Altered body balance and plantar pressure distribution in young adults with forward head posture

Hussein Youssef; Onur Aydoǧdu; Aysel Yildiz

doi:10.1016/j.jor.2024.07.016

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59 (); 68-75

doi:

10.1016/j.jor.2024.07.016

Altered body balance and plantar pressure distribution in young adults with forward head posture

Hussein Youssef^a,b,, Onur Aydoǧdu^b, Aysel Yildiz^b

a Neuroscience, Graduate School of Health Sciences, Koç University, Turkey

b Physical Therapy & Rehabilitation, Faculty of Health Sciences, Marmara University, Turkey

⁎Corresponding author: Hussein Youssef. HusseinAhmedYoussef@gmail.com

Received: 2024-6-27, Accepted: 2024-7-18, Published: 2024-7-23

Professor P K Surendran Memorial Education Foundation

Disclaimer:
This article was originally published by Reed Elsevier India Pvt. Ltd. and was migrated to Scientific Scholar after the change of Publisher.

Abstract

Forward head posture (FHP), a common postural issue, affects balance and may be linked to altered muscle activity and cervical spine alignment. This study investigated the impact of FHP on static balance and plantar pressure distribution in adults. We hypothesized that FHP would be associated with poorer balance and altered pressure distribution.

This case-control study investigated the impact of FHP on static balance and plantar pressure distribution in adults (n = 52). Participants were categorized based on craniovertebral angle (CVA), into FHP (CVA <47°) and control (CVA ≥47°) groups. Static balance was assessed using a NeuroCom® Balance Manager System, evaluating parameters like center of gravity sway and directional control. Plantar pressure distribution was measured with an Emed Pedobarography system during walking, analyzing maximum force, peak pressure, and contact area.

Participants with FHP showed poorer balance with eyes closed on foam compared to the control group. Additionally, the FHP group exhibited lower total maximum force and altered force distribution in both feet during walking. Correlations suggested that higher CVA degrees were associated with decreased balance and altered plantar pressure distribution. Despite, linear regression analyses revealed no significant predictive relationships between CVA and specific balance measures, it showed significant associations with several plantar pressure distribution parameters, including total maximum force exerted on both feet, maximum force on the forefoot, and peak pressure on the hindfoot.

These findings suggest that FHP may influence balance and plantar pressure distribution, with a potentially stronger effect on plantar pressure than balance parameters.

Abstract

Highlights

•FHP have a more pronounced effect on plantar pressure distribution than static balance.•FHP exhibited lower overall force exerted during walking and altered forefoot loading.•FHP may influence gait mechanics through a potential shift in center of gravity.

1 Introduction

The widespread availability of computers and the internet has led to a significant increase in the average time people spend using these technologies. While computers undoubtedly enhance work efficiency, excessive use can contribute to health problems like Visual Display Terminal (VDT) syndrome.¹

One common VDT-related issue is Forward Head Posture (FHP), affecting an estimated 66 % of the population.² FHP develops naturally across various age groups and is characterized by the head's anterior displacement in the sagittal plane relative to the neck and shoulders.³ This deviation from the ideal posture is compensated for by adjustments in the spine, with hyperextension in the upper cervical (C1-C3) region and flexion in the lower cervical (C4-C7) region.⁴ Such misalignment in the cervical spine can lead to various consequences. Studies suggest it can induce stress on the posterior cervical structures,⁵ impacting the length-tension relationship of muscles,⁶ increasing muscle activity,⁷ and limiting neck range of motion (ROM).⁸ Ultimately, this can lead to a decline in proprioception, or the ability to sense the position and movement of the neck.⁹ While neck pain is often associated with FHP, recent research suggests this connection might be age-dependent, with adults and older adults experiencing it more frequently than adolescents.¹⁰

Previous research has documented changes in muscle activity patterns associated with FHP. Studies report increased tension in the posterior cervical muscles alongside a significant reduction in activity of the deep anterior neck flexor muscles, particularly the longus colli and longus capitis.¹¹^,¹² Additionally, reduced activity has been observed in the deep extensor muscles, including the semispinalis cervicis and upper multifidus.¹³^,¹⁴ These deficits in deep cervical muscle activity are hypothesized to contribute to poor motor control of the cervical spine joints.¹⁵ In a standing position, FHP can further disrupt balance by shifting the center of gravity (COG) forward, pushing it outside the limits of stability.¹⁶ This altered biomechanical state leads to the gravity line passing further anteriorly from the cervical spine, increasing the moment arm and consequently, the tensile stress on the posterior cervical structures.

1.1

1.1 Determining the cause of balance impairments

While previous findings suggest that altered biomechanics due to FHP can contribute to balance impairments, the extent to which these impairments are solely attributable to FHP versus age-related factors or underlying neurological conditions remains to be elucidated. Notably, our previous study demonstrated that another postural abnormality, thoracic hyper-kyphosis, did not affect balance in a young population.¹⁷ However, due to the limitations of this single, low-powered study, further research with a larger sample size is necessary to confirm this association and determine the relative impact of FHP compared to other factors influencing balance. Therefore, while these results suggest the potential importance of FHP in balance, definitive conclusions regarding its prioritization within rehabilitation programs are premature.

While changes in body mechanics are known to be associated with foot alignment,¹⁸ current evidence suggests a correlation between posture stability and plantar pressure distribution primarily in participants with healthy posture.¹⁹^,²⁰ However, the relationship in those with postural misalignment remains less explored.

This study has two main objectives; primary objective, is to investigate whether static balance is affected by FHP, and secondary objective, is to examine the changes in plantar pressure distribution patterns associated with FHP.

2 Methods

2.1

2.1 Study design

This comaprative study, approved by the Marmara University Faculty of Medicine ethics committee (Protocol code: 09.2020.897), adhered to the Declaration of Helsinki. Adults over 18 were eligible, but those with a history of spine trauma/surgery, bone pathologies (e.g., arthritis), kyphotic deformities, spinal deformities/abnormalities, disc herniations, BMI exceeding 30 kg/m² (obesity), self-reported balance disorders, neurological/vestibular diseases, or recent medication use affecting balance/posture were excluded.

2.2

2.2 Sample size calculation

To ensure sufficient power to detect a moderate effect size (effect-size r = 0.37) as concluded by previously published study with similar aims¹⁶; for a two-tailed alpha level of 0.05 and a desired power of 80 %, a priori power analysis using G. Power software (v3.1.9.4; Franz Faul, University of Kiel, Kiel, Germany), indicated a minimum sample size of 52 participants.

2.3

2.3 Recruitment procedures

Participant recruitment for this study occurred between November 2019 and February 2020 at the Biomechanics and Performance Analysis Laboratory, Department of Physiotherapy and Rehabilitation, Faculty of Health Sciences, Marmara University, Istanbul, Türkiye. Upon arrival, each participant completed a questionnaire and underwent a comprehensive physical examination by the lead investigator to ensure they met the inclusion criteria and no exclusion factors were present. Individuals who qualified were categorized into two groups based on their Craniovertebral Angle (CVA) degrees. Those with a CVA less than 47° were assigned to the FHP group, while those with a CVA of 47° or higher were placed in the control group. Finally, all participants provided written informed consent before proceeding with the study.

2.4

2.4 Data acquisition

2.4.1

2.4.1 Craniovertebral angle (CVA)

CVA is an angle formed at the intersection of a line connecting the tragus of the ear and the spinous process of C7 with a horizontal line (imaginary line parallel to the ground). CVA is a guiding reference for determining FHP, CVA ≥52° - 55.02° ± 2.86° is considered within the normal range of the correct head posture,⁵ while CVA ≤47° was considered as -malalignment of the head posture- FHP,²¹ and highly valid angle to distinguish the severity of FHP.²²

A standardized photogrammetric method was used to assess CVA.²³^,²⁴ Participants stood in profile to a posture chart with a horizontal line one foot away. Markers were placed on anatomical landmarks: the 7th cervical vertebra (C7) and the left ear tragus.²⁵ The C7 height from the ground was measured and matched to the camera lens height (mobile camera iPhone 7 Plus, 12 megapixels with optical image stabilization). A tripod positioned 1.5 m from the participant's left foot ensured consistent image capture. Participants were instructed to stand straight with fully extended knees, feet shoulder-width apart on designated spots, and adopt a comfortable posture. Starting from this neutral position, they performed full head flexion and extension, then returned to their most comfortable neutral head position.²⁶ A laser pointer helped maintain eye level, and a point was marked directly in front of each participant's eye for reference 27. SurgiMap Spine software (Massachusetts, USA), validated for measuring spinal angles,²⁸ was used to analyze the captured images and calculate CVA.

2.4.2

2.4.2 Balance assessment

Objective evaluation of the static balance evaluated by the NeuroCom Balance Manager System ® static posturography device (45 × 45 cm NeuroCom® System Version 8.1 Balance Manager International, Clackamas, Oregon, USA). The main investigator introduced the aim of the balance assessment, also a brief demonstration of the main idea of this balance device was presented. To make the participants familiar with the assessment procedures, for detailed methodology we would refer to the methodology described in our previous study.¹⁷

The following tests were assessed for each participant. Modified Clinical Test of Sensory Interaction on Balance (mCTSIB) a test to assess balance control on different surfaces (firm vs. soft) and with eyes open or closed.²⁹ Limits of Stability refers to how far someone can move their body while staying balanced. It basically tests how well participants can control their center of gravity (COG) to move in different directions. Reaction Time (RT) this is how long it takes someone to react to something they see on a screen.³⁰ Movement Accuracy different aspects of how well participant can move a limb to a target point. It includes how fast they move (movement velocity), if they reach the target (endpoint), how far off target they go (max excursions), and how well they control the direction of their movement (directional control).³¹ Weight Shifting test assesses how well someone can voluntarily shift their weight back and forth, left and right, and forward and backward. It also measures how fast they can shift weight in these directions.

2.4.3

2.4.3 Planter pressure distribution

Plantar pressure distribution was evaluated using the Emed Pedobarography system (EMED AT, Novel GmbH, Munich, Germany). This system utilizes a capacitive pressure distribution platform embedded flush within the walking surface. During the assessment, participants walked barefoot at their self-selected comfortable speed across the platform at 50 Hz. To ensure data accuracy, participants completed a few familiarization trials before the main data collection, which consisted of five repetitions.³²^,³³ For each foot, pressure data was analyzed for four anatomical regions: toes, forefoot, midfoot, and hindfoot.³⁴ The following parameters were compared between the two groups: Maximum Force (N): The highest total force exerted within a specific region of the foot. Peak Pressure (kPa): The highest pressure recorded within a specific region of the foot. Contact Time (ms): The total duration of contact between the foot and the platform. Contact Area (cm²): The average area of pressure application during walking across the platform.

2.5

2.5 Statistical analysis

We used R-Studio (R 4.3.3) for data analysis and visualization. Descriptive statistics were calculated for participant demographics, including age, height, and body mass. Data distribution for normality was assessed by shapiro wilk test, normally distributed data were summarized using means and standard deviations, while medians and interquartile ranges were used for non-normally distributed data. Independent samples t-tests were used to assess significant differences between the two groups for data that followed a normal distribution. For data that did not follow a normal distribution, Mann-Whitney U tests were conducted. Spearman's rank correlation coefficient was employed to examine the relationship between various balance or plantar pressure distribution parameters and the Craniovertebral Angle (CVA) for variables that were not normally distributed. This analysis was performed using the ggstatsplot package in R.³⁵ Linear regression analysis was conducted on parameters that exhibited a significant correlation with CVA, as identified by the Spearman's rank correlation analysis. Finally, depending on the statistical approach, effect sizes calculated using Cohen's method. A significance level of p < 0.05 was chosen for all statistical tests.

3 Results

3.1

3.1 Descriptive statistics

The study involved fifty-two healthy participants. These individuals were categorized into two groups based on their Craniovertebral Angle (CVA) measurements: FHP (FHP) group (n = 25) and a normal cervical posture group (n = 27) (Table 1). A subgroup analysis was conducted for a subset of thirty participants who underwent plantar pressure distribution assessment (Table 2).

Table 1 Demographics of participants included in balance assessment.

		FHP Group	Control Group	Sig. (2-tailed)P	Confidence Interval (95 %)
Sample Size		25 (48.1 %)	27 (51.9 %)	_____	_____
Age (Years)∗∗		28.00 [24.00, 33.00]	25.00 [22.00, 31.50]	0.180	_____
Gender	Male n (%)	14 (56.0 %)	15 (55.6 %)	_____
Gender	Female n (%)	11 (44.0 %)	12 (44.4 %)	_____
Body mass (kg)∗		73.84 (13.73)	68.07 (9.29)	0.080	[-0.85: 12.40]
Height (cm)∗		171.24 (10.77)	169.00 (8.29)	0.403	[-3.16 : 7.63]
BMI (kg/cm²)		25.15 (3.99)	23.81 (2.74)	0.162	[-0.59 : 3.27]
CVA (Degrees)∗∗		41.90 [38.50, 45.10]	48.80 [47.90, 51.10]	<0.001	_____
NDI∗∗		0.00 [0.00, 4.00]	0.00 [0.00, 5.00]	0.779	_____

Table 2 Demographics of participants included in plantar pressure assessment.

		FHP Group	Control Group	Sig. (2-tailed) P	Confidence Interval (95 %)
Sample Size		15 (50.0 %)	15 (50.0 %)	_____	_____
Age (Years)∗∗		29.00 [25.00, 39.00]	24.00 [22.00, 42.00]	0.180	_____
Gender	Male n (%)	8 (53.3 %)	6 (40.0 %)	_____
Gender	Female n (%)	7 (46.7 %)	9 (60.0 %)	_____
Body mass (kg)∗		75.20 (15.77)	65.67 (8.86)	51	[-0.15 : 19.21]
Height (cm)∗∗		170.00 [162.50, 179.50]	165.00 [162.00, 171.00]	0.298	_____
BMI (kg/cm²)		25.89 (4.73)	23.49 (2.89)	0.105	[-0.56 : 5.36]
CVA (Degrees)∗∗		40.30 [37.40, 43.00]	48.80 [47.75, 50.30]	<0.001	_____
NDI∗∗		3.00 [0.00, 9.50]	2.00 [0.00, 8.50]	0.948	_____

3.1.1

3.1.1 Balance parameter groups comparisons

Statistical analysis revealed significant differences between the two groups (FHP vs. Control) for specific balance parameters measured with eyes closed on a foam surface (Foam EC) (p = 0.044) and left/right directional control (DCL) at both slow (p = 0.034) and moderate velocities (p = 0.049) (Fig. 1A). However, no significant differences were found for other balance parameters.

Mean difference between both FHP and control groups for A. balance parameters, and B. planter pressure distribution parameters.

Detailed group comparison for all balance parameters is in Supplemental Table 1.

3.1.2

3.1.2 Plantar pressure distribution comparisons

Statistical analysis identified significant differences between the groups for total maximum force exerted on both the right (p = 0.027) and left feet (p = 0.038) (Fig. 1B). Additionally, a trend towards significance was observed for force distribution on the forefoot of both the right (p = 0.08) and left feet (p = 0.054). No other significant differences were found for other plantar pressure distribution parameters. Detailed group comparison for all planter pressure distribution parameters is in Supplemental Table 2.

3.1.3

3.1.3 Balance parameter and CVA correlation

Following the correlation classification,³⁶ Spearman's rank correlation analysis was conducted to examine the relationship between CVA degrees and various balance parameters for both groups combined. This analysis revealed statistically significant correlations for the following parameters (Fig. 2A): Endpoint (EPE) Left (p = 0.03, r = 0.3): This indicates a “low correlation” with a confidence interval (CI) of [0.02, 0.54]. Max Excursions (MXE) Left Direction (p = 0.007, r = 0.37): This suggests a “low correlation” with a CI of [0.10, 0.59]. Left/Right Directional Control (DCL) Moderate Velocity (p = 0.04, r = 0.29): This shows a “low correlation” with a CI of [0.007, 0.53]. No significant correlations were observed for other balance parameters.

Spearman's rank correlation coefficients between craniovertebral angle (CVA) degrees with A. balance parameters, and B. plantar pressure distribution parameters.

3.1.4

3.1.4 Plantar pressure distribution and CVA correlation

Similar to the balance parameters, Spearman's rank correlation analysis was employed to investigate the relationship between CVA degrees and plantar pressure distribution parameters for both groups combined (Fig. 2B). Significant correlations were found for the following parameters: Total Maximum Force (Right Foot): (p = 0.01, r = −0.46) indicates a “low negative correlation” with a CI of [−0.71, −0.11]. This suggests that higher CVA degrees are associated with lower total maximum force exerted on the right foot. Total Maximum Force (Left Foot): (p = 0.008, r = −0.47) indicates a “low negative correlation” with a CI of [−0.72, −0.13]. Similar to the right foot, higher CVA degrees are linked to lower total maximum force exerted on the left foot.

Force Distribution on Forefoot (Right Foot): (p = 0.04, r = −0.38) indicates a “low negative correlation” with a CI of [−0.66, −0.01]. Higher CVA degrees are associated with a lower force distribution on the right forefoot. Force Distribution on Forefoot (Left Foot): (p = 0.009, r = −0.46) shows a “low negative correlation” with a CI of [−0.70, −0.11]. Similar to the right foot, higher CVA degrees are linked to a lower force distribution on the left forefoot. Peak Pressure on Hindfoot (Right Foot): (p = 0.02, r = −0.42) indicates a “low negative correlation” with a CI of [−0.68, −0.06]. Higher CVA degrees are associated with lower peak pressure on the right hindfoot.

Peak Pressure on Hindfoot (Left Foot): (p = 0.01, r = −0.46) shows a “low negative correlation” with a CI of [−0.71, −0.11]. Similar to the right foot, higher CVA degrees are linked to lower peak pressure on the left hindfoot. Peak Pressure on Forefoot (Right Foot): (p = 0.04, r = −0.38) indicates a “low negative correlation” with a CI of [−0.66, −0.01]. Higher CVA degrees are associated with lower peak pressure on the right forefoot. No other significant correlations were found for other plantar pressure distribution parameters.

3.1.5

3.1.5 Balance parameter and CVA relationship

Following the identification of significant correlations between CVA degrees and certain balance parameters, linear regression analyses were conducted to explore the predictive relationship between these variables. Here, CVA degrees served as the independent (predictor) variable, while the specific balance parameters acted as the dependent (outcome) variables. The analyses revealed no statistically significant associations between CVA degrees and the following balance parameters: Maximum Excursions (MXE) Left Direction (p > 0.11, R² = 0.051), Endpoint (EPE) Left (p > 0.17, R² = 0.068), and Left/Right Directional Control (DCL) Moderate Velocity (p > 0.06, R² = 0.025). These findings suggest that CVA degrees may not have a strong linear influence on these particular balance measures within the participant groups studied (Fig. 3A).

Scatter plots with regression analysis for craniovertebral angle (CVA) degrees vs. A. balance parameters, and B. plantar pressure distribution parameters.

3.1.6

3.1.6 Plantar pressure distribution and CVA relationship

Similar to the analysis of balance parameters (Fig. 3B), linear regression was employed to investigate the association between CVA degrees and significant plantar pressure distribution parameters (details presented in Table 3).

Table 3 Plantar pressure distribution and CVA linear regression.

	P value	Regression coefficient (R²)	Std. Error	Adjusted R-squared
Total Maximum force RT	0.004∗	−15.34	4.90	0.23
Total Maximum force LT	0.003∗	−15.15	4.71	0.24
Maximum force forefoot RT	0.015∗	−10.59	4.08	0.16
Maximum force forefoot LT	0.013∗	−10.25	3.86	0.17
Maximum force hindfoot LT	0.014∗	−8.98	3.41	0.17
Peak pressure hindfoot LT	0.007∗	−5.975	2.07	0.20
Peak pressure hindfoot RT	0.064	−4.056	2.10	0.08
Peak pressure forefoot RT	0.055	−12.486	6.26	0.09

3.2

3.2 Clinical significance of the results

Effect sizes were calculated using Cohen's traditional method,³⁷ which divides the mean difference between groups by the pooled standard deviation. For balance parameters, Foam EC showed a small effect (−0.34), while Left/Right Directional Control (DCL) exhibited a medium effect at both slow velocity (−0.547) and moderate velocity (−0.700). In terms of plantar pressure distribution, the total maximum force exerted on the right foot displayed a large effect (0.829), whereas the left foot showed a moderate effect (0.773). These results suggest that CVA may have a more substantial influence on some balance and plantar pressure distribution measures.

4 Discussion

While most balance parameters measured with the modified Clinical Test of Sensory Interaction on Balance (CTSIB) did not differ significantly between groups, participants with FHP (CVA <47°) exhibited poorer balance when standing on a foam surface with eyes closed compared to the control group (CVA ≥47°). This finding aligns with a previous study by that reported increased COG sway during similar conditions (eyes closed on foam).³⁸

Conversely, our study did not identify differences in the body's ability to maintain balance in various directions, except for left/right directional control, which corroborates findings from Lee's work.³⁸ This discrepancy might be explained by differences in participant populations. Kang et al. (2012) observed reduced motor control in heavy computer users with FHP, evidenced by altered Movement Velocity (MVL), Endpoint (EPE), and Max Excursions (MXE) within the forward/backward direction paramters of the limits of stability balance test. However, our participants likely had a wider range of computer usage habits, potentially explaining the lack of observed differences in these specific parameters.¹⁶ Correlation analysis revealed low-level associations between CVA degrees and parameters related to motor control during limits of stability tests (MXE and EPE).

The study identified significant differences in plantar pressure distribution between the groups. Participants with FHP displayed higher maximum force exerted on both feet during walking compared to the controls. Additionally, there was a trend towards significance for a reduced force distribution on the forefoot of both feet in the FHP group. These findings were further supported by correlation analysis, demonstrating a “low negative correlation” between CVA degrees and maximum force exerted on the feet, force distribution on the forefoot, and peak pressure on the hindfoot. This suggests that higher CVA degrees are associated with lower overall force applied during walking, potentially altered forefoot force distribution, and decreased peak pressure on the hindfoot.

The observed effects on plantar pressure distribution in the FHP group might be attributed to an anteriorly shifted COG. This could lead to increased forefoot loading as a compensatory mechanism to maintain balance while walking. The higher peak pressure on the hindfoot could further support this notion, suggesting a reduced ability to push off effectively during the gait cycle. This aligns with our hypothesis that FHP would influence plantar pressure distribution, potentially due to a deviation in COG positioning.

The current study has limitations that warrant consideration. First, the participant pool consisted of healthy adults without a history of other conditions. This limits the generalizability of the findings to the broader population, particularly individuals with FHP who may have co-existing health issues. Second, the study focused solely on FHP as a potential factor influencing balance. Other variables, such as core strength, lower limb proprioception, or footwear choices, could also play a role and were not evaluated here. Finally, The subgroup analysis for plantar pressure distribution may be underpowered due to limited sample size within each group.

Future research with larger, severe FHP, and more diverse populations alongside investigations into these additional factors would provide a more comprehensive understanding of how FHP interacts with other elements to influence balance control.

5 Conclusion

This study suggest that altered postural mechanics associated with FHP could be related to differences in plantar pressure distribution, potentially influencing gait mechanics. However, due to the observational nature of this study, we cannot definitively conclude that FHP causes changes in gait mechanics. Further research employing longitudinal or interventional designs is necessary to establish causal relationships between FHP, postural mechanics, and gait characteristics.

Conflicts of interest

The authors of this article confirm that they do not have any connections or involvement with any organization or entity that has a financial or non-financial interest in the subject matter discussed in this manuscript. The authors declare that they have no competing interests, and no party has or will provide any benefits to them or any organization they are associated with based on the results of this research. The study is being presented for the first time and has not been presented elsewhere.

Ethical statment

This case-control study, approved by the Marmara University Faculty of Medicine ethics committee (Protocol code: 09.2020.897), adhered to the Declaration of Helsinki.

Funding

The authors declare that there is no funding has been received to accomplish this article.

CRediT authorship contribution statement

Hussein Youssef: Conceptualization, Investigation, Methodology, Software, Formal analysis, Visualization, Writing – original draft. Onur Aydoǧdu: Supervision, Validation, Resources, Writing – review & editing. Aysel Yildiz: Supervision, Validation, Resources, Writing – review & editing.

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