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Upper body posture changes during sitting in female office workers with lower crossed syndrome

    https://doi.org/10.1142/S1013702525500039Cited by:0 (Source: Crossref)

    Abstract

    Background/Objective: Office workers are exposed to high levels of sedentary time. This sedentary time may have impacts on office workers which affect the normal movement patterns of sitting position caused by muscle tightness and weakness. The aims of this study were to investigate postural changes in lower crossed syndrome (LCS) on a head tilt angle (HTA), craniovertebral angle (CVA), sagittal shoulder angle (SSA), and trunk flexion angle (TFA) during 30 min sitting in female office workers.

    Methods: Fifty-four office workers who use computer for at least 4 h/day, work for at least 5 years were recruited. All subjects were evaluated their posture, muscle length and power and assigned into three groups: healty group (n=18), LCS type A (n=18), and LCS type B (n=18). Testing posture was 30min sitting at computer workstation and typing on standardized with video record. Then three pictures were captured at four points of time from VDO records. All angles were measured two-way mixed ANOVA and post-hoc Tukey test was used to analyse the data.

    Results: Subjects with LCS type B have less CVA, SSA, and TFA than healthy and participants with LCS type A significantly during sitting at 0, 10, 20 and 30min. There was no significant difference in HTA among the three groups.

    Conclusion: Subjects with LCS type B showed significant the upper body posture changes compared with other groups.

    Introduction

    Office workers typically spend a significant portion of their day in a seated position. Research indicates that these individuals maintain a sitting posture for approximately two-thirds of their working hours.1,2,3 Prolonged period of sitting is a risk for the development of musculoskeletal disorders (MSDs) in the workplace. These disorders manifest as discomfort in areas such as the neck, shoulders, and lower back.4,5,6,7,8,9 Extended periods of sitting induce neuromuscular and biomechanical changes in posture, particularly in the lumbopelvic hip complex. These alterations result in compensatory mechanisms that impact muscular activities, elevating stress on the spine and its associated soft tissues. Such postural adaptations pose a considerable risk to the overall musculoskeletal health of office workers.10,11

    Muscle imbalance, characterized by an imbalance in strength or flexibility between agonist and antagonist muscles or a disruption in their functional relationship over a joint, has emerged as a crucial factor in the development of many MSDs. This imbalance can lead to shifts in joint loading and alignment, prompting muscles to become either overactive or underactive, potentially resulting in tissue pathology. Additionally, this muscle imbalance leads to an altered crossed pattern that influences sagittal lumbopelvic hip alignment and control. Moreover, this altered lumbopelvic alignment affects the function of both upper and lower extremities and changes the centre of the body (COB) in a seated position.12,13

    The cross-pattern of lumbopelvic muscle imbalance or the lower crossed syndrome (LCS) is divided into two types — a LCS type A and a LCS type B. The LCS type A leads to an excessive anterior pelvic tilt and increased lumbar lordosis, often resisted by tightness of the hip flexors and low back extensors muscle combined with the weakness of the abdominal wall and gluteal muscles. In contrast, LCS type B leads to an increased posterior rotation of the pelvis and decreased lumbar lordosis, often resisted by tightness of the hip extensors (hamstrings and piriformis) and upper abdominal muscle combined with the weakness of lower abdominals, deep hip flexors, and low back extensors.13,14,15

    In sitting posture, there is an alteration occurring at hip joint, lumbar, thoracic, and cervical spine as well as muscle adaptation.16 According to a recent review, LCS affects the movement patterns of the lumbopelvic that affect the COB while sitting. Changes in the pelvis are associated with the lumbopelvic complex function, resulting in changing of posture and movement of the body.16,17,18,19 It might lead to abnormalities in the upper body, due to the lumbopelvic hip structure as there is a direct connection between both lower extremities and the upper extremities of the body. A study found that people with LCS type B had a decreased craniovertebral angle (CVA), sagittal shoulder angle (SSA), and trunk flexion angle (TFA) during sitting compared with healthy and people with the LCS type A.20 However, their study only investigated an immediate response. Sitting duration is the one of important factors which affect changed sitting posture.

    The primary objective of this investigation is to analyse the postural variations exhibited by individuals presenting with LCS, categorized into type A, type B, as well as those classified as healthy, during a prolonged period of seated posture lasting 30min. The evaluation of specific parameters including head tilt angle (HTA), CVA, SSA, and TFA. The study hypotheses were significant differences in these parameters among the three groups, as well as alterations over the duration of the sitting period.

    Materials and Methods

    This study was a cross-sectional study investigating postural changes in people with LCS in terms of HTA, CVA, SSA, and TFA during prolonged sitting compare with healthy people. This study was approved by the Kasetsart University Central Institutional Review Board (KUREC-HS63/013). The work described has been carried out in accordance with The Code of Ethics of the World Medical Association (Declaration of Helsinki) for experiments involving humans. All subjects signed written informed consent for participation in the study. Subjects were recruited from the Kasetsart University through online invitation posters and word of mouth.

    Subjects

    Fifty-four female adults with and without LCS aged 30–45 years participated in this study. The sample size was calculated with a confidence level at 0.05, a power of 0.95, and effect size of 0.80 using G*Power 3.1. Considering 10% dropout rate, total sample of 54 was found to be sufficient. LCS type A and type B groups=36 (n=18 per group) and healthy group (n=18). Inclusion criteria; female, age between 30 years and 45 years, using computer at least 4h/day4 and work experience of at least 5 years.6 have been examined and diagnosed by an ophthalmologist whether they have a normal-sight or not, if not, they had to wear suitable eyeglasses. Exclusion criteria: neurological disorders, pregnancy, or a history of spine, hip, or lower limb surgery or musculoskeletal problems in a past month.

    Evaluation

    Prior to data collection, subjects who met the inclusion criteria underwent a standardized physical examination including the following measurements: (1) standing posture assessed by the photographic method, (2) muscle length testing including iliopsoas length was assessed by using the Thomas test, rectus femoris length was assessed using the modified Thomas test,21 hamstrings length was assessed using the straight leg raise (SLR),22 thoracolumbar and lumbar extensors muscle were assessed using an inclinometer,23 and (3) muscle power testing in gluteus maximus, gluteus medius, abdominal muscle, hip flexors muscle, and back extensors muscle using a wireless muscle tester (Echo wireless muscle tester, JTECH, USA).24 Inclinometer was excellent test–retest reliability (ICC=0.91–0.93).23 All tests of hip strength demonstrated fair to excellent reliability across the full range of motion (ICC=0.620–0.900).25

    The LCS type A and type B subjects were classified following criteria used in previous studies.20 The LCS type A is tightness of the hip flexors and low back extensors muscle combined with the weakness of the abdominal wall and gluteal muscles. The LCS type B is tightness of the hip extensors (hamstrings and piriformis) and upper abdominal muscle combined with the weakness of lower abdominals, deep hip flexors, and low back extensors.

    Subjects were systematically assigned to groups corresponding to their specific condition classifications. Individuals presenting LCS type A were designated to an LCS type A group, whereas those diagnosed with LCS type B were assigned accordingly. Each subject underwent a thorough physical examination administered by an experienced physical therapist with 20 years of clinical proficiency in orthopaedic physical therapy. The study was conducted at the research laboratory of university.

    Instrumentation

    Two-dimensional (2D) photogrammetry techniques are inexpensive and user-friendly for measurement of joint angles during dynamic movement compared to three-dimensional (3D) systems, 2D techniques have good to excellent validity,26,27,28 although they restrict angular measurements to single planes. The single video camera (Sony digital camera LCS-U11, with shooting resolution of 640×840 pixels and speed at 70 frames per second) was used during a task performed in sitting postures.

    For 2D motion analysis (lateral view), six reflective markers were placed on the external canthus of the eye, the tragus of the ear, the acromion process, the spinous process of the seventh cervical vertebra (C7), the spinous process of the first lumbar vertebra (L1), and the midpoint of the greater trochanter (G.T.). All markers were attached on the right side of each subject’s body using double-sided tape by experienced physical therapist. A camera was placed parallel to the ground, 2m away from the subjects, on the right side of the subjects and the height of the camera, and centre of camera, were equal to the seventh cervical vertebra (C7).29 Three images were obtained at 0, 10, 20, and 30min in totally twelve images. Joint angles were measured from each image using Kinovea motion angle measuring program (version 0.8.15), a valid, precise, and reliable tool for measuring angles and distance data accuracy.30 Then three values of each angle were calculated and presented in mean with standard deviation (S.D.). Those who had two years of experience were assessed using Kinovea motion angle program. Furthermore, the intra-rater reliability of images measurement was done prior to data collection started (ICC=0.966, 95% CI=0.863–0.992).

    Experimental procedure

    In the computer workstation, subjects sat on adjustable chairs without back or armrests. Subjects maintained a neutral alignment of the head, neck, and back, with the hips and knees flexed at 90°. Both feet were positioned shoulder-width apart, firmly grounded. The shoulders exhibited slight flexion, while the elbows maintained a 90° angle of flexion.

    Researchers carefully adjusted each workstation to fit the subjects’ bodies, marking their footprints to ensure they stayed in the correct position.

    Upon prompt seating within the pre-established workstation setup, subjects started typing a standardized test for 30min. Subjects were reminded to maintain a consistent elbow flexion of 90° and ensure that their feet remained within the designated footprint throughout the testing session.

    Data analysis

    The joint angles (in degrees) were identified from images following these definitions.

    The CVA was defined as the relative angle formed by the horizontal line drawn through the C7 marker and the line joining the C7 with the right tragus of the ear markers.29,31

    The HTA was defined as the relative angle formed by the horizontal line drawn through the right tragus of the ear marker and the line joining the right tragus of the ear with the external canthus of eye markers.29

    The SSA was defined as the relative angle formed by the horizontal line and the line joining the C7 and the right acromion markers.31

    The TFA was defined as the relative angle between 2 lines extending from the right acromion to the L1 markers and the L1 to the right G.T. markers.8

    Statistic analysis

    Subject characteristics, HTA, CVA, SSA, and TFA data were tested for normal distribution using Shapiro–Wilk test. If data were normally distributed, the two-way mixed model ANOVA was used to evaluate differences of HTA, CVA, SSA, and TFA within-group and between groups. Post-hoc analysis was performed with the Tukey test. The level of significance was set at 0.05.

    Results

    Characteristics of subjects

    The results of this study showed no differences in the general characteristics, including age, weight, height, body mass index (BMI), working year, and computer use time per day, as shown in Table 1.

    Table 1. General characteristics of the subjects.

    CharacteristicHealthy (n=18)LCS type A (n=18)LCS type B (n=18)p-value
    Age (years)37.59±4.1537.75±4.3038.02±3.740.949
    Weight (kg)54.67±9.2755.22±8.9555.72±9.510.943
    Height (cm)158.50±3.11158.39±4.17160.94±6.130.185
    BMI (kg/m2)21.74±3.4921.99±3.3521.45±3.050.887
    Working year (years)9.82±4.729.98±4.2810.05±4.650.989
    Computer use time/day (h)6.67±0.846.42±0.846.39±0.610.498

    Notes: Values are means (S.D.), total n=54.

    BMI, body mass index.

    p<0.05.

    Upper body postures

    Head postures

    Head posture includes CVA and HTA. There were no significant differences in HTA among the three groups. However, the CVA in the LCS type B group was significantly less than a healthy group at baseline, 20min, and 30min of sitting (p<0.05, p<0.01). There was a significant difference between the baseline and 20 min of sitting in the LCS type B group (p<0.05) (Table 2).

    Table 2. The angles during 30-min sitting; healthy, LCS type A, and type B groups.

    Effect size (f)
    AnglesTimesHealthy (n=18)LCS type A (n=18)LCS type B (n=18)OverallHealthy versus type AHealthy versus type BType A versus type B
    CVA (deg)Baseline30.06 (8.93)26.89 (6.69)23.28 (6.29)**1.020.481.020.55
    10min29.39 (8.69)24.56 (8.35)23.50 (8.82)
    20min30.22 (9.42)25.44 (6.48)21.67(6.33)**,Δ1.290.721.280.56
    30min29.67 (8.62)25.83 (6.12)22.61 (5.29)**1.120.611.120.51
    HTA (deg)Baseline9.22 (1.79)9.33 (1.84)10.67 (2.28)
    10min9.00 (1.29)9.5 (2.82)10.28 (2.32)
    20min10.17 (2.09)9.44 (1.04)10.50 (1.89)
    30min9.67 (2.02)9.28 (2.79)10.17 (2.14)
    SSA (deg)Baseline50.39 (6.12)52.06 (5.23)45.33 (5.08)*,##1.221.220.881.17
    10min49.83 (10.25)51.94 (5.83)44.94 (5.33)#1.100.320.751.07
    20min48.61 (7.82)51.44 (5.11)43.00 (7.00)*,##,Δ1.360.450.891.34
    30min49.5 (7.9)49.78 (4.92)43.83 (5.36)*,#1.110.050.940.99
    Effect size (d)
    Baseline versus 20min1.065.171.21
    TFA (deg)Baseline107.06 (10.11)109.83 (9.49)99.50 (5.48)*,##1.510.391.071.46
    10min107.00 (10.14)109.89 (9.70)100.72 (8.91)#1.240.380.830.83
    20min106.78 (9.78)108.94 (8.83)98.94 (8.12)*,##1.440.300.301.37
    30min106.33 (10.77)109.11 (9.98)99.56 (7.37)#1.310.370.901.27

    Notes: Values are means (S.D.).

    CVA, craniovertebral angle; HTA, head tilt angle; SSA, sagittal shoulder angle; TFA, trunk flexion angle.

    p<0.05, **p<0.01 (comparison between healthy and LCS type A group, and comparison between healthy and LCS type B group); 95% CI.

    #p<0.05, ##p<0.01 (comparison between LCS type A and LCS type B group); 95% CI.

    Δp<0.05 (comparison within group between baseline and 20 min of sitting); 95% CI.

    Shoulder posture

    Shoulder posture includes SSA and TFA. When compared among three groups (Table 2), the SSA in the LCS type B group was significantly less than healthy and LCS type A group at baseline, 20min and 30min of sitting (p<0.05 and p<0.01). At 10 min of sitting, the LCS type B group was significantly less than the LCS type A group (p<0.05). There was a significant difference between baseline and 20min of sitting within the LCS type B group (p<0.05). At the same time, the TFA in the LCS type B group was significantly less than the healthy group at baseline and 20min of sitting (p<0.05). The TFA of the LCS type B group was significantly less than LCS type A at baseline, 20min (p<0.01), 10min, and 30min of sitting (p<0.05).

    Discussion

    In this study, the subjects with LCS type B showed a significant difference in the CVA, SSA, and TFA while sitting for 30min compared with healthy and subjects with LCS type A.

    The CVA in the LCS type B group was less than a healthy group significantly at baseline, 20min, and 30min of sitting, and there was a significant difference between baseline and 20 min of sitting within the LCS type B group. This might be due to the posterior tilt of the pelvis LCS type B causing spinal compensation including decreased lumbar lordosis, increasing thoracic kyphosis curve particularly, lower cervical spine found decreased lordosis curve, while upper cervical spine found decreased lordosis curve.32,33 In sitting posture, people with LCS type B are likely to have COB fall more anteriorly to ischial tuberosity presented as slump position with compensation of cervical spine as forward head.16,34,35

    The SSA in the LCS type B group was significantly less than healthy and LCS type A group at baseline, 20min, and 30min during sitting. For 10min of sitting, the LCS type B group was significantly less than the LCS type A group. There was a significant between baseline and 20min of sitting within the LCS type B group, possibly due to people with LCS type B having imbalanced muscles, which lead to alternated movements, increased thoracic kyphosis and forwarded head. In addition, the previous study reported increased thoracic kyphosis and decreased glenohumeral joint movement due to the tightness of the anterior longitudinal ligaments and upper abdominal muscles. In contrast, the extensor muscles and posterior ligaments of the dorsal spine were stretched.36 Forwarded head during sitting involves a combination of lower cervical flexion, upper cervical extension, and rounded shoulders or increased kyphotic of the upper thoracic.37,38

    The TFA in the LCS type B group was significantly less than the healthy group at baseline and 20min of sitting. The LCS type B group was significantly less than LCS type A at baseline, 20min, 10min, and 30min of sitting. People with LCS type B showed more flexed trunk than other groups because of upper abdominal muscles tightness, and the weakness of back extensor muscles causing the alteration in lumbar and thoracic spine alignment. In trunk full flexion, paraspinal muscle activities become absent, while passive structure is responsible for most of spinal stability. For long term effect, this may cause muscle disuse, weakness of paraspinal muscles and adaptive shortening of abdominal muscles.39

    People with LCS type B may have worse posture when sitting for a long time which could be explained by biomechanics of spine. The lumbar spine, cervical, and thoracic are interrelated both physically and biomechanically. Any changes in the lumbar lordosis may be due to postural changes in the thoracic and cervical spine while sitting with posterior pelvis tilts. The centre of gravity is above or behind the position of the ischial tuberosity on both sides, leading to increased lumbar kyphosis. A balanced body is maintained in a seated position by compensating for the movement of the thoracic and cervical spine by enhancing the kyphotic of the thoracic and lower cervical spine. The upper cervical spine then increases the lordotic curve to maintain balance.9,40 Butte et al.41 reported that sitting time (min/day) was a statistically significant predictor of poor hip posture.

    Only the CVA and SSA of participants with LCS type B were significant between baseline and 20min of sitting which might be explained by muscle fatigue and weakness in LCS type B. Previous studies have shown that healthy people tend to sit in a slump after 20min, this might explain why in this study the posture change in healthy group was not present over time.42 Another study reported that an anterior–posterior shift after 42.5min with coinciding increases of mean pressure in the thigh region. Overall discomfort increased significantly after about 90min of sitting.1 The testing time in our study was insufficient to observe any significant change in healthy group.

    The results of this study are useful for the physiotherapists, medical centres and companies’ office workers. However, this study has some limitations. First, the subjects in this study were females, so the results might not be generalized to males. Second, in the study the test time of the sitting task was set for 30min, to observe longer changes over time providing longer period of time is suggested for further study. Third, this study did not explore the relationship between LCS and upper postures. Fourth, this study did not observe muscle activity while sitting using an electromyography (EMG), so it was not possible to definitively identify changes in muscle activation of different types of muscle imbalance during sitting for 30min. Fifth, researchers did not determine the discomfort or pain during sitting for 30min. Further study is suggested to study more about the LCS and different types of sitting and sitting time, which may help to prevent and improve the management of body abnormalities that affect posture while sitting.

    Conclusion

    The LCS type B affected upper body posture, including the CVA, SSA, and TFA during sitting, more than other groups and worsened when subjects sat for long periods, which increased slump position with thoracic kyphosis and forwarded head. It could increase the risk of experiencing MSDs or discomfort. Thus, office workers have to manage their muscle imbalances. Further studies are needed on muscle imbalance and muscle activity in different sitting positions and time periods, to determine the discomfort or pain during holding these postures in both genders.

    Conflict of Interest

    The authors have no conflict of interest relevant to this paper.

    Funding Support

    This research did not receive any specific grant from funding agencies in the public, commercial, or non-profit sectors.

    Author Contributions

    Conception and design of the study, acquisition of data, analysis and/or interpretation of data were made by Pailin Puagprakong, Aris Kanjanasilanont. All authors contributed to the drafting and revising the paper critically for important intellectual content.

    ORCID

    Pailin Puagprakong  https://orcid.org/0000-0001-5131-1675

    Aris Kanjanasilanont  https://orcid.org/0000-0002-7728-377X

    Wannaporn S. Brady  https://orcid.org/0000-0001-7064-8724

    Kanphajee Sornkaew  https://orcid.org/0000-0001-9863-0825