Physical Therapy Korea

Kyphosis refers to excessive backward protrusion of the spine, and is caused by structural deformation of the spine itself or a reduction of joint movement caused by incorrect postural habits, rather than spinal diseases such as Scheuermann disease [1]. In cases with both structural and postural alignment problems, posture correction may be only partially successful, and postural errors may lead to the progression of kyphosis to structural injury. Structural changes, such as degenerative changes of the joints and kyphosis, restrict movement of the spine [2]. Each spinal vertebra has a 3.8° bony slope from back to front, forming a natural spinal curve of about 20°–40° degrees [3]. The normal thoracic kyphosis angle is < 40° [4]. When this angle is > 40°, it is diagnosed as thoracic kyphosis [5]. When the angle is > 60°, this deformity will cause extensive and persistent back pain or intercostal neuralgia, and even paralysis, and thus requires clinical treatment [6].

The thoracic kyphosis posture has a significant influence on the entire body, and an incorrect posture can lead to structural deformation of the spine. Long-term thoracic kyphosis causes narrowing of the intervertebral spaces between the thoracic vertebrae, and can affect breathing. Eventually, the heart will be compressed and unable to provide enough blood to supply oxygen to the body, and heart disease will slowly occur [7]. Collapse of the thoracic cavity will cause an abnormal breathing pattern, with shallow uneven breathing, a decrease in vital capacity, and pulmonary hypofunction [8]. In addition, people with kyphosis have an increased risk of vertebral osteoporosis and vertebral compression fractures [9,10]. Excessive kyphosis increases biomechanical pressure on the spine, which increases the risk of vertebral compression fractures. With increased age, these factors may lead to irreversible degeneration of the spine. Poor posture, with a reduction in the extension capacity of the spine, protrusion of intervertebral discs, and reduced strength of the extensor dorsalis [11] are potential causes of back pain and disability [12], and a decline in quality of life [13].

Kyphosis is affected by weight load and movement; greater rigidity of the thoracic vertebrae leads to improper posture control of the lumbar and cervical vertebrae, which in turn leads to compensatory behavior [14]. These factors accelerate the process of spinal degeneration, induce pain, and lead to severe pressure and tension on bones, joints, ligaments and muscles, thus weakening and elongating the muscles supporting the spine [15]. The normal sagittal alignment changes, which may lead to pain and dysfunction in the shoulders, pelvic girdle, and cervical [16], thoracic, and lumbar vertebrae [17]. This reduces normal movement [18]; individuals with kyphosis walk slowly and show decreased balance ability, which increases the risk of falls in middle-aged and elderly people [19], leads to complications such as fractures, and increases mortality [10].

The focus of most therapeutic exercises is to promote functional adaptation of dysfunctional muscles and improve muscle strength, flexibility, endurance, coordination, and spinal alignment. A spinal extension and intensive rehabilitation program reduced the symptoms and pain of kyphosis, and improved function [20]. During the training process, tension between the intervertebral discs and surrounding tissues can be reduced, the strength and endurance of the extensor dorsalis can be improved, and breathing capacity can be increased by extending the spine. To correct kyphosis, studies have usually been limited to strengthening exercises of the chest muscles. Kang et al. [21] proposed that correction of kyphosis should include not only extension of the chest muscles, but also strengthening of the muscles around the scapulae. This study aimed to demonstrate the effect of a spine extension device on the degree of thoracic kyphosis and extension angles, confirm reduction of the kyphosis angle and an increase in flexibility (i.e., spinal extension).

1. Participants

Thirteen subjects were recruited by convenience sampling. In this study, the subjects participated in the experiment every day for a week. All subjects provided informed consent before participation. People with neurological diseases, spinal surgery or spondylitis, abnormal sensation or motor ability, or difficulties in daily activities were excluded. The general characteristics of the participants are shown in Table 1. Ethics approval was granted by Inje University Ethics Committee for Human Investigations (IRB no. 2020-07-016-001), and informed consent was obtained from all participants.

Table 1 . General characteristics of research object (N=13).

Variable	Male = 5, Female = 8
Age (y)	22.3 ± 2.37
Height (cm)	161.3 ± 5.34
Weight (kg)	52.4 ± 4.16

Values are presented as mean ± standard deviation..

2. Equipment

A dual inclinometer is used to measure joint range of motion and spinal curvature, and is easy to operate and accurate. By comparing measurements obtained using a digital dual inclinometer with those of radiographs, the digital dual inclinometer was shown to be effective for measuring the angle of kyphosis [22]; it also has the advantage of reducing error and improving efficiency through automatic measurement [23]. In this study, an Acumar Dual Inclinometer (Lafayette Instrument Co., Lafayette, IN, USA) was used to compare the thoracic kyphosis angles and thoracic extension angle of participants before and after use of a spine extension device (Figure 1). The subjects stood with their legs shoulder width apart in a natural position, and looked straight ahead. The angle between the spinous processes of the first and 12th thoracic vertebrae was measured three times.

Figure 1. Dual inclinometer was used to compare the thoracic kyphosis angles.

In this study, we used the automatic spine extension machine (HEALTH U; J-WELL co., Ltd., Gimhae, Korea), which moves up and down with the upper and lower parts separated. It is designed to extend the spine downward, extend the muscles around the spine, and induce the extension of the thoracic spine (Figure 2).

Figure 2. The automatic spine extension machine (HEALTH U; J-WELL co., Ltd., Gimhae, Korea), which moves up and down with the upper and lower parts separated.

3. Experimental Method

The process of using the spine extension device was demonstrated to the subjects before the study. The experiment was performed for 15 minutes per day for seven days. The detailed method is as follows: the subject lay flat on the bed in a relaxed position with a towel used to keep them comfortable. The lower limbs were fixed, the arms were raised above the head, and the hands grasped the poles on the bed. The spine extension program can be adjusted from 10°–30°; of the five available angles in this range, the third one (20°) was used in this study. The total time spent on the bed was 15 minutes; during the exercise, the extension and contracting process was repeated slowly with the maximum extent reached two minutes before the end of the 15-minute period.

4. Statistical Analysis

SPSS Statistics for Windows (version 18.0; IBM Co., Armonk, NY, USA) was used for the statistical analysis. The Wilcoxon signed-rank test was used to analyze the data, and changes of thoracic kyphosis angle and thoracic kyphosis angle of thoracic extending before and after the experiment were compared. The level of statistical significance was set at p < 0.05.

In this study of 13 adults, the differences of thoracic kyphosis angles before and after using a spine extension device were compared. In the static position, the thoracic kyphosis angle before using the spine extension device was 25.9 ± 8.17°, while it was 21.3 ± 9.12° after using the bed (p = 0.046) (Table 2). The thoracic kyphosis angle when thoracic extending before using the spine extension device was 15.5 ± 9.84°, while it was 8.5 ± 10.48° after using the bed (p = 0.033) (Table 3).

Table 2 . Comparison of thoracic kyphosis angle before and after exercise (N=13).

	Before exercise	After exercise	p-value
Angle (°)	25.9 ± 8.2	21.3 ± 9.1	0.046

Values are presented as mean ± standard deviation..

Table 3 . Comparison of thoracic kyphosis angle when thoracic extending before and after exercise (N=13).

	Before exercise	After exercise	p-value
Angle (°)	15.5 ± 9.8	8.5 ± 10.5	0.033

Values are presented as mean ± standard deviation..

In this study of 13 adults in their 20s, the ability of a spine extension device to correct the angle of kyphosis was analyzed. The study took place over seven days and the daily sessions were 10 minutes in duration. The results showed that the angle of kyphosis of the spine was significantly reduced, and the thoracic kyphosis angle when thoracic extending was significantly improved, after using the spine extension device (all, p < 0.05). The kyphosis angle of the thoracic vertebrae improved by about 20%, and the extension range of the thoracic increased by about 45%. The results indicate that the use of a spine extension device promotes improvement of a thoracic kyphotic posture. While on the spine extension device, the extension angle starts low, and gradually increases to avoid stress on spinal extension. In addition, the spine extension device leans backward, and the gravity generated by the subject’s own weight helps to induce the spinal extension movement and ensure a slow and stable process. The subject puts their hands above their head, which leads to expansion of the thorax and greater extension of the thoracic spine.

Currently, spinal traction correction methods tend to involve only extension of the spinal muscles upwards and downwards, within a limited range. In a previous exercise program aiming to correct a kyphotic posture, the mobility of the back and spinal extension were targeted, and raising both hands above the head together was advocated. The degree of kyphosis of the thoracic cavity was reduced compared with the control group after extension the spine [24]. In a study of the effect of using an elastic band on the range of motion, posture correction, and functional motion of the spine when using a spinal stretcher, the group using an elastic band to lift the arms achieved remarkable results in terms of correcting kyphosis of the lumbar spine [25]. Regarding spinal mobility, back and waist flexion increased, as did extension mobility, and there was a positive impact on the alignment of the cervical vertebrae and upper body, as well as pelvic tilt. Another study reported that, after a spinal extension exercise program, the degree of kyphosis decreased, shoulder and neck function increased, flexibility of the spine increased, the chest muscles relaxed, chest expansion increased, and shoulder and neck pain decreased. Spinal extension helps to strengthen the extension and flexor muscles of the spine and waist, and also improves the symptoms of kyphosis [26]. Compared with a control group without exercise, a group that performed sports to increase the spine extension and flexibility achieved positive outcomes in terms of pain relief, reduced kyphosis, greater flexibility, and increased spine extension and length. When the length of the spine (C7–S3 vertebrae) increases, the chest expands; the higher the hands are lifted above the head, the more kyphosis improvement and chest expansion occur [27]. Based on these results, in this study the spine extension device was used with the arms raised above the head.

Song et al. [14] conducted a study of 30 patients with thoracic kyphosis, randomly divided into experimental and control groups. The results showed that compared with the control group, the thoracic kyphosis angle and “front head posture” (cranial vertebral and rotation angles) of the experimental group were significantly improved and hunchback was reduced. Their method could be used to treat patients with thoracic vertebral misalignment. The above research, among other studies on the muscle system involved in kyphosis, are in accordance with the results that we obtained using the spine extension device. When using a spine extension device, the shortened pectoralis major, pectoralis minor, superior trapezius, and anterior serratus muscles are completely stretched and relaxed. The mid- and lower trapezius muscles, which were only weakly stretched previously, are strengthened by participation in passive extension of the upper limbs and spine.

There were some limitations to this study: First; it only included healthy adults, most of the subjects had a normal kyphosis angle, as opposed to kyphosis. Second; as there were only 13 subjects, the data are insufficient to draw definitive conclusions. Third; the study was performed over seven days, and there was no follow-up. To induce changes in spinal bones, a longer exercise program would be required. Fourth; no restrictions were imposed on activities of daily living, which may have affected study results.

To improve the generalizability of our results, a longer treatment time would be required, along with consideration of personal characteristics such as height, weight, and the degree of kyphosis, as well as inclusion of subjects of different ages. Through analysis of spinal muscle and tensile strength on an individual basis, the effect of exercise could be improved and secondary injuries prevented. Future studies of kyphosis could combine extension exercises with the raising of the arms above the head, among other movements, to expand the treatment options. In addition, we propose the need for further research with the control group and randomized controlled trial research.

In this study, the thoracic kyphosis angle and thoracic extension angle of the subjects before and after using spine extension device were compared and analyzed, which proved that the spine muscle extension program can effectively improve the mobility of thoracic spine posture and extension angle. It is suggested that future related research should include patients with kyphosis in a wider age range to strengthen the accuracy of the current experiment.

None.

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. NRF-2020R1F1A1049191).

No potential conflict of interest relevant to this article was reported.

Conceptualization: WY. Data curation: JK, SP, HS, HC. Formal analysis: WY. Funding acquisition: WY. Investigation: JK, SP, HS, HC. Methodology: WY. Project administration: WY. Resources: WY. Software: WY. Supervision: WY. Validation: WY. Visualization: WY. Writing - original draft: YL, WY. Writing - review & editing: WY.