From: Man Ther. 2010 Aug 11. [Epub ahead of print]

In the management of neck pain disorders, McKenzie recommends performing neck extension exercises from a fully neck retracted position in order to achieve a maximum range of lower cervical extension. However, no study has investigated the impact of pre-positioning the neck prior to the extension exercise. This study compared end-range sagittal cervical segmental rotation and translation from three starting positions: the neck in neutral, retraction and protraction.

Twenty asymptomatic healthy volunteers were recruited. Lateral radiographs were taken in neutral and at each of the three end-range extension positions and differences in sagittal rotation angles and translation from the neck neutral posture were calculated at each segment.

The results indicated that there was a significant difference in the pattern of the sagittal segmental rotation but no difference in summed rotations (total extension) between the three conditions. Protraction generated significantly greater extension range at C1-2 and retraction produced significantly greater extension range at C6-7 than alternate conditions. In contrast, there was no significant difference in segmental translation values between the three conditions. These results indicate initial neck positions can influence cervical segmental extension range at C1-2 and C6-7.

From: Man Ther. 2010 Jul 19. [Epub ahead of print]

Extensive computer use amongst office workers has lead to an increase in work related neck pain. Aberrant activity within the three portions of the trapezius muscle and associated changes in scapular posture have been identified as potential contributing factors. This study compared the activity (surface electromyography) of the three portions of the trapezius in healthy controls (n=20) to a neck pain group with poor scapular posture (n=18) during the performance of a functional typing task.

A scapular postural correction strategy was used to correct scapular orientation in the neck pain group and electromyographic recordings were repeated. During the typing task, the neck pain group generated greater activity in the middle trapezius and less activity in the lower trapezius than the control group. Following correction of the scapula, activity recorded by the neck pain group was similar to the control group for the middle and lower portions.

These findings indicate that a scapular postural correction exercise may be effective in altering the distribution of activity in the trapezius to better reflect that displayed by healthy individuals.

From: Work. 2010 Jan;36(1):3-8

This study was designed to identify the effect of seat support characteristics on the neck and trunk muscles and forward head posture of visual display terminal (VDT) workers working at computers. 22 VDT workers with forward head posture were asked to perform computer work. Surface electromyography recorded the five neck and trunk muscles Forward head angle was analyzed with a 3-D motion analysis system. The significance of differences in the seat supports (hard, spongy, unstable) was tested.

Computer work seated on an unstable cushion-ball as compared to a spongy soft-cushion seat support showed significantly lower midcervical and L5 paraspinal muscle activity and significantly higher lower trapezius and internal oblique abdominal muscle activity. The mean forward head angle decreased in the order of spongy, hard, and unstable seat supports.

An unstable cushion-ball seat support may prevent work-related neck and upper limb disorders associated with forward head posture.

From: Spine (Phila Pa 1976). 2010 May 4. [Epub ahead of print]

Fluoroscopic assessment of the effects of commercially available spinal orthotics on lumbar vertebral motion as subjects performed flexion and extension maneuvers. To quantitate the effects of 3 commonly available, off-the-shelf, soft, and semirigid spinal orthoses on lumbar spinal motion.

Commercially available soft and semirigid orthoses are widely prescribed for patients with low back pain and, at times, following surgery. Despite this use, surprisingly little is known about the magnitude of their effects on lumbar vertebral motion.

Ten subjects (6 men and 4 women) with an average age of 27.0 +/- 5.3 years, underwent videofluoroscopic imaging as they performed a full flexion/extension cycle. Assessments, during which the subjects were unbraced or wearing either a soft lumbrosacral orthosis, a semirigid lumbrosacral orthosis, or a semirigid thoracolumbrosacral orthosis were performed in random order. Images were obtained at a rate of 3.75 Hz and digitally processed to determine the sagittal rotation of the L3-L5 vertebral bodies.

Each of the braces produced a statistically significant reduction in overall lumbar motion during the flexion maneuver but none had a detectable effect during extension. Relative effectiveness varied by vertebral level. At the L3-L4 level, only the semirigid thoracolumbrosacral orthosis had a statistically significant effect on intervertebral flexion movement (32%). At the L4-L5 level all the orthoses were effective (and statistically indistinguishable) in their ability to reduce intervertebral flexion movements ranging from 48% for the semirigid thoracolumbrosacral orthosis to about 15% to 20% for the 2 lumbrosacral orthoses. No effects were noted for any of the orthoses at the L5-S1 level.

From: Spine (Phila Pa 1976). 2004 Jan 1;29(1):100-4.

Lumbar spine stabilization with a thoracolumbosacral orthosis: evaluation with video fluoroscopy.

In this study, L3-L5 vertebral body motion was tracked fluoroscopically as individuals performed flexion-extension movements wearing different thoracolumbosacral orthoses. To assess the effect of custom fitted thoracolumbosacral orthoses on lumbar vertebral body motion.

Several methods have been used to evaluate dynamic vertebral motion in vivo. Controversy remains regarding the utility of a thoracolumbosacral orthosis in decreasing intervertebral motion in the lumbar spine. Dynamic motion of the vertebral bodies was assessed fluoroscopically under four conditions: without a brace, with a custom fitted thoracolumbosacral orthosis, with the thoracolumbosacral orthosis and thigh extender at 0 degrees or 15 degrees. Intervertebral motion, i.e., the rotation of one vertebral body with respect to the adjacent body in the sagittal plane, throughout the flexion-extension cycle was used to assess the effect of each condition.

The thoracolumbosacral orthosis reduced both the total L3-L5 range of motion and the intervertebral motion at each individual level. Total rotation at L3 with respect to horizontal was reduced from 70 degrees without a brace to 50 degrees with a thoracolumbosacral orthosis. Use of the thigh extender provided an additional reduction to 10 degrees. There was no difference between the 0 degrees and 15 degrees settings. Intervertebral motion was reduced by 40% at both L3-L4 and L4-L5 when comparing no brace to thoracolumbosacral orthosis and an additional 15% when a thigh extender was added.

In this study, a custom molded thoracolumbosacral orthosis reduced both total L3-L5 motion and intervertebral motion in the lower lumbar spine. These effects are enhanced if a thigh extender is used.

Sources: Bracing For Low Back Pain

From: Spine (Phila Pa 1976). 2010 May 4. [Epub ahead of print]

This article is a repeated measures observational study to investigate change in sagittal alignment of head and neck posture in response to adjustments of an office chair with and without a lumbar roll in situ. Forward head posture has been identified as a risk factor for neck pain, and there is evidence to show that ergonomic correction in sitting may reduce the incidence of pain. The effect placement of a lumbar roll has on cervical spine posture has not been previously investigated experimentally but rather, is assumed to have a positive influence on head and neck posture.

Thirty healthy male participants (18-30 years) were photographed while registered in the natural head resting position in each of 4 sitting positions with and without a lumbar roll in situ. Two positions incorporated adjustments to the back rest and 1 to the seat pan of the office chair. The craniovertebral angle, as a determinant of head and neck posture was measured from the set of digitized photographs obtained for each participant. Comparisons between the craniovertebral angle in all postural registrations were made using a mixed model analysis adjusted for multiple comparisons.

Of the positions examined, significant differences in the mean craniovertebral angles were found with the backrest of the chair at 100 degrees and at 110 degrees. With the lumbar roll in situ and the backrest position at 110 degrees, there was a significant increase in the mean craniovertebral compared with the angle without the lumbar roll in situ.

The degree of angulation of the backrest support of an office chair plus the addition of lumbar roll support are the 2 most important factors to be taken into account when considering seating factors likely to favorably change head and neck postural alignment, at least in asymptomatic subjects.

From: Man Ther. 2010 Apr 28. [Epub ahead of print]

This was a cross-sectional correlation study to explore the relationships between sagittal postures of thoracic and cervical spine, presence of neck pain, neck pain severity and disability. Moreover, the reliability of the photographic measurement of the sagittal posture of thoracic and cervical spine was investigated. Forty-five subjects without neck pain and forty-seven subjects with neck pain were recruited. Using a photographic method, the sagittal thoracic and cervical postures were measured by the upper thoracic and the craniovertebral angles respectively. The Numeric Pain Rating Scale and Chinese version Northwick Park Neck Pain Questionnaire were used to assess neck pain severity and disability. The upper thoracic angle was positively correlated while the craniovertebral angle was negatively correlated with the presence of neck pain. The upper thoracic angle was negatively correlated with the craniovertebral angles in subjects with neck pain. Similar to the craniovertebral angle, the upper thoracic angle was moderately correlated with the neck pain severity and disability. The upper thoracic angle was a good predictor for presence of neck pain even better than that of the craniovertebral angle.

From: Industrial Health. 2010;48(2):145-53

Frequent material handling activities found in construction work environments put substantial stress on the neck, shoulder, and lower back resulting in pain and discomfort. A number of studies have evaluated the prevalence of different types of musculoskeletal disorders among construction workers. A study of workers compensation claims in Washington (US) show that masonry and residential construction are among the top five industries having the highest risk of injuries. Among Swedish construction workers studied by Holmström et al., 41.1% had neck and shoulder disorders. Building construction is listed among the top ten high-risk industries for musculoskeletal disorders among the Taiwanese working population by Guo et al. Neck and shoulder disorders affect 26.3% of male and 32.1% of female among the Taiwanese construction workers.

Manual material handling activities are an inseparable part of any construction project. Epidemiologically, several review studies have clearly established a strong relationship between work activities requiring forceful arm exertions and the occurrence of neck disorders. Common neck disorders associated with work activities involving forceful arm exertions include degenerative disc disorders such as disc herniation or cervical spondylosis and in some cases more muscle specific disorders such as tension neck syndrome. Even though these disorders are prevalent among construction workers, very few studies have evaluated the underlying pathomechanism.

The purpose of this study was to evaluate physical risk factors (force and posture) associated with neck disorders among construction workers. The role of the major neck muscles during lifting tasks at shoulder height was evaluated biomechanically by studying muscle activity in the cervical region.

The activation of the sternocleidomastoid muscle was significantly affected by the neck posture. At each weight condition, the activation of the sternocleidomastoid muscle was significantly higher at the extended neck posture than the respective neutral and flexed neck postures. The activation of the sternocleidomastoid muscle at the neutral and flexed neck posture was found statistically identical at all weight conditions.

Neck posture significantly affected the activation of upper trapezius muscle along the C4 level. At 25% weight condition the muscle was found most active at the flexed neck posture; however, the values were statistically not significant. At 50% and 75% weight conditions, the muscle was found most active at the flexed neck posture followed by the neutral and extended neck posture. The increase in the activation level with the change in the neck posture from neutral to flexed and from extended to flexed was statistically significant. The increase in the activation level with the change in the neck posture from extended to neutral was statistically not significant.

The activation of upper trapezius muscle along C7 level was also significantly affected by the neck posture. At each weight condition, the muscle was most active at the flexed neck posture followed by the neutral and the extended neck posture. In terms of statistical significance, at 50% weight condition, the activation at the flexed neck posture was significantly higher than the corresponding extended neck posture. At 75% weight condition, the activation at the flexed neck posture was significantly higher than the corresponding extended and neutral neck postures.

The weight lifted substantially affected the contribution of the neck muscles. In the case of the anterior neck muscle (sternocleidomastoid muscle), increased muscle activation with increased weight was significant at extended neck posture and mostly for higher weights (50%, and 75%) at neutral and flexed neck postures. For the posterior neck muscles (upper trapezius muscle) along C4 as well as C7 levels, at all the neck postures, a significant weight-muscle activation relationship was observed. This observed increase in the activation of the upper trapezius muscle along the C7 level with the increase in the weight at the shoulder height is consistent with previous investigations.

Posture had a significant impact on the activation level of the neck muscles. Independent of the weight lifted the sternocleidomastoid muscle was most active at the extended neck posture. The muscle activation at the neutral and flexed neck postures was identical. The upper trapezius muscle was most active at the flexed neck posture followed by the neutral and extended neck postures. However, this neck posture dependent behavior of the upper trapezius muscle was found to be significant only at the higher weight conditions, i.e. while lifting 50% and 75% weights, flexed neck caused substantially higher muscle activation compared to the neutral and extended neck postures. Consistent with findings, previously, increased activation of the upper trapezius muscle along the C7 level, at the flexed neck posture was reported in a number of studies evaluating sitting work postures. Moreover the observed neck posture and muscle-activation trend is in agreement with the muscle force-length relationship i.e. lower activation at shorter length and higher values at increased length.

The upper trapezius muscle, especially along the C7 level, has been widely studied in occupational investigations to evaluate neck and upper extremity disorders. To the authors knowledge no previous study evaluating occupational tasks or forceful arm exertions has reported the activities of the sternocleidomastoid muscle and the upper trapezius muscle in the cervical region. While evaluating neck disorders, understanding the activation of these muscles is vital, as they are bigger (surface) muscles in the neck region and anatomically couple the shoulder to the skull. Such an anatomical orientation may require these muscles to support the shoulder during forceful arm exertions. In confirmation with the authors claim, the results of this study clearly show that, similar to the upper trapezius muscle along the C7, the activation of the sternocleidomastoid muscle and the upper trapezius muscle in the cervical region was sensitive to the lifting weight as well as neck posture.

Overall, the results of this study indicate that the neck muscles play an active role during lifting and holding tasks at shoulder heights. While translating EMG activation of the neck muscles into physical risk factors associated with neck disorders, it is important to understand the possible musculoskeletal disorders pathways. Armstrong et al. presented a conceptual model describing the pathways involved in the pathogenesis of cumulative neck and upper limb musculoskeletal disorders. During work activities, the internal forces acting upon the musculoskeletal system require a response by the body. The response could be physiological or biomechanical in nature e.g. increased circulation, local muscle fatigue etc. The cumulative work activities could require continued or excessive response, which might affect the body’s ability to deal with further responses. With the repetition and/or accumulation of this phenomenon over the time, the reorganization or the regeneration process of the body tissue might be affected, causing structural tissue deformation.

Routine construction work requires lifting objects to shoulder height repetitively. The sustained activity in neck muscles during these tasks can be linked to (1) reduced blood flow, (2) repetitive loading of tendons, (3) rupture of the muscle’s z-discs, and (4) contractile forces acting on the cervical spine. The repetitive loading of the muscles and tendons has been associated with muscle specific neck disorders such as tension neck syndrome, while that of cervical vertebrae has been associated with degenerative disorders such as disc herniation and cervical spondylosis. Thus active contribution of the neck muscles during the lifting and holding of heavy objects at shoulder height could be probable risk factors associated with prevalent neck disorders among construction workers.

Considering the inherent association of lifting tasks with the construction profession, alternative material e.g. light-weight concrete blocks, pre-blended mortar and grout mix1, methods, and tools (Vacuum lifters) could be used to minimize the potential of neck injuries among construction workers. Future studies could be performed to find alternative construction work strategies and also to validate existing interventions.

In summary, this study concludes that lifting and holding weights at shoulder height result in increased activity in the superficial neck flexors and upper trapezius which may be a source of neck musculoskeletal disorders prevalent among construction workers.

Source: Neck Disorders among Construction Workers

From: Med Eng Phys. 2010 Mar 16. [Epub ahead of print]

Whole-body vibration experiments with subjects under vertical vibration were performed to examine and evaluate effects of backrest inclination on vibration transmitted through seats to the human body by using biodynamic response parameters represented by apparent mass and vibration power absorption. The biodynamic response parameters of twelve male subjects, exposed to vertical random vibration at 0.8m/s(2) r.m.s., were characterized under three different backrest support conditions, with the upper body supported against backrest inclined at angles of 0 degrees (vertical), 10 degrees , and 30 degrees with respect to the vertical axis.

An increased backrest inclination angle resulted in reduction of the total power absorption calculated particularly the frequency range of 1-20Hz. Normalized apparent mass magnitudes showed a principal resonance at about 5Hz for each subject for a backrest supported vertically. A second resonant peak appeared at about 7.5Hz in addition to the primary resonant peak for a backrest inclined at an angle of 10 degrees and then became much steeper for a backrest inclined at angle of 30 degrees. For a backrest inclined at an angle of 30 degrees, the resonant peak at 5Hz was less apparent than in other backrest inclination postures. All subjects showed the second resonant peak at about 7.5Hz in the double-normalized vibration power absorption for a backrest inclined at an angle of 30 degrees. According to the evaluation of vibration absorption behavior performed in this study, backrest inclination angle is preferable between 10 degrees and 30 degrees from the viewpoint of prevention of low back pain disorder.

From: Man Ther. 2009 Dec;14(6):696-701. Epub 2009 Jul 25

Deep cervical flexor muscle activation is impaired with neck pain. This study investigated the effects of low load cranio-cervical flexion and neck flexor strengthening exercises on spatial and temporal characteristics of deep cervical flexor muscle activation during a neck movement task and a task challenging the neck’s postural stability.

Forty-six chronic neck pain subjects were randomly assigned to an exercise group and undertook a 6-week training program. Electromyographic activity was recorded from the deep cervical flexor muscle, sternocleidomastoid and anterior scalene muscles pre and post intervention during the cranio-cervical flexion test and during perturbations induced by rapid, unilateral shoulder flexion and extension. Cranio-cervical flexion neck exercises for training increased deep cervical flexor muscle electromyographic amplitude and decreased sternocleidomastoid and anterior scalene electromyographic amplitude across all stages of the cranio-cervical flexion test.

No change occurred in deep cervical flexor muscle electromyographic amplitude following strength training. There was no significant between group difference in pre-post intervention change in relative latency of deep cervical flexor muscle but a greater proportion of the cranio-cervical flexion group shortened the relative latency between the activation of the deltoid and the deep cervical flexor muscle during rapid arm movement compared to the strength group. Specific low load cranio-cervical flexion exercise changes spatial and temporal characteristics of deep cervical flexor muscle activation which may partially explain its efficacy in rehabilitation.

From: Work. 2010 Jan 1;35(1):3-14.

Little is known about how lumbar spine movement influences mechanical changes and the potential injurious effects of prolonged flexion associated with seated postures. The purpose of this study was to examine the postural responses and pain scores of low back pain sufferers compared with asymptomatic individuals during prolonged sitting in order to understand the biomechanical factors that may be associated with sitting induced low back pain.

Sixteen participants with sitting aggravated low back pain were age and gender matched with 16 asymptomatic participants. Tri-axial accelerometers were used to monitor lumbar spine angles during 90 minutes of seated computer work. Lumbar spine postures were examined using a movement pattern analysis of two types of postural adjustments, termed shifts (step-like adjustments larger than 5 degrees and fidgets (small change and return to approximately the same position).

The low back pain group reported large significant increases in low back pain while asymptomatic individuals reported little to no pain. On average, every participant fidgeted every 40 to 50 seconds. However, only the low back pain sufferers demonstrated a significant increase in the number of shifts over 90 minutes of seated work; the low back pain group shifted every 4 minutes in the last 30 minutes of sitting compared to every 10 minutes for the asymptomatic group. Low back pain sufferers also demonstrated larger amplitudes of shifts and fidgets when compared to the asymptomatic group.

Greater and more frequent movement was not beneficial and did not reduce pain in individuals with pre-existing low back pain. Future work to understand the biomechanical effects of proactively inducing movement may help to explain the paradox of the relationship between movement and pain.

Were the shift and fidget increases used to prevent further lower back pain. The article seems to relate sitting causes increased shifting and fidgeting in low back pain sufferers, however, the relationship is not clear. We note decreased pain associated with low back pain when using devices meant to increase movement like the backtivator and the active seat.