Is Interferential Current Before Pilates Exercises More Effective Than Placebo in Patients With Chronic Nonspecific Low Back Pain?

Archives of Physical Medicine and Rehabilitation journal homepage: www.archives-pmr.org Archives of Physical Medicine and Rehabilitation 2017;98:320-8

ORIGINAL RESEARCH

Is Interferential Current Before Pilates Exercises More Effective Than Placebo in Patients With Chronic Nonspecific Low Back Pain?: A Randomized Controlled Trial Katherinne Moura Franco, MS,a Yuri dos Santos Franco, MS,a Naiane Bastos de Oliveira, MS,a Gisela Cristiane Miyamoto, MS,a Matheus Oliveira Santos,b Richard Eloin Liebano, PhD,a Cristina Nunes Cabral, PhDa From the aMaster’s and Doctoral Program in Physical Therapy and bPhysical Therapy Department, Universidade Cidade de Sa˜o Paulo, Sa˜o Paulo, Brazil.

Abstract Objective: To determine whether interferential current (IFC) before Pilates exercises is more effective than placebo in patients with chronic nonspecific low back pain. Design: Two-arm randomized controlled trial, with a blinded assessor, and 6 months follow-up. Setting: Clinic of a school of physical therapy. Participants: The random sample consisted of patients (NZ148) of both sexes, with age between 18 and 80 years and chronic nonspecific low back pain. In addition, participants were recruited by disclosure of the treatment in the media. Interventions: Patients were allocated into 2 groups: active IFC þ Pilates or placebo IFC þ Pilates. In the first 2 weeks, patients were treated for 30 minutes with active or placebo IFC. In the following 4 weeks, 40 minutes of Pilates exercises were added after the application of the active or placebo IFC. A total of 18 sessions were offered during 6 weeks. Main Outcome Measures: The primary outcome measures were pain intensity, pressure pain threshold, and disability measured at 6 weeks after randomization. Results: No significant differences were found between the groups for pain (0.1 points; 95% confidence interval, 0.9 to 1.0 points), pressure pain threshold (25.3kPa; 95% confidence interval, 4.4 to 55.0kPa), and disability (0.4 points; 95% confidence interval, 1.3 to 2.2). However, there was a significant difference between baseline and 6-week and 6-month follow-ups in the intragroup analysis for all outcomes (P<.05), except pressure pain threshold in the placebo IFC þ Pilates group. Conclusions: These findings suggest that active IFC before Pilates exercise is not more effective than placebo IFC with respect to the outcomes assessed in patients with chronic nonspecific low back pain. Archives of Physical Medicine and Rehabilitation 2017;98:320-8 ª 2016 by the American Congress of Rehabilitation Medicine

Nonspecific chronic low back pain (CLBP) is described as mechanical musculoskeletal pain lasting >12 weeks without known cause.1,2 With a global prevalence of 31%,3 nonspecific CLBP is among the 4 most common diseases in the world.4 It is a

Supported by Sa˜o Paulo Research Foundation (process no. 2013/17303-6). Sa˜o Paulo Research Foundation was not involved in the data collection or analysis. Clinical Trial Registration No.: NCT01919268. Disclosures: none.

disease with great socioeconomic impact,5 which warrants the search for more effective treatment methods, especially given the minor effects of most current treatments. Nonspecific CLBP has a moderately favorable prognosis, with 41% of patients recovering after 12 months.6 The guidelines of clinical practice recommend supervised exercise as the best treatment for nonspecific CLBP.1,7 Trunk muscle exercises, such as aerobic, motor control, strength, and resistance exercises, and directional preference exercises that

0003-9993/16/$36 - see front matter ª 2016 by the American Congress of Rehabilitation Medicine http://dx.doi.org/10.1016/j.apmr.2016.08.485

Interferential current, Pilates, and pain promote the centralization of symptoms are recommended.1,7 One type of exercise available to physical therapists is the Pilates method,8 which is more effective than routine care and maintenance of physical activity at improving pain and disability in the short term, with clinically significant pain improvement.9 However, these improvements are similar to different forms of exercise and therapeutic massage.9 Analgesic electrical currents, including interferential current (IFC), can be used as adjuvant in the treatment of nonspecific CLBP,10-15 because of pain reduction in the short term.12,16-18 IFC is a medium-frequency alternating current with amplitude modulated at low frequency.19 There are 2 hypotheses to explain pain reduction: the release of endogenous opioids20-24 and the gate control theory of pain.25 A systematic review26 concluded that IFC combined with massage, traction, and horizontal therapy (ie, a medium-frequency current with a stimulation frequency oscillating at 100Hz between 4,400 and 12,300Hz)13 is more effective than placebo horizontal therapy in the treatment of patients with chronic diseases. However, studies that used IFC in the treatment of nonspecific CLBP did not compare its efficiency with placebo IFC.26 The Pilates method has a certain degree of difficulty, and patients with nonspecific CLBP may find it even more difficult to perform the exercises because of the pain and fear of a new painful episode.27 The use of IFC before exercise could facilitate performance and increase its efficiency, improving the clinical condition of patients with nonspecific CLBP. To date, no studies assessed whether the use of IFC before exercise therapy can lead to longer-lasting results in the treatment of nonspecific CLBP. Therefore, the objectives of this study were to determine whether the association of IFC with Pilates exercise is more effective than placebo current in improving pain intensity, pressure pain threshold (PPT), general and specific disability, global perceived effect, and kinesiophobia in patients with nonspecific CLBP in the short and medium term.

Methods Study design The study design was a 2-arm randomized controlled trial with a blinded assessor. Ethics committee and funding The study was approved by the Research Ethics Committee of Universidade Cidade de Sa˜o Paulo (process no. 18034113.7.0000.0064), and the protocol was published previously.28 Location The treatment was carried out at the clinic of the School of Physical Therapy of Universidade Cidade de Sa˜o Paulo, Sa˜o Paulo, Brazil, between October 1, 2013, and June 27, 2014.

List of abbreviations: CLBP chronic low back pain IFC interferential current PPT pressure pain threshold

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321 Participants Patients of both sexes were included according to the following criteria: nonspecific CLBP for at least 3 months; age between 18 and 80 years; nonathletes; and pain intensity 3.29 The exclusion criteria were as follows: contraindication to physical exercise30; pregnancy; serious spinal disorder; nerve root compromise; changes to sensitivity, allergy, skin infection, and/or lesion in the area of application of the current; cancer; pacemaker; previous spinal surgery; physical therapy treatment for nonspecific CLBP in the last 6 months; and regular practice of Pilates.

Randomization and concealed allocation A researcher not involved with data collection performed the randomization using random number generation in Microsoft Excel for Windows.a The allocation was concealed in sequentially numbered opaque sealed envelopes. After the assessment, the eligible patients were randomly allocated into the treatment groups by the physical therapists responsible for electrotherapy.

Interventions The treatment groups consisted of active IFC þ Pilates group, who received active IFC plus Pilates exercise program; and placebo IFC þ Pilates group, who received placebo IFC plus Pilates program. Eighteen treatment sessions were offered, distributed over 6 weeks, 3 times a week. In the first 2 weeks, participants were submitted only to active or placebo IFC for 30 minutes to promote prior pain reduction that could facilitate exercise and in an attempt to obtain a possible cumulative analgesic effect.31 During the 4 weeks, after electrotherapy, participants had additional Pilates sessions of 40 minutes. For electroanalgesia, we used a device that produces mediumfrequency alternating currents (Neurovectorb). Both groups received bipolar (premodulated) application with 2 channels at the site of pain,32 with parameters described previously.10,28 Electrotherapy was performed by 2 physical therapists other than the ones who did the Pilates treatment. In the active IFC þ Pilates group, the current amplitude was increased until the participant reported a strong but comfortable tingling sensation, and this procedure was repeated every 5 minutes.33 In the placebo IFC þ Pilates group, the device was on and all the parameters were adjusted as in the active IFC þ Pilates group, but the current amplitude did not reach the treated area. Every 5 minutes, the physical therapist asked the participant if he was comfortable without increasing the current amplitude. To indicate the end of the application, the device made the same sound as the active current. Patients were informed that they may feel some tingling, vibration, or absolutely nothing during current’s application. From the third week, both groups were submitted to the Pilates program, with exercises on the mat and on the Cadillac, Reformer, Ladder Barrel, and Step Chair machines.c Initially the patient was trained to isometrically contract the powerhouse muscles (eg, transversus abdominis, multifidus, and pelvic floor muscles) during exhalation, and then he/she was instructed to hold this contraction during all exercises to stabilize the spine.34,35 The level of difficulty and the patient’s preferences in relation to the exercises were individualized.28,36,37 Ten repetitions of each exercise were performed.38,39 The Pilates intervention was supervised by 2 physical therapists with 5 years of experience with the method. They were blinded to the type of electrotherapy that the participant received before the exercises.

322 Table 1

K.M. Franco et al Description of the outcome measures

Measure

Construct

Description

Pain Numerical Rating Scale37

Pain intensity

Handheld pressure algometer38

PPT

Roland Morris Disability Questionnaire37,39,40

Disability

Tampa Scale for Kinesiophobia41,42

Kinesiophobia

Patient-Specific Functional Scale37,43

Specific disability

Global Perceived Effect Scale37,44

Global perceived effect

It is an 11-point scale ranging from 0 to 10, in which 0 represents “no pain” and 10 represents “pain as bad as it could be.” The participant classified his average pain in the last 7d The PPT measurements were repeated 3 times for each point (lumbar and tibialis anterior) with a 30-s interval between repetitions. The mean of the 3 measurements was used for data analysis. The intraexaminer reliability performed before the beginning of the study and the assessment of the PPT were previously described28 It consists of 24 yes/no questions, with affirmative answers worth 1 point. The score is the sum of the points for each question. Scores close to 0 indicate less disability, and scores close to 24 indicate greater disability It consists of a 17-item questionnaire. The scores vary from 1 (“strongly disagree”) to 4 (“strongly agree”) points. For the total score, questions 4, 8, 12, and 16 had the scores inverted. The final score can vary from 17 to 68 points, and the higher the score, the greater the degree of kinesiophobia The participants identify 3 significant activities that are difficult or that they are unable to perform because of nonspecific CLBP. Next, they rate how able they feel to perform these activities on an 11-point scale (0e10), with 0 representing “unable to perform activity” and 10 “able to perform the activity at preinjury level.” The final score is the mean of the 3 ratings, and the higher the score, the greater the specific ability The patient was asked to compare the onset of symptoms to the last few days in the 11-point scale, which ranges from 5 to 5, with 5 representing “vastly worse,” 0 “no change,” and 5 “completely recovered.” The higher the score, the greater the recovery from the condition

Assessment of clinical outcomes Outcomes, eligibility criteria, clinical, demographic, and anthropometric data were assessed by a blinded assessor. Measurements of primary and secondary outcomes were conducted at baseline, in the 6-week follow-up, and in the 6-month follow-up. In the last 2 assessments, patients were asked not to provide information about the treatment to the assessor. The primary outcomes were pain intensity (Pain Numerical Rating Scale40), PPT (handheld pressure algometer41,d), and disability (Roland Morris Disability Questionnaire40,42,43) measured at 6 weeks after randomization. The secondary outcomes were pain intensity and disability after 6 months, kinesiophobia (Tampa Scale for Kinesiophobia44,45), specific disability (Patient-Specific Functional Scale40,46), and global perceived effect (Global Perceived Effect scale40,47) measured at 6 weeks and 6 months after randomization. Table 1 presents the description of each of these outcome measures.

Statistical analysis The study was designed to detect a clinically significant difference of 1 point between the groups in pain intensity in the Pain Numerical Rating Scale (SD, 1.84 points),40 100kPa in PPT (SD, 110kPa),48 and 4 points in the Roland Morris Disability Questionnaire (SD, 4.9 points).40,43 A statistical power of 80%, an a of .05, and a follow-up loss of 15% were considered.49 This sample calculation determined a sample of 148 participants. Double data entry was performed, and the intention-to-treat principle was followed. The statistician received the coded data and was blinded to the participants’ group allocation. Linear mixed models were used to evaluate the mean effects of the interventions and the group differences for all outcomes. This

analysis incorporated terms for the treatment groups, time (baseline, 6-wk follow-up, and 6-mo follow-up), and interaction terms “treatment groups” versus “time.” Repeated-measures analysis of variance with Bonferroni post hoc test was used to calculate intragroup differences. The level of significance was set at 5%, and SPSS version 19 for Windowse was used.

Results Of the 962 patients enrolled in the treatment, 397 (41.3%) were excluded because they could not be reached on the telephone number provided, 96 (10%) were excluded because of conflicting schedule, and 469 were triaged by telephone conversation (fig 1). Of these 469 (48.7%) patients, 255 (54.4%) were excluded because of the following criteria: cervical pain (nZ31, 12.3%), thoracic pain (nZ6, 2.4%), acute low back pain (nZ10, 3.9%), sporadic low back pain (nZ24, 9.4%), no pain of at least 3 on the Pain Numerical Rating Scale (nZ17, 6.8%), fibromyalgia (nZ29, 11.4%), spinal fracture (nZ7, 2.7%), spinal surgery (nZ10, 3.9%), serious spinal deformity (nZ1, 0.4%), ankylosing spondylitis (nZ1, 0.4%), cancer (nZ5, 2%), pain in other joints (nZ15, 6%), neurologic disease (nZ6, 2.4%), serious respiratory disease (nZ2, 0.8%), uncontrolled systemic hypertension (nZ4, 1.6%), pacemaker (nZ1, 0.4%), deafness (nZ3, 1.2%), dermatomyositis (nZ1, 0.4%), umbilical hernia (nZ1, 0.4%), pregnancy (nZ4, 1.6%), other physical therapy treatment in the last 6 months (nZ70, 27.6%), regular Pilates exercise (nZ4, 1.6%), and regular physical exercise (nZ2, 0.8%). Face-to-face assessments were booked for 214 patients, of whom 30 (14%) missed more than 2 appointments. A total of 184 patients were assessed, and 36 (19.6%) of them were excluded because of nerve root www.archives-pmr.org

Interferential current, Pilates, and pain

323

Screening of the eligibility criteria: n=469

Excluded (n=321, 68.4%): 291 (90.7%) ineligible 30 (9.3%) missed the assessment

Randomization: n=148

74 patients allocated to Active IFC + Pilates group

Allocation

74 patients allocated to Placebo IFC + Pilates group

(all received allocated intervention)

(all received allocated intervention)

72 were followed up at 6 weeks

71 were followed up at 6 weeks Follow-Up 72 were followed up at 6 months

73 were followed up at 6 months (72 for the outcome pain)

74 patients analyzed

Fig 1

Analysis

Flow diagram of the participants through the study.

compromise, leaving 148 patients who were included in the study between October 1, 2013, and May 19, 2014. Table 2 summarizes demographic characteristics of the participants. The groups were similar at baseline. In both groups, electrotherapy associated with physical exercise was the predominant treatment considering prior physical therapy (18.9% of the 41.9% who had physical therapy in the active IFC þ Pilates group and 9.5% of the 27% in the placebo IFC þ Pilates group). Electrotherapy alone was a common treatment, corresponding to 14.9% in the active IFC þ Pilates group and 8.1% in the placebo IFC þ Pilates group. Regarding the use of medication, 50% of the active IFC þ Pilates group and 47.3% of the placebo IFC þ Pilates group were taking medication at baseline, mainly analgesic drugs with 28.4% in the active IFC þ Pilates group and 29.7% in the placebo IFC þ Pilates group. In the 6-week follow-up, 32.4% of the active IFC þ Pilates group and 27% of the placebo IFC þ Pilates group were still taking

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74 patients analyzed

medication and this value changed to 36.5% in both groups in the 6-month follow-up. A total of 1332 sessions were provided per group. In each Pilates session, 3 to 19 exercises were performed, respecting the patient’s speed to perform the exercises and his/her physical ability. In the active IFC þ Pilates group, 176 absences were recorded (86.8% attendance). In the placebo IFC þ Pilates group, 172 absences were recorded (87.1% attendance). There was a loss of outcomes of 2 patients in the active IFC þ Pilates group and 3 in the placebo IFC þ Pilates group in the 6-week followup, and a loss of outcomes of 1 participant in the active IFC þ Pilates group (except for pain, which had a loss of 2 participants) and 2 participants in the placebo IFC þ Pilates group in the 6month follow-up. These follow-up losses occurred because patients could not be reached by the telephone number provided. In the case of the 2 losses of the outcome pain, there was an error of the blinded assessor.

324 Table 2

Variable

K.M. Franco et al Baseline characteristics of the participants Active IFC þ Pilates Group (nZ74)

Age (y) 43.915.5 Sex Male 23 (31.1) Female 51 (68.9) Low back pain 66.571.0 duration (mo) Weight (kg) 72.715.7 Height (m) 1.60.1 26.74.8 Body mass index (kg/m2) Marital status Single 28 (37.8) Married 37 (50.0) Divorced 6 (8.1) Widowed 3 (4.1) Academic level Incomplete 11 (14.9) primary education Complete primary 2 (2.7) education Incomplete 2 (2.7) secondary education Complete 24 (32.4) secondary education Incomplete 14 (18.9) tertiary education Complete tertiary 21 (28.4) education Income (Brazilian 4 (2.9) minimum wages) Physical therapy treatment Yes 31 (41.9) Other type of treatment Yes 6 (8.1) Use of medication Yes 37 (50.0) Pain intensity 6.51.8 (0e10) PPT (kPa) Lumbar 243.3100.2 Tibialis anterior 258.8112.7 Disability (0e24) 11.95.0 Kinesiophobia 41.17.0 (17e68) Patient-specific 4.11.8 disability (0e10) Global impression 0.42.7 of recovery (5 to 5) NOTE. Values are mean  SD or n (%).

Placebo IFC þ Pilates Group (nZ74) 43.614.1 17 (23.0) 57 (77.0) 71.782.1 72.915.9 1.60.1 26.85.5

25 (33.8) 34 (45.9) 12 (16.2) 3 (4.1) 4 (5.4)

5 (6.8) 2 (2.7)

25 (33.8)

14 (18.9)

24 (32.4) 5.2 (9.0)

20 (27.0) 7 (9.5) 35 (47.3) 6.71.6

220.698.9 233.685.0 12.14.4 41.47.7 4.41.6 1.42.5

Table 3 shows the inter- and intragroup comparison. No significant difference was found between groups in any of the outcomes assessed in 6-week and 6-month follow-ups (P<.05). However, both groups showed a significant improvement after the treatment in all outcomes, except PPT in the placebo IFC þ Pilates group in 6-week follow-up.

Discussion The results of this randomized controlled trial showed that there was no difference between the groups in any of the assessed outcomes. Both groups showed significant improvement in the outcomes after 6 weeks and 6 months of treatment, and the improvement in pain and disability was considered clinically significant.50 The application of analgesic electrical currents in the treatment of nonspecific CLBP is a widely used resource in physical therapy.26,38,39,51 This statement is corroborated by our findings, in which the participant’s most common prior treatment was electrotherapy alone or combined with exercise. However, the literature is still scarce on IFC. There is only 1 systematic review26 showing that IFC alone is not significantly better than placebo or comparison therapy (manual therapy, traction, massage), but as a combined treatment, IFC is significantly better than control and placebo for pain relief in the treatment of acute and chronic musculoskeletal disorders. Nevertheless, only 3 studies on IFC in the treatment of nonspecific CLBP were included in this review, and these studies did not compare its efficiency with placebo IFC.26 A recent study,14 that performed a single treatment session, found significant pain improvement in patients with nonspecific CLBP on comparing active IFC with placebo plus therapeutic alliance (defined as the working rapport or positive social connection between the patient and the therapist14). In this study, the group who received active IFC with reinforced therapeutic alliance showed a clinically and statistically significant difference with respect to pain whereas the group who received placebo IFC with limited therapeutic alliance showed a smaller effect with no clinical significance. This result differs from the findings of the present study, which did not show superiority of active IFC over placebo IFC. However, our result was similar to that of an older study52 that assessed the effect of active and placebo transcutaneous electrical nerve stimulation alone and combined with exercise in patients with nonspecific CLBP. A possible explanation would be that the neurologic mechanisms involved in the action of the placebo are similar to the mechanisms through which the analgesia currents act.12,20 This can be seen in neuroimaging studies that show that analgesia induced by placebo reduces neuronal activity in the brain’s pain processing areas and share the same neuronal network as endogenous opioid peptides.53-55 Increased values of the PPT are usually correlated with clinical pain improvement.26,56 Two studies14,48 assessed this outcome in connection with the use of IFC. The first study48 compared 3 groups of participants without pain submitted to pressure-induced pain (active and placebo IFC and a control group) and did not find a significant difference between groups, similarly to our study. The second study14 compared active and placebo IFC plus therapeutic alliance in patients with nonspecific CLBP and found no significant difference in PPT between groups, similar to our findings.

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Within-group and between-group differences at baseline and in 6-wk and 6-mo follow-ups Interventions, Unadjusted Mean  SD Baseline

Outcome Pain (0e10)

AIP

6-Wk Follow-Up

PIP

AIP

PIP

Between-Group Differences

Within-Group Differences Baseline vs 6-Wk Follow-Up (95% CI)

6-Mo Follow-Up

AIP

Baseline vs 6-Wk Follow-Up

Baseline vs 6-Mo Follow-Up

PIP

AIP

PIP

4.3* (3.4e5.1)

4.3* (3.5e5.0)

2.2* (1.2e3.2)

2.4* (1.7e3.2)

0.1 (0.9 to 1.0)

0.3 (1.2 to 0.6)

25.3 (4.4 to 55.0) 17.6 (14.1 to 49.2) 0.4 (1.3 to 2.2) 1.7 (0.7 to 4.2) 0.2 (0.8 to 0.6) 0.4 (0.7 to 1.4)

NA

6.71.6

2.22.1

2.52.4

243.3100.2

220.698.9

212.985.2

217.4110.0

NA

NA

27.3* (5.7e48.9)

3.3 (17.6 to 24.2)

NA

NA

258.8112.7

233.685.0

234.911.0

251.711.0

NA

NA

13.2 (12.6 to 38.9)

2.8 (21.9 to 16.3)

NA

NA

Disability (0e24)

11.95.0

12.14.4

4.24.1

4.85.1

6.35.6

6.86.2

8.0* (6.4e9.4)

7.5* (6.0e9.1)

5.7* (4.1e7.4)

5.4* (3.7e7.1)

Kinesiophobia (17e68)

41.17.0

41.47.7

34.36.6

36.17.9

36.67.8

38.78.3

7.0* (5.0e9.1)

5.2* (3.0e7.4)

4.3* (2.0e6.7)

2.5* (0.1e5.1)

Patient-specific disability (0e10) Global impression of recovery (5 to 5)

4.11.8

4.41.6

7.41.8

7.31.8

6.42.0

6.32.4

3.3* (3.9 to 2.7)

2.9* (3.4 to 2.4)

0.42.7

1.42.5

3.32.0

3.71.6

2.02.9

2.12.8

3.8* (4.7 to 2.9)

5.1* (6.0 to 4.3)

2.2* (2.9 to 1.5) 2.6* (3.6 to 1.5)

2.0* (2.7 to 1.3) 3.5* (4.7 to 2.3)

Tibialis anterior

4.32.6

Adjusted Mean Difference (95% CI)

AIP

6.51.8

PPT (kPa) Lumbar

4.42.8

PIP

Baseline vs 6-Mo Follow-Up (95% CI)

Interferential current, Pilates, and pain

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Table 3

NA

0.3 (1.4 to 2.1) 1.8 (0.7 to 4.2) 0.3 (0.4 to 1.0) 1.0 (2.0 to 0.0)

Abbreviations: AIP, active IFC þ Pilates group; CI, confidence interval; NA, not applicable; PIP, placebo IFC þ Pilates group. * Significant difference between groups: P<.05.

325

326 The results of our intragroup analysis showed a reduction in PPT in the active IFC þ Pilates group, unlike the increase shown by other studies. However, this reduction was not clinically significant and may have occurred because we assessed the PPT an average of 24 hours after the last treatment session, whereas other studies14,48 assessed it immediately after the application of the current. This interval was chosen to determine whether the PPT would remain high in the short term even without the active effect of the current, but that did not occur. We did not find studies that assessed disability in patients submitted to IFC. A recent systematic review9 shows that Pilates exercises are more effective than routine care and physical activity in the short term and lead to improvements equivalent to some forms of exercise and therapeutic massage. Two other studies38,57 also showed improved disability in the medium term in patients submitted to Pilates, similar to the present study, in which the 2 groups had a significant improvement in disability regardless of the use of current. Regarding the secondary outcomes of this study, the literature shows that Pilates acts by reducing the fear of movement and improving specific disability and global perceived effect in the short and medium term,38,39 but it is not superior to educational intervention,39 except for global perceived effect. We did not find any studies that assessed the action of IFC in these secondary outcomes. In relation to intragroup analysis, these findings corroborate the present study results. However, the intergroup analysis showed that the active current was not more effective than placebo in reducing the fear of movement or improving specific disability and global perceived effect. The major strength of the present study was its pragmatic approach, which allows the generalization of the results because of the similarity with clinical practice. The treatment was well conducted because the therapists had clinical experience, the sessions were individualized, and exercise progression respected the participant’s clinical condition. These exercises have been previously published,28 allowing the reproduction by other physical therapists with Pilates training. Moreover, the study was designed with an adequate sample to detect a significant clinical effect with low risk of methodological bias. Future studies should focus on the ideal assessment of the currents’ analgesic effect, including daily assessments of clinical improvement and the influence of this improvement in the treatment of patients with nonspecific CLBP. It would be interesting to compare active and placebo currents plus exercise with a group treated only with exercise to determine the most effective treatment and to estimate the placebo effect size of the analgesic current. The used IFC parameters in this study did not present any effects in the outcomes assessed; however, studies comparing different stimulation parameters are still necessary.

Study limitations Because the proposed intervention is exercise, it was not possible to blind all therapists and participants. Considering the risk of bias, the Pilates therapists were blinded to patient’s group allocation so as not to influence them during the exercise sessions. Each participant was also asked not to discuss the treatment with other participants to avoid finding out which electrotherapy group they belonged to.

K.M. Franco et al

Conclusions Active IFC plus Pilates exercises is not more effective than placebo IFC plus Pilates in improving pain intensity, PPT, disability, kinesiophobia, specific disability, and global perceived effect in the short and medium term in patients with nonspecific CLBP.

Suppliers a. Microsoft Excel for Windows; Microsoft. b. Neurovector; IBRAMED. c. Cadillac, Reformer, Ladder Barrel, and Step Chair machines; Metalife. d. Handheld pressure algometer: Somedic Inc. e. SPSS version 19 for Windows: IBM Corp.

Keywords Disability evaluation; Exercise movement techniques; Interferential current electrotherapy; Low back pain; Rehabilitation

Corresponding author Katherinne Moura Franco, MS, Master’s and Doctoral Program in Physical Therapy, Universidade Cidade de Sa˜o Paulo, Rua Cesa´rio Galeno 475, Tatuape´, Sa˜o Paulo, SP CEP 03071-000, Brazil. E-mail address: [email protected].

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