Physical Therapy Korea

The forward head posture (FHP) comprises extension of the upper cervical region and flexion of the lower cervical region [1]. In FHP, an individual’s head is in front of a vertical line passing through their center of gravity [2]. The FHP is the most common type of abnormal head posture associated with chronic neck pain; 60% of neck and shoulder pain patients report frequently assuming the FHP [3 -5]. FHP leads to lengthening and weakness of the anterior cervical muscle and shortening of the posterior cervical part [2]. FHP is commonly associated with shortening of the suboccipital muscles such as the rectus capitis posterior major, minor, oblique capitis superior, inferior, and posterior neck muscles such as the upper trapezius, semispinalis capitis, cervicis, splenius capitis, and cervicis [6]. Changes in the neck posture also lead to abnormal cervical movements, which in turn leads to muscle imbalance [7]. Due to this, FHP causes pain in the neck and dysfunction of the muscular skeletal system [8].

Previous studies have shown that a decrease in the craniovertebral angle (CVA) is associated with an increase in FHP [9]. The cranio-cervical flexion (CCF) muscle plays an important role in straightening and supporting the cervical spine [10]. The CCF muscles such as the longus colli and longus capitis provide stability to and help control the position of the cervical vertebrae [11,12].

Myofascial release is an effective therapy traditionally used for pain relief and relaxation of tensioned muscles [13]. Suboccipital release reduces tension in the deep upper cervical tissues and plays an important role in the cranio-cervical region [14]. Suboccipital release is reported to reduce the tightness and hyperactivity of the CCF muscle caused by FHP [15]. The mechanism of this change is as follows: it is believed that the Suboccipital release technique may help to relieve central sensitization by relaxing the upper cervical tissue [14]. Recently, self-myofascial release has been widely used in rehabilitation to improve myofascial mobility [16].

In physical therapists, wrist, hand, and finger pain is mostly related to their work [17]. More than 20% of physical therapists experience wrist and hand injuries, which limits their ability to perform manual therapy techniques [18]. Therefore, treatment tools are being developed that can protect the wrists and hand of physical therapists and provide effective treatment for patients. Common self-myofascial release tools include foam rollers and a variety of roller massage (RM) tools [19]. According to a systematic review published in 2015, the use of foam rollers and RM are effective interventions that increase the range of motion (ROM) and improve muscle performance before and after exercise [20]. RM is widely used for the knees, hips, and ankles; however, to the best of our knowledge, there are no studies regarding its effect on the suboccipital and neck muscles, especially in subjects with FHP [20].

The purpose of this study was therefore to investigate the immediate effects of RM on CCF ROM and strength in subjects with FHP.

1. Subjects

A total of 24 subjects with FHP (13 male and 11 female) were recruited (Figure 1). FHP was defined as CVA <53 degrees [21] and head tilt angle (HTA) >20.66 degrees [22]. The inclusion criteria were: patients with FHP, who agreed to fully understand the experiment and participate voluntarily. The exclusion criteria were: neurological findings, surgical history [23], regular medication or treatment to alleviate recent pain, acute neck pain [24], and sphagiasmus or temporomandibular joint disability [25]. Before beginning data collection, the experimental protocol was explained to all subjects by the principal investigator, and participants signed an informed consent form approved by the Yonsei University Wonju Institutional Review Board (approval number: 1041849-202012-BM-181-05).

Figure 1. Diagram of the study. FHP, forward head posture.

2. Instruments

An RM tool was used as an intervention to stretch the suboccipital and posterior neck muscles (RF-AC1929B-W; MTG Inc., Nagoya, Japan) (Figure 2). The RM tool consists of two round rollers and a streamlined handle. Holding the handle and moving forward and backward, the two rollers roll and stimulate the area.

Figure 2. RF-AC1929B-W (MTG Inc.), tools for roller massage.

A pressure biofeedback unit (PBU) is a device that sensitively measures pressure increase due to cervical nod (StabilizerTM; Chattanooga Group Inc., Hixson, TN, USA) (Figure 3). The PBU is a pressure transducer composed of a catheter, a sphygmomanometer, and a pressure bag consisting of three chambers. The pressure bag is made of an inelastic material. The range of the sphygmomanometer ranges from 0 mmHg to 200 mmHg, with a gap of 2 mmHg on the scale [26]. A change in the volume of the device pressure bag occurs due to movement or repositioning of the site using the PBU. It is visually displayed through a pressure gauge whether the muscles are used in the right way in the correct posture when performing a specific operation.

Figure 3. StabilizerTM (Chattanooga Group Inc.), the pressure biofeedback unit (PBU).

3. Procedure

All subjects were pre-tested for FHP, and RM was performed for 2 minutes when the subject criteria were confirmed. All subjects underwent measurement of the PBU pressure and CCF ROM before and after RM. The subject flexed the knee (hips 45° flexion, knees 90° flexion) in the supine position and pressure was applied using PBU on one hand. The RM intervention was applied to the subject’s suboccipital and posterior neck for 2 minutes with no sets [27]. The sitting subjects performed full flexion of the neck, the principal investigator was standing behind the subject, and the suboccipital and posterior neck was massaged vertically using a RM. To investigate the effect of RM intervention, we measured changes in PBU pressure and CCF ROM before and after the massage.

Principal investigator attached markers to both. One is the spinous process of C7, and the other is an external auditory meatus [28]. The CVA was measured as the angle between the line between C7 and the external auditory meatus and the horizontal line passing through C7 (Figure 4) [9]. When assessed clinically, FHP is determined by the CVA, with a smaller CVA indicating greater FHP [9].

Figure 4. Adhesive marker placement and postural angles. a, cranio-cervical angle; b, head tilt angle.

The head tilt angle (HTA) is the angle that is used to evaluate the head tilt and represents the upper cervical flexion or extension position. A greater HTA indicates an extension of the head relative to the cervical spine [29]. The HTA is formed with the external canthus and tragus and the horizontal line passing through the tragus (Figure 4) [30].

We used a measurement tool equipped with a smartphone-based inclinometer (Figures 5, 6). With the patient in the supine posture, the forehead and chin were leveled using hand-made smartphone-based measurement tools [31]. The CCF ROM was measured based on the horizontal state.

Figure 5. Smartphone-based inclinometer (horizontal and vertical).

Figure 6. Hand-made smartphone-based measurement tools.

Two PBUs were used for the subjects when measuring pressure. One was located in the upper cervical region. The upper cervical PBU measured pressure. Another PBU was placed in the lower cervical region. Lower cervical PBU observed the upper and lower thoracic movements. In the measurement, the lower cervical PBU was maintained at 40 mmHg. A PBU was used to measure the pressures of both. To measure the pressure of the CCF, CCF tests using PBU were performed. The pressure was the maximum pressure applied at a base pressure of 80 mmHg. The maximum voluntary contractile strength of the subjects was measured [32].

Image J imaging software (U.S. National Institutes of Health, Maryland, USA) was used to measure CVA and HTA. The digital camera was placed perpendicular to the ground, with its lens 80 cm from the lateral aspect of the subject and pointing directly at the subject’s shoulder to minimize parallax error [28]. The subject sat on the stool placed in the reference area, assuming a natural and relaxed position. The subject was asked to put both feet on the ground and to place the hands on the thighs while relaxing the back. Next, the principal investigator instructed the subject to fix their gaze on the point marked on the wall directly ahead.

4. Statistical Analysis

Statistical analyses were conducted using SPSS ver. 21.0 (SPSS Inc., Armonk, NY, USA). One-sample Kolmogorov–Smirnov test was used to confirm the assumption of normal distribution. The difference in PBU and CCF ROM data according to the two methods was compared using a paired t-test. The level of statistical significance (α) was set at 0.05.

The general characteristics of subjects are presented in Table 1.

Table 1 . Baseline demographic and clinical characteristics (N = 24).

Baseline characteristic	Data
Demographic characteristics
Age (y)	24.09 ± 2.334
Height (cm)	170.74 ± 7.533
Weight (kg)	64.96 ± 16.397
Sex
Male	13 (54.2)
Female	11 (45.8)
Clinical characteristics
CVA (°)	43.97 ± 3.688
HTA (°)	26.23 ± 3.284

Values are presented as number (%) or mean ± standard deviation. CVA, craniovertebral angle; HTA, head tilt angle. FHP satisfied CVA lesser than 53 degrees and HTA greater than 20.66°..

1. Changes in Cranio-Cervical Flexion Angle

CCF ROM was 8.82 ± 4.22 degrees before RM and 11.82 ± 5.06 degrees after RM. There was a significant difference in the CCF ROM (p = 0.002) (Figure 7).

Figure 7. CCF ROM comparison before and after the RM. CCF, cranio-cervical flexion; ROM, range of motion; RM, roller massage. *p < 0.05.

2. Changes in PBU Pressure of Cranio-Cervical Flexion

PBU pressure was 87.82 ± 4.36 mmHg and after RM was 90.43 ± 5.84 mmHg. There was a significant difference in the PBU pressure (p = 0.006) (Figure 8).

Figure 8. PBU pressure comparison before and after roller massage. PBU, pressure biofeedback unit. *p < 0.05.

We investigated changes in the CCF ROM and strength after performing RM using a roller to perform suboccipital and posterior neck muscle release in FHP patients. The study showed significant increases in CCF ROM and strength.

Fascia restriction of the suboccipital region may limit the normal movement of the muscles located in different directions [33]. FHP generally leads to a shortening effect of the suboccipital extensors. Most of the suboccipital muscles (rectus capitis posterior major, minor, oblique capitis superior, inferior) and longissimus capitis, semispinalis capitis, splenius capitis, sternocleidomastoid, and upper fibers of the trapezius, were shortened by an average of 6.1% in FHP compared to the neutral head posture. The resulting body imbalance causes abnormal stress on other parts of the body due to fascia continuity.

The immediate and significant improvement in the ROM can be explained by several mechanisms. First, the ROM increases because of the increase in tissue compliance due to changes in the fascia stimulation trigger point and viscoelastic characteristics of tissues and tissue adhesion after applying RM [20,34]. The second mechanism is increased flexibility of the suboccipital muscles after RM. The third mechanism involves metabolic reactions with heat generation. RM induces low-low-intensity friction on the skin. Low-intensity friction between the surface of RM and skin generates heat as metabolic reactions. Increased heat leads to ROM improvement due to viscoelasticity of the connective tissue and muscles [35]. Jeong et al. [36] reported that soft tissue relaxation in the posterior upper cervical region and an increase in deep flexor muscle activity increase the movement of the cervical spine. Moreover, it helps to restore the normal flexibility of the posterior cervical muscles and is reestablished into normal cervical ROM. They reported that cervical flexion using CROM increased by 17% after suboccipital relaxation [36].

Bradbury-Squires et al. reported that the self-myofascial release of the suboccipital muscle showed significant improvements in the left rotation and overall technical ROM of the head. Bradbury-Squires et al. applied an RM to the knee joint for 20 and 60 seconds. Bradbury-Squires et al. reported that knee joint ROM increased by 10% and 16% at 20 and 60 seconds, respectively, when compared to the control group [35]. Monteiro et al. [37] conducted roller-massager to the hamstring to measure the ROM change of the hip extension. As a result of performing RM for 60 seconds, the hip extension angle increased by 135%. In addition, when RM was performed for 120 seconds, the hip flexion angle increased by 21% [37]. Halperin et al. [38] conducted a study to apply RM to plantar flexors. According to this, RM has an effect on ankle ROM and has a large effect when applied with static stretching [38]. In Heredia’s study, Suboccipital release significantly improved head position by significantly increasing the CVA of subjects with FHP [14].

Studies on muscle strength and muscle performance have produced a variety of results. Halperin et al. [38] showed a significantly greater force when RM and static stretching were performed together than static stretching (8.2%). Vastus lateralis RMS EMG was 3% and 7% less, respectively, with 20- and 60-second RMs, respectively, than the control conditions. In addition, the VL RMS EMG was approximately 4% less than that for 20 second with a 60-second RM [38]. Grabow et al. [39] improved knee flexion ROM without reducing strength and jump performance after quadriceps roller massage. Healey et al. [40] measured the isometric force after RM. There were no effects on performance in this study. After RM, the isokinetic knee extension was measured at 90°/s. No improvement was observed immediately after applying the RM [27].

Several researchers have suggested mechanisms for muscle strength production. A study has shown that increased muscle strength is associated with increased muscle temperature [41], and some studies show that the fascia limitation of the muscles is released [42]. In addition, some studies have reported that phosphorylation of myosin regulatory light chains is a factor, but additional studies are needed [43]. According to the general upper crossed syndrome, cranio-cervical flexor muscle weakening and suboccipital myofascial stiffness occur simultaneously [44]. As the stiffness of the suboccipital myofascial structures decreases the strength of the CCF, releasing the suboccipital structures may be a way to improve the strength of the deep cervical flexors [45].

Physical therapists often experience work-related musculoskeletal disorders in the course of their job performance. Because of this, 70% of physical therapists visit the hospital [46]. Work-related musculoskeletal disorders due to performing manual orthopedic techniques is reported to be experienced by 67.8% of physical therapists [47]. Various methods should be devised to prevent such physical therapist injuries. Physical therapy techniques using tools such as RM will be a good alternative to effectively relax the fascia while preventing hand and finger injury and pain.

There are some limitations to consider in this study. First, other studies have reported that musculotendinous stiffness returns to baseline after 30 minutes to 1 hour. Therefore, in the future, the same content should be applied in the long term to determine the effectiveness of RM. Second, we recruited subjects aged 20 years. Due to their limited age group, it is difficult to generalize to other populations. Finally, there was no control group that can be compared with RM, so it was difficult to clarify the intervention effect of this study.

In this study, we examined the immediate CCF ROM and strength changes when applying RM to subjects with FHP. Immediately after application of RM to the suboccipital and posterior neck in subjects with FHP, CCF maximum muscle strength and CCF ROM were increased. The results of this study suggest that RM can be applied as an alternative method for improving CCF ROM and strength in subjects with FHP.

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

Conceptualization: SK, JJ, OK. Data curation: SK, JJ, OK. Formal analysis: SK, JJ, OK. Investigation: SK, JJ, OK. Methodology: SK, JJ, OK. Project administration: SK, JJ, OK. Resources: SK, JJ, OK. Software: SK, JJ, OK. Supervision: SK, JJ, OK. Validation: SK, JJ, OK. Visualization: SK, JJ, OK. Writing - original draft: SK, JJ, OK. Writing - review & editing: SK, JJ, OK.