al. 2004; Yelland et al. 2004; Koldas Doğan et al. 2008; Tekur et al. 2008) investigated the effect of exercise therapy compared to usual care. Four of these studies had an intermediate or long-term follow-up. Statistical pooling of three studies (Frost et al. 2004; Koldas Doğan et al. 2008; Tekur et al. 2008) showed a significant decrease in pain intensity and disability in favour of the exercise group (WMD −9.23 (95% CI −16.02, −2.43)) and −12.35 (95% CI −23.00,−1.69), respectively. One study (Koldas Doğan et al. 2008) reported on pain and disability at short-term follow-up, and found no statistically significant differences between the exercise group and the control group receiving home exercises. Two studies (Niemistö et al. 2003; Frost et al. 2004) showed a statistically significant pooled WMD for disability at intermediate follow-up of −5.43 (95% CI −9.54, −1.32). One study (Niemistö et al. 2003) found a statistically significant difference at intermediate follow-up for pain relief for

176

the exercise group compared to the usual care group. Three studies (Frost et al. 2004; Yelland et al. 2004; Niemistö et al. 2005) reported on pain and/or disability at longterm follow-up. The pooled WMD for pain was not statistically significant (−4.94 (95% CI −10.45, 0.58)); the WMD for disability was statistically significant in favour of the exercise group (WMD −3.17 (95% CI −5.96, −0.38)). One study (Hildebrandt et al. 2000) reported recovery at post-treatment and during intermediate and long-term follow-up. There was a statistically significant difference between the groups at 3 and 6 months follow-up in favour of the exercise group compared with usual care (P < 0.001). Eighty percent of the patients in the exercise group regarded themselves recovered at 3 months follow-up versus 47% in the usual care group. There is low quality evidence (serious limitations, imprecision) for the effectiveness of exercise therapy compared to usual care on pain intensity and disability.

Exercise therapy vs. back school/education Three studies with a high risk of bias were identified (Williams et al. 2005; Donzelli et al. 2006; Goldby et al. 2006). Post-treatment results for disability were reported in two studies, with a significant pooled WMD of −11.20 (95% CI −16.78, −5.62). One study reported on pain posttreatment and found no statistically significant difference between both intervention groups (Williams et al. 2005). The pooled mean differences for pain and disability at 3 months follow-up were −7.63 (95% CI −17.20, 1.93) and −2.55 (95% CI −10.07, 4.97), respectively. Two studies (Donzelli et al. 2006; Goldby et al. 2006) reported intermediate outcomes on pain, and three studies (Sherman et al. 2005; Donzelli et al. 2006; Goldby et al. 2006) reported on disability. The pooled WMDs showed no statistically significant differences between the groups: −5.58 (95% CI −16.65, 5.48) and −4.42 (95% CI −9.90, 1.05), respectively. Only one study (N = 346) reported long-term outcomes, and these were not statistically significantly different between the groups (Goldby et al. 2006). The data provided very low quality evidence (serious limitations, imprecision and inconsistency) that there was no statistically significant difference in effect on pain and disability at short-term and intermediate follow-up for exercise therapy compared to back school/ education.

Exercise therapy vs. behavioural treatment Three studies, one with a low risk of bias, were identified comparing exercise therapy with a behavioural treatment (Elnaggar et al. 1991; Yozbatiran et al. 2004; Williams et al. 2005). Two studies reported post-treatment pain and disability and the pooled WMDs were 1.21 (95% CI −5.42, 7.84) and 0.34 (95% CI −2.64, 3.31), respectively.

Effectiveness of exercise therapy for chronic non-specific low back pain

Chapter | 15 |

Table 15.2  Summary effect estimates for exercise therapy in chronic low back pain patients

1.  Exercise vs. no treatment/sham/placebo/waiting list controls Outcome or subgroup

Studies

Participants

Statistical method

Effect estimate

1.1  Pain post-treatment

5

268

Mean difference (IV, random, 95% CI)

−4.51 (−9.49, 0.47)

1.2  Disability post-treatment

6

331

Mean difference (IV, random, 95% CI)

−3.63 (−8.89, 1.63)

1.3  Pain during intermediate follow-up

2

137

Mean difference (IV, random, 95% CI)

−16.46 (−44.48, 11.57)

2.  Exercise therapy vs. usual care Outcome or subgroup

Studies

Participants

Statistical method

Effect estimate

2.1  Pain post-treatment

2

108

Mean difference (IV, random, 95% CI)

−9.23 (−16.02, −2.43)

2.2  Disability post-treatment

3

188

Mean difference (IV, random, 95% CI)

−12.35 (−23.00, −1.69)

2.3  Disability during intermediate follow-up

2

267

Mean difference (IV, random, 95% CI)

−5.43 (−9.54, −1.32)

2.4  Pain at long-term (12 months) follow-up

2

301

Mean difference (IV, random, 95% CI)

−4.94 (−10.45, 0.58)

2.5  Disability at long-term (12 months) follow-up

3

377

Mean difference (IV, random, 95% CI)

−3.17 (−5.96, −0.38)

3.  Exercise therapy vs. back school/education Outcome or subgroup

Studies

Participants

Statistical method

Effect estimate

3.1  Disability post-treatment

2

139

Mean difference (IV, random, 95% CI)

−11.20 (−16.78, −5.62)

3.2  Pain at short-term (3 months) follow-up

3

200

Mean difference (IV, random, 95% CI)

−7.63 (−17.20, 1.93)

3.3  Disability after shortterm (3 months) follow-up

3

200

Mean difference (IV, random, 95% CI)

−2.55 (−10.07, 4.97)

3.4  Pain at intermediate (6 months) follow-up

2

141

Mean difference (IV, random, 95% CI)

−5.58 (−16.65, 5.48)

3.5  Disability at intermediate (6 months) follow-up

3

241

Mean difference (IV, random, 95% CI)

−4.42 (−9.90, 1.05)

4.  Exercise vs. behavioural treatment Outcome or subgroup

Studies

Participants

Statistical method

Effect estimate

4.1  Pain post-treatment

2

146

Mean difference (IV, random, 95% CI)

1.21 (−5.42, 7.84)

4.2  Disability post-treatment

2

146

Mean difference (IV, random, 95% CI)

0.34 (−2.64, 3.31)

4.3  Pain during intermediate follow-up

3

258

Mean difference (IV, random, 95% CI)

−2.23 (−7.58, 3.12)

4.4  Disability during intermediate follow-up

3

258

Mean difference (IV, random, 95% CI)

1.97 (−3.55, 7.48) Continued

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Clinical evidence of control approach

Table 15.2  Summary effect estimates for exercise therapy in chronic low back pain patients—cont’d 4.5  Pain during long-term follow-up

3

247

Mean difference (IV, random, 95% CI)

−0.88 (−6.34, 4.58)

4.6  Disability during long-term follow-up

3

243

Mean difference (IV, random, 95% CI)

2.77 (−3.43, 8.96)

5.  Exercise vs. TENS/laser/passive modalities Outcome or subgroup

Studies

Participants

Statistical method

Effect estimate

5.1  Pain post-treatment

5

286

Mean difference (IV, random, 95% CI)

−9.33 (−18.80, 0.13)

5.2  Disability post-treatment

5

286

Mean difference (IV, random, 95% CI)

−2.59 (−8.03, 2.85)

5.3  Pain during short-term follow-up

2

162

Mean difference (IV, random, 95% CI)

1.72 (−6.05, 9.50)

5.4  Disability during short-term follow-up

2

162

Mean difference (IV, random, 95% CI)

1.02 (−0.38, 2.42)

6.  Exercise vs. manipulation/manual therapy Outcome or subgroup

Studies

Participants

Statistical method

Effect estimate

6.1  Pain post-treatment

3

395

Mean difference (IV, random, 95% CI)

5.67 (1.99, 9.35)

6.2  Disability post-treatment

3

398

Mean difference (IV, random, 95% CI)

2.16 (−0.96, 5.28)

6.3  Pain during short-term follow-up

2

326

Mean difference (IV, random, 95% CI)

−1.33 (−10.44, 7.79)

6.4  Disability during short-term follow-up

2

326

Mean difference (IV, random, 95% CI)

0.29 (−3.15, 3.72)

6.5  Pain during intermediate follow-up

3

461

Mean difference (IV, random, 95% CI)

−0.49 (−12.22, 11.23)

6.6  Disability during intermediate follow-up

3

461

Mean difference (IV, random, 95% CI)

2.38 (−5.16, 9.93)

6.7  Pain during long-term follow-up

4

515

Mean difference (IV, random, 95% CI)

2.09 (−2.94, 7.13)

6.8  Disability during long-term follow-up

5

553

Mean difference (IV, random, 95% CI)

−0.70 (−3.14, 1.74)

All three studies reported intermediate and long-term follow-up on pain intensity and disability. For intermediate follow-up the pooled WMDs for pain and disability were −2.23 (95% CI −7.58, 3.12) and 1.97 (95% CI −3.55, 7.48), respectively. Long-term results showed a pooled WMD for pain intensity of −0.88 (95% CI −6.34, 4.58) and a pooled WMD for disability of 2.77 (95% CI −3.43, 8.96). There is low quality evidence (serious limitations, imprecision) that there are no statistically significant differences between exercise therapy and behavioural therapy

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on pain intensity and disability at short- and long-term follow-up.

Exercise therapy vs. TENS/laser therapy/ultrasound/massage Five studies, two with a low risk of bias, were identified comparing exercise therapy with passive therapies such as TENS, low-level laser therapy, ultrasound and thermal therapy (Deyo et al. 1990; Kankaanpaa et al. 1999; Gur et al. 2003; Chatzitheodorou et al. 2007; Koldas Doğan et al. 2008). The pooled WMD for post-treatment pain

Effectiveness of exercise therapy for chronic non-specific low back pain intensity was −9.33 (95% CI −18.80, 0.13) and for posttreatment disability −2.59 (95% CI −8.03, 2.85). Two studies (Deyo et al. 1990; Koldas Doğan et al., 2008) reported on short-term pain intensity and disability and the pooled mean differences were 1.72 (95% CI −6.05, 9.50) and 1.02 (95% CI −0.38, 2.42), respectively. One study with a low risk of bias (Kankaanpaa et al. 1999) reported intermediate and long-term outcomes, and found a statistically significantly difference for pain intensity of 16.8 and 21.2 points, respectively, in favour of exercise therapy. Also a statistically significant difference was found for disability. Low quality evidence (serious limitations, inconsistency, imprecision) was provided that there is no statistically significant difference in effect between exercise therapy compared to TENS/laser/ultrasound/massage on the outcomes pain and disability at short-term follow-up.

Exercise therapy vs. manual therapy/manipulation Five studies, two with a low risk of bias, were identified comparing exercise treatment with spinal manipulation or manual therapy (Goldby et al. 2006; Gudavalli et al 2006; Ferreira et al. 2007; Chown et al. 2008; Marshall and Murphy 2008). Post-treatment data were available for three studies. The pooled WMDs for pain intensity and disability were 5.67 (95% CI 1.99, 9.35) and 2.16 (95% CI −0.96, 5.28), respectively. One study reported a statistically significant difference in global perceived effect posttreatment (Ferreira et al. 2007) in favour of spinal manipulation. Two studies reported short-term effects on pain intensity and disability and the pooled WMDs were −1.33 (95% CI −10.11, 7.79) and 0.29 (95% CI −3.15, 3.72), respectively (Goldby et al. 2006; Gudavalli et al. 2006). Intermediate results on pain and disability were reported by three studies (Ferreira et al. 2007; Goldby et al. 2006; Gudavalli et al. 2006) and the pooled WMDs were −0.49 (95% CI −12.22, 11.23) and 2.38 (95% CI −5.16, 9.93), respectively. All studies reported long-term results on disability and the pooled WMD was −0.70 (95% CI −3.14, 1.74). Four studies reported long-term results on pain intensity and the pooled WMD was 2.09 (95% CI −2.94, 7.13). Global perceived effect was reported by one study during intermediate and long-term follow-up. No statistically significant differences between groups were found in this study (Ferreira et al. 2007). The data provided low quality evidence (inconsistency, imprecision) that there was no statistically significant difference in effect (pain intensity and disability) for exercise therapy compared to manual therapy/manipulation at short- and long-term follow-up.

Exercise therapy vs. psychotherapy One study with a high risk of bias was identified (Machado et al. 2007). Post-treatment results showed a statistically

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significant difference in disability scores between both groups in advantage of the exercise group. No posttreatment differences between both groups were found for pain intensity. At 6 months follow-up, both disability and pain intensity scores were lower in the exercise group compared to the psychotherapy group, but not statistically significant.

Exercise therapy vs. other forms of exercise therapy Eleven studies compared different exercise interventions with each other (Elnaggar et al. 1991; Johannsen et al. 1995; Tritilanunt and Wajanavisit 2001; Rittweger et al. 2002; Yozbatiran et al. 2004; Lewis et al. 2005; Sherman et al. 2005; Ferreira et al. 2007; Roche et al. 2007; Harts et al. 2008; Mannion et al. 1999). Data from these studies could not be pooled because of the heterogeneity of the types of interventions. Two studies found statistically significant differences between different exercise interventions. One study (Tritilanunt and Wajanavisit 2001), with a high risk of bias, reported statistically significant difference in pain relief at 3 months follow-up of an aerobic exercise training programme compared with a lumbar flexion exercise programme of 3-months. One large trial (Ferreira et al. 2007) with a low risk of bias (N = 240) compared a general exercise programme (strengthening and stretching) with a motor control exercise programme (improving function of specific trunk muscles) of 12 weeks. The motor control exercise group had slightly better outcomes (mean adjusted between group difference function 2.9 and global perceived effect 1.7) than the general exercise group at 8 weeks. Similar group outcomes were found at 6 and 12 months follow-up. A total of nine studies did not find any statistically significant differences between the various exercise interventions (Elnaggar et al. 1991). Sherman et al. (2005) compared a 12-week yoga (viniyoga) programme with a 12-week conventional exercise class programme. Backrelated function in the yoga group was superior to the exercise group at 12 weeks.

Motor control exercise In 2009 Macedo and colleagues published a systematic review on motor control exercise for persistent (subacute, chronic and recurrent) non-specific low back pain. Fourteen randomized controlled trials were included. The authors reported that seven trials found that motor control exercise was better than minimal intervention or as supplement to another intervention in reducing pain at short-term follow-up (WMD 14.3, 95% CI 20.4, 8.1), intermediate follow-up (WMD 13.6, 95% CI 22.4, 4.1), and long-term follow-up (WMD 14.4, 95% CI 23.1, 5.7) and in reducing disability at long-term follow-up (WMD 10.8, 95% CI 18.7, 2.8). There were no differences in

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disability at short-term and intermediate-term follow-up. Short-term follow-up was defined as less than 3 months, intermediate-term follow-up as between 3 and 12 months, and long-term follow-up as more than 12 months. Four trials found that motor control exercise was better than manual therapy for pain (WMD 5.7, 95% CI 10.7, 0.8), disability (WMD 4.0, 95% CI 7.6, 0.4), and quality-of-life (WMD 6.0, 95% CI 11.2, 0.8) at intermediate follow-up, but the effects were small. There were no differences at short-term and long-term follow-up. Five trials found that motor control exercise was better than other forms of exercise in reducing disability at shortterm follow-up (WMD 5.1, 95% CI 8.7, 1.4). Macedo et al. (2009) concluded that in patients with chronic low back pain, motor control exercise is more effective than minimal intervention and beneficial when added to another therapy for pain at all time points and for disability at long-term follow-up only. Motor control exercise is not more effective than manual therapy or other forms of exercise.

DISCUSSION OF RESULTS The effectiveness of exercise therapy No significant treatment effects of exercise therapy compared to no treatment/waiting list controls were found on pain intensity and disability. Compared to usual care, pain intensity and disability were significantly reduced by exercise therapy at short-term follow-up. Motor control exercise was more effective than minimal intervention and beneficial when added to another therapy for pain at all time points and for disability at long-term follow-up only. This overview included 11 studies comparing different types of exercise treatments with each other. Very small to no differences were found in these studies. The Cochrane review published in 2005 on the effectiveness of exercise for low back pain found evidence for the effectiveness on pain and function in chronic patients (Hayden et al. 2005). We also found evidence for the effectiveness for exercise therapy compared to usual care. However, we applied strict inclusion criteria regarding chronic low back pain, so our meta-analyses excluded some of the studies included in the Cochrane review, but also included some new studies. Nevertheless, results are comparable despite the new studies that are conducted in the last years. It is therefore also striking that the quality of the included studies was still generally poor resulting in a potentially high risk of bias. Blinding of the patient and blinding of the care provider were not properly conducted in many studies. Blinding of patients is also difficult in many RCTs investigating the effectives of exercise therapy. The quality of future RCTs in the field of back pain should be improved to reduce bias in systematic reviews

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and overviews, as it has been demonstrated that statistical pooling of trials with a high risk of bias may result in overestimation of treatment effects. Of particular note is the heterogeneity among the studies. This heterogeneity could have been caused by differences in interventions, differences in control groups, duration of the intervention and the risk of bias of the different studies. Therefore, the results of the meta-analyses with heterogeneity should be interpreted with some caution. Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate. These studies should focus on specific populations and these should be well described. Further, more studies are needed to investigate the different forms of exercise interventions and finally, the description of these studies should include the compliance and co-interventions of the study groups. The evidence on motor control exercise for chronic low back pain seems promising. Many types of exercises for low back pain are not strongly supported by pathophysio­ logical or biomechanical studies. Aerobic exercises for low back pain, for example, were developed based on general principles of sports medicine. However, the underlying mechanisms of action of motor control exercise are supported by several studies (Hides et al. 1996; Hodges and Richardson 1996, 1998). Motor control exercise was developed based on the principle that individuals with low back pain have a lack of control of the trunk muscles, for example, the transversus abdominis and the multifidus muscles. The idea is to use a motor learning approach to retrain the optimal control and coordination of the spine. The intervention involves the training of pre-activation of the deep trunk muscles, with progression toward more complex static, dynamic and functional tasks integrating the activation of deep and global trunk muscles. Although motor control exercise was more effective than minimal intervention for chronic low back pain, there were no differences when compared to other types of exercises. It is still unclear which patients respond best to which type of exercise. Whether individuals with reduced motor control benefit more from motor control exercise should be evaluated in future studies. Identifying subgroups of patients that benefit more from one intervention than another is one of the biggest challenges in low back pain research. Some promising initiatives have been published, such as the McKenzie method (McKenzie and May 2003), classification-based algorithm (Fritz et al. 2003), primary care back pain screening tool (Hill et al. 2008), and the Orebro Musculoskeletal Pain Screening Questionnaire (Linton and Hallden 1998).

Evidence-based practice Opponents of evidence-based practice have criticized using the randomized controlled trial in a dogmatic way

Effectiveness of exercise therapy for chronic non-specific low back pain and refused to acknowledge that other study designs may also produce valid data about the outcome of interventions (Borgerson, 2009). The focus on randomized trials as the paradigm of study design to answer any clinical question is obviously wrong. Randomized trials are the gold standard for questions related to the effectiveness of preventive or therapeutic interventions, but not necessarily the best option for answering questions related to adverse effects, prognosis or diagnosis. Also, evidence on effectiveness from non-randomized observational studies may be utilized if little evidence from randomized trials is available. There are also situations in which effectiveness cannot be assessed by randomized trials because of practical or ethical reasons. Although rare, before–after experiments are sometimes valued in evidence-based medicine. If the treatment results in a dramatic effect and if the natural course of the condition is stable, bias can be ruled out as an explanation. Insulin for diabetes, suturing for repairing large wounds and defibrillation for ventricular fibrillation, for example, are interventions that were accepted without any evidence from randomized trials (Glasziou et al., 2007). In general, however, randomized controlled trials are the preferred design to evaluate effectiveness of therapeutic interventions. There are examples where empirical

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evidence has resulted in better treatment in practice. Advising low back pain patients to stay active rather than lie in bed is one example (Deyo et al., 1986; Malmivaara et al., 1995). Bed rest had been the mainstay of treatment for low back pain for decades, until randomized controlled trials showed that staying active is more beneficial than staying in bed. Without these randomized trials, physicians may never have changed their practice and might still be advocating bed rest for low back pain.

Implications for practice Exercise therapy is not effective for acute low back pain. Exercise therapy is effective for chronic low back pain, but there is no evidence that any type of exercise is clearly more effective than others. Subgroups of patients with low back pain may respond differently to various types of exercise therapy, but it is still unclear which patients benefit most from what type of exercises. Adherence to exercise prescription is usually poor, so supervision by a therapist is recommended. If home exercises are prescribed, strategies to improve adherence should be used. Patient’s preferences and expectations should be considered when deciding which type of exercise to choose.

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