Cervical Erector Spinae Muscles Research Articles

Neck and shoulder strains under various head flexing positions while standing and sitting with and without back support for male and female smartphone users

This study recruited 30 young participants (15 men and 15 women) to examine the smartphone usage patterns in three postures (standing, supported sitting, and unsupported sitting) and at five head angle (HA) positions (0°-40°). Cervical erector spinae (CES) and upper trapezius (UTZ) muscle activity, neck flexion (NF), gaze angle (GA), viewing distance (VD), and discomfort scores were collected. Results showed that HA and posture almost affected all responses, while CES muscle activity, NF, and VD differed between sexes. Strain in the neck and shoulder region increased with HA increase. Particularly, when the HA exceeded 20°, the discomfort scores considerably increased. Unsupported sitting should be avoided during smartphone use because of relatively poor responses in all variables. However, both standing and supported sitting have their respective benefits. Sex-related differences were typically observed in the standing position, with women tending to have lower NF but higher CES muscle activity compared with men. Practitioner summary: Although smartphones have become daily necessities, the overall quantitative neck and shoulder strain of using smartphones in different postures is rarely evaluated. We suggest that maintaining the HA within 20° is recommended because of relatively low load on the neck and shoulders. An unsupported sitting should be avoided during smartphone use.

A Flight Helmet-Attached Force Gauge for Measuring Isometric Neck Muscle Strength.

INTRODUCTION: Fighter pilots must withstand high Gz-forces that can damage the cervical spine. Strength of the cervical musculature is of vital importance when it comes to preventing these G-induced neck injuries. However, there is very little evidence on valid neck muscle strength measurement methods for fighter pilots. The aim of this study was to examine the validity of a commercial force gauge attached to a pilot's helmet for measuring isometric neck muscle strength.METHODS: A total of 10 subjects performed maximal isometric cervical flexion, extension, and lateral flexion with the helmet-attached gauge and with a weight stack machine, which was used as a reference. Electromyography (EMG) activities were recorded from the right and left sternocleidomastoids and cervical erector spinae muscles during all measurements. Paired t-tests, Pearson correlation coefficient, and Wilcoxon's test were used to analyze the data.RESULTS: Difference of mean force values between the devices was statistically significant in all directions. Pearson correlation coefficient varied between 0.73 and 0.89 and it was highest in cervical flexion. EMG activities were significantly different only in the left CES during flexion.DISCUSSION: The helmet-attached gauge is a valid tool for measuring isometric neck muscle strength and is best used as a means to compare individual differences in strength levels or to track the progress of strength development.Nyländen P, Virmavirta M, Sovelius R, Kyröläinen H, Honkanen T. A flight helmet-attached force gauge for measuring isometric neck muscle strength. Aerosp Med Hum Perform. 2023; 94(6):480-484.

Evaluation of surface electromyography of selected neck muscles during the whiplash mechanism in aware and unaware conditions due to safe punching in kickboxing

BackgroundKickboxing is considered as a combat sport in progress, in which injuries are frequent and significant, and close injury monitoring is highly recommended. Sports injuries to the head and neck are estimated to cause 70% deaths and 20% permanent disabilities although they are much less common than those to the limbs. Whiplash mechanism involves the rapid extension (opening) and flexion (bending) of neck. The purpose of the current study was to investigate the electromyographic activity of selected muscles in the whiplash mechanism in aware and unaware conditions of the safe punching in kickboxing so that we can design special exercises.MethodIn the present study, 24 male kickboxing athletes aged 18–40 years were selected based on a purposive sampling method. The surface electromyography (EMG) signals of muscles were recorded with and without awareness of safe punching by using a nine-channel wireless EMG device. Additionally, a nine-channel 3D inertial measurement unit (IMU, wireless,) was utilized to determine the acceleration, kinematics, and angular velocity of the subjects’ head. The statistical dependent t-test was applied to compare the EMG activity of each muscle, as well as its participation ratio.ResultsThe results of statistical analysis represented a significant increase in the EMG activity of sternocleidomastoid (p = 0.001), upper trapezius (p = 0.001) and cervical erector spinae muscles (p = 0.001), as well as the neck extension and flexion angles between the athletes aware (open eyes) and unaware (closed eyes) of the safe punching.ConclusionIn this study, the EMG activity of the sternocleidomastoid, upper trapezius, and cervical erector spine muscles in the aware condition was significantly different from the activity under unaware condition. In fact, the intended muscles exhibited significantly different behaviors in preventing extension and flexion in the two conditions.

목 굴곡 각도에 따른 스마트폰 사용이 목세움근과 위등세모근의 근피로도에 미치는 영향

This study investigated the effect of smartphone use by smartphone users" various angles on neck fatigue after using smartphone. Fifteen participants playing the game tasks for 20 min and Neck muscle fatigue was measured by extension the neck for 30 seconds in a supine position before and after using the smartphone at various neck flexion angles. At each neck flexion angle, there was no difference in the degree of muscle fatigue of the Upper Trapezius(UT) when extension of the neck between groups and within the group at both before and after using the smartphone. In the Cervical Erector Spinae(CES), there was no difference in fatigue at each neck flexion angle, but the difference in muscle fatigue within the groups was confirmed that the left side had more muscle fatigue after using the smartphone than before using the smartphone at a 45° flexion angle. In conclusion, smartphone users should be instructed not to adopt a neck flexion angle of 45° during smartphone use, as there is a link between these neck flexion angle ranges and increased CES muscle fatigue. Practitioner summary: This study proved that we should try to avoid a 45° neck flexion angle when using a smartphone.

Investigation of Flexion-Relaxation Ratio Symmetry in Subjects with and without Non-Specific Chronic Neck Pain

Introduction: Neuromuscular imbalance between right and left sides of Cervical Erector Spinae (CES) muscles can induce pain by applying the asymmetric loads on the spine incorrectly. This study evaluated the symmetry of the right and left cervical flexion-relaxation ratio (FRR) in patients with Non-Specific Chronic Neck Pain (NSCNP) and healthy subjects.We aimed to investigate the symmetry of FRR on the right and left sides of the CES muscles in individuals with and without NSCNP.Materials and Methods: A total of 25 patients with NSCNP and 25 healthy subjects participated in this study. The surface electromyography activity of CES muscles during four phases of flexion and extension tasks were measured and recorded. Unilateral FRR in the right and left sides of CES muscles was calculated and compared in each group.Results: Only in NSCNP patients, FRR in the right CES muscle was significantly higher than that in the left one (P<0.05). Also, FRR for bilateral CES muscles was significantly higher in healthy subjects than in NSCNP patients (P<0.001).Conclusion: The study results indicated a greater FRR asymmetry in CES muscles in NSCNP patients than in healthy subjects. This asymmetry is probably due to the dominance of the limb. Moreover, asymmetric FRR as a kind of neuromuscular imbalance may cause pain due to imposing asymmetric loads on spine structures.

Influence of neck flexion angle on gravitational moment and neck muscle activity when using a smartphone while standing

This study compares the effects of different neck flexion angles on neck gravitational moment and muscle activity of users that stand and operate a smartphone. Thirty-two healthy young adult smartphone users performed texting tasks for three minutes at four different neck flexion angles (0°, 15°, 30°, and 45°) while standing. Neck gravitational moment and cervical erector spinae (CES) and upper trapezius (UT) activity were investigated. When the neck flexion angle increased, the gravitational moment of the neck increased significantly. The muscle activity of CES significantly increased when the neck flexion angle increased, whereas that of UT decreased. The lowest gravitational moment of the neck at 0° flexion was consistent with the lowest CES muscle activity and the lowest neck discomfort score. In conclusion, for texting while standing, adults should maintain their neck posture at 0° flexion to reduce the gravitational force acting on the cervical spine and alleviate neck discomfort. Practitioner Summary: During smartphone use when standing, excessive neck flexion (30° and 45° flexion) should be avoided. The suggested neck posture when operating a smartphone while standing is 0° flexion. Abbreviations: CES: cervical erector spinae; UT: upper trapezius; COG: centre of gravity; MSDs: musculoskeletal disorders; CROM: cervical range of motion; sEMG: surface electromyography; VAS: visual analogue scale; MVCs: maximum voluntary contractions.

Cervical flexion relaxation phenomenon in patients with and without non-specific chronic neck pain.

The cervical flexion relaxation phenomenon (FRP) is a myoelectric silence of neck extensor muscles which occurs after a certain degree of flexion. Impaired flexion relaxation can impose the vertebral structures to excessive loading resulting from the persistence of muscular contraction. This study aimed to investigate the incidence or absence of FRP in cervical erector spinae (CES) and upper trapezius muscles in patients with chronic neck pain (CNP). Twenty-five patients with CNP and 25 healthy volunteers were recruited. They accomplished cervical flexion and extension from a neutral position in four phases in the sitting position. The surface electromyography activity of both CES and upper trapezius muscles was recorded in each phase. Cervical flexion and extension movements were simultaneously measured using an electrogoniometer. FRP in CES was observed in 84% and 36% of healthy subjects and CNP patients, respectively. Flexion relaxation ratio (FRR) in CES was lower in CNP patients than in healthy subjects (mean diff = 1.33; 95% CI: 0.75-1.91) (P< 0.001). Only in CNP patients, FRR in right erector spinea was significantly higher than that in the left erector spinea (P= 0.04). FRP incidence in CNP patients was less than in healthy subjects. Moreover, this phenomenon begins later in CNP patients than in healthy subjects indicating prolonged activity of CES muscles during flexion in the CNP group. The difference between FRR in the right and left sides of erector spinea muscles can result in CNP.

Effect of neck flexion angles on neck muscle activity among smartphone users with and without neck pain

This study examined the differences in neck muscle activity at various neck flexion angles in smartphone users with and without neck pain. Forty-four participants performed texting tasks for 1 min and 30 s. Neck muscle activity and pain in the neck were measured at different neck flexion angles. There was a difference in neck muscle activity for each of the neck flexion angles; the Cervical Erector Spinae (CES) muscle activity increased while the Upper Trapezius (UT) muscle activity decreased when at increased neck flexion angles. At neck flexion angle of 0°–15°, the activity of both CES and UT muscles were acceptably low. Smartphone users with neck pain had slightly higher muscle activity levels than smartphone users without neck pain. In conclusion, smartphone users should consider adopting neck flexion angles between 0 and 15 degrees during smartphone use as there is an association between this neck flexion angle range and reduced CES muscle activity. Practitioner summary: This study demonstrated that both smartphone users with and without neck pain should try to keep their neck flexion angle between 0° and 15° when using their smartphone. This would reduce neck muscle activity and the risk of developing neck disorders associated with smartphone use.

Application of the Cervical Flexion Relaxation Ratio to Investigate the Impact of Torso-borne Load Redistribution

Students and military personnel often carry heavy torso loads (e.g. backpacks) which can lead to pain in the shoulders and back. To minimize pain associated with torso loads, load redistribution devices have been developed to off-load weight from the shoulders to the hip. Previous studies have used the cervical flexion relaxation ratio (cFRR), a measure of muscle activity between the extension and flexion phase of forward head motion, to correlate backpack loads with the potential of developing neck pain. PURPOSE: Using the cFRR, assess the impact of redistributing torso-borne loads and whether changes in cFRR are observed following prolonged load carriage. METHODS: Twelve volunteers walked at 1.34 m·s-1 at 0% grade for 40 min while wearing a torso-borne baseline load of 27 kg and two load distribution conditions to offload shoulder pressure. Flexible pressure sensors monitored pressure distribution at the shoulders and hips. To capture cFRR, bilateral EMG sensors with integrated tri-axial accelerometers were placed on the cervical erector spinae muscle bellies. EMG data were sampled at 2 kHz, demeaned, band pass filtered from 30 to 500 Hz, and full wave rectified. cFRR (Table 1) was measured pre-walk and post-walk and outcomes were submitted to repeated measures ANOVA based on load conditions, side of body and time. RESULTS: The average pressure measured at the shoulders for the baseline load (3.76 ± .90 kPa) was significantly higher than the two load distribution conditions (1.55± 1.68 kPa, p = .001; 1.72± 1.12 kPa, p < .0005, respectively). There were no main effects due to load condition or body side (p > .074). However, there was a significant main effect of time (p = .033). CONCLUSION: The load distribution equipment successfully shifted pressure from the shoulders to the hips, however this did not correlate with an improvement in cFRR. Changes in cFRR were observed pre- vs. post-walk indicating that the cFRR measure is sensitive to load carriage over time.Table 1: cFRR

Disturbance of neck proprioception and feed-forward motor control following static neck flexion in healthy young adults

The highly complex proprioceptive system provides neuromuscular control of the mobile cervical spine. Static neck flexion can induce the elongation of posterior tissues and altered afferent input from the mechanoreceptors. The purpose of this study was to examine the effect of prolonged static neck flexion on neck proprioception and anticipatory postural adjustments. Thirty-eight healthy participants (20 females and 18 males) between the ages of 20–35 years with no history of neck, low back, and shoulder pain enrolled in this study. Neck proprioception and anticipatory muscle activity were tested before and after 10-min static neck flexion. For assessment of neck proprioception, each participant was asked to perform 10 trials of the cervicocephalic relocation test to the neutral head position after active neck rotation to the left and right sides. Anticipatory postural adjustments were evaluated during a rapid arm flexion test. Following the flexion, the absolute and variable errors in head repositioning significantly increased (p < 0.05). The results also showed that there was a significant delay in the onset of myoelectric activity of the cervical erector spinae muscles after flexion (p = 0.001). The results of this study suggested that a 10-min static flexion can lead to changes in the neck proprioception and feed-forward control due to mechanical and neuromuscular changes in the viscoelastic cervical spine structures. These changes in sensory-motor control may be a risk factor for neck pain and injury.

The effect of static neck flexion on mechanical and neuromuscular behaviors of the cervical spine

Occupations that involve sustained or repetitive neck flexion are associated with a higher incidence of neck pain. Little in vivo information is available on the impact of static neck flexion on cervical spinal tissue. The aim of this study was to assess changes in mechanical and neuromuscular behaviors to sustained neck flexion in healthy adults. Sixty healthy subjects aged 20–35 years participated in this study. The participants were exposed to static neck flexion at a fixed angle of full flexion for 10 min. Mechanical and neuromuscular responses of the cervical spine to sudden perturbations were measured pre- and post-exposure. Magnitude of load-relaxation during flexion exposure, stiffness, peak head angular velocity, and reflexive activities of cervical muscles were recorded. Effective neck stiffness decreased significantly, especially in female participants (P = 0.0001). The reflexive response of the cervical erector spinae muscles to head perturbation delayed significantly (P = 0.0001). Peak head angular velocity was significantly increased after exposure to neck flexion for 10 min, especially in female participants (P = 0.001). In the present study, static flexion resulted in changes in mechanical and neuromuscular behavior of the cervical spine, potentially leading to decreased stiffness of the cervical spine. The results confirm the importance of maintaining a correct head and neck position during work and improving the work environment to reduce the cervical spinal load and work-related neck pain.

Trunk Posture Influences Neck Angle When Reading A Tablet Computer

In 2013, 64% of American households owned a handheld computer device (e-reader, tablet, smartphones, etc.). The presence of these devices has grown more quickly than our understanding of their effects on musculoskeletal disorders. Their use on a tabletop or a person’s lap causes increased head and neck flexion, as well as an inreased gravitational moment produced by the weight of the head (Straker et al., 2009, Young et al., 2012, Vasavada et al., 2015). A limitation to these studies is that they keep a standard trunk position throughout all tasks; however, people can also assume a semi-reclined position when reading a tablet. The purpose of this study was to determine the influence of a semi-reclined trunk position on neck and head flexion angle, and cervical erector spinae muscle activity. Nineteen participants (10 male, 9 female) read off of a tablet in four postures: with the tablet in their lap, on a tabletop, off of a standard computer monitor, and semi-reclined to an angle of 30 degrees from the vertical. Having the tablet on the lap ( M=16%MVC, SD=8%MVC) significantly increased muscle activity of the cervical erector spinae ( p=.0023) compared to reading off of a monitor or in the semi-reclined position (approximately 10%MVC). Neck and head flexion angles significantly increased ( p&lt;.001) when reading the tablet off the lap (neck M=56.8o, SD=17.3o; head M=53.4o, SD=12.9o) versus the computer (neck M=6.4o, SD=6.4o; head M=8.2o, SD=7.4o), however, the head angle during semi-reclined reading stayed more vertical despite having the highest increase in neck flexion angle (neck M=71.6o, SD=14.0o; head M=19.7o, SD=9.2o). In the semi-reclined position, the gravitational moment of the head is second smallest for the four reading positions. In theory, this is desired as the moment that must be produced by the musculature and surround tissues would be less. The downside to this posture is that many of the neck extensor muscles may still not be in optimal force and moment production position. Many of the neck muscles that assist with extension originate from C5 to T5 and insert on C5 and above (Vasavada et al., 1998). At 30 degrees of neck flexion, the moment generating capability of the spenius and semispinalis muscles are decreased compared to when at a neutral position and fascicle length of splenius cervicis, capitis, and semispinalis capitis muscles experience changes of more than 70% of optimal length (Vasavada et al., 1998). While many of the extensor muscles only show moment arms that vary by 1 cm or less, for some there can be about a 2-3 cm changes as one goes from a flexed to extended neck posture (Vasavada et al., 1998). These combined changes mean that the force producing capabilities of the neck extensor muscles may be compromised a semi-reclined position. Future studies should report torso angle to properly analyze biomechanical risk factors during handheld computer use and compare results between studies.

The prediction of neck extensor force using surface electromyography.

The relationship between muscular force and electromyography (EMG) has been investigated by numerous researchers. EMG has not previously been used as a means of estimating force in the cervical erector spinae (CES). Use EMG of the CES musculature to indirectly predict neck extension force. Isometric contractions of the CES muscles were studied at increasing levels of contractile force across all participants (n= 12) to produce an individualised force-EMG relationship. The method of least squares was used to determine the linear regression trend line for the force-EMG relationship. The validity of these individual `correlation curves' was demonstrated through further, blinded, investigation. A linear relationship was identified for the individualised correlation curves that gained in strength for < 50% maximum voluntary contraction (MVC; R2> 0.8 for 80% of trials). The prediction of muscle force from the correlation curves was found to be statistically similar to the equivalent experimental data (p> 0.05). Given the tendency of EMG to slightly overestimate force in most cases, an adjustment coefficient was calculated to reduce the error in the predicted force data. This study reports a validated method using EMG to indirectly acquire CES muscular force, which has application for clinicians and research scientists working in fields including sport and rehabilitation.

Effect of static neck flexion in cervical flexion-relaxation phenomenon in healthy males and females

Neck pain is a common musculoskeletal disorder, especially among skilled workers who must keep their necks in a flexed position frequently during the day. The present study investigated changes in cervical flexion-relaxation phenomenon parameters after sustained neck flexion. The participants were 40 healthy subjects grouped by gender (20 females, 20 males). They were exposed to static neck flexion at the full angle of cervical flexion for 10min. Each subject underwent three trials of cervical flexion and re-extension before and after this period. Differences in onset and cessation angle of flexion-relaxation phenomenon, maximum neck flexion angle, amplitude of neck muscle activation and flexion-relaxation ratio were evaluated. The maximum neck flexion angle significantly increased after sustained flexion. The onset of flexion-relaxation was significantly delayed during flexion, but cessation angle remained unchanged. Myoelectric activity of the cervical erector spinae muscles increased significantly after maintaining flexion, especially in female subjects. The flexion-relaxation ratio also decreased significantly. It was concluded that 10min of static flexion results in a delay in flexion-relaxation phenomenon and a shortened silence period. Also the cervical erector spinae muscles are required to be active longer and generate more activity. These neuromuscular changes may be a risk factor for neck pain.

Analysis of cervical and shoulder neuromuscular activity during adapted swimming with and without a snorkel: Implications for rehabilitation

Summary Objective Compare the activation of the cervical and shoulder muscles in the execution of adapted swimming with and without a snorkel. Methods and subjects This study uses cross-sectional, analytical inference analysis. We studied the musculature of the right shoulder and cervical spine of 16 healthy participants. We examined seven muscles with surface electromyography including the cervical erector spinae, trapezius, infraspinatus, pectoralis, anterior deltoid, middle deltoid and latissimus dorsi. Each participant was measured in five complete cycles of adapted swimming. Results There was significantly more activity in the infraspinatus muscle (increased by 18%, P = .020) and significantly less activity in the cervical erector spinae muscle (decreased by 27%, P = .050) when using a snorkel compared to not using a snorkel. Conclusion Using a snorkel during adapted swimming produces changes in the level of muscle activation in the shoulder and neck. An increase in infraspinatus and a decrease in cervical erector spinae activity due to reduced head movement and an absence of significant cervical rotation when using a snorkel may lead to increased resistance and work for the shoulder. Finally, the metacentric effect on the arm decreases because the arm does not come out of the water.

Effects of Cervical Flexion on the Flexion-relaxation Ratio during Smartphone Use.

[Purpose] The purpose of this study was to measure the cervical flexion-relaxation ratio (FRR) and intensity of neck pain and identify the differences according to postures adopted while using smartphones. [Subjects] Fifteen healthy adults with no neck pain, spinal trauma, or history cervical surgery participated in this study. [Methods] The activity of the cervical erector spinae muscle was recorded while performing a standardized cervical flexion-extension movement in three phases (flexion, sustained full flexion, extension). And neck pain intensity was recorded using a visual analog scale (VAS) with values between 0 and 10. Postures held while using a smartphone are distinguished between desk postures and lap postures. The FRR was calculated by dividing the maximal muscle activation during the extension phase by average activation during the complete flexion phase. [Results] No significant differences were found in the FRR between desk posture, lap posture, and baseline, though the intensity of the neck pain increased in the lap posture. [Conclusion] The FRR could be a significant criterion of neuromuscular impairment in chronic neck pain or lumbar pain patients, but it is impossible to distinguish neck pain that is caused by performing task for a short time. Prolonged lap posture might cause neck pain, so the use of smartphones for a long time in this posture should be avoided.

A comparative investigation of flexion relaxation phenomenon in healthy and chronic neck pain subjects

The cervical flexion relaxation phenomenon (FRP) is a neck extensor myoelectric "silence" that occurs during complete cervical and lumbar flexion. In contrast to low back pain, the changes that occur during FRP in chronic neck pain (CNP) patients are still not clear. The aim of this study was to assess the characteristics of this phenomenon in the cervical region in CNP patients and controls. Twenty-two women (23 ± 2.62 years) with chronic non-specific neck pain and 21 healthy women (23.4 ± 1.68 years) participated in this study. They accomplished a cervical flexion and extension from neutral position. Neck angle and surface electromyographic activity of cervical erector spinae (CES) and upper trapezius muscles were recorded. Appearance, onset and offset angle of the FRP were analysed and compared between the two groups. There were significant differences in the appearance of FRP between the two groups (P ≤ 0.001). The FRP in the CES muscles was observed in 85.7 % of healthy subjects and in 36.3 % of CNP patients, and no FRP was observed in the upper trapezius. Results of this study show that the onset and offset of FRP parameters were significantly different between the two groups (P ≤ 0.001). The results of the present study indicate that FRP in CNP patients was seen less than the healthy subjects, and moreover the FRP period was reduced in CNP patients. Our results also suggest that the changes in FRP of CNP patients may be due to the increased CES activity in these patients.

Comparing Biofeedback With Active Exercise and Passive Treatment for the Management of Work-Related Neck and Shoulder Pain: A Randomized Controlled Trial

Ma C, Szeto GP, Yan T, Wu S, Lin C, Li L. Comparing biofeedback with active exercise and passive treatment for the management of work-related neck and shoulder pain: a randomized controlled trial. Objectives To compare the effects of biofeedback with those of active exercise and passive treatment in treating work-related neck and shoulder pain. Design A randomized controlled trial with 3 intervention groups and a control group. Setting Participants were recruited from outpatient physiotherapy clinics and a local hospital. Participants All participants reported consistent neck and shoulder pain related to computer use for more than 3 months in the past year and no severe trauma or serious pathology. A total of 72 potential participants were recruited initially, of whom a smaller group of individuals (n=60) completed the randomized controlled trial. Interventions The 3 interventions were applied for 6 weeks. In the biofeedback group, participants were instructed to use a biofeedback machine on the bilateral upper trapezius (UT) muscles daily while performing computer work. Participants in the exercise group performed a standardized exercise program daily on their own. In the passive treatment group, interferential therapy and hot packs were applied to the participants' necks and shoulders. The control group was given an education booklet on office ergonomics. Main Outcome Measures Pain (visual analog scale), neck disability index (NDI), and surface electromyography were assessed preintervention and postintervention. Pain and NDI were reassessed after 6 months. Results Postintervention, average pain and NDI scores were reduced significantly more in the biofeedback group than in the other 3 groups, and this was maintained at 6 months. Cervical erector spinae muscle activity showed significant reductions postintervention in the biofeedback group, and there were consistent trends of reductions in the UT muscle activity. Conclusions Six weeks of biofeedback training produced more favorable outcomes in reducing pain and improving muscle activation of neck muscles in patients with work-related neck and shoulder pain.

Relationship between Active Cervical Range of Motion and Flexion–Relaxation Ratio in Asymptomatic Computer Workers

A high prevalence and incidence of neck and shoulder pain is present in the working population, especially sedentary workers. Recent findings have indicated that the flexion-relaxation (FR) ratio in the cervical erector spinae (CES) muscles might be a significant criteria of neuromuscular impairment and function. Additionally, the active cervical range of motion (ROM) is frequently used for discriminating between individuals with pain and those who are asymptomatic. The purpose of the present study was to examine the relationship between the active cervical ROM and the FR ratio in a sample of regular visual display terminal (VDT) workers. In total, 20 asymptomatic male VDT workers were recruited. Active cervical ROM was measured by a cervical ROM (CROM) instrument. Surface electromyography (EMG) was used to collect myoelectrical signals from the CES muscles, and the FR ratio was calculated for statistical analysis. Pearson correlation coefficients were used to quantify the linear relationship between the active cervical ROM and the FR ratio. The values obtained for the FR ratio in the right CES muscles correlated significantly with the active cervical ROM measured in flexion (r=0.73, p<0.01), left lateral flexion (r=0.64, p<0.01), and left rotation (r=0.60, p<0.01). Flexion (r=0.74, p<0.01) and right lateral flexion (r=0.61, p<0.01) positively correlated with the left FR ratio. Extension and right rotation showed either a very weak or no correlation with the mean value of the right and left FR ratio. Our findings suggested that the cervical FR ratio had a positive correlation with cervical movements, and that changes of the activation patterns in CES demonstrated as cervical FR ratio are associated with reduction of the cervical range of motion including flexion and lateral flexion. In addition, muscular dysfunction of the CES could occur in regular computer workers prior to occurrence of pain; this means that the FR ratio could be used to evaluate the potential risk of neck discomfort in computer workers.

Surface electromyography signals from neck muscles during different craniocervical postures in a lateral recumbent position

Objective To survey cervical myoelectric signals during craniocervical flexion, neutral and extension postures, and to explore the evidence that proper head position can alleviate cervical muscle fatigue in a lateral recumbent position. Methods Surface electromyography (sEMG) signals were detected from the sternocleidomastoid, upper trapezius and erector spinae muscles of 30 young subjects bilaterally during craniocervical flexion,neutral and extension postures in the left lateral recumbent position. The integrated trace area (IEMG) and median frequency (MF) were estimated. Results The average IEMG of the sternocleidomastoid muscles was significantly lower in flexion than in extension bilaterally. The average IEMG of the erector spinae muscles was lower in extension than in flexion bilaterally, and the difference was again significant. The IEMGs of the upper trapezius muscle showed no significant difference on average in the three postures bilaterally. There was no significant MF difference in any of the muscles. Conclusions The muscles in the cervical back were less activated during craniocervical extension in a lateral recumbent position. A little cranicocervical extension is optimal while resting in a lateral recumbent position. Key words: Surface electromyography;  Lateral recumbent position;  Sternocleidomastoid muscle;  Cervical erector spinae muscle;  Upper trapezius muscle