INTRODUCTION
Scoliosis is a disease in which the spine deviates or rotates laterally from its normal vertical line, and it can cause decreased spinal movement, weakening of muscles near the spine, reduced pulmonary function, respiratory dysfunction, chronic pain, and psychological suffering (Asher and Burton, 2006; Weinstein et al., 2003). Scoliosis can be classified as idiopathic, congenital, neurofibromatosis, and neuromuscular. Among these types of scoliosis, approximately 80% of patients with scoliosis have adolescent idiopathic scoliosis (AIS), which typically occurs around 10 years of age when healthy bone maturation occurs during adolescence. Idiopathic scoliosis (IS) is diagnosed when there are no known causes besides spinal deformity involving a lateral curvature with a Cobb angle ≥10° (Wick et al., 2009). In other words, because IS does not show specific symptoms, early diagnosis is often difficult; however, early detection and treatment are important since it is easy to miss the proper treatment window (Weinstein, 1989).
Treatment guidelines for IS are determined based on age, residual growth, size and condition of the curvature, and underlying diseases. In particular, there is a high probability of incurvation of the spine being progressive in adolescents; therefore, aggressive, early treatment may be able prevent further spinal deformity to a certain degree. However, if the proper treatment period is missed, cardiopulmonary dysfunction may be caused by severe curvature of the spine (Banjar, 2003). Therapeutic approaches for IS include surgical and conservative treatments. Surgical treatment is considered when the Cobb angle is ≥40°, whereas conservative treatment typically involves wearing assistive devices, spinal adjustment therapy, and exercise therapy (Carman et al., 1985; Falk et al., 2015; Maruyama et al., 2011).
Exercise therapy for IS is considered important for maintaining spinal function when the Cobb angle is <20°. In particular, because changes in trunk muscle strength because of IS can lead to postural imbalance, improving IS has been suggested to be important (Mcintire et al., 2007; Mooney et al., 2000). Accordingly, extension exercise for shortened muscles and resistance exercise for strengthening the muscles near the spine have been reported to be effective for IS (Negrini et al., 2003). In other words, the effects of exercise therapy for IS can be attributed to spine stabilization for muscle imbalance that occurs from asymmetric posture in the trunk.
Moreover, the effects of core stabilization exercise have been demonstrated recently for alleviating chronic lower back pain in patients, improving performance in athletes, and preventing sports injuries in athletes (Akuthota et al., 2008; Hodges, 2003; Huxel Bliven and Anderson, 2013; Kibler et al., 2006). Core stabilization exercise has been suggested as effective for increasing lumbar stability by enhancing cooperation between cocontraction of extensor and flexor muscles and neuromuscular control function (Barr et al., 2005). Based on this information, core stabilization exercise may be used effectively to increase lumbar muscle strength and improve neuromuscular imbalance, which are the causes of IS.
However, studies on the therapeutic effects of using core stabilization exercise in patients with AIS are still lacking. Accordingly, the objective of the present study was to identify the effects of core stabilization exercise on the Cobb angle and lumbar muscle strength of patients with AIS.
MATERIALS AND METHODS
Subjects
Subjects in the present study consisted of primary school students who were confirmed to have scoliosis on a radiologic examination performed during their visit to the National Fitness Center in Seoul, Korea. An orthopedic specialist made the diagnosis based on a Cobb angle ≥10°. Among the primary school students who were diagnosed as having scoliosis, those with a Cobb angle ≥20° were excluded; as a result, 29 primary school students with a Cobb angle 10°–20° who received treatments for scoliosis for the past 6 months participated in the study. Depending on whether they participated in a 12-week core stabilization exercise program, subjects were divided into the exercise (n=14) or control (n=15) group. An explanation of the study procedures was given to all participants, and subsequently, the voluntary decision to participate from the students and informed consent from their parents were received. Physical characteristics of the subjects are shown in Table 1.
Measurement items and methods
All tests were performed in the Sports Medicine Lab of the National Fitness Center. After measuring subjects’ height and weight using a scale (Jenix, Seoul, Korea), the Cobb angle, flexibility, and lumbar muscle strength tests were performed, as explained in the following.
Cobb angle test
The Cobb angle test was performed by an orthopedic specialist by measuring the thoracic and lumbar Cobb angles on anterior and posterior spine radiographs taken in standing position. The Cobb angle was measured as the vertically intersecting angle after determining the vertebrae above the apex and below the apex, which are the most tilted from the concave side of the curvature of the spine (Deacon et al., 1984).
Flexibility test
The flexibility test was performed by having subjects bend their upper body forward. After performing sufficient stretching before the flexibility test, subjects sat on an examination table and bent their upper body forward as much as possible with their legs fully extended. This motion was performed and measured twice, and the maximum value from the two measurements was recorded.
Lumbar muscle strength test
The lumbar muscle strength test was performed using the Biodex 3.0 (Biodex Medical Systems, Shirley, NY, USA), an isokinetic muscle strength analyzer, to measure the muscle strength involved in lumbar flexion and extension. Before the lumbar muscle strength test, subjects were given 10 min for the stretching and warm-up exercise, and the actual test was performed after they were familiar with the lumbar flexion and extension test method. Lumbar flexor and extensor muscles were measured five times at 30°/sec, and the maximum value from the five measurements was recorded.
Core stabilization exercise program
The exercise group participated in the spine stabilization exercise program, which consisted of three 60-min sessions per week for 12 weeks. Each exercise session consisted of a 10-min warm-up exercise, 40-min core stabilization exercise, and 10-min cool-down exercise. The warm-up and cool-down exercise were comprised of 10 min of stretching and breathing exercises. The core stabilization exercise was designed with consideration of spinal adjustment and strengthening of the abdominal and lumbar muscles. All exercises were performed with supervision to ensure all exercise motions were performed accurately.
The core stabilization exercise program included pelvic tilt, cat-camel pose (back raises), basic trunk curl (crunch), bridge (with knee extension), double-leg abdominal press, supermans, arm/leg raises, quadruped arm/leg raises, and hand walkouts. Each type of exercise was performed in 3 sets of 12 repetitions. The rating of perceived exertion was used to set the exercise intensity to somewhat difficult.
Statistical analysis
SAS (version, 9.1; SAS Institute, Cary, NC, USA) was used calculate the mean and standard deviation values for data processing in the present study. To determine inter-group mean differences, repeated-measure two-way analysis of variance was used to analyze the main and interaction effects. The significance level (α) was set to P<0.05.
RESULTS
Changes in thoracic and lumbar Cobb angles
As shown in Table 2, the thoracic Cobb angle did not have any interaction effects between groups and treatments. The lumbar Cobb angle had interaction effects between groups and treatments (P<0.001). Post hoc test results indicated that the exercise group had a significant decrease in the thoracic and lumbar Cobb angles from pre-exercise to postexercise (P<0.01), whereas the control group did not have a significant difference in the thoracic and lumbar Cobb angles between these periods.
Changes in flexibility and lumbar muscle strength
As shown in Table 3, flexibility had significant interaction effects between groups and treatments (P<0.001). Post hoc test results indicated that the exercise group had a significant increase in flexibility and lumbar muscle strength from pre-exercise to postexercise (P<0.001), whereas the control group had a significant decrease in flexibility and lumbar muscle strength between these periods (P<0.01).
Lumbar flexion muscles had interaction effects between groups and treatments (P<0.001). Post hoc test results indicated that the exercise group had a significant increase in lumbar flexion from pre-exercise to postexercise (P<0.01), whereas the control group did not have a significant difference in lumbar flexion between these periods.
Lumbar extension muscles had interaction effects between groups and treatments (P<0.01). Post hoc test results indicated that the exercise group had a significant increase in lumbar extension from pre-exercise to postexercise (P<0.001), whereas the control group did not show a significant difference in lumbar extension between these periods.
DISCUSSION
Results of the present study showed that in the exercise group, the lumbar Cobb angle decreased, whereas flexibility and lumbar muscle strength increased.
IS refers to a disease with a Cobb angle ≥10° that involves three-dimensional deformation, including deformation in the coronal, sagittal, and axial planes, and it occurs mostly during adolescence, which represents a growth period before and after the age of 10 years (Reamy and Slakey, 2001). If the proper treatment period for IS is missed, cardiopulmonary dysfunction may occur from severe curvature of the spine, which can also have a negative impact on patients’ quality of life due to psychological and social issues (Dirocco and Vaccaro, 1988; Freidel et al., 2002). Improving the Cobb angle is key to treating IS, and in patients with progressive deformation, it is necessary to implement measures that can prevent exacerbation of the condition (Hresko, 2013). Accordingly, exercise, wearing assistive devices, and surgical therapy are being studied as alternatives for treating IS. Exercise therapy is effective in relatively mild cases with a Cobb angle ranging between 10° and 20° (Weiss et al., 2006).
According to a recent study, the importance of biomechanical functions of core muscles is being emphasized for their ability to stabilize the spine in terms of cooperation between deep and surface muscles (Hibbs et al., 2008). Accordingly, core stabilization exercise is effective for controlling one’s movements to maintain a neutral position of the spine, which is why it is widely used for patients with lower back pain, athletes, and healthy people (Barr et al., 2005). Results in the present study showed a decrease in the thoracic Cobb angle after core stabilization exercise, but the differences were not significant. However, the lumbar Cobb angle did significantly decrease. Similar to the present study, Gür et al. (2016) reported that a 10-week core stabilization exercise program decreased thoracic and lumbar Cobb angles in primary school students with scoliosis. Park et al. (2016) also reported that a 10-week core stabilization exercise program for college students with scoliosis decreased their Cobb angle. Other precedent studies also reported that core stabilization exercise alleviated thoracic kyphosis and lumbar lordosis in the sagittal plane of the spine and effectively improved spinal alignment (Hirano et al., 2012; Katzman et al., 2007). Therefore, core stabilization exercise can be viewed as a useful treatment modality for reducing the Cobb angle in patients with AIS.
Moreover, IS can induce changes in muscles near the spine, and in particular, weakening of the lumbar muscle strength can cause spinal instability. Consequently, it is important to provide stability to the spine while increasing lumbar muscle strength. Regarding core stabilization exercise, cooperative contraction of lumbar flexion and extension muscles plays an important role in spinal stability (Akuthota and Nadler, 2004; Lederman, 2010). Results of the present study showed that flexibility, and lumbar flexion and extension muscle strength increased significantly after core stabilization exercise. These findings are consistent with the results of precedent studies that reported that lumbar stabilization exercise increases lumbar and truncal muscle strength in patients with lower back pain (Moon et al., 2013; Yílmaz et al., 2003). As our results indicated, core stabilization exercise is effective for improving lumbar range of motion and muscle strength in patients with IS. This can be attributed to the fact that core stabilization exercise plays a role in enhancing muscle functions from co-contraction of deep muscles and cooperation of surface muscles.
Consequently, core stabilization exercise can be considered to have a positive effect on the normal physiological curvature of the spine in patients with AIS, as it decreases the Cobb angle and strengthens lumbar muscles. Therefore, core stabilization exercise can be an effective treatment modality for patients with who have asymmetric spine alignment.
In conclusion, the present study’s results showed that in the exercise group, the lumbar Cobb angle decreased and lumbar muscle strength increased. Therefore, core stabilization exercise is an effective exercise for reducing the Cobb angle and improving lumbar muscle strength in patients with AIS.
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