LOW BACK PAIN (LBP) is very common, and yet little is

BRIEF REPORT Aerobic Exercise Training in Addition to Conventional Physiotherapy for Chronic Low Back Pain: A Randomized Controlled Trial Carol W. Chan, PT, MSc, Nicola W. Mok, PT, PhD, Ella W. Yeung, PT, PhD ABSTRACT. Chan CW, Mok NW, Yeung EW. Aerobic exercise training in addition to conventional physiotherapy for chronic low back pain: a randomized controlled trial. Arch Phys Med Rehabil 2011;92:1681-5. Objective: To examine the effect of adding aerobic exercise to conventional physiotherapy treatment for patients with chronic low back pain (LBP) in reducing pain and disability. Design: Randomized controlled trial. Setting: A physiotherapy outpatient setting in Hong Kong. Participants: Patients with chronic LBP (N 46) were recruited and randomly assigned to either a control (n 22) or an intervention (n 24) group. Interventions: An 8-week intervention; both groups received conventional physiotherapy with additional individually tailored aerobic exercise prescribed only to the intervention group. Main Outcome Measures: Visual analog pain scale, Aberdeen Low Back Pain Disability Scale, and physical fitness measurements were taken at baseline, 8 weeks, and 12 months from the commencement of the intervention. Multivariate analysis of variance was performed to examine betweengroup differences. Results: Both groups demonstrated a significant reduction in pain (P.001) and an improvement in disability (P.001) at 8 weeks and 12 months; however, no differences were observed between groups. There was no significant difference in LBP relapse at 12 months between the 2 groups ( 2 2.30, P.13). Conclusions: The addition of aerobic training to conventional physiotherapy treatment did not enhance either short- or longterm improvement of pain and disability in patients with chronic LBP. Key Words: Exercise; Low back pain; Physical therapy modalities; Rehabilitation. 2011 by the American Congress of Rehabilitation Medicine LOW BACK PAIN (LBP) is very common, and yet little is known about its etiology or pathogenetic mechanism. 1 The reported lifetime prevalence for LBP is as high as 84%. 2 Chronic LBP develops in 5% to 10% of persons with acute LBP, 3 with pain persisting for more than 12 weeks. Chronic LBP is also a costly epidemic, with both direct health care and indirect costs (such as reduced productivity) imposed on the society. Notably, chronic LBP is associated with various physical, emotional, and psychosocial dysfunctions that eventually cause deterioration in the quality of life. Disuse and physical deconditioning are commonly evident in individuals with chronic LBP. 4,5 In addition, insufficient exercise was acknowledged as a risk factor for the development of LBP. 6 As such, exercise therapy for both primary and secondary prevention of LBP has been advocated as a priority research area. Exercise programs involve a mixture of training modes ranging from specific motor control exercise of the trunk muscles, strengthening, stretching, and/or aerobic training to more complex training programs. 7-9 The isolated effect of aerobic exercise therapy has been examined in individuals with chronic LBP. 10,11 The results revealed that aerobic exercise induced a short-term improvement in depression 10,11 and a reduction of pain and disability 10 in people with chronic LBP, when compared with electrotherapy to the lower back 10 and a waiting list control. 11 However, it has been argued that various exercise treatments could only cause a small but not clinically relevant change in people with chronic LBP when the effect of various exercise was studied alone. 12 In view of the multiple problems within the biopsychosocial spectrum presented by people with chronic LBP, it has been suggested that a combined (rather than a single) treatment approach should be considered for contemporary clinical trials. 13 The purpose of this study was to examine the effect of the addition of an 8-week, individually supervised, and progressive aerobic exercise program to conventional physiotherapy treatment for patients with chronic LBP. We tested the hypothesis that additional aerobic exercises would further improve physical fitness, pain, and disability in patients with chronic LBP. METHODS 1681 From the Centre for Sports Training and Rehabilitation, Department of Rehabilitation Sciences, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong. Presented in part to the Hong Kong Physiotherapy Association, December 8 9, 2007, Hong Kong. Supported by the Department of Rehabilitation Sciences, Hong Kong Polytechnic University and Department of Physiotherapy, David Trench Rehabilitation Centre. No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit on the authors or on any organization with which the authors are associated. Trial Registration Number: ISRCTN23753357. Reprint requests to Ella W. Yeung, PT, PhD, Centre for Sports Training and Rehabilitation, Dept of Rehabilitation Sciences, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, e-mail: ella.yeung@polyu.edu.hk. 0003-9993/11/9210-00403$36.00/0 doi:10.1016/j.apmr.2011.05.003 Participants Forty-six subjects (10 men, 36 women; mean age SD, 46.0 10.2y) were recruited from the Department of Physiotherapy at the David Trench Rehabilitation Centre, Hong Kong. The progress of subjects through the randomized trial is presented in figure 1. Inclusion criteria included subjects with LBP symptoms for at least 12 weeks and declared medically fit to ALBPS LBP METs List of Abbreviations Aberdeen Low Back Pain Disability Scale low back pain metabolic equivalents

1682 AEROBIC EXERCISE FOR CHRONIC LOW BACK PAIN, Chan Fig 1. CONSORT flow chart indicating flow of subjects through the trial. Abbreviation: VAS, visual analog scale. undertake physical fitness testing and exercise. Exclusion criteria included cardiac, systemic, or inflammatory disease, or a workers compensation client. Subjects were randomly allocated to the control (conventional physiotherapy, n 22) or the intervention (aerobic training and conventional physiotherapy, n 24) group, using a random number table concealed in sealed envelopes. All procedures were approved by the Institutional Medical Research Ethical Committee and were conducted in accordance with the Declaration of Helsinki. Conventional Treatment Both groups received conventional physiotherapy treatments that are commonly used clinically for chronic LBP, including electrical modalities (interferential therapy, ultrasound, or heat pack), passive segmental mobilization to the lumbar spine into end range, back mobilization exercise, abdominal stabilization exercise, and back care advice (ergonomic principles, proper posture, and lifting techniques). The choice of treatment was made by the physiotherapist based on the assessment findings. Aerobic Training Subjects in the intervention group received an additional aerobic training program for 8 weeks, individually prescribed and supervised by a physiotherapist. This duration was chosen to allow physiologic adaptations to aerobic training. 14 The target exercise heart rate was calculated by using the percentage of heart rate reserve method: (maximal heart rate resting heart rate) (intensity fraction) resting heart rate. The exercise intensity was set at 40% to 60% of heart rate reserve 15 and gradually progressed up to 85%, at a 5% increment each week. Subjects heart rates were monitored with a polar heart rate monitor. a The rating of perceived exertion (Borg CR-10 scale) 16 was also used to provide a complementary estimation to exercise intensity. To achieve the recommended aerobic improvement, 15 subjects performed 20 minutes of exercise, 3 times a week. Two training sessions were given and were supervised by the physiotherapist. Subjects were also instructed to perform at least 1 additional training at home each

AEROBIC EXERCISE FOR CHRONIC LOW BACK PAIN, Chan 1683 week. Home exercise adherence was recorded by each subject on a log sheet. The mode of exercise included treadmill walking/running, stepping, or cycling exercises, as preferred by the subject. Physical Fitness Measurements Physical fitness parameters included aerobic capacity, back extensor muscular endurance, lower back and hamstring muscle flexibility, and percentage of body fat. Aerobic capacity testing was performed according to the modified Bruce protocol on the treadmill. 15 The first 2 stages were performed at 2.74km/h at 0% and 5% grade, respectively. The third stage corresponds to the first stage of the standardized Bruce protocol. At 3-minute intervals, the inclination was increased by 2% with a concomitant increase in speed. The Sorensen test for lumbar extensor endurance was performed with the subject holding the upper body unsupported in a horizontal prone position and the lower body fixed to the plinth. The sit-and-reach test for flexibility was evaluated with the Flex-Tester. b The percentage of body fat was assessed by obtaining skinfold measurements of 3 sites (chest, abdomen, and thigh in men; triceps, suprailiac, and thigh in women) with skinfold callipers c and by using the Siri equation. 14 Outcome Measures The primary study outcomes were (1) pain measured with a 100-mm visual analog scale, and (2) functional disability using a validated Chinese version of the Aberdeen Low Back Pain Disability Scale (ALBPS). 17 The secondary study outcomes were the physical fitness parameters. The level of pain, ALBPS, and fitness parameters were measured at baseline and 8 weeks. At the 12-month follow-up, the subjects were contacted by telephone and asked to complete the ALBPS. The number of LBP relapses was also obtained. This was defined as an LBP episode that required medical consultation after discharge from the study. Data Analyses Intention-to-treat analysis was carried out for all analyses. Outcomes variables were compared across time by using analysis of variance for continuous variables and chi-square analysis for categorical variables. A multivariate analysis of variance test was performed to examine between-group differences. All analyses were conducted using the SPSS version 16.0. d Values are presented as mean SD. The significance level was set at equal to.05. RESULTS There was an overall exercise attendance rate of 91.3%. Table 1 presents the baseline demographic characteristics of the subjects. No significant differences were found between the Table 1: Baseline Characteristics of Subjects Baseline Characteristics Control (n 22) Intervention (n 24) Age (y) 46.0 11.5 47.1 8.3 Men/women 5/17 5/19 Duration of current symptom (mo) 14.1 21.5 11.8 13.7 Recurrence of LBP 6 (27.2) 2 (8.3) Area of LBP Local LBP and above knee 10 (45.5) 13 (54.2) Below knee, not nerve root 7 (31.8) 7 (29.1) Below knee, nerve root 5 (22.7) 4 (16.7) Physical activity (MET min wk 1 ) None: 0 10 (45.5) 14 (52.2) Light: 1 to 450 2 (9.1) 3 (10.9) Moderate: 450 750 1 (4.5) 4 (8.7) Vigorous: 750 9 (40.9) 13 (28.2) Physical fitness parameters Body fat percentage (%) 23.1 7.8 24.9 7.2 VO 2 max (ml kg 1 min 1 ) 40.4 6.9 39.0 4.7 Back extensor endurance (s) 42.8 34.9 46.5 28.1 Sit-and-reach test (cm) 19.2 9.1 22.0 9.3 Pain and disability scores Pain score VAS (mm) 59.5 21.5 59.5 13.9 ALBPS score 30.8 13.9 28.8 11.0 NOTE. Values are mean SD, n, or n (%). Abbreviations: VAS, visual analog scale; VO 2 max, maximum oxygen consumption. 2 groups. Based on the American College of Sports Medicine s age-adjusted standards, 43.5% and 47.8% of the subjects ranked below the 50th percentile for maximum oxygen consumption and body fat percentage, respectively, and 74% of the subjects had flexibility classified as fair to poor. 15 An average of 35.6 14.1 minutes of aerobic exercises at 5.60 1.30 metabolic equivalents (METs) was performed at each session. Most subjects (83.3%) were able to reach the target intensity range of 50% to 85% HRR at the end of the 8-week intervention. Eighty-one percent (n 18) of the subjects chose walking, jogging, or running as the preferred mode of aerobic exercise training. Seventy-seven percent of the subjects in the intervention group performed additional aerobic exercises at home for at least 30min/wk. A mean of 486.9 323.7 MET min wk 1 was accrued for subjects in the intervention group. At 8 weeks, significant improvements in pain and functional disability were reported in both groups (P.001). Improvements in disability were sustained in both groups at 12 months when compared with the baseline (P.001). However, no significant differences were detected in pain and disability between the 2 groups at either time (table 2). The intervention Pain and Disability Scores Table 2: Pain and Disability Scores at 8 Weeks and 12 Months Follow-up Control (n 22) Intervention (n 24) Difference in Mean Change Scores Baseline 8wk 12mo Baseline 8wk 12mo (95% CI) at 8wk Difference in Mean Change Scores (95% CI) at 12mo Pain score (0 100) 59.5 21.5 34.5 21.1* NT 59.5 13.9 31.5 20.9* NT 3.0 ( 10.2 to 16.2) NA Disability score (0 100) 30.8 13.9 20.8 13.0* 24.0 15.1* 28.8 11.0 19.0 12.7* 18.4 15.2* 0.22 ( 6.0 to 5.5) 3.9 ( 0.6 to 8.4) NOTE. Values are mean SD or as otherwise indicated. Abbreviations: CI, confidence interval; NA, not applicable; NT, not tested. *Compared with baseline, P.001.

1684 AEROBIC EXERCISE FOR CHRONIC LOW BACK PAIN, Chan Table 3: Physical Fitness Parameters Before and After 8-Week Intervention Control (n 22) Intervention (n 24) Physical Fitness Parameters Baseline 8wk P Baseline 8wk P Body weight (kg) 58.5 9.5 58.2 9.4.13 59.8 8.5 59.2 8.4.02* Body mass index (kg/m 2 ) 22.8 2.9 22.7 2.9.24 23.49 3.0 23.3 3.0.02* Body fat percentage (%) 23.1 7.8 22.2 7.8.04* 24.9 7.2 24.2 7.0.03* VO 2 max (ml kg 1 min 1 ) 40.4 6.9 40.2 7.3.74 39.0 4.7 40.3 5.2.02* Back extensor endurance (s) 42.8 34.9 49.9 37.1.11 46.5 28.1 59.1 27.5.005* Sit-and-reach test (cm) 19.2 9.1 24.0 8.4.001* 22.0 9.3 26.2 9.7.001* NOTE. Values are mean SD or as otherwise indicated. Abbreviation: VO 2 max, maximum oxygen consumption. *Statistically significant. group improved in all physical fitness parameters, while the control group improved only in flexibility and percentage of body fat. However, there were no significant differences between groups for changes in physical fitness parameters (table 3). Chi-square analysis revealed no significant difference between groups ( 2 2.30, P.13) in the incidents of LBP relapse at the 12-month follow-up. DISCUSSION This study investigated the effect of adding an aerobic exercise program to conventional physiotherapy in people with chronic LBP. The results indicated that the addition of supervised aerobic exercise training did not enhance the improvement in pain and disability. There was significant short-term improvement in pain and disability in both groups, which reaffirms the findings of the meta-analysis on exercise therapy for the management of LBP by Hayden et al. 18 In this metaanalysis, the authors suggested that exercise therapy, including abdominal stabilization exercise, seems to be slightly effective at pain reduction and functional improvement for chronic LBP. In the present study, back mobilization and abdominal stabilization exercise were included as conventional treatment, which might contribute to the improvement as evidenced by the improvement in pain and functional disability as well as flexibility (note: the sit-and-reach test requires lumbar spine mobility) in both groups. We opted not to measure pain at the 12-month follow-up because it has been acknowledged that fluctuation in pain level seems to be one of the characteristic features in chronic LBP; in addition, the intensity of pain is not associated with activity level in people with chronic LBP. 19,20 Thus, only ALBPS and the number of LBP relapses were assessed at the 12-month follow-up in this study. The aerobic exercise training had no adverse effects on the subjects. The poor physical fitness level evident in our patients is consistent with the findings of previous studies, 4,5 which suggest the importance of aerobic exercise for chronic LBP. Although the intervention group showed an improvement in all fitness parameters after 8 weeks, the magnitude of change may be too small. The poor baseline fitness level is a major limiting factor in this study; perhaps the loading stimulus is too small to result in noticeable effects on pain and disability. The subjects may have benefited from a more intense exercise program of longer duration, increased frequency, or both. In the metaanalysis that examined intervention characteristics that could improve outcomes for patients with chronic LBP, it was shown that individually designed and supervised exercise is more effective. 21 We consider the ongoing supervision from the physiotherapist as an integral part of an individualized exercise therapy intervention. In this study, the physiotherapist monitored the subjects adherence to the exercise training program, as evidenced by the ability of most subjects to reach the target intensity range. In the long-term, adherence might improve if the subjects become aware of the benefits of, and their bodies response to the exercises. They could learn to modify the exercises according to their fitness level and fluctuations in pain level. Study Limitations There are several limitations to consider in this study. First, our sample size was relatively small to detect significant improvements in outcomes. Second, the nature of the aerobic exercise training made it impossible to conceal treatment allocation to the subjects or the investigators. The lack of blinding of the outcome assessors to group allocation may result in bias. Furthermore, changes in physical fitness parameters were not assessed at 12 months, making it difficult to identify long-term changes. CONCLUSIONS The findings of this study revealed that in patients with chronic LBP, the addition of aerobic training to conventional physiotherapy treatment did not lead to improvement of pain and disability at the short- and long-term follow-up beyond that achieved with conventional physiotherapy alone. We thank Raymond Cheung, PhD, for statis- Acknowledgment: tical advice. References 1. Deyo RA, Rainville J, Kent DL. What can the history and physical examination tell us about low back pain. JAMA 1992;268:760-5. 2. Walker BF. The prevalence of low back pain: a systematic review of the literature from 1966 to 1998. J Spinal Disord 2000;13:205-17. 3. Frymoyer JW. Back pain and sciatica. N Engl J Med 1988;318: 291-300. 4. Verbunt JA, Seelen HA, Vlaeyen JW, et al. Disuse and deconditioning in chronic low back pain: concepts and hypotheses on contributing mechanisms. Eur J Pain 2003;7:9-21. 5. Van der Velde G, Mierau D. The effects of exercise on percentile rank aerobic capacity, pain and self-rated disability in patients with chronic low back pain: a retrospective chart review. Arch Phys Med Rehabil 2000;81:1457-63. 6. WHO Scientific Group on the Burden of Musculoskeletal Conditions at the Start of the New Millennium. The burden of musculoskeletal conditions at the start of the new millennium. World Health Organ Tech Rep Ser 2003;919:i-x, 1-218. 7. Moseley L. Combined physiotherapy and education is efficacious for chronic low back pain. Aust J Physiother 2002;48:297-302. 8. Moffett JK, Torgerson D, Bell-Syer S, et al. Randomised controlled trial of exercise for low back pain: clinical outcomes, costs, and preferences. BMJ 1999;319:279-83.

AEROBIC EXERCISE FOR CHRONIC LOW BACK PAIN, Chan 1685 9. UK BEAM Trial Team. United Kingdom Back Pain Exercise and Manipulation (UK BEAM) randomised trial: effectiveness of physical treatments for back pain in primary care. BMJ 2004;329: 1377-84. 10. Chatzitheodorou D, Kabitsis C, Malliou P, Mougios V. A pilot study of the effects of high-intensity aerobic exercise versus passive interventions on pain, disability, psychological strain and serum cortisol concentrations in people with chronic low back pain. Phys Ther 2007;87:304-12. 11. Sculco AD, Paup DC, Fernhall B, Sculco MJ. Effects of aerobic exercise on low back pain patients in treatment. Spine J 2001;1:95-101. 12. van Middlekoop M, Rubinstein SM, Kuijpers T, et al. A systemic review on the effectiveness of physical and rehabilitation interventions for chronic non-specific low back pain. Eur Spine J 2011;20:19-39. 13. Jull G, Moore A. Systemic reviews assessing multimodal treatments. Man Ther 2010;15:303-4. 14. American College of Sports Medicine. ACSM s resource manual for guidelines for exercise testing and prescription. 6th ed. Philadelphia: Lippincott Williams & Wilkins; 2010. 15. American College of Sports Medicine. ACSM s guidelines for exercise testing and prescription. 8th ed. Philadelphia: Lippincott Williams & Wilkins; 2009. 16. Borg G. Applications of the scaling methods. Champaign: Human Kinetics; 1998. 17. Leung AS, Lam TH, Hedley AJ, Twomey LT. Use of a subjective health measure on Chinese low back pain patients in Hong Kong. Spine 1999;24:961-6. 18. Hayden JA, van Tulder MW, Malmivaara AV, Koes BW. Metaanalysis: exercise therapy for nonspecific low back pain. Ann Intern Med 2005;142:765-75. 19. Liszka-Hackzell JJ, Martin DP. An analysis of the relationship between activity and pain in chronic and acute low back pain. Anesth Analg 2004;99:477-81. 20. Huijnen IPJ, Verbunt JA, Roelofs J, Goossens M, Peters M. The disabling role of fluctuations in physical activity in patients with chronic low back pain. Eur J Pain 2009;13:1076-9. 21. Hayden JA, van Tulder MW, Tomlinson G. Systematic review: strategies for using exercise therapy to improve outcomes in chronic low back pain. Ann Intern Med 2005;142:776-85. Suppliers a. Polar A1 HRM; Electro Oy, Professorintie 5, 90440 Kempele, Finland. b. Novel Products Inc, PO Box 408, Rockton, IL 61072-0408. c. Harpenden skinfold calliper HSK-BI; British Indicators, Baty International, Victoria Rd, Burgess Hill, West Sussex, RHI5 9LR, United Kingdom. d. SPSS Inc, 233 S Wacker Dr, 11th Fl, Chicago, IL 60606.