The Efficacy of Manual Therapy and Pressure Biofeedback-Guided Deep Cervical Flexor Muscle Strength Training on Pain and Functional Limitations in Individuals with Cervicogenic Headaches: A Randomized Comparative Study

Objective This study aimed to compare the efficacy of manual therapy and pressure biofeedback-guided DCFM strength training on pain intensity and functional limitations in individuals with CGH. Trial Design. A double-blinded, two-arm parallel group randomized comparative design. Methods After applying the eligibility criteria, sixty out of eighty-nine CGH patients were recruited from King Saud University Medical Center in Riyadh and randomly allocated to intervention groups using simple random sampling. Group 1 underwent pressure biofeedback-guided DCFM strength training and conventional treatment, while Group 2 received manual therapy and conventional treatment for three consecutive weeks. The main outcome measures were scores on the visual analog scale (VAS) and the headache disability index (HDI). One assessor and two physical therapists were blinded to group allocation. Results Sixty out of eighty participants aged 29–40 years were randomized into intervention groups (n = 30/group; age (mean ± standard deviation): group 1 = 35.0 ± 2.82; group 2 = 34.87 ± 2.60), and their data were analyzed. A significant improvement (95% CI, p < 0.05) was observed within each group when comparing the VAS and HDI scores between baseline and postintervention. In contrast, between-group comparisons for the outcome score of VAS and HDI revealed nonsignificant differences in the first, second, and third weeks after intervention, except for the VAS score, which showed a significant difference in weeks 2 and 3 after intervention. Cohen's d-value indicated that the intervention effect size for reducing pain was larger in group 1 than in group 2 at weeks 2 and 3. Conclusion Compared with manual therapy, pressure biofeedback-guided DCFM strength training showed a greater reduction in pain intensity (assessed using the VAS) at weeks two and three. However, both treatments were equally effective in lowering headache-related functional limitations in patients with CGH. This trial is registered with ClinicalTrial.gov PRS (Identifier ID: NCT05692232).


Introduction
Cervicogenic headache (CGH) is unilateral pain that starts in the neck and is referred from bony structures or soft tissues of the neck. It is a common and severe debilitating illness that primarily afects adult females; however, it afects both sexes aged between 20 and 60 years [1]. Every type of headache contributes to the prevalence rate of CGH, which afects 2.5% of adults and ranges from 0.4% to 15% [2][3][4]. CGH is idiopathic in origin, but some prominent probable variables, including biopsychosocial factors, i.e., biological, social, and psychological factors, contribute to the source of CGH. Biological factors include physical health, tiresome working habits with faulty biomechanics (e.g., forward head posture), heavy lifting, degenerative disc problems, and road trafc accidents; psychological factors include anxiety, sleep disturbance, and quality of life; and social factors include family circumstances (married/divorced/widow/single) and social relationships (self-esteem/coping skill/social skill) [4][5][6].
Te cervicogenic headache pathophysiology involves merging pain signals from multiple neck structures on top of the trigeminocervical nucleus in the brainstem [7]. Tis merging occurs through the top three (T1-T3) cervical nerves, which collect input from the occipital and trigeminal nerves [5]. Cervical spine malfunctioning or impairments, including disc herniation, whiplash injuries, osteoarthritis, muscle imbalances, and poor posture at the cervical level, can lead to irritation or compression of these structures, thereby activating pain pathways [1]. Moreover, activating nociceptive pathways and releasing infammatory mediators contribute to generating and preserving pain [4].
In CGH, the frontal-temporal and orbital regions of the head are afected by the unilateral referred pain of the top three cervical spinal nerves that originates from one side of the posterior head and neck [6,[8][9][10]. However, a few mechanisms support the origin of neck pain and might be a reason for cervicogenic headache in forward head posture (FHP) among white-coat working professionals [11][12][13]. Te deep cervical fexor muscle (DCFM) action line is anterior to the motion axis; it stabilizes the atlantooccipital and intervertebral joints and allows coordinated movement at the cervical spinal joint [12]. Improper functioning of these muscles may result in insufcient coordination, activation, overload, and weak support on cervical structures, progressing to neck pain and abnormal neck posture [12,13].
Criteria for diagnosing CGH have been set by the International Headache Society (IHS) [14][15][16]. Tese requirements are as follows: (A) neck and occipital region pain are localized and may radiate to the forehead, orbital region, temples, vertex, and ears. (B) Particular neck movements or prolonged neck posture causes or exacerbates pain. (C) Presence of a minimum of 1 of the following 3 conditions: (1) limitations to resistance to passive neck movement; (2) alterations in shape, feel, tone, or reaction to active and passive stretching and contraction of the neck muscles; (3) unusual neck muscle pain. (D) At least 1 of the following is revealed by radiological examination: (1) improper fexion/ extension movement; (2) an abnormal stance; (3) pathologies other than spondylosis and osteochondritis include fractures, congenital anomalies, bone cancer, and rheumatoid arthritis. Each letter heading in the IHS diagnostic criteria must be satisfed to approach a diagnosis [14,16].
Tere is a pattern of typical symptoms that people with CGH experience; however, there may be some variation in their complaints. Symptoms typically start in the neck and progress to the head; furthermore, the symptoms are typically unilateral and do not switch sides. Te pain can range in severity from a deep, dull ache to a heavy pressure that is either mild or severe [14,15]. Cervicogenic headaches might start when a patient wakes up, develop over the day, or worsen, especially with prolonged neck postures or movements. Although this kind of headache can start at any age, it frequently worsens over time and may or may not be accompanied by a history of neck injury or cervical joint degenerative disease [14][15][16].
In previous studies, researchers have reported that people with neck pain and headaches showed a 43%-46% decrease in isometric cervical fexor muscle strength [17]. Others have demonstrated that people with cervicogenic headaches had much reduced overall cervical fexor muscle strength [18][19][20]. Electromyography activity for DCFM applied through a craniocervical fexion test (CCFT) confrmed the association between the weakness of DCFM and neck pain. Te DCFM was recognized as a weaker performer than superfcial upper cervical fexors and was suggested to be aimed at managing neck pain [7,18,21].
Te role of manual therapy is limited in the treatment of headaches. Despite not being suitable for all forms of headaches, scientifc evidence supports the use of a few manual therapies, such as cervical spinal exercises, spinal joint mobilization and manipulation, trigger point therapy, physical therapy using heat and cold packs, ultrasound, electrical stimulation, massage, acupuncture, and cognitive pain approaches, which are based on a nociceptive pain theory and aim to modulate central nervous system hypersensitivity, in the treatment of tension-type and cervicogenic headaches [22][23][24][25][26][27][28]. It has been demonstrated that passive cervical spine mobility or manipulation is useful in lowering or alleviating CGH. Following mobilization treatment, there are improvements in headache frequency, duration, and intensity, and a decrease in the need for headache pain medication has been recorded [25][26][27][28][29]. Although it has not been demonstrated that muscular tightness is a signifcant component of CGH, CGH has been linked to limits in cervical muscle strength, endurance, performance, and control [7,20,29,30].
In CGH patients, the combination of manual treatment and muscle reeducation efectively reduced headaches and enhanced function [7,18,21]. In addition, a seven-week intervention study by Jull and Richardson reported that a combination of manipulative therapy and therapeutic exercises using pressure biofeedback resulted in a signifcant percentage (72%) of participants in the active treatment groups experiencing a decrease in headache frequency by 50% or more assessed at a 12-month follow-up. In addition, 42% of participants reported substantial relief of 80%-100%, suggesting that these fndings have clinical signifcance [31]. Furthermore, few previous studies have reported using muscle reeducation and strengthening of the deep neck fexors to treat CGH, despite studies being conducted to evaluate the individual efectiveness of pressure biofeedback and manual treatment on headaches [7,[17][18][19][20][27][28][29]. Te impact of pressure biofeedback-guided DCFM strength training and manual therapy on pain has been compared in a study; [31]; however, functional impairment in people with CGH has not been compared in any study. Terefore, this study aimed to determine the efcacy of pressure

Sample Size.
A computer program G * Power, version 3.10.1, was used to determine the appropriate sample size. A pilot study was conducted with 12 unmatched samples at baseline to determine the intervention efect size on the outcome score of the VAS. An a priori t test (unpaired t test) was performed, keeping the power at 0.80 (80%), the level of signifcance alpha set at 0.05, the mean diference at 2.25, the standard deviation diference at 0.90, the efect size at 0.5, and the correlation between the variables at 0.33. Te analysis revealed that a sample of 24 individuals in each group was required to obtain an adequate sample size for this study. In addition, we accounted for a 20% dropout rate (total N � 60).

Study Setting.
Sixty participants diagnosed with CGH by a consultant neurological physician were referred to the University Medical Center's outpatient physiotherapy department (OPD) for neck discomfort/pain treatment. Te study was completed from February to September, 2022. Handy pamphlets, posters, and large banners were used in and around the OPD building to attract patients to participate in this study.

Study Participants.
Sixty participants were recruited for the study based on the inclusion and exclusion criteria. Te inclusion criteria were as follows: the participants exhibited unilateral head pain without side shift or bilateral head pain with a dominant side that hurts more than the other side, sustained awkward head positioning, and external pressure over the upper cervical or occipital region on the symptomatic side, recurrent CGH and chronic mechanical neck discomfort for three to twelve months, and showed positive to cervical fexion rotation test. Te following conditions qualifed as exclusion factors: a negative cervical fexion rotation test; subjects with a history of the following conditions: a fractured vertebral column or previous surgery on it; spinal stenosis; a prolapsed disc; TMJ dysfunction or headaches involving the autonomic nervous system; vertigo or visual disturbance; or a congenital condition of the cervical spine.
2.6. Procedures. During seven-month screenings based on this study's inclusion and exclusion criteria, sixty participants were recruited and randomly assigned to groups 1 and 2 using simple random sampling. Te participants' serial numbers were assigned equally to both groups using an online, website-based randomization program (https:// www.randomization.com). Te randomized numbers associated with the group number were distributed to each patient in a concealed envelope to avoid selection bias by the study supervisor, who was not blinded to group allocation. Before receiving their prescribed intervention, all participants completed and submitted the consent form. An assistant physiotherapist took a baseline measurement of the demographic characteristics and results of the study at reception. Two physiotherapists were blinded to group assignment and carried out one intervention (pressure biofeedback-guided DCFM strength training) and the other (manual therapy) for each respective group. An assistant physiotherapist was also blinded to group assignment and assessed VAS and HDI at baseline (preintervention), the second week, the third week, and the ffth week after the intervention. Each outcome measurement was conducted at least twice, and the mean was incorporated into the analysis. Figure 1 is the CONSORT (2010) fow diagram showing the study's procedures, such as participant enrollment, randomization, group allocation, follow-up, and data analysis.

Outcome
Measures. Te participants' pain intensity was measured on a 10-cm visual analog scale (VAS) with zero (0) at one end and ten (10) at the other, signifying no pain and the worst pain possible, respectively. Te participants were instructed to place a mark between 0 and 10 on the VAS scale to indicate their actual amount of pain during the week/ night. Te VAS has been shown to be a valid and reliable instrument with the least detectable change for measuring headaches and other chronic pain [32]. Te individuals' functional limitations were assessed using a beta version of the headache disability index (β-HDI) [33,34]. Te aim of this tool is to detect the functional and emotional challenges that participants may be experiencing due to their headaches. It is a reliable and valid 25-item self-assessment scale with two domains (functional: 12 items and emotional: 13 items) evaluating function limitations and emotional expression due to headaches. Te participants were told to select "YES," "SOMETIMES," or "NO" for each item that relates to their subjective functional limitations and emotional feelings/expressions owing to headaches. Using this scoring system, a "YES" response to each given line was awarded 4 points, a "SOMETIMES" response was awarded 2 points, and a "NO" response was awarded 0 points. Te minimum and maximum scores of the HDI range from zero (0) to one hundred (100), respectively. Te sum of the scores for each item was determined by the fnal score; a score of score of 10 to 28 indicated a light disability, scores from 30 to 48 indicated moderate disability, scores from 50 to 68 indicated severe disability, and scores of 72 or greater indicated a complete profle [33,34].

Intervention.
Both groups 1 and 2 commonly received conventional treatment (i.e., moist heat pads). Group 1 performed pressure biofeedback-guided DCFM strength training, while Group 2 received manual therapy.

Pressure Biofeedback-Guided DCFM Strength Training.
Participants from Group 1 performed the DCFM strength training exercise described by Jull [11,12]. Tey assumed a supine lying position, keeping the cervical spine neutral and ensuring a stabilizer pressure biofeedback unit (Chattanooga group, Hixson, TN) placed beneath the cervical lordosis. Te pressure sensor was infated at 20 mm·Hg. Te therapist stood by the side and asked the participants to nod their heads slowly. As the DCFM was activated, the cervical lordosis gently fattened, and the pressure sensor measured increased pressure. Te activation score is the maximum pressure that can be maintained for 10 seconds. Multiplying the target pressure by the number of successful repetitions yields the muscle's holding ability performance index. Te ideal performance of the upper cervical fexor muscles would register on the pressure sensor as an increase in pressure of 10 mm·Hg held for 10 seconds, ten times on alternate days for three weeks.

Manual Terapy.
A slow, sustained elongation of muscles [35] with a holding period of 7-10 seconds and a superfcial oscillatory mobilization [36] with 1-2 oscillations per second for 30 seconds per session was performed on the DCFM in a supine position and at the cervical spine (C0-C5) in a prone lying position, respectively, as part of the manual therapy. Te therapist stood behind the head while performing sustained elongation of the muscles and stood by the side while performing superfcial oscillatory mobilization.

Conventional Intervention.
Te participants received hot water fomentation applied over the shoulder and neck region in a long sitting position for ffteen minutes per session, fve days a week for four weeks [37]. Te heating temperature of the hot pack was adjusted to bearable (before it could burn) by towel folding or unfolding, depending upon the participant's perception.

Result
Sixty (females, 33; males, 27; mean age, 34.95 years) out of eighty-nine participants with chronic mechanical pain diagnosed with CGH were randomly allocated to either group (N � 30/group; group 1, males: 13 and females: 17; group 2, males: 14 and females: 16) in this study. A Shapiro-Wilk test for normality reported an overall homogenous distribution of the demographic characteristics and study outcomes within each group (Table 1). Figure 2 shows the participants' demographic characteristics mean and standard deviation scores within each group (1 vs. 2). Table 2 provides comprehensive details of the descriptive statistics, such as sample size for each group at each interval, means, standard deviations, and 95% confdence interval for the means (lower and upper limits), minimum, maximum, frst quartile, median, and third quartile.

Within-Group Analysis.
Te within-group analysis for the variables VAS and HDI revealed a statistically signifcant improvement (95% CI, p < 0.05) when comparing the postintervention values at diferent time intervals to the baseline scores within each group (1 and 2), as shown in Table 3.

Between-Group Analysis.
Nevertheless, between-group (1 vs. 2) analysis of VAS and HDI outcomes revealed nonsignifcant (95% CI, p > 0.05) mean diferences at all time points, except for VAS2 and VAS3, where signifcant mean diferences were discovered, as shown in Table 4. Moreover, Figures 3 and 4 also compare outcome mean scores between groups (1 vs. 2) at multiple time points, such as baseline and weeks 1, 2, and 3 after intervention.
Furthermore, Cohen's d-value indicated that the intervention efect size for reducing pain was larger in group 1 than in group 2 at weeks 2 and 3 ( Table 5).

Discussion
Tis study compared the efcacy of pressure biofeedbackguided DCFM strength training to cervical isometric exercises on pain and functional limitation in patients with cervicogenic headaches. Te results of the study indicate that DCFM strength training using pressure biofeedback was more efective at reducing pain intensity and functional limitations, thereby increasing the endurance capacity of the DCFM over a 3-week period for the treatment of CGH. A referred pain reported in any head portion generated by a primary nociceptive source in the musculoskeletal tissues innervated by cervical nerves is defned as CGH by Te World Cervicogenic Headache Society (WCHS) [38].
Tis study provides preliminary evidence that such a trial is feasible. Manual therapy targeted to active TrPs in the sternocleidomastoid muscle may reduce headache and neck pain intensity and boost the motor function of the deep cervical fexors, PPT, and active CROM in persons with CGH and active TrPs in this muscle [39,40]. Studies with larger sample sizes focused on long-term impacts are needed [40,41]. Te combination of physical therapy and muscle reeducation proved efective in alleviating this patient's headaches and enhancing his function [8].

Pain Research and Management
Numerous researchers have investigated the anatomic basis of CGH, including the distribution of referred pain, to pinpoint the segmental location of symptomatic joints. Using fuoroscopically guided intraarticular injections, these authors demonstrated that C0-1, C1-2, and C2-3 are the segments most likely to refer pain to a location that would be experienced as a headache [8,18,27,28]. Tis patient's articular dysfunction appeared to be localized to the upper three cervical segments, which is consistent with the fndings of previous investigations on referral patterns. Manual examination of these regions replicated the patient's headache symptoms. Manual therapy has been demonstrated to reduce headache frequency, duration, and severity [21,22,32,37]. Following manual therapy intervention, the researchers also discovered a decrease in analgesic use in addition to improving mobility and alleviating pain [7,21,22,32,36]. As segmental mobility increased during treatment, the provocativeness of the accessory movements    Pain Research and Management diminished. By the fourth session, the altered quality of movement assessed manually was minimal, and manual assessment ceased to elicit headache symptoms. Te current scientifc evidence supports the use of manual therapy in treating tension-type and cervicogenic headaches; however, the results are inconsistent. Tese disparate outcomes may be attributable to not all manual therapies being suited for all types of headaches, or not all headache patients will beneft from manual therapy. Based on a nociceptive pain rationale, this research provides examples of manual therapies for tension-type and cervicogenic headaches that modulate central nervous system hypersensitivity, including trigger point therapy, joint mobilization, joint manipulation, exercise, and cognitive pain methods [8,[39][40][41].
Tese results imply that DCFM strengthening exercises employing a pressure biofeedback unit are more benefcial than traditional exercise alone in lowering headache frequency in persons with CGH. Te roller massage technique may be recommended to augment the initial ROM and strength of the CCF in individuals with a forward head posture [35].

Limitations.
Despite its benefts, this study also had limitations. Tis study compared a manual therapy (single intervention approach) with a conventional intervention to alleviate the symptoms of patients with CGH. However, comparing a multimodal approach with a conventional intervention to manage the symptoms would have been an

Conclusion
Compared with manual therapy, pressure biofeedbackguided DCFM strength training showed a greater reduction in pain intensity (VAS) at weeks two and three. However, both treatments were equally efective in lowering headache-related functional limitations in patients with CGH. While managing patients with CGH, the physical therapist should select one of the two intervention regimens based on the desired goals.

Data Availability
Te dataset for the results of this study will be available from the corresponding author upon reasonable request.

Consent
Informed consent was obtained from all subjects involved in the study.

Conflicts of Interest
Te authors declare that there are no conficts of interest.