The relationship between the active cervical range of motion and changes in head and neck posture after continuous computer screen work
From: Ind Health. 2009 Apr;47(2):183-8
Poor posture is a common finding in physical therapy evaluations of patients with musculoskeletal complaints. The upper spine has been of particular interest to physical therapists treating disorders of the cervical and thoracic spine, the shoulder, and the temporomandibular region. Many studies have attempted to identify head and neck postures that would reduce the risk of developing musculoskeletal pain of the neck and trunk.
The effects of the head and neck posture depend on the characteristics of a task. Visual display terminal (computer screen) work typically involves remaining for a long time in a fixed position. Sezto et al. found that individuals increase their forward head posture during computer screen work, which involves an excessive anterior position of the head in relation to the theoretical plumb line perpendicular to the body’s center of gravity, and can be considered similar to a protracted position of the cervical spine in which the lower cervical vertebrae are flexed in a forward glide and the upper cervical vertebrae are extended. This causes a shortening of the posterior cervical and suboccipital muscles, lengthening and weakness of the anterior neck muscles, weakness of the scapula retractor muscles, and increased stress on the ligaments. The imbalances created by this position decrease muscular efficiency, and extra muscular action is needed to hold the head and neck in a stable position. Fredriksson et al. reported that neck and shoulder pain was associated with computer screen work in both men and women.
The head and neck posture of an individual can influence soft-tissue relationships in the cervical region. Neck postural changes can lead to neck pain via associated changes in cervical movement patterns, so it is necessary to evaluate cervical spine kinematics in both normal subjects and in patients with neck pain. Reductions in the cervical range of motion (ROM) have implications for the safety and efficiency of functional activities and lead to a loss of corrective or protective reactions, which contribute to a loss of balance in the soft tissue extensibility around a joint. A study has also shown that a decreased cervical ROM is associated with poor sitting postures, such as forward head posture. ROM losses can occur from inactivity and structural changes of the tissues in the cervical spine, and result in an increase in connective-tissue density, shortening of collagen tissue, and muscle fibrosis.
Goniometer-based systems such as the CROM can reliably measure uniplanar cervical spine movement and the Spin T is a three-dimensional goniometer with demonstrated accuracy and reliability for measuring cervical spine mobility. Norton and Ellison also obtained good reliability and validity for Metrecom measurements on inanimate objects with known dimensions. The head and neck posture when performing computer work has been commonly evaluated in the sagittal plane based on two-dimensional posture or movement.
The association between forward head posture and neck pain has not been clearly defined, but a mechanism for the development of neck pain from habitual postures has been demonstrated. Studies of the effect of sustained forces have indicated that a single posture should not be sustained for longer than 1 h). McGill and Brown have shown that 20 min in a position of sustained loading can induce creep in soft tissues, with recovery taking longer than 40 min. Sustained forces produce time-dependent deformation and adaptations in soft tissue). Short duration stretching produces temporary deformation of soft tissues, but 1 h of stretching might be sufficient for long-term soft-tissue adaptations. Therefore, a longterm habitual posture can result in abnormal loading of ligaments and muscles that might ultimately contribute to a reduction in the cervical ROM and to the development of neck pain. Yoo et al. suggested that it is necessary to frequently change the sitting posture when performing long-term computer screen work.
Examining the active cervical ROM forms an important part of patient evaluations and has been studied in primary researches of work-related neck and upper-limb disorders. Therefore, primary studies need to investigate the association between cervical ROM and poor habitual posture. The purpose of this study was to elucidate the relationship between the active cervical ROM and changes in cervical posture after continuous long-term computer screen work.
A previous study found that workers using computer screens had increased forward neck flexion compared to those with relaxed sitting postures. Increased forward neck flexion may result in increased tension in posture-stabilizing muscles as well as increased compressive forces in the articulations of the cervical spine, resulting in a higher risk of work-related musculoskeletal disorders. Slumping over documents and staring all day at a computer screen screen do great damage to muscles, exacerbating tension and tightness around neck and shoulders.
This study was designed to identify the relationship between the active cervical ROM and the changes in the mean craniocervical and cervicothoracic angles after computer screen work. The authors hypothesis was that these parameters are significantly correlated. This study showed that the active neck extension angle was negatively correlated with the mean craniocervical angle and that the active neck flexion angle was negatively correlated with the mean cervicothoracic angle. This shows that, after long-term computer screen work, subjects with a more limited ROM of neck extension would exhibit a change in the craniocervical angle and those with a more limited ROM of neck flexion exhibit a larger change in cervicothoracic angle. The authors also suggest that treatments for poor cervical posture should focus on recovering the normal ROM of neck flexion and extension. The significant correlations between the upper trapezius muscle activity and head-neck angles found in studies represent important evidence of a link between muscle activity and postural control. The authors propose that the change in craniocervical angle would be related with shortening of the scalenus muscles in deep muscles, because shortening of scalenus muscles can cause limited range of motion in neck extension. The change in cervicothoracic angle would be related to shortening of the levator scapular muscle in deep muscles, because shortening of the levator scapular muscle can cause limited range of motion of neck flexion.
Jull et al. found that patients with neck pain put higher demands on their superficial neck muscles than do healthy people, to compensate for weakness of the deep muscles. The role of deep muscles for maintenance of cervical posture was verified in a computer model, which showed regions of local segmental instability if only the large superficial muscles of the neck were stimulated to produce movement, particularly in a ideal posture. Specific postural re-education exercise, initiated with the formation of a neutral lumbopelvic posture, should therefore be viewed at this time as a component of rehabilitation, providing a simple means for the patient to recruit the deep postural muscles of the cervical spine in a functional way regularly throughout the day. Postural patterns are maintained by a complex arrangement of input modified by habits. Poor postural patterns eventually result in chronic pain symptoms, which have been shown to be predictably caused by limited range of motion or shortening or lengthening of muscles. The authors suggest that an effective treatment program should include individually determined exercises based on postural muscle balance.
Only left lateral flexion in lateral flexion angles was negatively correlated with the change in cervicothoracic angle. All subjects were right-handed. Generally, they spend the majority of their day sitting at desks testing or studying. These tasks usually involve right-handed mouse work. It is possible that the constant use of this work causes shortening of muscles such as the upper trapezius. Habitually shortened muscle length, with the individual not moving through a complete range of motion on a daily basis, might cause adaptive changes in muscle length with a habitual forward head posture. The length/tension relationship of a muscle will adapt to the new resting length. Head posture will affect cervical range of motion in normal individuals as well as in individuals with neck pain.
The authors found that the active neck extension angle was negatively correlated with the mean craniocervical angle and that the active neck flexion angle was negatively correlated with the mean cervicothoracic angle. The authors suggest that treatments for poor cervical posture should focus on recovering the normal ROMs of neck flexion and extension. Also, the cervical ROMs of neck extension and flexion could be useful data for predicting changes in the head and neck posture after long-term computer screen work.
