Pilates for low back pain

ABSTRACT BACKGROUND: Non-specific low back pain is a major health problem worldwide. Interventions based on exercises have been the most commonly used treatments for patients with this condition. Over the past few years, the Pilates method has been one of the most popular exercise programmes used in clinical practice. OBJECTIVES: To determine the effects of the Pilates method for patients with non-specific acute, subacute or chronic low back pain. METHODS: Search methods: We conducted the searches in CENTRAL, MEDLINE, EMBASE, CINAHL, PEDro and SPORTDiscus from the date of their inception to March 2014. We updated the search in June 2015 but these results have not yet been incorporated. We also searched the reference lists of eligible papers as well as six trial registry websites. We placed no limitations on language or date of publication. Selection criteria: We only included randomized controlled trials that examined the effectiveness of Pilates intervention in adults with acute, subacute or chronic non-specific low back pain. The primary outcomes considered were pain, disability, global impression of recovery and quality of life. Data collection and analysis: Two independent raters performed the assessment of risk of bias in the included studies using the 'Risk of bias' assessment tool recommended by The Cochrane Collaboration. We also assessed clinical relevance by scoring five questions related to this domain as 'yes', 'no' or 'unclear'. We evaluated the overall quality of evidence using the GRADE approach and for effect sizes we used three levels: small (mean difference (MD) < 10% of the scale), medium (MD 10% to 20% of the scale) or large (MD > 20% of the scale). We converted outcome measures to a common 0 to 100 scale when different scales were used MAIN RESULTS: The search retrieved 126 trials; 10 fulfilled the inclusion criteria and we included them in the review (a total sample of 510 participants). Seven studies were considered to have low risk of bias, and three were considered as high risk of bias. A total of six trials compared Pilates to minimal intervention. There is low quality evidence that Pilates reduces pain compared with minimal intervention, with a medium effect size at short-term follow-up (less than three months after randomization) (MD -14.05, 95% confidence interval (CI) -18.91 to -9.19). For intermediate-term follow-up (at least three months but less than 12 months after randomization), two trials provided moderate quality evidence that Pilates reduces pain compared to minimal intervention, with a medium effect size (MD -10.54, 95% CI -18.46 to -2.62). Based on five trials, there is low quality evidence that Pilates improves disability compared with minimal intervention, with a small effect size at short-term follow-up (MD -7.95, 95% CI -13.23 to -2.67), and moderate quality evidence for an intermediate-term effect with a medium effect size (MD -11.17, 95% CI -18.41 to -3.92). Based on one trial and low quality evidence, a significant short-term effect with a small effect size was reported for function (MD 1.10, 95% CI 0.23 to 1.97) and global impression of recovery (MD 1.50, 95% CI 0.70 to 2.30), but not at intermediate-term follow-up for either outcome. Four trials compared Pilates to other exercises. For the outcome pain, we presented the results as a narrative synthesis due to the high level of heterogeneity. At short-term follow-up, based on low quality evidence, two trials demonstrated a significant effect in favour of Pilates and one trial did not find a significant difference. At intermediate-term follow-up, based on low quality evidence, one trial reported a significant effect in favour of Pilates, and one trial reported a non-significant difference for this comparison. For disability, there is moderate quality evidence that there is no significant difference between Pilates and other exercise either in the short term (MD -3.29, 95% CI -6.82 to 0.24) or in the intermediate term (MD -0.91, 95% CI -5.02 to 3.20) based on two studies for each comparison. Based on low quality evidence and one trial, there was no significant difference in function between Pilates and other exercises at short-term follow-up (MD 0.10, 95% CI -2.44 to 2.64), but there was a significant effect in favour of other exercises for intermediate-term function, with a small effect size (MD -3.60, 95% CI -7.00 to -0.20). Global impression of recovery was not assessed in this comparison and none of the trials included quality of life outcomes. Two trials assessed adverse events in this review, one did not find any adverse events, and another reported minor events. AUTHORS CONCLUSIONS: We did not find any high quality evidence for any of the treatment comparisons, outcomes or follow-up periods investigated. However, there is low to moderate quality evidence that Pilates is more effective than minimal intervention for pain and disability. When Pilates was compared with other exercises we found a small effect for function at intermediate-term follow-up. Thus, while there is some evidence for the effectiveness of Pilates for low back pain, there is no conclusive evidence that it is superior to other forms of exercises. The decision to use Pilates for low back pain may be based on the patient's or care provider's preferences, and costs.


E
xercise therapy is one of the most common treatments for nonspecific low back pain (LBP), especially for chronic symptoms, and it is widely recommended in clinical practice guidelines. 1,24][5] Pilates was developed in the 1920s by Joseph Pilates and consists of comprehensive body conditioning, which aims to develop better body awareness and improve posture. 4,5ilates exercises mainly involve isometric contractions of the core muscles, responsible for stabilization of the spine, both while moving or at rest.The reported benefits of Pilates exercises include improvements in strength, range of motion, coordination, balance, muscle symmetry, flexibility, proprioception (awareness of posture), body definition, and general health. 6,7][9][10][11][12][13][14] However, different findings have been reported in these studies and a well-conducted systematic review is needed to better inform clinicians, patients, and policy makers about the effectiveness of this intervention in patients with nonspecific

Data Sources and Searches
The search was conducted in CENTRAL, MEDLINE, EMBASE, CINAHL, PEDro, and SPORTDiscus databases without restrictions on language or date of publication.We used the search strategies developed by the Cochrane Back and Neck Review Group.We searched all databases from the date of their inception to June 2015.We also searched the following trial registries: Australian New Zealand Clinical Trials Registry, National Research Registry, Clin-icalTrials.gov,metaRegister of Controlled Trials, Brazilian Registry of Clinical Trials, and the World Health Organization International Clinical Trials Registry Platform.We scanned the reference lists from previous published reviews on Pilates as well as the reference lists from the eligible randomized trials.We considered only full-text papers, written in any language, regardless of the date of publication.

Study Selection
We only included RCTs in this review and we did not consider trials that used quasi-random allocation procedures.We included studies that enrolled adult participants aged 16 or older with acute, subacute, or chronic nonspecific LBP who were recruited from primary, secondary, or tertiary care (seeking care for back pain or recruited from the community).We excluded studies that included patients with any contraindication to exercise therapy, pregnancy, serious spinal pathology (i.e., cancer, fracture, cauda equina syndrome, and inflammatory diseases) and studies that included more than 5% of participants with evidence of nerve root compromise.Two pairs of review authors independently screened titles and abstracts for potentially eligible studies.We used full-text papers to determine the final inclusion in the review.We resolved disagreements between review authors through discussion or by the arbitration of a third review author when consensus could not be reached.
We considered any type of exercise therapy that followed the Pilates method.We judged trials to have evaluated Pilates if (1) the study explicitly stated that the intervention was based on the Pilates principles (i.e., centering, concentration, control, precision, flow, breathing, and posture) or at least three of these elements 15 or (2) the therapists who provided the interventions had previous training in Pilates or were certified as Pilates instructors.The primary outcomes were pain intensity, disability, global impression of recovery, and quality of life.The secondary outcomes were return to work and any adverse effects.

Data Extraction and Quality Assessment
Two independent review authors extracted the bibliometric data, the study characteristics, the characteristics of the participants, the description of the interventions, the duration of follow-up assessments, the outcomes assessed, the study results, and the time periods for outcome assessment defined as: short term (<3 months after randomization), intermediate term (!3 months and <12 months after randomization), and long term (!12 months after randomization).When there were multiple time points that fell within the same category we used the one that was closer to the end of the treatment (short term), 6 months (medium term), and 12 months (long term).
We assessed the risk of bias in the included studies using the Cochrane risk of bias assessment tool. 16,17Two review authors (B.T.S. and T.P.Y.) independently performed the risk of bias assessment and resolved possible disagreements between review authors by discussion, or arbitration by a third review author (C.M.) when consensus could not be reached.We scored each of the 12 risk of bias items as ''high,'' ''low,'' or ''unclear'' risk.We defined a study with an overall low risk of bias as having low risk of bias on six or more of these items.

Data Synthesis and Analysis
For all continuous outcomes, we quantified the treatment effects with the mean difference (MD).To accommodate the different scales used for these outcomes, we converted outcomes to a common 0 to 100 scale.For dichotomous outcomes, we calculated the risk ratios for experiencing the positive outcome.We used effect sizes and 95% confidence intervals (CIs) as a measure of treatment effect.We considered between-group differences of at least 20% as clinically important. 18For effect sizes, we defined three levels as small (MD <10% of the scale), medium (MD 10%-20% of the scale), or large (MD >20% of the scale). 19We used Review Manager 5 for all analyses.
The assessment of heterogeneity was based on visual inspections of the forest plots (e.g., overlapping CIs) and more formally by the x 2 test and the I 2 statistic. 16We combined results in a meta-analysis using a random-effects model if I 2 <50%.If substantial heterogeneity was present, we did not combine the results but instead presented them as a narrative synthesis.If I 2 values were slightly higher than 50% but we identified no clear heterogeneity by visual inspection, we combined the results within a meta-analysis.
We assessed the overall quality of the evidence for each outcome using the GRADE approach. 16Factors that may decrease the quality of the evidence are study design and risk of bias (downgraded if more than 25% of the participants were from studies with a high risk of bias); inconsistency of results (downgraded if significant heterogeneity was present by visual inspection or if the I 2 value was greater than 50%); indirectness (generalizability of the findings; downgraded if more than 50% of the participants were outside the target group); imprecision (downgraded if fewer than 400 participants were included in the comparison for continuous data and there were fewer than 300 events for dichotomous data 20 ); and other factors (e.g., reporting bias, publication bias).We considered single studies with fewer than 400 participants for continuous or dichotomous outcomes inconsistent and imprecise, providing ''low-quality evidence,'' which could be downgraded to ''very low-quality evidence'' if there were further limitations on the quality of evidence. 21We reduced the quality of the evidence for a specific outcome by a level, according to the performance of the studies against these five factors and we described them as follows.
High-quality evidence: there are consistent findings among at least 75% of RCTs with low risk of bias, consistent, direct, and precise data, and no known or suspected publication biases.Further research is unlikely to change either the estimate or our confidence in the results.Moderate-quality evidence: one of the domains is not met.Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate.Low-quality evidence: two of the domains are not met.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 evidence: three of the domains are not met.We are very uncertain about the results.No evidence: no RCTs were identified that addressed this outcome.

RESULTS
The searches retrieved 126 trials, of which 10 were included in this review (Figure 1).A total of 510 participants were enrolled in the included trials, and we included data from 478 participants in the meta-analyses.All participants had chronic LBP and were middle aged (mean: 38 yr), ranging from 22 to 50 years of age.The duration of the treatment programs ranged from 10 to 90 days, and the treatment frequency varied from one to four sessions per week.The duration of all sessions was approximately 1 hour for all included studies, and the mean number of sessions was 15.3, ranging from six to 30 sessions.The study characteristics are described in detail in Table 1.
In total, we considered 70% of the studies to have a low risk of bias, which represents 83.7% of all participants.More than half of the included trials met the criteria for allocation concealment, 5,11,23 -26 one trial blinded both participants and assessors, 22 one trial blinded only the participants, 23 and seven trials blinded only the assessors. 5,7,11,24 -26A total of eight trials provided adequate information about missing data and were able to keep losses below 20% for short-and intermediate-term outcomes, though none of the trials report long-term followup. 5,9,11,13,22 -24,26Published or registered protocols were available for four trials. 11,23,24,26We did not assess publication bias with funnel plots because too few studies were included in the meta-analysis.The results from the risk of bias assessment are presented in Figure 2.

ANALYSIS
We used two comparisons for this review: (i) Pilates versus minimal intervention or no intervention 5,7,9,11,24,25 and (ii) Pilates versus other types of exercises. 13,22,23,27The summary of evidence is presented in Table 2.

Effect of Pilates Versus Minimal Intervention
There is low-quality evidence (downgraded due to imprecision and risk of bias) that Pilates is better than minimal intervention for pain at short term with a medium effect size (MD À14.05, 95% CI À18.91 to À9.19; P < 0.001, n ¼ 265, six trials), 5,7,9,11,24,25 and moderate-quality evidence (downgraded due to imprecision) for intermediate term, with a medium effect size  (MD À10.54, 95% CI À18.54 to À2.62, n ¼ 146, two trials) 11,24 (Figure 3).There is low-quality evidence (downgraded due to imprecision and inconsistency) that Pilates improves disability at shortterm follow-up compared with minimal intervention, with a small effect size (MD À7.95, 95% CI À13.23 to À2.67; P ¼ 0.003, n ¼ 248, five trials), 5,7,11,24,25 and moderate-quality evidence for an effect at intermediate term, with medium effect size (MD À11.17, 95% CI À18.41 to À3.92, n ¼ 146, two trials). 11,24or global impression of recovery, there is low-quality evidence (downgraded due to imprecision and inconsistency) of a significant short-term effect in favor of Pilates, with a small effect size (MD 1.50, 95% CI 0.70-2.30,For ''pain'' and ''disability'' outcomes, a negative effect size value represents an effect in favor of Pilates.For ''function'' and ''global impression of recovery'' outcomes, a positive effect size value represents an effect in favor of Pilates.Ã Statistically significant difference (P < 0.05).y These comparisons were not included in the meta-analysis due to high heterogeneity.CI indicates confidence interval.n ¼ 86, one trial), 11 but not for intermediate-term followup. 11For function, there is low-quality evidence (downgraded due to imprecision and inconsistency) that there is a significant short-term effect, with a small effect size (MD 1.10, 95% CI 0.23-1.97,n ¼ 86, one trial), 11 but no differences were found for intermediate term. 11nly one trial 24 evaluated quality of life but the estimates for the physical and mental components were not available in the publication and the authors did not provide this information on request.One trial assessed adverse events, but none were reported. 11None of the trials reported return to work outcomes.

Effect of Pilates Versus Other Exercises
We did not combine the results for pain at short-term and intermediate-term follow-up in a meta-analysis due to the high level of heterogeneity, but reported results descriptively.Based on low-quality evidence (downgraded due to imprecision and inconsistency), at short-term follow-up, two trials (n ¼ 94) reported a significant effect in favor of Pilates, 13,22 but one trial (n ¼ 87) did not find significant differences between groups. 27At intermediate-term followup, based on low-quality evidence (downgraded due to imprecision and inconsistency), one trial (n ¼ 64) reported a significant effect in favor of Pilates, 23 and one trial (n ¼ 87) reported a nonsignificant difference in pain intensity. 27or disability, there is moderate-quality evidence (downgraded due to imprecision) that there is no significant difference between Pilates and other exercises at shortterm (MD À3.29, 95% CI À6.82 to 0.24, n ¼ 149, two trials) 26,27 or intermediate-term follow-ups (MD À0.91, 95% CI À5.02 to 3.20, n ¼ 151, two trials). 23,27Only one trial 27 evaluated quality of life but the estimates for the physical and mental components were not available in the publication and the authors did not provide this information on request.None of the trials reported adverse events or return to work for this comparison (Figure 4).
For function, no differences were found for short term based on one study (n ¼ 87), 27 but there is low-quality evidence (downgraded due to imprecision and inconsistency) that there is a significant intermediate-term effect, with a small effect size (MD À3.60, 95% CI À7.00 to À0.20, n ¼ 87, one trial). 27

DISCUSSION
Of the 10 studies included in this systematic review, six (n ¼ 265 participants) compared Pilates to minimal intervention and four (n ¼ 245 participants) compared Pilates to other exercises.For the short-term follow-up, Pilates was more effective than minimal intervention for improving pain, disability, function, and global impression of recovery, and at intermediate-term follow-up Pilates led to better pain intensity and disability outcomes, but was not superior to minimal intervention in terms of function and global impression of recovery.The effect sizes varied from small to medium for this comparison.On the other hand, Pilates appears not to be more effective than other exercises for pain intensity and disability.For function, one study found a small significant effect at intermediate-term, but not at short-term follow-up.
Our findings are in accordance with the clinical practice guidelines 1 and previous reviews of exercise for low back pain, 28 which recommend exercise therapy for patients with chronic LBP, but with no clear difference in effectiveness among the various forms of exercise.In a recent review of Pilates for LBP, the authors reported a statistically significant short-term effect for pain and disability compared to usual care and physical activity, but for the comparison with other exercises reported the evidence was conflicting. 14iyamoto et al 11 found a small short-term effect on pain intensity and disability when comparing Pilates to minimal intervention but did not report an effect when compared to other types of exercises. 11These findings are consistent with our review although we found some medium effect sizes for the comparison with minimal intervention and we considered the results for pain intensity compared to other exercises too heterogeneous to be combined in a metaanalysis.The review by Lim et al 10 found a small significant effect on pain intensity in the short term compared to minimal intervention but not on disability. 10This previous review did not find any significant effect for the comparison with other exercises; however, the authors included only one trial 29 and one thesis 30 in this comparison.Finally, another systematic review concluded that no definite conclusions can be drawn except that further better quality research is needed. 12In this review, the authors only included four trials, each one with a different control group, making any comparison or conclusions difficult.
The strengths of this review include the use of the highquality methods of the Cochrane Collaboration.We also used the GRADE system to assess the quality of evidence.The main limitation of this review is the low number of trials and small sample sizes per comparison, outcome, and follow-up period, which also prevented us from conducting a sensitivity analysis.An additional limitation is the potential for publication bias in the trials included.Although it was not possible to assess publication bias using funnel plots, as too few studies were included, we found one completed trial (from 2011) that was not yet published, which may indicate potential publication bias.Moreover, the source of funding should be considered due to potential financial conflicts from industry-sponsored research. 31,32One trial received funding from a Pilates clinic to conduct the study. 26The remaining trials were not funded.
Pilates appears to be an effective treatment compared to minimal intervention, but when compared to other types of exercises the effect sizes tend to be smaller or no difference in effectiveness is observed.The evidence on the effectiveness of Pilates for LBP is of low to moderate quality and limited to patients with chronic LBP.There is an urgent need for large, high-quality trials evaluating Pilates for LBP.Most trials included fewer than 40 participants in total, 5,7,9,13,25 or were unregistered, 5,7,9,13,22,25 and none of the trials included long-term follow-up.Additionally, future trials should include an economic evaluation of the Pilates method to guide clinical choices between competing treatment options.

CONCLUSION
No definite conclusions or recommendations can be made as we did not find any high-quality evidence for any of the treatment comparisons, outcomes, or follow-up periods investigated.However, there is low-to moderate-quality evidence that Pilates is more effective than minimal intervention in the short and intermediate term as the benefits were consistent for pain intensity and disability, with most of the effect sizes being considered medium.It was less clear whether Pilates was more effective than other exercises for pain intensity, disability, and function as the results across outcomes were contradictory.However, a small effect favoring other exercises was found for function at intermediate-term follow-up.The decision to use Pilates for chronic low back pain may be based on the patient's or care provider's preferences and costs.

Key Points
There is low-to moderate-quality evidence that Pilates provides better outcomes than minimal intervention.There is no conclusive evidence that Pilates is superior to other forms of exercises.Further large, high-quality trials evaluating Pilates for low back pain are needed.

Figure 1 .
Figure 1.Flowchart of the study.

Figure 2 .
Figure 2. ''Risk of bias'' summary: review author's judgments about each risk of bias item for each included study.

Figure 3 .
Figure 3. Forest plot of comparison between Pilates and minimal intervention for the outcome pain.CI indicates confidence interval; IV: Inverse Variance; SD, standard deviation.

Figure 4 .
Figure 4. Forest plot of comparison between Pilates and other exercises for the outcome disability.CI indicates confidence interval; IV: Inverse Variance; ODI: Oswestry Disability Index; SD, standard deviation.

TABLE 1 .
Characteristics of the Included Studies

TABLE 2 .
Summary of Findings and Quality of Evidence for All Outcomes Included in This Review