Effect of core stabilization exercises on cervical sagittal balance parameters in patients with forward head posture: a randomized controlled trial in Egypt

Article information

Asian Spine J. 2025;19(1):85-93

Publication date (electronic) : 2025 January 20

doi : https://doi.org/10.31616/asj.2024.0328

Ahmed Mahmoud Mohamed Shabana, Abeer Farag Hanafy, Ahmad Salamah Yamany, Reda Sayed Ashour

Department of Biomechanics, Faculty of Physical Therapy, Cairo University, Giza, Egypt

Corresponding author: Ahmed Mahmoud Mohamed Shabana, Demonstrator of Biomechanics, Faculty of Physical Therapy, Cairo University, 7 Ahmed El Zayat Street, Ben El-Sarayat, Ad Doqi, Al Giza, 11432 Egypt, Tel: +20-37617691, Fax: +20-37617692, E-mail: ahmedshabana300@cu.edu.eg

Received 2024 August 9; Revised 2024 October 6; Accepted 2024 November 1.

Abstract

Introduction

Forward head posture (FHP) is a poor habitual neck posture resulting from the prolonged inherence of a static awkward position [1]. It is associated with muscle imbalance and joint decentration, particularly at the atlanto-occipital joint, C4–C5 segment, glenohumeral joint, cervicothoracic joint, and T4–T5 segment [2]. FHP has been viewed as a cervical sagittal imbalance and is defined as an increase in C2–C7 sagittal vertical alignment (SVA). Lately, cervical sagittal vertical alignment (cSVA) has been found to be the most relevant parameter of cervical sagittal balance (CSB) in distinguishing symptomatic subjects from asymptomatic subjects [3].

Core stabilization exercises (CSEs) are frequently recommended for managing back pain. These exercises improve control over the lumbopelvic region, enhance mobility, and reduce back pain, each with a unique rationale for their efficacy [4].

Because lumbopelvic alignment is strongly related to FHP, improving control over the lumbopelvic region may influence head posture [3]. Therefore, this study investigated the effects of 6-week CSEs on the cSVA, Cobb’s angle, and Neck Disability Index (NDI) score of patients with FHP.

Materials and Methods

Instrumentation

X-ray Imaging System and ImageJ

A GE HealthCare radiography system (GE HealthCare, Chicago, IL, USA) was used to obtain lateral-view images of the patients’ cervical spine before and after training (Fig. 1). These images were analyzed using ImageJ (National Institutes of Health, Bethesda, MD, USA) to measure the CSB parameters because they demonstrated acceptable high test–retest reliability [7].

Fig. 1

Measuring the cervical sagittal parameters. (A) The GE Healthcare–Radiography System, (B) lateral photographing position, (C) Cobb’s angle, and (D) the cervical sagittal vertical alignment.

The assessed CSB included the cSVA and Cobb’s angle. Cobb’s angle is the intersection angle that lies between the line perpendicular to the line parallel to the lower endplate of C2 and the line perpendicular to the line parallel to the lower endplate of C7 (Fig. 1C). The cSVA was determined by measuring the horizontal distance between the plumb line drawn from the C2 centroid and the C7 posterosuperior corner (Fig. 1D).

NDI

The NDI was used to measure self-rated impairment in individuals with neck pain [8]. It has 10 sections with six items. Each section had a maximum score of 5, with the first box receiving “0” and the last box receiving “5.” The sum of all section scores is then computed. The score is stated on a scale of 0–50, with (0) being the best possible result and (50) being the worst.

Digital camera and Kinovea

A Canon Power Shot A 490, 3.3 optical zoom, 10-megapixel camera (Canon, Tokyo, Japan) was used to take lateral photographs to objectively measure the CVA in patients with FHP (Fig. 2A) [9]. The images were analyzed using Kinovea (https://www.kinovea.org/). Kinovea is valid and reliable software for obtaining angle and distance data from coordinates [10]. The CVA is the angle between a horizontal line passing across C7 and a line passing from C7 to the tragus of the ear (Fig. 2B).

Fig. 2

Measuring the craniovertebral angle. (A) A Canon Power Shot A 490, 3.3 optical zoom, 10 mega pixels camera. (B) The craniovertebral angle.

PALM pelvic inclinometer

A caliper–inclinometer instrument (Performance Attainment Associates, Saint Paul, MN, USA) was used to measure the pelvic angle (Fig. 3). The intratester and intertester reliability of the PALM in measuring pelvic position were very good (0, 89) to excellent (0, 98) [11].

Fig. 3

The PALM inclinometer with bubble inclinometer and two caliper arms.

Procedures

This study involved a pretest–posttest control group design. Patients were assessed before and after 6 weeks of intervention [12]. The outcome measures were cSVA, Cobb’s angle, and NDI score. The procedure included three phases: pre-training, training, and post-training.

Pre-training phase

The study aims, equipment, and procedures were explained to the patients. The patients provided informed consent for participation. Pelvic alignment and CVA angle were assessed. Finally, each patient was randomly assigned to one of the two aforementioned groups.

The patients were instructed to rate their degree of neck impairment using the NDI. Cervical X-ray images were obtained to measure the cSVA and Cobb’s angle. Finally, group (A) was instructed to follow the CSE and PCE programs, whereas group (B) was instructed to follow only the PCE program.

Training phase

CSE program

This study used the CSE program used by Akuthota et al. [4]. This program started with restoring normal muscle length and mobility through warm-up exercises, such as cat and camel stretching (Fig. 4A, B), and a brief aerobic program of 10 repetitions for two sets. The next phase included the following exercises:

Fig. 4

Core stabilization exercise program: cat stretch (A), camel stretch (B), abdominal bracing (C), bracing with heel slide/starting position (D), bracing with heel slide/ending position (E), bracing with heel lift/starting position (F), bracing with heel lift/ending position (G), quadruped arm lifts with bracing (H), quadruped leg lifts with bracing (I), bracing with bridging (J), side plank exercise (K), quadruped posture with alternate arm and leg lifts (L), and curl-up exercise (M).

Abdominal bracing exercise: Patients contracted the abdominal muscle with deep diaphragmatic breathing for 8 seconds in 30 repetitions (Fig. 4C). Training was advanced once these activation techniques were mastered and the transversus abdominis was “awakened.”

Bracing with heel slide: The patients braced the abdomen with deep breathing and slid the heel for 30 repetitions for each heel (Fig. 4D, E).

Bracing with heel lift: Patients braced the abdomen with deep breathing and lifted the heel toward the abdomen for 8 seconds for 30 repetitions for each heel alternately (Fig. 4F, G).

Quadruped arm lifts with bracing: The patient assumed a quadruped position with abdominal bracing, deep breathing, and arm lift that was maintained for 8 seconds for 30 repetitions for each arm alternately (Fig. 4H).

Quadruped leg lifts with bracing: From the quadruped position, patients braced the abdomen with a leg lift for 8 seconds while taking a deep breath for 30 repetitions for each leg alternately (Fig. 4I).

Bracing with bridging: The patients were instructed to perform bridging with abdominal bracing, holding the position for 8 seconds while taking a deep breath for 30 repetitions (Fig. 4J).

Side plank with bracing: This entails keeping the body in a straight line on one side, with the elbow or hand supporting the upper body and the feet stacked or staggered. The side plank with abdominal bracing and deep breathing was maintained for 8 seconds for 30 repetitions on both sides (Fig. 4K).

Quadruped posture with alternate arm and leg lifts: Patients were instructed to assume a quadruped posture with alternate arm and leg lifts with abdominal bracing and deep breathing, holding for 8 seconds for 30 repetitions on both sides alternately (Fig. 4L).

Curl-up: Patients braced their abdomen with regular breathing before starting the curl-ups; the position was then held for 8 seconds for 30 repetitions (Fig. 4M). It only takes a half sit-up; thus, the hip flexors do not participate in the exercise.

PCE program

The program included strengthening exercises (deep cervical flexors and scapular retractors) and stretching of the cervical extensors (suboccipital muscles) and pectoral muscles.

Deep cervical flexor strengthening (chin-in exercise): From the supine position, patients were instructed to tuck their chin-in and down, holding the position for 8 seconds for 12 repetitions. After 2 weeks, if they could complete three sets of 12 repetitions correctly, they progressed to the chin tuck with head lift exercises. Patients were instructed to tuck their chin-in with a head lift and hold the position initially for 2 seconds and then for 4 seconds. They performed three sets of 12 repetitions for 2 weeks (Fig. 5A, B).

Fig. 5

The postural correctional exercise program: chin in exercise (A), chin tuck with head lift (B), shoulder retraction from standing with elastic band (C), chin drop stretching exercise (D), and pectoralis major muscle stretch by therapist (E).

Scapular retractors strengthening: From the standing position, the patients pinched the inferior angles of the scapula together and retracted them using an elastic band (Fig. 5C). These exercises were performed in three sets of 12 repetitions. Each repetition was performed with a 6-second hold of the two shoulder blades as closely as possible [13].

Cervical extensor stretching (chin drop stretching): The patients were seated to stretch the suboccipital muscles and then slowly nodded while tipping their heads toward their upper spine with hand assistance for 30 seconds for three repetitions (Fig. 5D).

Pectoralis major muscle stretch: The patient sat down with their hands behind their head, the shoulders were abducted and turned outward at 90°, and the arm was elevated to approximately 135° to stretch the costal division (Fig. 5E). At the limit of the range of motion, passive stretching was performed with a 30-second hold and a 2-minute rest period after each repetition. The exercise was performed 3 times in each session.

Post-training phase

The training program was applied 3 times per week for 6 weeks. Patients were reassessed for all parameters 6 weeks after training.

Results

General characteristics

Initially, the sample size was calculated based on the anticipated effect size and standard deviations reported in previous literature using G*Power (Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany; http://www.gpower.hhu.de/) (α=0.05, power=0.8, and effect size=0.5), resulting in 37 participants [14]. Fifty-one patients were assessed for eligibility (Fig. 6). Of the 51 patients, 11 were excluded because they did not meet the inclusion criteria. Forty patients were randomly allocated into two equal groups: groups (A) and (B). Four patients withdrew from the study, and the data of the 36 remaining patients who completed the study were analyzed. The statistical analysis of their demographic data revealed nonsignificant differences between the two groups (p>0.05) (Table 1).

Fig. 6

Flow diagram for patients’ enrollment.

Table 1

Demographic data and one-way multivariate analysis of variance tests for the two tested groups of patients with forward head posture

Data analysis

Mixed-Design MANOVA revealed significant within-subject effects (p=0.001, F=19.236) and nonsignificant between-subject effects for the dependent variables (p=0.345, F=1.179). Furthermore, a significant interaction was observed between the two independent variables: tested group and testing time for the dependent variables (p=0.001, F=9.819).

The pairwise comparisons revealed nonsignificant differences in the pre-training mean values of all measured variables between the two groups (p>0.05). Furthermore, nonsignificant differences in the post-training mean values of the cSVA and Cobb’s angle were observed between the two groups (p>0.05). However, a significant reduction in the mean post-training NDI value was detected in group (A) compared with those in group (B) (p<0.05).

Furthermore, the mean cSVA and NDI values exhibited significant reductions (p<0.05), whereas the mean values of Cobb’s angle exhibited nonsignificant changes (p>0.05) after training compared with those before training in group (A). However, group (B) demonstrated nonsignificant reductions in the post-training mean values of cSVA and Cobb’s angle (p>0.05), with a significant reduction in the mean NDI score (p<0.05) compared with pre-training values. Table 2 presents the results of the statistical analyses.

Table 2

Descriptive statistics and multiple pairwise comparison tests of the dependent variables in the experimental and control groups pre- and post-training

Discussion

The improvements observed in group (A) following the incorporation of CSEs into PCEs can be interpreted by the research of Norris [15]. This research indicated that CSEs improve neuromuscular system functionality, leading to better mobility in the lumbar–pelvic–hip chain, appropriate muscle balance, effective acceleration and deceleration, and proximal stability. Furthermore, the transversus abdominis (TA) muscle was reported to be recruited 15 ms before the initiation of upper-limb movement. The TA or lumbar multifidus muscles are also recruited during cervical stabilization exercises [14]. As stated by Akuthota et al. [4], abdominal hollowing exercises, which may engage the TA, and abdominal bracing exercises, which stimulate several muscles, including the TA and external and internal obliques, are crucial initial steps in developing the CSE program.

Our findings may be explained by the findings reported by Berthonnaud et al. [16], who proposed viewing the pelvis and spine in the sagittal plane as a continuous linear chain from the head to the pelvis [16]. In this model, the shape and orientation of each anatomical segment affect the neighboring segment to maintain a stable posture with minimal energy use. Moreover, higher correlations between shape and orientation characteristics are more likely to arise in the spine’s highly mobile parts, including the lumbar and cervical regions. The less mobile thoracic spine does not appear to adapt or compensate as readily to changes in the shape or orientation of the pelvic, lumbar, or cervical spine.

Furthermore, Yuk et al. [17] reported that the cSVA is the most commonly used parameter for analyzing global sagittal balance. They found a correlation between cervical cord compression and whole-spine sagittal malalignment. Their findings suggest a positive association between cervical cord compression and sagittal balancing measures. Thus, sagittal imbalance in individuals with lumbar diseases indicates a high risk of cervical stenosis, which leads to cervical myelopathy.

The findings of our study revealed a significant improvement in the cSVA in group (A) and a nonsignificant improvement in group (B) after training. This was not surprising because of the strong correlation between the cSVA and lumbopelvic parameters. Knott et al. [18] demonstrated that various factors affect an individual’s overall sagittal balance; however, the positions of the pelvis and lower spine have a greater impact on the cSVA than the positions of the upper back and neck.

Yuk et al. [17] revealed that the parameters predicting the Cervical Cord Compression Index were the cSVA and C7–S1 SVA (a global spinal sagittal balance parameter). The C7–S1 SVA is the horizontal distance between the posterior superior corner of the sacrum and the plumb line descending from the center of C7. In contrast, a retrospective observational study of cervical radiographic analysis of 111 asymptomatic adolescents reported no correlation between the lumbosacral and cervical regional sagittal alignment parameters [19]. However, the authors did not examine the correlation between lumbosacral parameters and cSVA.

The post-training improvement in NDI values in both groups may be explained by the relationship between the neuroforaminal areas and CSB parameters. The neuroforaminal areas exhibited an inverse relationship with the T1 slope angle (T1S). T1S is the angle formed by a horizontal line and the superior endplate of the T1 vertebral body. As the T1S increased (>25°) (simulating upper thoracic hyperkyphosis and thus FHP), the neuroforaminal area decreased due to cervical extension. Therefore, these patients often experience coexisting nerve root compression symptoms [3].

During hyperkyphosis (increased T1S), the neural foraminal area narrows to its maximum. T1S reduction causes segmental flexion of C2–C7 segments, resulting in a gradual increase in the foraminal area at all mid-to-lower cervical segments, thereby reducing nerve root compression symptoms and cervical radiculopathy.

Furthermore, alterations in global sagittal alignment were reported to be closely associated with poor health-related quality of life. Furthermore, cervical spine malalignment in the sagittal plane is associated with headaches, neck pain, and poor health-related quality of life [20]. Thus, the considerable improvements in NDI scores in group (A) compared with those in group (B) may be attributed to greater global and regional sagittal alignment.

Prolonged contraction of the suboccipital muscles can cause painful trigger points that are responsible for neck pain associated with FHP [3]. Excessive contraction of these muscles may strain the pain-sensitive dura mater through myoneural bridges, resulting in neck pain and cervicogenic headache [21]. According to Patwardhan et al. [3], chin-in exercises can reduce anterior head offset (C0–C7 SVA), stretch the suboccipital muscles, and decrease occipito-atlanto-axial hyperextension [3]. Furthermore, Lee et al. [22] reported that these exercises activate the underactive longus colli and deactivate the hyperactive sternocleidomastoid. Considering the previous interactions, NDI scores were significantly improved after training.

Our findings revealed nonsignificant improvement in Cobb’s angle in both groups after training compared with pre-training scores. However, the descriptive statistics exhibited reductions in the mean post-training values in both groups. These findings were consistent with those of Alijani and Rasoulian [20], who demonstrated no association between Cobb’s angle and spinopelvic characteristics.

A literature review revealed that this study may be one of the few practical studies to clinically investigate the relationship between the cervico-thoraco-lumbo-pelvic chain. Buyukturan et al. [14] proved that cervical stability training was beneficial to individuals with cervical disk herniation. However, the inclusion of core stabilization training provided no further substantial benefit. This may be due to differences in the applied CSE program. The program by Buyukturan [14] did not emphasize the “big three” exercises mentioned by McGill [23], which are essential components of the CSE program used in this study. Furthermore, the number of repetitions per set was lower (only 7–10 repetitions) than that applied in this study (30 repetitions).

From a surgical perspective, individuals with preoperative cervical sagittal translation experience more axial neck pain postoperatively; however, another study discovered that preoperative cervical sagittal imbalance was associated with significantly worse functional results following cervical fusion [24]. In individuals with a clinical diagnosis of cervical spondylotic myelopathy, there was a strong correlation between the modified Japanese Orthopedic Association scores and cSVA. In patients with multilevel posterior cervical fusions, the cSVA was observed to be positively correlated with NDI scores. The same study reported that considering the strong association between cervical sagittal malalignment and quality of life outcomes, a cSVA of 40 mm may constitute an upper limit, with values over this upper limit causing clinical concern [24]. Furthermore, laminoplasty has been demonstrated to worsen health-related quality of life scores by increasing cervical kyphosis and cSVA. Regarding cervical lordosis measured using Cobb’s angle, restoration of cervical lordosis has traditionally been the aim after surgery; however, studies have not shown any significant associations between postoperative cervical lordosis and functional outcome measures, such as pain and NDI [25]. Furthermore, a clear correlation was observed between worse postoperative functional outcomes and high preoperative NDI scores in patients undergoing anterior cervical discectomy and fusion. Accordingly, the results of this study are relevant spine surgeons. Adding CSEs to PCEs not only improves modified Japanese Orthopedic Association scores but also decreases preoperative cSVA values, thereby improving the postoperative functional outcomes and health-related quality of life of the patients.

Our prospective study has the privilege of being stringently designed. It involved both radiographic parameters (cSVA and Cobb’s angle) and functional disability scales (NDI). Moreover, the authors thoroughly investigated the clinical symptoms and physical abilities of the patients. Traditionally, the view of the cervico-thoraco-lumbo-pelvic relationship has always been an absolute theoretical one, and practical intervention has been very limited. Therefore, the relationship was always ambiguous and debated. Our study already filled the gap between theoretical and practical aspects. From this perspective, we propose that therapeutic and surgical approaches should consider the relationship among various spinal segments. This study was limited by the inability to generalize the results beyond the specified age group. Adult patients were the focus because they exhibit a higher incidence of FHP [26] and because age influences the measured variables [27]. Further studies with extended follow-up periods are necessary to determine the duration of the benefits observed and to provide direct evidence of the longevity of the effects beyond that timeframe. Future studies with larger sample sizes are recommended to validate and strengthen these findings.

Conclusions

Adding CSEs to PCEs is more effective in improving the cSVA and neck-related disability than using PCEs alone in managing FHP.

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