Abstract
BACKGROUND:
Many studies have emphasized the importance of stabilization exercises (SE) for the management of non-specific low back pain (NSLBP), yet there is no study assessing all aspects of core stability in comparing SE and other exercises.
OBJECTIVE:
To investigate the effects of SE on pain and core stability by using core stability tests that focus on all aspects of core stability in patients with NSLBP.
METHODS:
Thirty-seven individuals with chronic NSLBP were randomly divided into two groups as SE and conventional exercises (CE). Both groups underwent the progressive exercise program three days per week for six weeks. The assessments were conducted before and after the exercise programs. The outcome measures included pain, disability, trunk strength, trunk flexor, extensor and lateral flexor endurance, function, flexibility, and motor control during eyes open/closed.
RESULTS:
All assessment parameters except motor control during eyes open improved after SE (p < 0.05). Also, all assessment parameters except motor control during eyes open/closed and lateral trunk endurance improved after CE (p < 0.05). When comparing groups for gain scores, there were more significant improvements in pain during activity, endurance and function after SE (p < 0.05).
CONCLUSIONS:
SE is more effective than CE in reducing pain during activity and improving core stability regarding functionality and endurance.
Introduction
Low back pain (LBP) stands out as the leading cause of work loss because people suffering from this musculoskeletal disorder come up against recurrent symptoms causing functional impairment. LBP is one of the first four causes of general disability among 328 diseases, according to the study of the 2017 Global Burden of Disease [1]. Also, LBP reaches a peak between the ages of 30–50 years, so it frequently affects a population at a time of career advancement [2]. The previous studies have indicated that LBP affects the economy negatively due to work loss of the working-age population and health expenditures [2, 3].
Only a small proportion of people with LBP have a well understood pathological cause such a vertebral fracture, malignancy, infection or osteoporosis. Non-specific LBP (NSLBP) is usually defined as pain and discomfort, localized below the costal margin and above the inferior gluteal fold, not assignable for a recognizable, known pathologic disorder [4]. Unless “red flags” exist, the patient should be encouraged to remain as active as possible. The recommendation of active modalities improves return to work rates; therefore, guidelines recommend the use of supervised patient-centered active exercises. However, there is no consensus regarding which type of exercise therapy is most effective [3, 6].
Stabilization exercises, also known as segmental stabilization exercises or core stabilization exercises, are increasingly being popular to be an effective treatment modality for NSLBP [7, 8]. Stabilization exercises aim to improve the activity of the local stabilizing muscles, also called core muscles, such as transversus abdominis and lumbar multifidus, which is the main difference of this exercise modality over conventional exercises [7, 9]. The increasing number of studies emphasizing the role of the core muscles in the lumbar stabilization has led to the development of many clinical methods to assess the function of these muscles [10–12]. Several studies have suggested that stabilization exercises improve core stability in patients with LBP; however, only the core endurance or lumbopelvic functional tests were used to assess core stability in these studies [13–15]. The multifactorial functions of the core muscles involve many parameters such as strength, flexibility and motor control, not only endurance or functionality [9, 12].
In the evidence-based literature, there are clinical tests that focus on all aspects of core stability and have been found to be highly reliable [11, 12]. However, no study which used psychometrically sound clinical tests to assess the effects of stabilization exercises on different aspects of core stability. In the light of this information, the aim of this study was to investigate the effects of stabilization exercises by using core stability tests that focus on all aspects of core stability compared to conventional exercises in patients with NSLBP. Based on the findings of previous studies and our clinical experiments, we hypothesized that stabilization exercises would improve all aspects of core stability.
Materials and methods
Design and setting
This study has a randomized-controlled trial design. The participants were recruited from the Department of Neurosurgery at Dokuz Eylul University Hospital. The assessments and exercise programs were administered in the School of Physical Therapy and Rehabilitation, Dokuz Eylul University.
This study has been approved by the Noninvasive Research Ethics Board of the Dokuz Eylul University (Protocol Number: 2307-GOA, Approval Number: 2015/23-05) and all participants provided written informed consent before the participation in the study.
Participants
Patients with chronic NSLBP were included in the study. Inclusion criteria were as follows: 1. being aged between 30 and 55 years, 2. Having LBP more than three months (chronic), (3) having a diagnosis of NSLBP. All participants were screened for a lumbar magnetic resonance imaging scan, and NSLBP was diagnosed by the neorosurgeon (OK) according to the guideline poblished in 2006 [16]. The exclusion criteria were as follows: 1. previous spinal surgery, 2. story of spinal fracture, 3. pregnancy, 4. osteoporosis, 5. cancer, 5. radiculopathy, 6. vertigo, 7. neuromuscular or cardiopulmonary disease that prevents the person from doing exercises, 8. physiotherapy received in the last six months, and 9. use of analgesics during the study period.
Procedure
Participants were randomly divided into two groups: stabilization exercises and conventional exercises. Both groups underwent the progressive exercise program three days per week for six weeks. Participants were assessed with the core stability assessment battery including partial curl-up test for strength, trunk flexor test, Sorensen test and left/right bridge test for endurance, 30-second sit-to-stand test for function, sit and reach test for flexibility, and unilateral stance test (UST) with eyes open (EO) and eyes closed (EC) for motor control. The level of disability and pain were also assessed. All assessments were performed by the same physiotherapist (YSS) two days before and after the exercise program, and then the exercise programs were also performed under the supervision of the same physiotherapist (AY) who has four years of postgraduate relevant experience.
Randomization
Eligible patients with NSLBP were divided into two groups with a 1:1 allocation by a simple randomization method using an online Research Randomizer Program (available at https://www.randomizer.org/) by an independent researcher.
Interventions
All patients underwent the progressive exercise program three days per week for six weeks. The exercise sessions initially took an average of 40 minutes and were increased to 60 minutes as the program progressed. A home exercise program was not recommended, so all participants exercised only three days a week under the physiotherapist supervision (AY). For stabilization exercises, the lumbar segment was located in the neutral position in each exercise step, and then transverse abdominal and pelvic floor muscles were contracted during the expiration phase of diaphragmatic respiration [17]. The neutral position here does not mean that the lumbar lordosis angle is zero, but instead it refers to the lumbar vertebrae posture where the patient feels most comfortable and pain-free. The patients were also trained in how they could utilize this position effectively in their lifetime. Stabilization exercises were progressed according to patients’ ability to activate transverse abdominal muscle assessed manually by the abdominal drawing-in maneuver [18]. Progression was made changing patient position, so exercises were performed in the supine, prone, quadruped, bridge, sitting positions, and lastly with a Swiss ball, moreover, the patients were asked to perform additional limb movements while maintaining the neutral position [17]. Each exercise was maintained for 5-to-10 seconds and was repeated 10-times. The conventional exercises were given to improve the strength and flexibility of lumbopelvic muscles. They consisted of cat-camel exercises for spinal mobility, posterior pelvic tilt and double knee to chest for stretching the trunk extensor muscles and strengthening abdominal muscles, cycling in supine for strengthening the abdominal muscles and coordinating anterior and posterior lumbar muscles, bridging exercises for strengthening the trunk extensor and gluteal muscles, and lower abdominal crunch in the supine position for strengthening the abdominal muscles [19]. For each session, the strength exercises were given the dosage with 2–4 sets of 8–12 repetitions, and the flexibility exercises were given with the dosage with 4–10 repetitions at 10–30 seconds stretching time. Conventional exercises were progressed according to the pain tolerance and fatigue of each patient by increasing the exercise intensity parameters including holding time and number of repetitions gradually.
Outcome measures
Disability and pain assessment
The Oswestry Disability Index (ODI) and the visual analog scale (VAS) were used to assess disability and pain, respectively. The ODI is a self-reported, valid, reliable and responsive condition-specific questionnaire that is the most commonly used outcome measure for patients with LBP. The total score can range from 0 to 50. Higher scores mean to have more disability [20]. The Turkish version of the ODI was shown to have good comprehensibility, internal consistency and validity. The intensity of LBP at rest and during activity was assessed with VAS, which consists of a horizontal 100 mm long line, with endpoints of “no pain” and “worst pain imaginable” [21].
Core Stability Assessments
Strength assessment: The partial curl-up test was used as an isoinertial strength test [12]. Participants were asked to perform as many full curl-ups as possible within one minute or within the time when the patient finished the test due to pain.
Endurance assessment: The trunk flexor, Sorenson (trunk extensor), and bilateral side bridge tests were used to assess core stability related endurance [12]. Participants were asked to hold a static position related to each test for as long as possible. The side bridge tests were stopped when the side-lying position was lost or when the hips touched the table. The trunk flexor and Sorenson tests were stopped when the patient disrupted the position.
Flexibility assessment: The sit-and-reach test was performed to assess flexibility. Participants completed three reaches and the best reach was recorded as the score [12].
Functionality assessment: The 30-second sit-to-stand test was used to assess functionality. Participants were asked to stand up and sit down from a chair as many times as possible within 30 seconds [11].
Motor control assessment: UST with EO and EC was used to assess balance control as an indicator for motor control. Participants were asked to stand on the foot of their choice, while the other foot raised as it was near but not touching the ankle of their stance limb. Each participant was asked to focus on a spot on the wall at eye level in front of him/her for the duration of the eyes open test. The investigator used a stopwatch to measure the amount of time the participant was able to stand on one limb. Time commenced when the participant raised the foot off the floor. Time ended when the subject either: (1) used his/her arms, (2) used the raised foot (moved it toward or away from the standing limb or touched the floor), (3) moved the weight-bearing foot to maintain his/her balance (i.e., rotated foot on the ground), (4) a maximum of 45 seconds had elapsed, or (5) opened eyes on EC trials [12].
Sample size calculation and statistical analysis
The required sample size was calculated according to the effect size (1.18) between the change difference after a core stabilization and conventional exercise program obtained from a previous study [14]. The sample size was calculated as 34 (17 for each group) for 90%power and alpha error probability = 0.05 with G*Power (version 3.1.9.2, Düsseldorf University, Germany). It was decided to recruit at least 37 participants to account for possible dropouts (10%).
In total, 44 patients with NSLBP were assessed for eligibility. Two participants refused to participate due to their working time. Forty-two participants were randomly divided into two groups as Stabilization Exercises (n = 21) and Conventional Exercises (n = 21). Participants who have at least 80%attendance to the exercise program were included in the statistical analysis. One participant left the study due to pregnancy. Four participants who have less than 80%attendance to the exercise program were excluded in the statistical analysis. The statistical analysis was performed on 37 patients (Fig. 1). Shapiro-Wilk test was used to check the normal distribution of the variables. Parametric tests were used due to data was normally distributed. Independent-samples t-test was used to compare two groups for demographic and baseline clinical characteristics. The changes in outcomes from baseline to sixth weeks were determined using the paired sample t-test. The mean difference scores (the change from pretest to posttest) were analyzed in an analysis of variance (Stabilization Exercises vs. Conventional Exercises) as the independent variable. The statistical significance was set at p < 0.05. The statistical analysis was conducted using IBM SPSS Statistics for Windows (Version 25.0.; IBM Corp., Armonk, NY, USA).
Flowchart of the study.
No significant difference was found between the groups in terms of baseline demographic and clinical characteristics (p > 0.05) except for the ODI (p = 0.015) and left bridge test (p = 0.025) (Table 1).
Demographic and baseline clinical characteristics of the participants
Demographic and baseline clinical characteristics of the participants
*p < 0.05, p1: Independent-samples t-test. ODI: Oswestry Disability Index, 30 s STS: 30-second sit-to-stand test, UST: Unilateral stance test, EO: Eyes open, EC: Eyes closed. Data values were presented as mean (standard deviation) for continuous variables, and count (n) and percentage (%) for categorical variables.
Compared to baseline, there were significant improvements in all outcome measures (p < 0.05) except for the UST-EO right and left (p > 0.05) in the stabilization exercises group (Table 2). Also, all outcome measures, except for the UST-EO right and left, UST-EC right and left, and left/right bridge test, improved in the conventional exercises group (p < 0.05) (Table 2).
Clinical characteristics at sixth week and the change from baseline to the sixth week
*p < 0.05, p2: Paired sample t-test for stabilization exercises group, p3: Paired sample t-test for conventional exercises, p4: ANOVA on the change scores. ODI: Oswestry Disability Index, 30 s STS: 30-second sit-to-stand test, UST: Unilateral stance test, EO: Eyes open, EC: Eyes closed. Data values were presented as mean (standard deviation) for clinical characteristics at sixth week, and mean (standard eror) for the change from baseline to the sixth week.
The analysis of gain scores revealed that stabilization exercises were superior to conventional exercises in pain during activity, right/left bridge test, Sorensen test, trunk flexor endurance test, and 30-second sit-to-stand test (p < 0.05) (Table 2).
The current study aimed to investigate the effects of stabilization exercises by using core stability tests that focus on all aspects of core stability in patients with NSLBP comparing with conventional exercises. The results have shown that both exercise modalities reduced pain and disability and improved most of the core stability parameters. However, stabilization exercises are more effective in reducing pain during activity and improving core stability parameters regarding functionality and endurance than conventional exercises.
Since LBP has been reported to be the leading cause of general disability and work loss, especially in the working-age population, the optimal management of this disorder has been frequently investigated [1–3]. Stabilization exercises are increasingly being popular to be an effective approach to reduce pain and disability [7, 8]. A systematic review published in 2014 has suggested that there is strong evidence that stabilization exercises are not more effective in reducing pain and disability than other active exercises in the long-term follow up of patients with LBP [22]. In contrast, another systematic review published in 2017 has suggested that segmental stabilization exercises may be more effective than conventional exercises for pain reduction and improvement in disability in patients with LBP [8]. The result mentioned previously is consistent with our result suggesting that although both exercises are effective in reducing pain and disability, stabilization exercises are more effective in reducing pain during activity. However, there were no differences in pain at rest between both exercises in the current study. It has been suggested that individuals with LBP have decreased and delayed deep core muscle activation during different types of movement involving walking, upper and lower limb movements, also decreased recruitment of deep core muscles during isometric leg tasks [23–26]. It has been suggested that stabilization exercises improve the activity of deep core muscles [27, 28]. Also, our results showed that stabilization exercises are more effective in improving functionality parameter of the core stability, which was assessed by the 30-second sit-to-stand test, than conventional exercises. The 30-second sit-to-stand test has been suggested to be related to pain during activity in individuals with LBP [11]. The superiority of stabilization exercises in improving the function of the deep core muscles may explain that it is more effective in reducing pain during activity. Besides, it has been suggested that there is a significantly reduced deep core muscle activation in patients with LBP compared to asymptomatic controls in unstable conditions, in contrast to static positions [29]. The result mentioned previously supports that stabilization exercises are more effective than conventional exercises in reducing pain during activity, not in reducing pain at rest, because it increases the function of core muscles.
The assessment of the core stability has been used to be an important outcome measure due to the increasingly emphasized role of core muscles in providing segmental stabilization. Several studies have reported that stabilization exercises improve core stability in pateints with LBP; however, only the core endurance or lumbopelvic functional tests were used to assess core stability in these studies [13–15, 31]. Javadian et al. showed that routine exercise plus stabilizing exercises is more effective in improving pain, disability and flexor, extensor and lateral flexor muscles endurance than routine exercise only in patients with lumbar segmental instability [13]. Shamsi et al. reported that both core stability and traditional trunk exercises reduce pain and disability and improve lumbopelvic function, but there are no statistically significant differences between both exercises in patients with chronic LBP [14]. Further, Shamsi et al. showed that core stability exercise is not more effective than general exercise for improving trunk flexor, extensor and lateral flexor endurance and reducing disability and pain in patients with chronic NSLBP [15].
The multifactorial functions of the core muscles involve not only endurance or functionality but also parameters such as strength, flexibility and motor control [9, 12]. In the evidence-based literature, clinical tests that focus on all aspects of core stability have existed and these tests have been found to be highly reliable [11, 12]. In the current study, we used a core stability assessment battery that focuses on all aspects of the core stability and has been previously found to be highly reliable, founding that stabilization exercises are more effective in improving core stability parameters regarding functionality and endurance than conventional exercises. Further, stabilization exercises improved the UST-EC right and left, which assesses the motor control parameter of the core stability, but conventional exercises did not improve it. The result that stabilization exercises were found to be more effective in increasing trunk endurance might be associated with motor control improvement. Better trunk endurance has been associated with better postural stability in previous studies [32, 33].
Some previous studies have investigated the effects of different exercise modalities on the function of core muscles by assessing the cross-sectional thickness and electromyography activity of the related muscles [28, 34]. Laboratory methods such as ultrasound and electromyography provide objective data. However, there is also a need for simple, low-cost, easy-to-use and reliable assessment batteries to use in the research and clinical practice settings. Hence, the core stability assessment battery which was used in our study, whose parameters have been previously found to be highly reliable, can be used by clinicians and researchers to assess the effects of therapeutic interventions on all components of core stability.
Limitations
There are several limitations that need to be addressed. The main limitation of the study is the absence of any follow-up. Future research is needed to determine the effects of stabilization exercises on pain, disability and core stability in the long-term compared to conventional exercises. Secondly, the stabilization exercises group had more disability compared to the conventional exercises group at baseline, which was the result of our simple randomization method applied using an online Research Randomizer Program. Thirdly, as we stated in the interventions section, a home exercise program was not recommended and all participants exercised only three days a week under the physiotherapist’s supervision. However, we did not collect data regarding the type or level of physical activity at home or at work. Also, we included patients having LBP lasting longer than three months (chronic), but we did not conclusively register how long participants have been experiencing pain. Further, although most guidelines have recommended the exercise for LBP, a multidisciplinary approach including exercise was recommended in the recent studies [6, 35]. Our study may be a reference to the type of exercise which has been recommended in the clinical setting.
Conclusion
The results have shown that both stabilization exercises and conventional exercises reduced pain and disability and improved most of the core stability parameters in the patients with NSLBP. However, stabilization exercises were more effective in reducing pain during activity and improving core stability parameters regarding functionality and endurance compared to conventional exercises. Since LBP stands out as the leading cause of work loss, especially in the working-age population, the results of the study may be useful to improve work performance in workers with LBP. Further, the core stability assessment battery, whose parameters have been previously found to be highly reliable in the patients with NSLBP, can be used by the clinicians and researchers to assess the effects of therapeutic interventions on all components of core stability.
Conflict of interest
None to report.