Comparison of isokinetic exercise versus standard

Clinical Rehabilitation 2009; 23: 238–247

Comparison of isokinetic exercise versus standard exercise training in patients with chronic low back pain: a randomized controlled study Filiz Sertpoyraz, Sibel Eyigor, Hale Karapolat, Kazim Capaci and Yes im Kirazli Department of Physical Medicine and Rehabilitation, Faculty of Medicine, University of Ege, Bornova, Izmir, Turkey Received 22nd May 2008; returned for revisions 10th September 2008; revised manuscript accepted 27th September 2008.

Objective: To compare the effectiveness of an isokinetic exercise programme and a standard exercise programme in patients with chronic low back pain in terms of pain, mobility, disability, psychological status and muscle strength. Design: A randomized controlled trial. Setting: An outpatient rehabilitation clinic. Subjects: A total of 40 patients with low back pain were included in the study. Interventions: Patients with low back pain were randomly allocated into group 1 (n ¼ 20, isokinetic exercises) and group 2 (n ¼ 20, standard exercise). Main measures: Outcome measures included a visual analogue scale (VAS) for pain, fingertip-to-floor test for spinal mobility, Modified Oswestry Low Back Disability Questionnaire (MOLBDQ), Beck Depression Inventory and isokinetic muscle testing. Results: The isokinetic and standard exercise groups demonstrated significant improvement in the VAS, fingertip-to-floor test, MOLBDQ, Beck Depression Inventory scores, and muscle strength compared with the baseline that persisted until the end of the first month (P50.05). Comparison of both exercise groups in terms of these parameters obtained at the end of the treatment and at the first month after treatment showed no significant difference (P40.05). Conclusion: Isokinetic and standard exercise programmes have an equal effect in the treatment of low back pain, with no statistically significant difference found between the two programmes. The standard exercise programme was easily performed and had a low cost, making it the preferred option for exercise.

Introduction

Address for correspondence: Sibel Eyigor, Department of Physical Therapy and Rehabilitation, Faculty of Medicine, Ege University, 35100 Bornova, Izmir, Turkey. e-mail: [email protected], [email protected] SAGE Publications 2009 Los Angeles, London, New Delhi and Singapore

Low back pain is a common clinical condition in developed countries and regarded as an important health problem due to the high treatment costs and disability the condition causes.1 Patients with chronic low back pain experience various physical, social and psychological problems, and their quality of life is considerably disturbed.2,3 10.1177/0269215508099862

Isokinetic exercise for chronic low back pain Conventional treatment of patients with chronic low back pain focuses on relieving pain, reducing disability and helping patients return to their daily activities. In the contemporary treatment of low back pain, a multidisciplinary rehabilitation programme that includes functional restoration, cognitive behavioural therapy and exercise programmes that require active patient participation is employed rather than passive treatment methods.1,4–6 Although there is no general consensus about the most effective treatment yet,6,7 several clinical guidelines recommend exercise therapy for the management of patients with chronic low back pain because of the therapy’s potential to relieve pain and improve function.8,9 Exercise therapy is commonly used for the treatment of low back pain in clinical practice worldwide, but exercise types show significant diversity. Although the effect of exercise on pain and disability caused by low back pain is well known,1,8–10 several issues such as type and duration of exercise and the selection of suitable patients are still controversial due to differences and deficiencies in the methodology of the studies. An ideal exercise method or the superiority of one specific exercise to another has not been established until now. Although recent reviews confirmed the beneficial effects of a exercise programme on pain and disability due to chronic low back pain, no recommendations have been made concerning the specific type of exercise to be used.2,3,5–7 The positive effect of exercise on patients with chronic low back pain is consistent with the results that indicate the trunk muscles of patients with chronic low back pain are weaker than those of asymptomatic individuals.11,12 Weakness of the trunk extensors is a well-established correlation of chronic low back dysfunction.13 Measurements of trunk muscle strength are frequently employed in studies that evaluate the effectiveness of exercise on patients with low back pain.12 The isokinetic trunk device was developed as a tool for objective assessment of back muscle strength, but the isokinetic device can also be used as an exercise device other than objective measurement of muscle strength.14 However, isokinetic devices necessitate an experienced user, a specified time and a special place; therefore, there are limited studies in the

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literature concerning the use of isokinetic devices as exercise devices for low back pain.14 To our knowledge, no study on chronic low back pain has compared an isokinetic exercise programme with a standard exercise programme and assessed muscle strength objectively. For this reason, we aimed to compare the effectiveness of an isokinetic exercise programme with a standard exercise programme in patients with chronic low back pain in terms of pain, mobility, disability, psychological status and muscle strength.

Methods Participants Forty patients aged 20–45 years who had had low back pain for at least six months were recruited for the study. All patients presented to the outpatient clinic of the Department of Physical Therapy and Rehabilitation of Ege University Faculty of Medicine Hospital between January 2007 and December 2007. Among these, patients who had been diagnosed by an experienced physical therapy and rehabilitation specialist (third author) with mechanical low back pain (lumbar disc herniation (protrusion, bulging)), lumbar osteoarthritis (spondylosis, facet joint arthrosis) by history, physical examination, and radiological and laboratory examinations and also had pain localized only to the low back were enrolled in the study. Standing anteroposterior and lateral radiographs of the lumbar vertebrae and computerized tomography (CT) of lumbar vertebra region of each study patient were obtained. Patients were excluded if they had acute and severe low back pain, radicular symptoms, significant spinal stenosis, compression of nerve roots, extruded lumbar disc herniation, spondylolisthesis, neurologic deficits, spinal infection, inflammatory low back pain, spinal surgery history, malignity, pregnancy, severe obesity, serious cardiovascular disease, major depression, severe cognitive impairment or severe musculoskeletal impairment (inability to participate in the training regimen), or if they had been a member of a regular exercise programme within the last six months.

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Out of the 42 patients recruited, two refused to participate in the study. The patients who consented to participate were initially assessed by the first author. Then the researcher randomized each patient into one of the two groups by opening sealed envelopes. The randomization list was generated by a blinded researcher (the fourth author, experienced in biostatistics) using a table of random numbers. The randomization results were kept in sealed envelopes, one for each patient. Forty patients were randomized either to the isokinetic exercise programme (n ¼ 20) or the standard exercise programme (n ¼ 20). No dropouts occurred in either group; 20 patients in the isokinetic exercise group and 20 patients in the standard exercise group completed the study (Figure 1). Before enrolment, all subjects were informed about the study, and signed informed consent forms were obtained. Approval of the local ethics committee was obtained as well. All the subjects were assessed for their age, sex, height, weight, body mass index (body weight (kg)/height (m)2), duration of pain and demographic characteristics.

Assessments The following assessment parameters were measured at baseline, after the third week (at the end of the exercise programme) and after the seventh week.

Visual analogue scale The patients graded their low back pain on a 10-cm scale, anchored with the descriptors ‘no pain’ at one end and ‘pain as bad as it could possibly be’ at the other end. Maximum pain severity was assessed by a blind-testing physician using the standard visual analogue scale (VAS).7

Fingertip-to-floor test for spinal mobility Mobility of the trunk in forward flexion was measured with a tape measure. This test describes the spinal mobility in centimeters, and decreased distance indicates increased lumbar flexion.1,15

Modified Oswestry Low Back Disability Questionnaire This questionnaire is a disease-specific, selfreported measure of functional disability with documented reliability and construct validity. The Modified Oswestry Low Back Disability Questionnaire (MOLBDQ) asks the patient to rate his or her level of function in 10 areas, with each area scored from 0 to 5. The total score is expressed as a percentage, with 100% representing total disability and 0% representing no disability.16

Beck Depression Inventory Depressive symptoms were measured by the Beck Depression Inventory. The Beck Depression Inventory items are based on attitudes and symptoms that are commonly observed among depressed patients but uncommon among the non-depressed. The items assess emotional, behavioural and somatic symptoms. The Beck Depression Inventory consists of a 21-item selfrated questionnaire in which an item is scored from 0 to 3 (higher scores represent most severe symptoms).17

Muscle strength The maximal voluntary force capacity was measured using a Cybex Norm Computerized Isokinetic Dynamometer (Cybex II), Cybex Company, New York. Positioning was standardized according to the manufacturer’s manual. The axis of rotation was set at the intersection point of the mid-axillary line and the lumbosacral junction, which was approximately 3.5 cm below the top of the iliac crest. Vertical standing position was determined as the anatomical zero position. Pads and belts (pelvic belt, popliteal pad, thigh pad, sacral pad, scapular pad and chest pad) stabilized the chest, pelvis and lower limbs, and exact positions were noticed. The lower body was stabilized in a slightly bentknee position (15 of knee flexion) by the tibial popliteal, and thigh pads. The range of motion (ROM) was limited from 10 of extension to 80 of flexion. Isokinetic muscle strength was always measured at the same time of day and by the same

Isokinetic exercise for chronic low back pain

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Number of patients eligible for the study n = 42

Exclusion Refused to participate (n = 2)

Total number of patients registered (n = 40) Randomized (randomized number table)

Isokinetic exercise group (n = 20) No drop-out

Outcome data 3rd week n = 20 with data

Follow-up (1 month) No drop-out

Outcome data 7th week n = 20 with data

Figure 1

Standard exercise group (n = 20)

No drop-out

Outcome data 3rd week n = 20 with data

Follow-up (1 month) No drop-out

Outcome data 7th week n = 20 with data

Flow diagram of the study.

investigator throughout the study, in order to minimize the bias of the investigator and the daily fluctuations in muscle stiffness of the subjects. The subjects were all given verbal encouragement to perform the activities as quickly as they could, in order to increase compliance with the programme. The reliability

of the Cybex device has been found to be high in concordance with the literature18,19 in the measurements made between healthy volunteers and the intra-rater and the inter-rater before the device was routinely used. None of the subjects had any previous experience with any strength measurement procedure.

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Before testing, subjects were familiarized with both the test equipment and the test protocol. In addition, the equipment was calibrated before each test. For the isokinetic assessment, all the patients were first required to perform a 10-minute warm-up walk. Each test protocol started with a warm-up session that included two submaximal repetitions of the trunk flexion and extension, performed at 90 /s angular velocity. To assess the isokinetics, the dynamometer angular velocities were at 60 /s and 90 /s. For each subject, trunk flexion and extension contractions with maximal effort were performed with five repetitions at each velocity. Between each test repetition, the subject rested for 20 seconds. Muscle strength was expressed using the peak torque (PT) given in foot pounds (ft lb): PT 60 (PT value at 60 ), PT 90 (PT value at 90 ) and PT%BW; PT body weight (BW) values at 60 and 90 /s speed were used for evaluation.

Exercise programme A warm-up exercise in the form of a 10-minute walk was performed by both groups before the main exercise session. The patients in the first group (the isokinetic exercise group) underwent a three-week isokinetic exercise programme for five days a week on a Cybex Norm Computerized Isokinetic Dynamometer, Cybex Company, New York. After the warm-up session, the main assessment procedure was performed with the same testing position. Each subject’s trunk flexion and extension contractions with maximal effort were performed with five repetitions at 60 and 90 /s angular velocities with 60-second rests between sets, three sets, under a physician’s supervision. The subjects were verbally motivated by telling them to perform the activities as fast as and as hard as they could, in order to increase compliance with the programme. Patients in the second cohort (the standard exercise group) were subjected to a three-week exercise programme. Exercises were performed with a frequency of five days a week at the rehabilitation unit under a physiotherapist’s supervision. The exercise programme included passive lumbar extension, passive lumbar flexion,

pelvic tilt, strengthening of flexor muscles, strengthening of extensor muscles, spine mobilization and stretching exercises, and each patient performed each exercise in the programme either 10 times once a day or 5 times twice a day. Mean exercise time was 40 minutes for both groups. Patients were informed to avoid certain movements and positions (standing or sitting for long periods, slouching in a soft armchair, leaning over to pick up something on the floor, wearing tight, restrictive clothing or very high heels, heavy weight carrying, constipation, old, sagging bed mattresses) and informed that they actually had to take care for their low back pain.

Follow-up measurements All of the measurements were repeated after intervention and a one-month follow-up by the same physician who made the initial assessments. At the end of three weeks, the exercise programme was suspended after measurements were taken.

Statistical analysis The results were analysed using the Statistical Package for Social Sciences (SPSS) version 10.0 for Windows (SPSS Inc., Chicago, IL, USA). Descriptive statistical methods were used to evaluate sociodemographic characteristics. A P-value below 0.05 was considered statistically significant. Baseline demographics and clinical characteristics were compared using the Mann–Whitney U-test for numeric data and chisquare tests for nominal data. The independent samples t-test was used to compare groups for parameters obtained before and after rehabilitation. The Mann–Whitney U-test was employed for a comparison of pre- and post-exercise differences between the two groups. Friedman repeated measurements variance analysis and post-hoc Bonferroni corrected Wilcoxon test were used to analyse the change in selected parameters over time.


Results The isokinetic and standard exercise groups showed no difference in demographic and clinical characteristics (Table 1, P40.05). The isokinetic exercise group demonstrated significant improvement in the VAS, fingertipto-floor test, MOLBDQ, and Beck Depression Inventory scores compared to the baseline, which persisted until the end of the first month (Table 2) (P50.05). Additionally, the PT and PT%BW values at all degrees showed significant increases after the treatment, which persisted until the end of the first month (P50.05, Table 2). The standard exercise group also demonstrated significant improvement in the VAS, fingertipto-floor test, MOLBDQ and Beck Depression Inventory scores compared to the baseline, which persisted until the end of the first month (Table 2) (P50.05). The PT and PT%BW values

Table 1 Demographic and clinic characteristics of exercise groups and control group Isokinetic (n ¼ 20) Standard (n ¼ 20) Age, years, mean SD Female/male, n (%) Education, n (%) Primary High school University Occupation, n (%) Housework Retired Employee Worker

38.75 7.81

38.25 7.36

16/4 (80/20)

15/5 (75/25)

5 (25) 7 (35) 8 (40)

2 (10) 8 (40) 10 (50)

8 (40) 1 (5) 8 (40) 3 (15)

5 2 9 4

LBP duration, months, mean SD No. of LBP attacks, mean SD Diagnosis, n (%) Lumbar disc herniation Degenerative disease

28.65 25.28

45.80 51.69

2.55 1.90

3.80 3.28

17 (85)

15 (75)

3 (15)

5 (25)

LBP, Low back pain; SD, standard deviation.

(25) (10) (45) (20)

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at all degrees also showed significant increases after the treatment, which persisted until the end of the first month (P50.05, Table 2). Comparison of both exercise groups in terms of VAS, fingertip-to-floor test, MOLBDQ, Beck Depression Inventory scores and muscle strength obtained at the end of the treatment and at the first month showed no significant difference (Table 2) (P40.05).

Discussion In this study, patients with low back pain were randomized to isokinetic and standard exercise programmes, and the efficacies of both programmes were compared. Since the primary goals in treatment of patients with low back pain are alleviating pain, preventing disability and depressive symptoms, and increasing mobility and muscle strength, these goals were satisfactorily achieved for both groups. The two treatment groups showed no significant difference regarding these variables. Chronic low back pain is one of the main health problems in developed countries due to its complicated and expensive treatment. Pain is defined as the most common and challenging characteristic of this disease.20 Treatment guidelines for chronic low back pain have stated the effectiveness of exercise on pain.21,22 Our goal to reduce the pain was achieved in both groups. Exercise has been shown to be more effective on pain than any other type of conservative treatment method either by relevant studies or meta-analysis.7,20–22 However, studies that compared different types of exercises have shown that they have similar effectiveness on pain.4,5,23 Likewise, in a study that compared isokinetic exercise with standard physiotherapy, pain relief was achieved for both groups without a significant difference.14 In this study, both treatment groups performed exercises and strengthened their low back muscles that are assumed to be related to low back pain; therefore, our results that indicate no difference between the groups are considered to be consistent with the literature.24 Mobility is known to decrease in patients with low back pain; thus, spinal mobility measurements

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are recommended in these patients to demonstrate functional performance.15,25 We found both treatment groups had better fingertip-to-floor test results without a significant difference between the groups. However, Calmes et al. did not obtain any improvement in mobility with a two-week exercise programme.14 A poorly defined correlation of spinal mobility, muscular flexibility, low back pain and neuromuscular imbalance indicates that there may be various factors that affect mobility.15 Differences in techniques, duration and types of treatment periods and diverse patient characteristics hinder explanation of the controversial results. Due to the favourable effects of increased muscle strength by exercise on spinal mobility, we believe that prescribing exercise to patients with low back pain will increase the success rate in clinical practice. The aetiology of chronic low back pain and associated disability is multifactorial and best understood with a biopsychosocial model.6 Exercise programmes have been shown to provide improvement in the disability of these patients.7,26,27 A reduction in the subjects’ self-rated disability

has been determined as the most important predictor of success in the treatment of chronic low back pain, considering pain intensity, backto-work and subjective rating of success.28 The improvement in the MOLBDQ scores of both groups without a significant difference between the groups may be explained by the performance of exercise programmes for both groups. In a study that compared lumbar stabilization exercises with a no-treatment group, the stabilization group showed an improvement in MOLBDQ scores with a significant difference in favour of the stabilization exercise group.27 Patients who received an active treatment method (i.e. exercise), were shown to have better disability scores, and no difference was determined between the exercise groups.5,7,20,26 Considering these results, we believe that increasing daily activities of life, which is a major determinant of successful treatment, should be included in the goals of treatment and rehabilitation. The paraspinal muscles play a vital role in the stability of the back, and dysfunction of this stabilizing system may contribute to the development

Table 2 Comparison of both exercise groups in terms of VAS, fingertip-to-floor test, MOLBDQ, Beck Depression Inventory scores and muscle strength obtained at the end of the treatment and at first month

VAS Fingertip-to-floor MOLBDQ BDI Flexion PT60 PT90 PT%BW60 PT%BW90 Extension PT60 PT90 PT%BW60 PT%BW90

Isokinetic exercise (mean SD) (n ¼ 20)

Standard exercise (mean SD) (n ¼ 20)

Pre

Post

Follow-up

Pre

Post

Follow-up

4.85 0.93 9.65 11.34 16.60 8.12 8.30 6.46

1.30 1.45* 2.40 4.67* 9.40 6.81* 6.45 5.81*

0.55 0.99* 1.70 3.75* 7 5.21* 5.11 4.90*

5.40 1.27 13.72 14.45 18.80 7.79 10.40 7.97

1.20 1.43* 3.60 6.43* 10.45 5.78* 6 5.94*

0.75 1.58* 2.70 4.56* 8.55 7.55* 5.95 7.37*

41.05 33.79 24.60 20.54 26.99 21.16 16.56 12.70

68.65 28.87* 53.35 23.10* 47.32 20.42* 37.25 18.10*

77.57 26.51* 58.63 22.56* 52.41 14.80* 39.86 13.40*

29.21 31.46 18.73 21.63 20.62 21.97 12.75 14.83

54 39.09* 37.50 32.69* 35.91 25.27* 25.25 42.49*

63.30 44.84* 47.60 41.08* 40.85 25.11* 30.18 23.27*

24.35 13.12 13.95 10.56 16.11 8.49 9.96 7.15

38.95 13.05* 23.95 11.71* 28.09 11.96* 17.53 9.34*

47.26 18.44* 30.73 16.97* 32.47 11.94* 21.90 11.57*

18.42 16.14 11.57 13.70 15.20 17.63 9.27 13.24

39.70 34.10* 22.75 23.31* 26.40 21.55* 16.02 16.43*

44 36.55* 30.35 23.31* 28.64 20.94* 18.88 17.45*

SD, Standard deviation; PT, peak torque, PT%BW 60, PT body weight value at 60 /s; PT%BW 90, PT body weight value at 60 /s; VAS, visual analogue scale; MOLBDQ, Modified Oswestry Low Back Disability Questionnaire; BDI, Beck Depression Inventory. *P50.05.

Isokinetic exercise for chronic low back pain and persistence of low back pain.12 Weakness of the trunk extensors is a well-established correlation of chronic low back pain and dysfunction.13 In addition, low back pain that lasts more than a month has been shown to affect the strength of trunk flexors and extensors.21 Thus, exercise programmes are important for preventing atrophy and restoration of the strength of paraspinal muscles.12 Exercise programmes have been proved to increase muscle strength and endurance.14,21,22 In our study, both exercise programmes lasting for three weeks were also shown to increase muscle strength. Leggett et al. also reported improvement in the strength of back muscles from an exercise programme that was scheduled twice a week for eight weeks.29 Urzica et al. also showed improvement in isometric muscle strength with a fourweek rehabilitation programme.30 Calmes et al. also reported similar results showing improvement in muscle strength from a two-week isokinetic exercise programme in their small group of patients without a significant difference compared with the standard exercise programme.14 In the relevant studies, the recommended exercise period ranged between two and eight weeks. This time range is rather long. The repetitions of exercises and numbers of sessions per week also show great diversity among the studies. As a result, different studies in the literature reported increased muscle strength using various exercise types for various time periods.15,21,22,31 This means that exercise types cannot be clearly delineated due to the varied methodologies of the studies, lack of randomization and a control group, small number of patients, patient characteristics, and differences in duration and repetition of exercises. We believe that our results may provide some clues for future studies and treatment guidelines on this subject. In addition to the effects on pain, muscle strength and functional outcomes, exercise therapy is also considered to play an important role in the management of depressive symptoms.7 Several studies have described the importance of psychological factors in patients with chronic low back pain.24,25 In our study, both groups showed an improvement in Beck Depression Inventory scores, and no difference was observed between the groups. Gaskell et al. obtained better scores on the Hospital Anxiety and Depression Scale

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with a five-week exercise programme.32 Numerous studies in the literature have demonstrated improvement in psychological symptoms following exercise and have found no significant differences between different rehabilitation programmes.4,5,23 Controversial results concerning psychological symptoms have been reported to be similar using the most effective exercise type.7,25 Although studies indicate a correlation between psychological status and low back pain, this factor is frequently ignored in clinical practice and in the assessment of the effectiveness of rehabilitation programmes. Our study is the first study that compares the effect of isokinetic and standard exercise programmes on muscle strength in patients with chronic low back pain with an objective assessment of isokinetic muscle strength. Only one study has been found in the literature that compares the effect of isokinetic and standard exercise programmes on low back pain.14 However, that study had a very small number of patients, the exercise period was only two weeks, muscle strength was not measured by an isokinetic trunk device, and no psychological assessment was made. Our study employed a relatively short exercise and follow-up period and was conducted under supervision; therefore, no patient dropout occurred. Although short, our study had a follow-up period. Short-term follow-up in our study occurred because of patient transport problems, their concerns about staying in the study, and their loss of interest in coming to hospital after their symptoms had been resolved. Exercise programmes were carried out under supervision, which resulted in higher patient compliance, attendance at exercise programmes and patient satisfaction. None of the patients experienced complications throughout the treatment and follow-up period. Patients were evaluated in a comprehensive manner, including pain, mobility, disability, muscle strength and psychological status. The small number of patients in the groups and the short follow-up time can be considered the main limitations of our study. A larger population with a longer follow-up period could increase the power of the study. The lack of isometric muscle strength measurements is another limitation. This was not used as an evaluation criterion,

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because in their study Renkawitz et al. showed that isometric muscle strength had no influence on patients with low back pain.15 Also, for future studies, the long-term effects of treatment on quality of life, cost-effectiveness, back-to-work and recurrence of low back pain should be investigated. Although no difference was demonstrated between the isokinetic exercise and standard exercise programmes in the treatment of low back pain in our study, isokinetic exercise programmes have the advantage of providing objective data and enhancing motivation with visual and auditory stimuli. On the other hand, the need for expensive devices, experienced personnel, specified time and patient compliance are important disadvantages. Standard exercise programmes have the advantages of being easily applicable, efficient and less expensive, and can be performed in any place. Therefore, standard exercise programmes seem to be superior in this context. However, it is possible that the effectiveness of both programmes may depend upon the fact that they were carried out in hospital conditions under supervision. Therefore, we believe that comparative studies in the future should include a group of exclusive home exercise training programmes. Such studies would definitely help in determining exercise protocols for the treatment of low back pain.

Clinical messages Isokinetic and standard exercise programmes have an equivalent effect in the treatment of people with low back pain. The standard exercise programme proved to be easily performable with low cost, and may be the preferred option for exercise in people with low back pain.

Funding We have not had a financial relationship for this article.

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