Effects of an eight-week lumbar stabilization exercise programme on selected variables of patients with chronic low back pain

Background: Lumbar stabilisation exercise has been shown to reduce pain and disability in patients with low back pain but information on its potential benefits in term of back muscle endurance is scarce. Objective: This study was aimed at investigating the effects of augmenting conventional physiotherapy with lumbar stabilization exercises on selected variables of patients with non-specific chronic low back pain (NSCLBP). Methods: Forty individuals with NSCLBP aged 20-60 years were assigned to one of experimental or control groups (20 in each). The experimental group had lumbar stabilisation exercises in addition to conventional therapy (transcutaneous electrical nerve stimulator and infrared) which was the only treatment for the control group. Both groups were treated thrice weekly. Participants’ pain intensity, disability index, kinesiophobia level and back muscle endurance were evaluated at baseline and after 8 weeks. Results: There was significant reduction in pain intensity (experimental: 6.74±1.37; 3.48±1.09; control: 6.57±1.40; 2.96±1.13) and disability index (experimental: 46.60±16.67; 26.55±14.78; control: 32.10±16.16; 24.60±15.27) and increase in back muscle endurance (experimental: 11.05±8.39; 14.30±19.24s; control: 10.85±9.79; 13.90±11.63s) for both groups. Experimental group had significantly greater reduction (p < 0.05) in disability index than the controls (p = 0.048). Conclusion: Augmenting conventional physiotherapy with lumbar stabilisation exercises achieved better reduction in disability than conventional therapy alone in patients with NSCLBP.


Introduction
Low back pain (LBP) is a common problem which affects the majority of adults at least once in their lifetime. 1 It is a health challenge of global concern and is as common as a headache affecting all age groups and races. 1,2 It is pain and discomfort localised below the costal margin and above the inferior gluteal folds with or without leg pain (sciatica). 3,4 An acute episode of LBP usually resolves over a period of two to four weeks for 90% of patients, however, the recurrence rate of an acute episode is high, especially within the following 12 months. 5 This recurrence leads to chronic low back pain (CLBP) which is associated with high economic and health care burden costs. 5 The lifetime and one year prevalence of LBP is about 60-80% and 34% respectively. 6,7 Men have a higher risk for recurrence than women and the highest recurrence has been reported among individuals between 25-44 years. 7 Low back pain is one of the most common musculoskeletal problems that bring patients to the hospital 8 and the third leading cause of disability and associated absenteeism from work. 7 Low back pain is strongly associated with high level of disability which implies a significant inability to engage in meaningful and necessary activities of daily living. 9 Clinical studies have also suggested that consideration of excessively negative orientation toward pain (pain catastrophizing) and kinesiophobia are important in managing chronic low back pain and associated disability. 10,11,12 Kinesiophobia describes fear of movement and re-injury; 11 it is an irrational and debilitating fear of physical movement and activity resulting from a feeling of vulnerability to painful injury or re -injury. 13 Individuals who catastrophize pain are likely to become fearful of pain, and this results in pain-related fear which is associated with avoidance behaviors, particularly, the avoidance of movement and physical activity. 12 The individual may withdraw from activities of daily living and family. 12 Moreover, pain-related fearis reportedly associated with increased bodily awareness and pain hypervigilance. Pain hypervigilance, in addition to depression and disuse, are associated with increased pain levels and experience. 12 Studies have reported significant decrease in back extensor muscle endurance in patients with LBP; 14,15 these are postural muscles that aid in maintaining the upright standing posture and controlling lumbar forward bending. It is thought that decreased back muscle endurance causes muscular fatigue and consequently overloads soft tissue and the passive structures of the lumbar spine, resulting in low back pain. 16 Reduced back extensor muscle endurance has been identified as an important risk factor for LBP 17 and there is an inverse relationship between pain intensity and static back extensors endurance among patients with long-term mechanical LBP. 18 Decreased back muscle endurance could be either a cause or consequence of LBP. 19,20 Hence, assessment of back muscle endurance is crucial in the prediction, prevention and rehabilitation of LBP.
Lumbar stabilisation exercises (LSE) and other exercise programs fall within a paradigm of therapeutic exercises used in treatment of LBP. 21 They are exercises aimed at improving the activation patterns of trunk muscles, in order to relieve lumbar pain and limitation through trunk muscle contraction. 21,22 This exercise approach has become very popular as opposed to passive modalities such as; ultrasound, transcutaneous electrical nerve stimulation (TENS), short-wave diathermy, and massage that only aim to reduce symptoms but do not in any way alleviate a patient's predisposition to recurrent episode. The vulnerability of LBP recurrence is not completely understood 23,24 however, instability of the lumbar motion is considered an important cause. 25,26 Richardson and Jull 26 submitted that core stability exercises can be used to reactivate and improve the motor control of the multifidus (a core spinal stabilizer), and therefore prevent further episodes of LBP. Kim et al 27 reported that an eight-week LSE increased paraspinal muscle strength and the crosssectional areas of multifidus psoa major muscles in patients with degenerative disc disease. Long term LSE, as a single therapy or in combination with other treatments, can reduce pain and disability in CLBP and prevent a recurrent pain episode. 28,29 Although physiotherapy research has made headway with regard to classification of patients with LBP into treatment-based homogeneous subgroups, evidence was also found in support of LSE's effectiveness in decreasing pain and improving function even in a heterogeneous group of patients with CLBP. 29 França et al 30 reported that a six-week LSE resulted in reductions in pain and functional disorder index by 0.06 points and 1.80 points respectively and they concluded that stabilisation exercises were a beneficial therapy. The work of Kumar 31 also showed that LSE are effective for patients with symptomatic lumbar segmental instability.
In spite of all available evidence in support of LSE in the management of non-specific chronic low back pain (NSCLBP), there is still dearth of studies on whether recovered cross-sectional area of the multifidus muscle following lumbar stabilisation exercises resulted in improved endurance of back muscles. Information on the efficacy of LSE among Nigerians with NSCLBP also appears sparse. Therefore the purpose of this study was to investigate the effects of an 8-week lumbar stabilisation exercise training programme on pain intensity, disability, kinesiophobia and back muscle endurance among individuals with low back pain

Methods
A quasi-experimental study involving patients with non-specific chronic low back pain (NSLBP) was performed. The participants gave their written informed consent once the trial procedure was explained to them. They were patients diagnosed of mild to moderate non-specific low back pain(of at least 12 weeks duration) by the orthopaedic surgeon and/or family physician. The participants were also attending an out-patient Physiotherapy at the Department of Physiotherapy, FMC, Owo, Ondo State, Nigeria. Individuals with specific spine pathology (such as tuberculosis spine, spinal fracture and tumour), those with co-morbidities such as infection and referred pain from internal organs were excluded from the study. Pregnant women with low back pain and patients with LBP who were 18 years or younger were also excluded from the study.
Participants were allotted numbers once they became available and assigned to one of experimental or the control groups.

Intervention Experimental Group
Participants received Infrared radiation (using BL-220 Infrared lamp, MT03009201 model) for 15 minutes, Transcutaneous Electrical Nerve stimulation (using model DX66053, pain modulation mode) for 10 minutes and back education in form of counselling on recurrence and prevention. All participants were given a copy of the back pain prevention instructional booklet by Odebiyi 32 for home guide.
The lumbar stabilisation exercise protocol was taught in three phases: Phase 1: Development of the perception of isolated isometric specific contraction of stabilizing muscles; the phase involved teaching of isometric contraction of tranversus abdominis and multifidus muscles Phase 2: Exercises in closed chain, low velocity and low load; the purpose was to maintain local muscle synergy contraction, while gradually progressing load cues through the body using weight bearing closed chain exercises. The protocol and progression for lumbar stabilisation exercises as employed in this study is summarized in Table 1.

Control group
Control group participants received all the treatments given to the experimental group except lumbar stabilisation exercises. Participants were treated twice weekly.

Assessments
Pain Intensity: The Visual Analogue Scale (VAS) was used to assess participants' pain intensity. They were instructed to mark the point that corresponded to the intensity of their present pain on the VAS.The point marked was measured with a ruler and recorded as pain intensity (PI). 33

Kinesiophobia
The Tampa Scale of Kinesiophobia (TSK) Questionnaire was administered on the participants to assess their kinesiophobia level (fear of movement

Disability Index
Participants' disability index was evaluated using the Revised Oswestry Disability Questionnaire (RODQ). It's a ten-section self-administered questionnaire with six levels each, assessing the limitation of various activities of daily living. The range of possible scores ranges from 0 (best health) to 100 (worst health). The total was then divided by total score and expressed in percentage to produce disability index. 35

Back muscle endurance
The prone double straight-leg raise test was used to assess participants' back muscle endurance. The participant lay on the plinth in prone-lying position, hips extended, with the hands underneath the forehead and the arms perpendicular to the body. The participant was then instructed to raise both legs until knee clearance was achieved. The researcher monitored knee clearance by sliding one hand under the thighs. The time taken by participant to maintain knee clearance monitored with a stopwatch (Quartz, USA) was recorded in seconds as back muscle endurance. 36

Data Analysis
The data were analysed using Statistical Package for Social Sciences(SPSS) Version 20.0.A minimum sample size of 34 (17 per group) was estimated for the study at α = 0.05, power = 80% and effect size = 0.8 using the Cohen's table 37 . Assuming attrition rate of 10%, a total of 40 participants were recruited for the study. A large effect size of was obtained from an initial pilot study conducted.
Shapiro Wilk test performed to test for normality showed that the data for the four outcomes tested in this study are normally distributed.The data was summarized by using descriptive statistics of mean, standard deviation and 95% confidence intervals. Independent and paired t-tests were used for between and within group respectively for comparisons of participants' variables. Since the experimental group had significantly higher disability index scores than the control group at baseline, Analysis of Covariance (ANCOVA) was used to compare the effects of the two interventions used in this study adjusting for baseline values of all tested measures (covariates). Statistical significance was set at 0.05

Results
All forty participants completed the protocol. The participants' demographic and baseline selected disease-related variables are presented in table 2.  A between-group comparison computed with baseline values as covariates is presented in Table  4; the experimental group had a significantly greater reduction in disability than the controls (p = 0.048), effect size: 0.102) at the end of 8 th week. The groups' baseline difference in disability was adjusted for by using baseline values as covariates. *denotes significance at p ≤ 0.05 PI -pain intensity scores, DI -disability index scores, KIN-kinesiophobia scores, BME -back muscle endurance

Discussion
This study was carried out to compare the effects of lumbar stabilisation exercise plus conventional physiotherapy and conventional physiotherapy alone on pain intensity, disability, kinesiophobia and back muscle endurance among individuals with chronic low back pain.The results suggest that lumbar stabilization exercise plus conventional therapy and conventional therapy in isolation are similar in their effects on pain, kinesiophobia and back muscle endurance. The combined treatment however appears more beneficial in terms of reduced disability.
There was a significant improvement in pain intensity, disability and back muscle endurance but not in kinesiophobia after 8 weeks of treatment in both groups. Reduction in pain intensity and disability was not surprising, since all participants received infrared radiation and Transcutaneous electrical nerve stimulation (TENS) which have been reported as being efficacious in relieving chronic low back pain and associated disability. 38,39 Moreover, both groups also received back education and were given an instructional manual for follow-up at home. Reduction in pain and consequent improvements in function following lumbar stabilisation exercise have been attributed to improved activation patterns of trunk muscles and relieved lumbar pain and incapacity through trunk muscle contraction. 21,43 Weakness and lack of motor control of deep trunk muscles, such as the lumbar multifidus (LM) and transversus abdominis (TrA) muscles are consistent with LBP. 5,44 Individuals with chronic LBP are predisposed to delayed recruitment and insufficient control of the TrA. 45,46 It was opined that the emergence of biomechanical, neurophysiological, and histochemical dysfunctions in the LM of patients with LBP, such as atrophy occurs in the ipsilateral painful level. 47 Reduction in the size of the MF was also suggested deteriorating lumbar stability and cause painful structures or new injuries, thereby inducing pain and functional disabilities. 48 Deficits of MF causing low back pain and disability as well the resultant instability in local regions as would not be reversed naturally and that is a crucial factor for increased recurrence rate of LBP. 5 Spinal instability induces pain, reduces endurance and flexibility, and restricts the range of motion of the lumbar joints and all contributes to disability. 49 Stabilisation exercises are hence indicated for the prevention of the recurrence of pain induced by damage to the musculoskeletal system and consequent improvement of functional activities. 50 The systematic review by Hauggaard and Persson 24 also revealed moderate evidence of improved disability and or pain level following specific spinal stabilisation exercises.
The superiority of LSE programme over the conventional treatment in terms of reduced disability is promising. Participants in the control group did not receive any supervised active exercises like their experimental counterparts who underwent a wellstructured and supervised exercise programme. The finding is however not consistent with the work of Cairns et al 51 which showed no difference in the disability mean changes of individuals with recurrent LBP who had specific spinal stabilisation exercises and conventional physiotherapy. Oswestry Disability Questionnaire (ODQ) was the measuring tool in this study while Cairns and colleagues used Roland Morris Disabilty Questionnaire (RMDQ).Differences in the construct of both instruments might account for the variation in findings. There are also differences relating to frequency and intensity of exercise as well as sample size between both studies, Koumantakis et al 42 also found that general exercises produced significantly greater reduction in disability than general exercises plus spinal stabilisation exercises. There are also differences relating to measuring instruments (ODQ vs RMDQ) and sample size (40 vs 55) between the present study and the work of Koumantakis et al. 42 Furthermore, the present study involved participants with LBP of different subgroups whereas the aforementioned investigators involved patients with LBP of homogeneous aetiology.

Limitations of study
A major limitation of this study was lack of randomization in assigning participants into groups. This would have ensured an even distribution of population characteristics between the groups. The significant difference in disability index observed between the groups at baseline was however adjusted for in data analysis.

Conclusion/Recommendation
Augmenting conventional Physiotherapy with lumbar stabilisation exercises achieved better reduction in disability than conventional Physiotherapy alone.
Future studies should improve on sample size for improvements in external validity. Further, conducting a randomized controlled trial design may also strengthen the internal validity of the study. Designing a follow-up phase with the intent of observing the incidence of recurrence of low back pain may shed more light on the sustainability of the effects of LSE in the management of NSCLBP.