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Isometric Exercise for the Cervical Extensors Can Help Restore Physiological Lordosis and Reduce Neck Pain: A Randomized Controlled Trial

Alpayci, Mahmut MD; İlter, Server MD

American Journal of Physical Medicine & Rehabilitation: September 2017 - Volume 96 - Issue 9 - p 621–626
doi: 10.1097/PHM.0000000000000698
Original Research Articles

Objective: The aim of this study was to investigate whether isometric neck extension exercise restores physiological cervical lordosis and reduces pain.

Design: Sixty-five patients with loss of cervical lordosis were randomly assigned to exercise (27 women, 7 men; mean age, 32.82 ± 8.83 yrs) and control (26 women, 5 men; mean age, 33.48 ± 9.67 yrs) groups. Both groups received nonsteroidal anti-inflammatory drugs for 10 days. The exercise group received additional therapy as a home exercise program, which consisted of isometric neck extension for 3 mos. Neck pain severity and cervical lordosis were measured at baseline and at 3 mos after baseline.

Results: Compared with baseline levels, cervical lordosis angle was significantly improved in the exercise group (P < 0.001) but not in the control group (P = 0.371) at the end of 3 mos. Moreover, the exercise group was significantly superior to the control group considering the number of patients in whom cervical lordosis angle returned to physiological conditions (85.2% vs. 22.5%; P < 0.001). At the end of 3 mos, pain intensity was significantly reduced in both groups compared with baseline levels (for all, P < 0.001). Nevertheless, considering the change from baseline to month 3, the reduction in pain was about twice in the exercise group compared with the control group (P < 0.001).

Conclusions: Isometric neck extension exercise improves cervical lordosis and pain.

From the Yuzuncu Yil University Hospital, Department of Physical Medicine and Rehabilitation, Van, Turkey.

All correspondence and requests for reprints should be addressed to: Mahmut Alpayci, MD, Yuzuncu Yil University Hospital, Department of Physical Medicine and Rehabilitation, Van, 65100, Turkey.

Financial disclosure statements have been obtained, and no conflicts of interest have been reported by the authors or by any individuals in control of the content of this article.

Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s Web site (www.ajpmr.com).

The natural alignment of the cervical spine is lordotic. This natural lordosis is believed to be an ideal posture in terms of biomechanical principles. Loss of natural lordosis leads to disrupted biomechanics in the cervical spine because the axial load is shifted anteriorly as lordosis is lost, and thus, the increased compressive forces trigger a progressive degenerative process, resulting in cervical kyphosis.1–3 In addition, loss of cervical lordosis is associated with undesirable clinical outcomes such as neck pain, upper thoracic and shoulder pain, as well as tension and cervicogenic headaches and decreased quality of life outcomes.3–5 Therefore, for many reasons, loss of physiological cervical lordosis should be taken seriously, and therapy should aim not only symptomatic relief but also restoration of physiological lordosis. However, there is currently a lack of clinical evidence for an effective treatment modality that could significantly improve cervical lordosis.

Several clinical conditions have been proposed to contribute to the development of decreased cervical lordosis, including muscular spasms, trauma, congenital defects, muscular dystrophies, amyotrophic lateral sclerosis, ankylosing spondylitis, tumor, infection, or surgical complications, although the exact etiology and mechanisms remain unclear in most cases.6–8 Xiaolong et al.8 reported correction in cervical lordosis after extensor strengthening in a case with cervical kyphosis, which occurs after loss of cervical lordosis. The authors suggested that weakness of the neck extensors could be the initiating factor for adolescent idiopathic cervical kyphosis. If this hypothesis is correct, application of neck extensor exercises may be a corrective treatment in patients with loss of cervical lordosis and may prevent cervical kyphosis occurring.

As in dropped head syndrome, which is characterized by severe weakness of the neck extensors with or without involvement of neck flexors,9 mild to moderate weakness of cervical extensors may lead to an alteration of head-neck posture, which resembles loss of cervical lordosis. One reason for loss of cervical lordosis to be more common among women10 may be associated with the fact that women have lower muscle strength than men do.11 These hypothetical data form a reasonable basis for strengthening cervical extensors in patients with loss of cervical lordosis. Moreover, in a recent study, Alpayci et al.12 revealed that the cervical isometric extension/flexion strength ratio was significantly lower in patients with loss of cervical lordosis compared with controls (1.21 ± 0.34 and 1.46 ± 0.33, respectively; P = 0.004). The authors concluded that neck extensor strengthening exercises may be suitable for patients with loss of cervical lordosis.

Exercise programs that focus on strengthening of the cervical musculature have been found to be beneficial11,13 and exercise interventions are commonly used to improve neck muscle function and thereby decrease pain and disability.13–15 However, to the best of the authors' knowledge, no previous study has examined an exercise protocol specifically in patients with loss of cervical lordosis, and the effect of isolated isometric neck extension exercise has not been investigated previously. The aim of this study was to determine whether isometric cervical extension exercise improves physiological curvature of the cervical spine and reduces neck pain intensity.

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METHODS

The present study was conducted on patients (ranging in age from 18 to 45 yrs) who applied to the Department of Physical Medicine and Rehabilitation Outpatient Clinic at Yuzuncu Yil University Hospital between April 2014 and August 2015. The study protocol was approved by the local ethical review board (Decision No: 04; Date: April 18, 2014), and a written informed consent was obtained from all patients before their involvement. In addition, the study was registered in The American Economic Association's Registry for Randomized Controlled Trials with approval number AEARCTR-0001013.

This was a 3-mo, prospective, observer-blinded, randomized controlled study with two measurement points (baseline and 3 mos). Patients were randomly assigned to two treatment groups using sequentially numbered cards by a researcher (SI). Neck pain severity at rest was measured on a 10-cm visual analog scale and cervical lordosis was assessed on lateral cervical radiographs according to the posterior tangent technique by an assessor (MA) who was blinded to treatment allocation.8,16 Radiographs of the cervical spine were obtained at the time of admission and then at 3-mo follow-up. Total curvature of the cervical spine, which refers to the angle between the posterior wall of the C2 and C7 vertebral bodies,16 was measured in each patient. The posterior tangent technique has been shown to provide a good intraobserver and interobserver reliability, with a smaller standard error of measurement than four-line Cobb methods.17 However, there are no standard values reported in the literature for the definition of a normal cervical lordosis. As defined by Grob et al.,8,16 loss of cervical lordosis or straightness of the total curvature was considered as +4 to −4 degrees and lordotic and kyphotic as < −4 and > +4 degrees, respectively.

Patients were diagnosed with loss of cervical lordosis according to the total curvature of the cervical spine by a physiatrist, who excluded any other medical conditions. Patients with any of the following conditions were excluded from the study: structural disorders of the cervical spine, such as kyphosis (> +4 degrees), block vertebra, and cervical rib; history of cervical trauma or surgery; clinically evident cervical radiculopathy; fibromyalgia; myofascial pain syndrome; shoulder problems (tendinitis, bursitis); inflammatory rheumatic diseases such as ankylosing spondylitis and rheumatoid arthritis; severe psychiatric illness; and other poor medical conditions. In addition, the patients without neck pain or with only mild pain (visual analog scale <4 cm) were excluded as well. Inclusion criteria were as follows: age between 18 and 45 yrs, motivation for home exercise program, and having a constant neck pain or a pain that lasted 15 days or more within the last month.

All patients received nonsteroidal anti-inflammatory drug (etodolac 600 mg/day for 10 days). The control group received no additional treatment and the exercise group received additional therapy of home exercise program consisting of isometric neck extension for 3 mos. All participants were contacted by telephone two times a month to increase their motivation. To improve exercise adherence, a simple exercise protocol was designed and an education including combination of theoretical knowledge and practical application of exercise was given to the exercise group. During exercise, the patients sat in an upright position and placed their hands at the back of the head. The patients then tried to push the head backward while resisting backward motion with the hands (3 × 30 secs/day). The erect posture of the spine and neutral head position were maintained throughout the exercise. Written instructions were provided to all patients in the exercise group to perform a 3-mo period of exercise on their own.

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Statistical Analyses

Statistical analysis was performed using the Statistical Package for Social Sciences for Windows version 16.0 (SPSS Inc, Chicago, IL), with statistical significance set at P < 0.05. The normality of continuous variables was analyzed using Kolmogorov-Smirnov test. The chi-square test or the Fisher's exact test were used for the comparison of dichotomous variables between the groups, Student's t test was used for the comparison of normally distributed continuous variables, and Mann-Whitney U test was used for the variables with nonnormal distribution. For intragroup comparisons of continuous variables, paired t test was used for normally distributed variables and Wilcoxon's test was used for the variables with nonnormal distribution.

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RESULTS

Figure 1 presents the CONSORT flow diagram demonstrating the progression through the study. There were no significant differences in age, sex, body mass index, and pain duration between the two groups (Table 1). At baseline, there was no significant difference in cervical lordosis angle or neck pain intensity between the groups (Table 2).

Compared with baseline levels, cervical lordosis angle was significantly improved in the exercise group (P < 0.001) but not in the control group (P = 0.371) at the end of 3 mos. Cervical lordosis angle changed approximately 9 degrees with exercise but remained relatively unchanged in the nonexercise control group. Considering the number of patients in whom cervical lordosis angle returned to physiological conditions, the exercise group was significantly superior to the control group (85.2% vs. 22.5%; P < 0.001) (Table 2). Figure 2 shows the recovery of cervical lordosis in a patient at the end of 3 mos.

At the end of 3 mos, the pain intensity was significantly reduced in both groups compared with baseline levels (for all, P < 0.001). Nevertheless, from baseline to 3-mo follow-up, there was significant difference between the two groups in terms of pain intensity (P < 0.001). The reduction in pain was about twice in the exercise group compared to the control group (Table 2).

In the subgroups that included only the patients with a positive change in cervical lordosis, the angle change was 10.72 ± 6.21 in the exercise subgroup (n = 29) and 5.26 ± 4.63 in the control subgroup (n = 7) (P = 0.032).

In acute and chronic pain subjects, there were similar changes in cervical angle (7.31 ± 6.68 vs. 10.34 ± 6.44; P = 0.183) and pain (3.50 ± 2.32 vs. 4.08 ± 1.59; P = 0.752) in the exercise group. In the control group, acute and chronic pain patients were similar in terms of the changes in cervical angle (0.87 ± 3.25 vs. 0.52 ± 3.94; P = 0.492) and pain (1.44 ± 1.40 vs. 1.60 ± 1.59; P = 0.774). However, the exercise group was superior to the control group in terms of angle changes both in acute (7.31 ± 6.68 vs. 0.87 ± 3.25; P = 0.021) and chronic (10.34 ± 6.44 vs. 0.52 ± 3.94; P < 0.001) pain subjects. The exercise and control groups were statistically similar in terms of the changes in pain in acute pain subjects (3.50 ± 2.32 vs. 1.44 ± 1.40; P = 0.055), whereas the chronic pain subjects in the exercise group demonstrated superior changes compared with the control group in terms of pain severity (4.08 ± 1.59 vs. 1.60 ± 1.59; P < 0.001).

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DISCUSSION

In this study, a 3-mo isometric neck extension exercise program was initiated together with 10-day nonsteroidal anti-inflammatory drug in patients with loss of cervical lordosis and significant positive effects were observed in cervical lordosis angle and neck pain intensity. Between baseline and 3-mo follow-up, the exercise group was significantly superior to the control in terms of improvement in both angle and pain. In addition, the 3-mo home exercise program including isometric neck extension was well tolerated by the patients.

Although there is a consensus that a lordotic curvature brings about a physiological condition for the cervical spine,16 some clinicians believe that loss of cervical lordosis is a normal variant. However, this belief seems to be based on the small percentage of segmental kyphotic cervical regions reported in asymptomatic groups of subjects.2,4 As pointed out by Harrison et al.,2 it cannot be concluded that cervical kyphosis is a normal variant. The lack of complaints may only mean that there was no pain at the time of examination. However, segmental kyphosis has been found to be approximately four times higher in neck pain patients than in asymptomatic subjects.4 Similarly, it has been shown that in normal (pain-free), acute, and chronic neck pain groups, hypolordosis was higher in the chronic pain group than in the acute pain group and the lowest in the normal group.18 Taken together, these data suggest that cervical hypolordosis is associated with neck pain and as neck pain duration increases, cervical kyphosis occurs, or vice versa. Because cervical kyphosis (> +4 degrees) is an advanced form of loss of cervical lordosis (−4 to +4 degrees), reduction in cervical hypolordosis may prevent cervical kyphosis developing.

Loss of cervical lordosis is a common physical finding, but unfortunately, it is not taken seriously enough. Understanding the effects of loss of cervical lordosis is crucial for the motivation of cervical spine rehabilitation. Loss of cervical lordosis leads to altered and disrupted biomechanical loading and thus causes a degenerative cascade leading to cervical spondylosis and kyphosis.1 Therefore, restored lordosis should be the main target of the treatment in asymptomatic subjects as well. In addition, loss of physiological cervical lordosis has been associated with numerous consequential health problems, including decreased vital lung capacity and vertebral artery hemodynamics, cervicodorsal, shoulder and headache pain, and temporomandibular disorders.17,19 Moreover, as lordosis is reduced, spinal canal diameter is also reduced, changing the overall structure of the cervical spine. Studies have shown a relationship between forward flexion of the cervical spine (reduced lordosis) and spondylotic myelopathy, dural degeneration, decreased cord width and cord length, demyelination of the cord and neuronal loss, and possibly an early death.20–25 As a result, for many reasons, loss of cervical lordosis should be taken seriously, and therapy should target not only symptomatic relief but also improvement of natural lordosis.

There is currently a lack of clinical evidence for an effective treatment modality that could significantly restore cervical lordosis. For this reason, and because it introduced a specific exercise program for loss of cervical lordosis, the present study is of prime importance. On the other hand, many patients are frequently noncompliant with home exercise programs.26 Considering that the exercise program used in this study was clear and simple, and considering that rate of compliance increased as the number of exercises decreased,27 the present study may provide a high compliance with exercise in patients with loss of cervical lordosis.

On the other hand, the finding that indicated that cervical lordosis returned to physiological conditions in more than 20% of the patients in the control group should be considered as an intriguing result. Although their conditions were not as expressive as those of the exercise group, it is clear that cervical lordosis somehow returned to physiological conditions in these subjects. A reason for this finding may be the effect of the analgesic used initially because pain and muscular spasms may lead to decreased cervical lordosis. Considering that pain intensity was significantly reduced at the end of 3 mos, it can be claimed that the analgesic used initially may have broken a possible pain/spasm vicious circle in the control group. However, because the etiology and exact underlying mechanisms remain unclear in most cases, the pain reduction in the control group may be multifactorial. Nevertheless, depending on the subgroups that included only patients whose cervical lordosis returned to physiological conditions, the exercise subgroup was significantly superior to the control subgroup in terms of the changes in the cervical lordosis angle.

This study has some limitations regarding study design and its contributions. First, the posterior tangent technique was used because of the lack of a standardized method for measuring loss of cervical lordosis. Nevertheless, good interobserver and intraobserver reliability of this technique has been previously demonstrated.28 Second, the present study was performed with only a limited-angle range (+4 to −4 degrees). For this reason, the findings of this study may be not necessarily valid for more advanced angle ranges like kyphosis (> +4 degrees). Third, because osteoarthritis commonly begins after 45 yrs of age, only young individuals (aged 18–45 yrs) were included. Consequently, the results cannot be generalized to older patients, particularly patients with cervical spondylosis. Fourth, the angle measurement method used does not define hyperlordosis, and thus, the angle < −4 degrees was considered as physiological cervical lordosis in this study. Fifth, although there was no significant difference in the number of acute or chronic pain patients in both groups, the results should be confirmed for homogenous groups that consist of only acute or chronic neck pain patients with loss of cervical lordosis. Sixth, the exercise program chosen for this study might not be the optimal protocol in the management of patients with loss of cervical lordosis because this is the first study to investigate the effects of isometric neck extension exercise on loss of cervical lordosis and there is no standardized exercise protocol for loss of cervical lordosis. Seventh, the P value (0.057) showing the similarity of two groups in terms of baseline cervical lordosis angle is not sufficiently strong. Nevertheless, the definition of loss of cervical lordosis involving narrow angle range (−4 to +4 degrees) and the statistical analyses including both intragroup and intergroup comparisons can reduce this limitation. Finally, an intention-to-treat analysis could have been planned in the study design and then used to compensate a possible problem caused by the loss allocation rate and follow-up. However, to the best of the authors' knowledge, this is the first study to demonstrate a corrective effect of neck extensor exercise on loss of cervical lordosis; therefore, despite these several limitations, this study's results are still valuable.

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CONCLUSION

In this study, the effect of a 3-mo isometric neck extension exercise initiated together with 10-day nonsteroidal anti-inflammatory drug on cervical lordosis angle and neck pain intensity was investigated in patients with loss of cervical lordosis. The results demonstrated that isometric cervical extension exercise improves physiological curvature of the cervical spine and reduces neck pain severity.

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SUPPLEMENTARY CHECKLIST

CONSORT Checklist: http://links.lww.com/PHM/A386

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Keywords:

Randomized Controlled Trial; Neck Pain; Exercise; Physiotherapy; Musculoskeletal Disorders

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