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. 2025 Jun 1;37(6):250–255. doi: 10.1589/jpts.37.250

Relationship between the degree of forward head posture and the shear elastic modulus of the upper trapezius in young men, and the difference in these variables between those with and without neck/shoulder pain and/or stiffness

Hiroto Suzuki 1, Yuto Ohara 2, Masahiro Iwata 3, Yuji Asai 3, Shingo Matsuo 3,*
PMCID: PMC12153242  PMID: 40511318

Abstract

[Purpose] To investigate the relationship between the degree of forward head posture (FHP) and stiffness of the upper trapezius (UT) in young men, and the difference in these variables between those with and without neck/shoulder pain and/or stiffness. [Participants and Methods] In this cross-sectional study, we measured the craniovertebral angle (CVA) to evaluate the degree of FHP, and used ultrasound shear wave elastography to measure the shear elastic modulus of the UT (SEMUT) to evaluate muscle stiffness in 40 young men. We evaluated the relationship between the CVA and SEMUT in all participants. We compared the CVA and SEMUT between participants with and without neck/shoulder pain and/or stiffness. [Results] There was a weak negative correlation between the CVA and SEMUT in the total cohort (ρ=−0.338). However, the CVA and SEMUT did not significantly differ between participants with and without neck/shoulder pain and/or stiffness. [Conclusion] Our results suggest that a greater degree of FHP might lead to greater neck/shoulder muscle stiffness. However, the subjective symptoms of neck/shoulder pain and/or stiffness in young men were not consistent with the objective measurements of the CVA and SEMUT, which suggests that clinicians should assess both the subjective symptoms and objective measurements.

Keywords: Neck/shoulder pain, Craniovertebral angle, Muscle stiffness

INTRODUCTION

Musculoskeletal symptoms in the neck, shoulder, and arms have recently become common problems due to the use of digital devices such as personal computers, smartphones, and tablets1,2,3,4,5,6,7). Studies have revealed that the use of these devices induces changes in the neck postural alignment into the so-called forward head posture (FHP)8, 9). In the FHP, the head is in an anterior position in relation to the theoretical plumb line, which is perpendicular to a horizontal line through the center of gravity of the body10). A recent systematic review and meta-analysis reported that adults with neck pain show increased FHP compared with asymptomatic adults, and that the FHP is significantly correlated with neck pain in adults and older adults11). Additionally, Greenfield et al.12) reported that the degree of FHP is significantly greater in individuals with shoulder pain than in those without shoulder pain. Therefore, it is thought that the FHP contributes to neck and shoulder pain. However, other studies have reported conflicting results. For example, Sarig Bahat et al.13) recently reported that there are no significant differences in FHP between individuals with neck pain and asymptomatic individuals. Therefore, there is a need to further investigate the factors related to neck and shoulder pain.

With respect to the neck and shoulder muscles, Taş et al.14) reported that patients with chronic neck pain have greater stiffness of the upper trapezius (UT), levator scapulae, and sternocleidomastoid muscles compared with asymptomatic individuals. Therefore, it is also thought that stiffness of the neck and shoulder muscles contributes to neck and shoulder pain. Moreover, it has been hypothesized that there would be a significant relationship between the degree of FHP and the stiffness of the neck and shoulder muscles. However, previous studies have reported conflicting results. For example, female office workers with neck pain have increased FHP and stiffness of the UT15), and the use of lumbar lordosis assistive support for patients with FHP improves the degree of FHP and the muscle tone, viscoelasticity, and stiffness of the UT16). In contrast, Ertekin and Günaydın17) reported that there is no relationship between the stiffness of the UT and pectoralis minor muscles and the degree of FHP in patients with neck pain. Additionally, Kocur et al.18) reported that FHP has no impact on the stiffness, tone, and elasticity of superficial neck muscles in healthy, mildly symptomatic office workers.

To resolve these discrepancies between studies, the relationship between the degree of FHP and the stiffness of neck and shoulder muscles requires more detailed investigation. Moreover, there is a need to investigate the differences in the degree of FHP and the stiffness of neck and shoulder muscles between individuals with and without neck/shoulder pain and/or stiffness. This information may help clinicians understand the factors related to neck/shoulder pain and/or stiffness, and may lead to the establishment of prevention and treatment methods for neck/shoulder pain and/or stiffness in the clinical setting. However, to the best of our knowledge, few studies have investigated these issues simultaneously. Therefore, the purpose of the present study was to investigate the relationship between the degree of FHP and the stiffness of the UT, and to evaluate the difference in these variables between individuals with and without neck/shoulder pain and/or stiffness.

PARTICIPANTS AND METHODS

The cross-sectional study included 40 young men who were voluntary participants (mean ± standard deviation: age, 20.6 ± 1.3 years; height, 171.6 ± 6.2 cm; weight, 63.0 ± 8.3 kg; body mass index, 21.4 ± 2.2 kg/m2) (Table 1). All participants were informed about the study purpose and protocol and provided written informed consent for participation. The exclusion criteria were a history of surgery on the neck, back, or upper extremities, and neurological disorders. The participants were divided into two groups according to the presence or absence of temporary or chronic subjective symptoms comprising neck/shoulder pain and/or stiffness, regardless of the severity of symptoms (Table 1). The study measurements were conducted between 9:00 am and 6:30 pm. The study protocol was approved by the Human Research Ethics Committee of Nihon Fukushi University (approval number: 24-027-01) and the study was conducted in accordance with the Declaration of Helsinki.

Table 1. Participant characteristics and the values of the craniovertebral angle and shear elastic modulus of the upper trapezius.

Participants with pain
and/or stiffness (n=20)		 Participants without pain
and/or stiffness (n=20)		 All participants (n=40)
Age (years) 20.5 ± 1.2 20.8 ± 1.3 20.6 ± 1.3
Height (cm) 171.8 ± 6.4 171.4 ± 6.3 171.6 ± 6.2
Weight (kg) 63.6 ± 7.3 62.4 ± 9.3 63.0 ± 8.3
Body mass index (kg/m2) 21.5 ± 2.0 21.2 ± 2.4 21.4 ± 2.2
Craniovertebral angle (°) 55.3 ± 5.2 53.6 ± 4.7 54.4 ± 5.0
Shear elastic modulus of the upper trapezius (kPa) 55.3 ± 20.5 49.5 ± 12.0 52.4 ± 16.8
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Values are expressed as the mean ± standard deviation.

The craniovertebral angle (CVA) was measured to evaluate the degree of FHP. The participants were asked to sit naturally on a chair with their hips and knees flexed at 90 degrees19, 20) (Fig. 1a). Subsequently, they were asked to perform large amplitude cervical flexion and extension before gradually decreasing their movements and coming to rest in the most comfortable head and neck position21). This position was then photographed from the right lateral side of the participants using a digital camera with the wide-angle zoom function19, 22). The digital camera (COOLPIX P500, Nikon, Tokyo, Japan) was positioned on a tripod horizontally parallel to the participant’s head/neck region at a distance of 80 cm22). Anatomical markers were positioned on the tragus of the ear and the C7 spinous process19, 20). Based on the method used in previous studies17, 19, 20), the CVA was measured as the angle formed by the intersection of the line drawn from the tragus to the C7 spinous process and the horizontal line using ImageJ software (National Institute of Health, Maryland, MA, USA) (Fig. 1b).

Fig. 1.

Fig. 1.

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Positioning for the measurements of the craniovertebral angle and the shear elastic modulus of the upper trapezius (a). Measurement of the craniovertebral angle (b).

The shear elastic modulus of the UT was measured at the same position as the measurement of the CVA to evaluate muscle stiffness using ultrasound shear wave elastography (Aixplorer, SuperSonic Imagine, Aix-en-Provence, France) with a linear array probe (SL10-2 liner ultrasound transducer) using the musculoskeletal mode. Based on the method used in previous studies17, 23, 24), the measurement location in the UT was the midpoints of the lines joining the acromial processes and the seventh cervical spinous process. To remove the influence of muscle contraction, participants were asked to relax completely and not make any voluntary contractions of the neck, shoulder, and upper extremity muscles throughout the measurements of the shear elastic modulus of the UT. The region of interest was a rectangular-shaped region between the superficial and deep aponeurosis near the central point of the muscle belly that was as large as possible while not including artefacts25). A circular area that was as large as possible with the exclusion of the aponeuroses was drawn around the center of the region of interest26,27,28), and the shear elastic modulus (kPa) of the UT was calculated from the shear wave speed that was automatically determined within the circle29,30,31). The shear elastic modulus of the UT was measured three times on both the dominant and non-dominant sides, and the mean values of the total six measurements were used for further analysis. To remove the influence of variability between assessors, the measurements and analyses of the shear elastic modulus of the UT were performed by only one assessor.

The test–retest reliability values for all dependent variables were confirmed by calculating the intraclass correlation coefficients and coefficients of variation. The intraclass correlation coefficients and coefficients of variation were 0.656 and 3.9%, respectively, for the CVA and 0.769 and 9.62%, respectively, for the shear elastic modulus. Thus, there was substantial reliability for all measurements.

We assessed the normality of the data using the Shapiro–Wilk test. This test showed that both the CVA and the shear elastic modulus of the UT were not normally distributed. Therefore, non-parametric tests were applied. Spearman’s rank-order correlation analysis was conducted to analyze the correlation between the CVA and the shear elastic modulus of the UT in all participants. The correlations were judged to be very weak (correlation coefficient <0.2), weak (correlation coefficient 0.20–0.39), moderate (correlation coefficient 0.40–0.59), strong (correlation coefficient 0.60–0.79), or very strong (correlation coefficient 0.80–1.00). In addition, we performed the Mann–Whitney U test to compare the CVA and the shear elastic modulus of the UT between the participants with and without neck/shoulder pain and/or stiffness. Analyses were performed using IBM SPSS statistics version 24.0 (IBM Corp., Armonk, NY, USA). The statistical significance threshold was set at p<0.05. Results are expressed as means ± standard deviations.

RESULTS

The Spearman’s rank-order correlation analysis showed a weak negative correlation between the CVA and the shear elastic modulus of the UT in the total cohort (ρ=−0.338, p<0.05) (Fig. 2). However, the CVA (p=0.23, effect size: 0.19) and the shear elastic modulus of the UT (p=0.50, effect size: 0.11) did not significantly differ between the participants with and without neck/shoulder pain and/or stiffness (Table 1).

Fig. 2.

Fig. 2.

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Relationship between the craniovertebral angle and the shear elastic modulus of the upper trapezius in all participants

DISCUSSION

In this study, we investigated the relationship between the CVA and the shear elastic modulus of the UT regardless of the presence or absence of neck/shoulder pain and/or stiffness, and simultaneously evaluated the differences in these variables between participants with and without neck/shoulder pain and/or stiffness. The use of ultrasound shear wave elastography to objectively measure the stiffness of the UT is a unique strength of our study. The most important finding was that there was a weak negative correlation between the CVA and the shear elastic modulus of the UT for young men. However, the CVA and the shear elastic modulus of the UT did not significantly differ between participants with and without neck/shoulder pain and/or stiffness.

The result of the analysis of the relationship between the CVA and the shear elastic modulus of the UT was consistent with our hypothesis that participants with a greater degree of FHP would have greater stiffness of the UT. Moreover, this finding was also consistent with a study that reported that female office workers with neck pain have increased FHP and stiffness of the UT15). Other studies have revealed that FHP induces greater neck muscle activity measured by electromyography (EMG)32, 33). For example, Khan et al.32) showed that the EMG activity of the UT and sternocleidomastoid muscles is significantly increased both at rest and during activity in participants with FHP compared with those without FHP. Moreover, Nishikawa et al.33) showed that the FHP group exhibit greater muscle activity of the UT and greater subjective fatigue compared with the normal group. These previous findings suggest that a greater degree of FHP induces greater neck/shoulder muscle activity, which would induce greater stiffness and subjective fatigue of the neck/shoulder muscles and lead to neck/shoulder pain and stiffness. Therefore, we considered that maintaining good neck postural alignment would be effective in preventing or improving neck/shoulder pain and/or stiffness. However, these factors were only weakly correlated in the present study, which might limit the clinical implications of the relationship between the degree of FHP and the stiffness of the neck/shoulder muscles in young men. In contrast to our findings, Ertekin and Günaydın17) reported that there is no relationship between the stiffness of the UT and pectoralis minor muscles and the degree of FHP in patients with neck pain, while the stiffness of the left UT is positively correlated with the shoulder angle related to the rounded shoulder posture. Therefore, further studies are warranted to investigate the relationship between the degree of FHP, rounded shoulder posture, and stiffness of the neck/shoulder muscles in greater detail, and to investigate whether improvements in the neck/shoulder posture and stiffness of neck/shoulder muscles lead to improvements in neck/shoulder pain and/or stiffness.

Contrary to our hypothesis, we found that the CVA and the shear elastic modulus of the UT did not significantly differ between young men with and without neck/shoulder pain and/or stiffness. This result indicates that the subjective symptoms of neck/shoulder pain and/or stiffness for young men were not consistent with the objective measurements of the degree of FHP and the stiffness of the UT. This suggests that it is important for clinicians to assess both the subjective symptoms and objective measurements of young men in the clinical setting. This result differs from the results of previous studies. For example, a recent systematic review and meta-analysis reported that adults with neck pain show increased FHP compared with asymptomatic adults11). In addition, another systematic review and meta-analysis indicated that participants with chronic neck pain have greater stiffness of the UT than the control group34). This discrepancy between the present study and these previous studies might be caused by differences in the degree of neck/shoulder pain and/or stiffness. The previous studies that reported a difference in the CVA or muscle stiffness between participants with and without neck pain included participants with chronic neck pain or a greater intensity of neck pain than those in the present study10, 14, 15, 34). Indeed, Kim and Shin35) reported that pain intensity is significantly correlated with the degree of FHP in patients with non-specific neck pain. Furthermore, we included participants who did not feel neck/shoulder pain and/or stiffness all the time but felt temporary pain or stiffness after performing activities such as typing and studying and those who felt only neck/shoulder muscle stiffness without pain in the symptomatic group in the present study. Therefore, it is likely that the participants in the present study had less severe neck/shoulder pain and/or stiffness than the participants in these previous studies, and these differences in the characteristics of the participants might have affected the results of the present study; however, we did not assess the details of pain and stiffness, such as the severity, intensity, and duration. In contrast, Taş et al.14) reported that the pain intensity is not correlated with stiffness of the UT, levator scapulae, and sternocleidomastoid, while patients with chronic neck pain have greater stiffness of these muscles. Their study included both men and women with an average age approximately 15 years older than the average age in the present study14). Therefore, it is also likely that demographic characteristics might have affected the results of the present study. Further studies are required to investigate the differences in the CVA and the muscle stiffness in accordance with the severity, intensity, and duration of neck/shoulder pain and/or stiffness in detail among men and women of all ages. Moreover, previous studies have reported that neck fatigue/pain, the CVA, and neck/shoulder muscle stiffness are impaired during or after the use of digital devices5, 9, 36,37,38). Therefore, further studies are also required to investigate the differences in the changes in the CVA and the muscle stiffness during or after using digital devices in accordance with the severity of neck/shoulder pain and/or stiffness.

The present study has some limitations. First, this study only included young men. Future studies should include men and women of all ages to improve the generalizability of the findings. Second, we did not assess the muscle activities that affected muscle pain and stiffness. Future studies should assess the muscle activities using EMG. Third, the time of day at which measurements were performed was different for each participant. This might have influenced the degree of pain and stiffness because the load and fatigue of the neck/shoulder muscles is likely to increase as the day progresses. Fourth, although the intraclass correlation coefficients and coefficients of variation showed substantial reproducibility in the present study, the reproducibility values for the CVA and shear elastic modulus of the UT were lower than those reported in previous studies24, 39). Therefore, the accuracy of the measurements might have influenced the present results.

In conclusion, our results suggest that a greater degree of FHP might lead to greater stiffness of the neck/shoulder muscles in young men. Therefore, we considered that maintaining good neck postural alignment through treatment and/or educational guidance would be effective in reducing and preventing the load and fatigue of the neck/shoulder muscles that causes neck/shoulder pain and/or stiffness. However, the subjective symptoms of neck/shoulder pain and/or stiffness in young men were not consistent with the objective measurements of the degree of FHP and the stiffness of the UT. To treat and improve neck/shoulder pain and/or stiffness in young men, it is important for clinicians to assess both the subjective symptoms and objective measurements in the clinical setting.

Funding

No funding was received for conducting this study.

Conflict of interest

All authors declare that there are no potential conflicts of interest.

Acknowledgments

We thank Dr Kelly Zammit, BVSc, from Edanz (https://jp.edanz.com/ac) for editing a draft of this manuscript.

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