Sternocleidomastoid Activity Research Articles

Effect of screen configuration on the neck angle, muscle activity, and simulator sickness symptoms in virtual reality.

There is a lack of information about the optimal setup of multiple screen configurations in virtual reality (VR) office work. The objective of this study was to evaluate the effects of different screen configurations on neck flexion, rotation, neck muscle activity, and simulator sickness symptoms during Virtual Reality (VR) office work. Twelve participants (7 males; 21 to 27 years old) performed copy-paste and drag-drop tasks in three different screen configurations (single screen, primary-secondary screen, and double screen) in a randomized order. Optical motion capture system, electromyography (EMG) device, and simulator sickness questionnaire (SSQ) were used to measure the users' responses. Neck rotation angles, muscle activities, and VR sickness were significantly affected by the screen configurations (p < 0.021). The primary-secondary screen showed the highest right rotation angle (median: -33.47°) and left sternocleidomastoid (SCM) muscle activities (median: 12.57% MVC). Both single (median: 22.42) and primary-secondary (median: 22.40) screen showed the highest value of SSQ. The screen configurations in VR could be an important design factor affecting the users' physical demands of the neck and VR sickness symptoms. Asymmetric neck rotations caused by the primary-secondary screen conditions should be avoided.

Evolving Dynamics of Neck Muscle Activation Patterns in Dental Students: A Longitudinal Study.

Cervical pain has been linked to increased motor unit activity, potentially associated with the initiation and progression of chronic neck pain. Therefore, this study aimed to compare the time-course changes in cervical superficial muscle activation patterns among dental students with and without neck pain throughout their initial semester of clinical training. We used an online Nordic Musculoskeletal Questionnaire for group allocation between neck pain (NP) (n = 21) and control group (CG) (n = 23). Surface electromyography (sEMG) of the sternocleidomastoid and upper bilateral trapezius was recorded before starting their clinical practice and after their first semester while performing a cranio-cervical flexion test (CCFT) in five increasing levels between 22 mmHg and 30 mmHg. After the first semester, both the CG (p < 0.001) and NP (p = 0.038) groups showed decreased sternocleidomastoid activation. The NP group exhibited a concomitant increase in upper trapezius coactivation (p < 0.001), whereas the muscle activation pattern in asymptomatic students remained unchanged (p = 0.980). During the first semester of clinical training, dental students exhibited decreased superficial flexor activity, but those with neck pain had increased co-contraction of the upper trapezius, likely to stabilize the painful segment. This altered activation pattern could be associated with further dysfunction and symptoms, potentially contributing to chronicity.

Myoelectrical activity of sternocleidomastoid muscle in smartphone-addicted versus non-addicted individuals

BackgroundOver the past decade, smartphone users have substantially increased, raising concerns about potential musculoskeletal problems associated with long-term use. Prolonged smartphone usage may cause discomfort in the thumb, shoulder, and neck that can be exacerbated over time, thereby affecting the electrical activity of several muscles, such as the sternocleidomastoid muscle (SCM). Accordingly, we aimed to examine the impact of smartphone addiction on the myoelectric activity of the SCM.Design and methodForty-four smartphone users, both male and female, aged 18–30 years, were recruited from the Faculty of Physical Therapy, Cairo University, in this observational study. The participants were equally allocated into two groups, A and B, based on their Smartphone Addiction Scale-Short Version (SAS-SV) scores. Group A consisted of smartphone-non-addicted users who scored below 31 for males and 33 for females, whereas group B included smartphone-addicted users who scored over 31 for men and 33 for females. Additionally, the electromyography (EMG) device was used to monitor the electrical activity during rest and maximum voluntary contraction (MVC).ResultsThe results showed a significant difference (P < 0.0001) in the electrical activity of the left and right SCMs between the two groups at rest but a nonsignificant difference during MVC.ConclusionSmartphone addiction significantly impacts the myoelectric activity of the SCM at rest among young adult smartphone users, but this impact is not significant during MVC.

The effect of myofascial techniques on the electrical activity of the neck muscles

Introduction. Research by foreign scientists often present the results of studies of the effects of specific osteopathic techniques on the body. Myofascial techniques are dynamic low-amplitude techniques in which the myofascial complex of tissues is rhythmically stretched in areas where their mobility is limited. In one study of paravertebral muscles using surface electromyography (sEMG) before and after myofascial techniques, a statistically significant (p&lt;0,05) decrease in their electrical activity was obtained. No publications devoted to the study of the effect of myofascial techniques on the electrical activity of the neck muscles were found.The aim is to study the effect of myofascial techniques on the electrical activity of the neck muscles in individuals with increased tone of these muscles.Materials and methods. A prospective study was conducted in the Department of Osteopathy of Mechnikov North-West State Medical University in which 30 apparently healthy volunteers who did not present active complaints, aged from 23 to 35 years, took part, with a median of 25 years. Inclusion criteria were palpation-determined increased tone of the sternocleidomastoid and upper trapezius muscles. Non-inclusion criteria were the presence of diseases and/or conditions that are an absolute contraindication to osteopathic correction, a history of neck injuries; taking medications that affect muscle tone at the time of the study; neuromuscular diseases. At the beginning of the study, all volunteers underwent palpation of the upper trapezius and sternocleidomastoid muscles on both sides. The degree of increase in muscle tone was assessed in points: 1 — weak; 2 — medium; 3 — strong; 0 — normal tone. Next, they underwent myofascial mobilization techniques: longitudinal and unilateral lateral mobilization of the soft tissues of the neck, separate mobilization of the sternocleidomastoid muscles. Before, immediately after, and three days after the session, muscle tone was recorded using surface electromyography (sEMG), which was performed on a wireless monitoring complex for electrophysiological signals «Kolibri» (OOO NMF «Neurotech», Russia). At rest, the average and maximum amplitude of electrical activity of the sternocleidomastoid and upper trapezius muscles was measured. The recording was made synchronously from the right and left sides of the body.Results. The sEMG indices of muscles with different tone based on the results of subjective assessment were statistically highly significant (p=0,0001). Moreover, according to the A(avg) indicator, the range diagrams either did not intersect or intersected only slightly. The electrical activity of the sternocleidomastoid muscles after myofascial mobilization techniques decreased statistically significantly and remained at the same level for 3 days (p=0,01). Such dynamics were observed in both the average and maximum amplitude of electrical activity. The amplitude of electrical activity of the right sternocleidomastoid muscle was slightly greater than that of the left (all subjects were right-handed), but these differences did not reach statistical significance (p&gt;0,05). After treatment, there was a trend towards a decrease in the asymmetry of electrical activity between the left and right sternocleidomastoid muscles, both middle and maximum, but these changes were not statistically significant (p&gt;0,05). The electrical activity of the upper part of the right trapezius muscle decreased statistically significantly after treatment and remained at this level for 3 days (p=0,01). The left trapezius muscle was excluded from the study due to technical reasons.Conclusion. The study showed that osteopaths (who are completing residency training in osteopathy) palpably distinguish between normal muscle tone and its increase in weak and moderate degrees. One session of myofascial mobilization techniques leads to a decrease in the tone of the sternocleidomastoid muscles and the upper part of the right trapezius muscle according to sEMG. Such changes occur immediately after the session and then persist for at least three days in young people with increased tone of these muscles. Surface electromyography can be used to objectively record and measure the results of specific osteopathic techniques. This is important for increasing the evidence of clinical research in osteopathy.

Real time ultrasound imaging shows changes in deep neck flexor activation during exercise in individuals with mechanical neck pain.

Deep neck flexor muscle atrophy and increased superficial neck muscle activation are associated with disability and pain intensity in individuals with neck pain. There is a lack of evidence to support direct assessment of deep neck flexor muscles in a non-invasive way during exercise performance to help determine the effectiveness of different neck strengthening exercises. Compare longus colli (LC) and sternocleidomastoid (SCM) activation between individuals with and without neck pain using real time ultrasound (RTUS) during a series of craniocervical exercises. This cross-sectional cohort study recruited 10 control and 10 neck pain participants to complete four deep neck flexor activation activities involving varying levels of craniocervical flexion. Dimensions of the LC and SCM were measured using RTUS at rest and during exercise. Independent t-tests assessed baseline differences and analysis of variance examined activation changes. At rest, the neck pain group had significantly smaller cross-sectional area and thickness of the LC compared to the control group (p< 0.05). During exercise, the neck pain group showed significantly larger increases in LC thickness and cross-sectional area across exercise compared to the control group, with no differences in SCM activation between groups. Despite atrophy, individuals with neck pain can activate their deep neck flexor muscles appropriately without activating their superficial neck flexor muscles in a supine series of craniocervical flexion exercise as measured by non-invasive ultrasound imaging.

Influence of Upper Trapezius and Sternocleidomastoid Muscle Activation according to Cervical Flexion Angle in Sitting Posture

Influence of Upper Trapezius and Sternocleidomastoid Muscle Activation according to Cervical Flexion Angle in Sitting Posture

The effect of deep neck flexor endurance on craniovertebral angle changes and neck and shoulder muscle activities during a computer task

ABSTRACT The deep neck flexors are important for maintaining neck posture by stabilizing and supporting it through low-intensity contraction, ensuring static endurance. The subjects performed computer tasks after having their deep neck flexor endurance measured using a pressure biofeedback unit. The craniovertebral angle (CVA) and the muscle activities were measured while participants were completing computer tasks for 10 min. The deep neck flexor endurance was significantly negatively correlated with CVA changes at 0–2 min. The deep neck flexor endurance was significantly negatively correlated with sternocleidomastoid muscle and upper trapezius activity at 0–2 min. The deep neck flexor endurance negatively predicted CVA changes at 0–2 min and explained 28.8% of the variance in the CVA changes. The lower the deep neck flexor endurance, the earlier the simultaneous changes occurred in the CVA and the neck and shoulder muscle activities during computer tasks.

Predictive Contribution of the Superficial Neck Muscles to Short-Latency Rate of Force Development of the Head and Neck.

To evaluate the contribution of splenius capitis, sternocleidomastoid, and upper fibers of trapezius activation to the gains in rate of force development (RFD) of the head and neck during maximum voluntary ballistic contractions. RFD gain was facilitated by a single-session intervention for maximum voluntary ballistic contractions in the anterior direction, oriented at 45° to the midsagittal plane, which require active restraint of axial rotation. Muscle activation for the agonist (sternocleidomastoid) and 2 antagonists (splenius capitis and upper fibers of trapezius) was evaluated. The study sample included 12 physically active men (mean age, 22.6y). RFD (N·m·s-1; 0-100ms) and integrated muscle activity (50ms before and 100ms after force onset) were measured at 10 minutes, 20 minutes, and 2 days postintervention, relative to baseline. Muscle activation predictive of RFD gains was evaluated by linear regression analysis. RFD reproducibility was evaluated using the coefficient of variation of the typical error. The intervention yielded a 1.95- to 2.39-fold RFD gain (P ≤ .05), with greater RFD gain for participants with a lower peak moment of force (<10.9N·m) than those with a higher peak moment (≥10.9N·m) at baseline (P ≤ .002). For the low group, 65% to 74% of the RFD gain was predicted by ipsilateral sternocleidomastoid activation, with ipsilateral splenius capitis activation predicting 77% to 92% of RFD gain for the high group. Absolute peak and impulse of static force were greater for the high than for the low group (P ≤ .04). RFD reproducibility was high (coefficient of variation of the typical error ≤ 14.4%). The agonist- and antagonist-focused synergies might reflect different functional priorities, higher RFD gain compared with higher head-neck force.

Effectiveness of the sternocleidomastoid muscle contraction asymmetry and filter: cervical vestibular evoked myogenic potential.

This study aimed to determine the precautions that can be taken to increase the reliability of the vestibular evoked myogenic potentials test without being affected by the asymmetry of the sternocleidomastoid muscle and the issues that should be considered in the interpretation of vestibular evoked myogenic potential results if these precautions are not taken. Individuals with sternocleidomastoid muscle activity of less than 30 μV in cervical vestibular evoked myogenic potential testing and an asymmetry ratio of more than 0.35 were excluded. In our study, individuals were divided into different groups according to sternocleidomastoid muscle asymetry. A total of 53 individuals were included in the study. Intergroup comparisons were made to determine the effect of electromyogram scaling and filter use on amplitude asymmetry ratio according to sternocleidomastoid muscle asymmetry. Keeping the sternocleidomastoid muscle asymmetry not exceeding 10 μV maximises the reliability of cervical vestibular evoked myogenic potentials. As a result of our study, it can be concluded that in clinical applications the asymmetry should not exceed 20 μV.

호흡 패턴 재교육 운동이 전방 머리 자세를 가지는 목 통증 환자에게 미치는 영향

Objective: The purpose of this study was to examine the effects of cervical stabilization exercise(CSE) combined with breathing pattern re-education exercise(BPRE) compared CSE on pain, disability, muscle activity, and range of motion(ROM) in neck pain(NP) patients with forward head posture(FHP). Method: BPRE+CSE(n=15) and Conservative physical therapy(CT)+CSE(n=15) groups were received treatment three times per week for four weeks, respectively. A numeric pain rating scale(NPRS), neck disability index(NDI), ROM, and surface electromyography(SEMG) activities of sternocleidomastoid (SCM) muscle and scalene muscle were measured before and after the treatments for each group. A paired t-test was conducted to test the changes before and after the treatments and an independent t-test was performed to evaluate the difference between groups. Results: In NPRS, NDI, ROM and muscle activity both BPRE+CSE and CT+CSE showed differences (p&lt;.05). BPRE+CSE showed more reduction in NPRS, NDI and muscle activity more increase in ROM(p&lt;.05). Conclusion: These results suggest that the BPRE can pain relief, recovery from neck disability, ROM, and muscle activity for NP patients with a FHP.

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.

Isometric chin tuck exercise with and without scapular postural correction for patients with chronic neck pain: a longitudinal study

Background/Aims Chronic neck pain is common in individuals with poor posture and motor control impairments. There has been increased interest in scapular postural correction in conjunction with the isometric chin tuck exercise. The aim of this study was to investigate the clinical efficacy of scapular postural correction while performing isometric chin tuck exercises for the improvement of neck pain, neck and shoulder alignment and superficial neck muscle activity in patients with chronic neck pain. Methods A total of 32 participants with chronic, non-specific neck pain were randomly divided into two groups (groups A and B, both n=16), who performed isometric chin tuck exercises alone or isometric chin tuck with scapular postural correction respectively. The participants were instructed to perform five sets of the exercise with 10 repetitions for 6 weeks. Measurements were taken pre- and post-intervention to determine Neck Disability Index scores, postural parameters (head, cervical and shoulder angle) and superficial cervical muscle activity (sternocleidomastoid, anterior scalene, splenius capitis). Analysis of covariance was used to compare the post-intervention scores. Results Significant differences were observed between groups A and B in the cervical angle (F1,29=4.538, P=0.042) and shoulder angle (F1,29=8.357, P=0.007), when compared to baseline values. Both group A (t=12.097, P&lt;0.001) and group B (t=8.032, P&lt;0.001) showed a significant reduction in Neck Disability Index scores compared to baseline scores. Both group A and group B showed a significant decrease in sternocleidomastoid (group A: t=6.637, P&lt;0.001; group B: t=10.143, P&lt;0.001), anterior scalene (group A, t=5.484, P&lt;0.001; group B, t=8.063, P&lt;0.001), and splenius capitis (group A, t=8.591, P&lt;0.001; group B, t=8.258, P&lt;0.001) muscle activity compared to baseline values. Conclusions Isometric chin tuck alone and isometric chin tuck combined with scapular postural correction both showed significant reductions in neck pain and superficial neck muscle activity. Additional scapular postural correction training significantly increased the cervical angle and decreased the shoulder angle.

Exploratory Study on Central Sensitization and Bioelectrical Activity of the Selected Masticatory Muscles in Subjects with Myopia

Myopia is one of the most common eye disorders involving abnormal focusing of light rays. The studies recognize the association between the stomatognathic and visual systems. This compound may have a neurological basis associated with disorders such as central sensitization. The main aim of this study was to evaluate the influence of central sensitization on the bioelectrical activity of selected muscles of the masticatory organ in subjects with myopia. Selected masticatory and cervical spine muscles were analyzed using an eight-channel BioEMG III electromyograph. Central sensitization was analyzed using the central sensitization inventory. Statistical analysis revealed significantly higher scores on the central sensitization inventory in subjects with axial myopia compared to subjects without refractive error. Repeated positive correlations were observed in the sternocleidomastoid muscle activity and negative correlations in the digastric muscle activity during open and closed eyes in myopic subjects. Subjects with myopia have an increased score in the central sensitization inventory. The increase in the central sensitization inventory score is connected with the changes within the electromyographic activity of the masticatory and neck muscles. The effect of central sensitization on masticatory muscle activity in myopic subjects requires further study.

The Influence of Visual Input on Electromyographic Activity and Patterns of Masticatory and Cervical Spine Muscles in Emmetropic Caucasian Subjects by Gender

(1) Background: The objective of the research was to analyze the change of visual input on electromyographic activity and patterns of masticatory and cervical spine muscles in emmetropic Caucasian subjects by gender. Supposedly, visual input should not influence activity and electromyographic patterns of masticatory and cervical spine muscles in emmetropic Caucasian subjects by gender. (2) Methods: After applying the inclusion criteria, 50 emmetropic Caucasian subjects were included in the study. Four muscle pairs were analyzed: the temporalis muscle (TA), the masseter muscle (MM), the digastric muscle (DA), and the sternocleidomastoid muscle (SCM), during resting and functional activity. (3) Results: It was observed that there were no significant statistical differences in activity and bioelectrical patterns between open and closed eyes in women and men, with the exception of clenching on dental cotton rollers in DA-left and DA mean between tests in women. The observed statistical results had a small effect size, successively equal to 0.32 and 0.29. (4) Conclusions: Changes in the influence of visual input do not affect electromyographic activity and patterns of masticatory and cervical spine muscles in emmetropic Caucasian women and men.

Effects of hanger reflex on the cervical muscular activation and function: A surface electromyography assessment.

Introduction: Cervical muscular dysfunction is closely associated with disorders and neuromuscular diseases of the cervical spine, and the hanger reflex (HR) has the potential to become a rehabilitation method. The muscular electrophysiology mechanism of HR is unclear. This study aims to identify the impacts of HR on cervical rotators’ myoelectrical activity and function. Methods: We designed a self-control clinical trial, and asymptomatic volunteers were continuously included from 1 September 2021 to 30 April 2022 in our department. Rotation tasks were performed on both sides under each of the situations: no HR, unilateral HR, and bilateral HR. Surface electromyography (SEMG) was used to detect the myoelectrical activity of agonistic splenius capitis (SPL), upper trapezius (UTr), and sternocleidomastoid (SCM). The co-contraction ratio (CCR) during rotation tasks was calculated. Correlation analyses and multiple linear regression were performed. Results: Finally, 90 subjects were enrolled (power >90%). The adjusted EMG value (aEMG) of SPL UTr, SCM, and rotating CCR under the unilateral HR and bilateral HR were higher than no HR; the aEMG of SPL and rotating CCR under the bilateral HR were higher than the unilateral HR. Multiple linear regression showed that HR pattern and age were the independent affecting factors for the aEMG of SPL (p < 0.001, p < 0.001), UTr (p < 0.001, p < 0.001), and SCM (p < 0.001, p < 0.001); BMI was an independent affecting factor for the aEMG of SPL (p < 0.001) and SCM (p < 0.001); HR pattern was the only affecting factor for CCR (p < 0.001). Conclusion: HR can increase the cervical rotators’ myoelectrical activities and rotating CCR, and the effects of bilateral HR are greater than unilateral HR, suggesting that bilateral HR has a greater clinical potential to become a rehabilitation method for treating cervical neuromuscular disorders.

The influence of idiopathic chronic neck pain on upper trapezius and sternocleidomastoid muscle activity and elasticity during functional reaching: A cross-sectional study

It remains unclear whether idiopathic chronic neck pain is associated with changes in muscle stiffness alongside alterations in neuromuscular control. Therefore, the purpose of this study was to determine the influence of idiopathic chronic neck pain on the muscle stiffness and muscle activity of the upper trapezius and sternocleidomastoid muscles during the maintenance of unilateral and bilateral functional reaching tasks. Surface electromyography (EMG) and ultrasound shear wave elastography were collected from the sternocleidomastoid and upper trapezius muscles in 18 individuals with idiopathic chronic neck pain and 18 matched healthy controls. Participants completed three functional reaching tasks; 1) unilateral forward reach, 2) bilateral forward reach, and 3) unilateral upward reach, and held at the top of each reaching movement for data to be collected bilaterally. A univariate ANOVA was utilized for each outcome measure (mean EMG amplitude and shear wave velocity) and each reaching task. Individuals with idiopathic chronic neck pain exhibited significantly lower upper trapezius activation during bilateral reaches without corresponding changes to stiffness during similar trials. Similarly, this cohort exhibited decreased sternocleidomastoid stiffness during forward reaching, without corresponding activation changes. Lastly, women demonstrated consistently higher sternocleidomastoid activation and stiffness when compared to men. These findings indicate individuals with idiopathic chronic neck pain may adapt their movement strategies, possibly for pain avoidance. The demonstrated changes in muscle stiffness independent of changes in muscle activity highlight the importance of evaluating both muscle stiffness and activation in individuals with idiopathic chronic neck pain prior to designing rehabilitation programs.

Electromyographic Activity of Sternocleidomastoid Muscle in Individuals With Neck Pain and Healthy Volunteers: A Reliability and Between-Group Differences Examination

ObjectivesThe purpose of this study was to evaluate the electromyographic activity of the sternocleidomastoid muscle during the performance of the craniocervical flexion test (CCFT) in individuals with neck pain and healthy volunteers, assess the reliability of this method, and examine possible between-population differences. MethodsElectromyographic activity of the sternocleidomastoid muscles of 22 individuals with neck pain and 22 healthy participants was recorded during the 55 stages of the CCFT. Pain (visual analog scale) and disability (Neck Disability Index) levels and pain duration were recorded for the participants with neck pain. Reliability of electromyography was evaluated with the intraclass correlation coefficient, standard error of measurement, and minimum detectable change. ResultsWithin-day reliability indices of electromyographic activity were very good to excellent (intraclass correlation coefficients, 0.86-0.98; standard error of measurement, 1.8%-7.6%; minimum detectable change, 5.0%-21.1%). For the head-lift normalization method, 2-way analysis of variance revealed significant between-group differences (P < .02); however, these were not clinically significant when reliability test-retest error was considered. Differences between contraction levels were significant (P < .001); however, the group by contraction level interaction factor was nonsignificant. Therefore, the between-groups electromyographic increases noted with increasing contraction levels were similar. No correlation was identified between participants’ electromyography data and pain or disability. ConclusionIn participants with moderate pain, disability, and pain duration, no clear alterations in electromyographic activity of the sternocleidomastoid could be detected with the CCFT. Reliability of the test used was very good.

Effects of Craniocervical Flexion on Suprahyoid and Sternocleidomastoid Muscle Activation in Different Exercises.

This study aims to investigate the effects of craniocervical flexion (CCF) on the activation of suprahyoid and sternocleidomastoid (SCM) muscles in Shaker and Resistant Jaw Opening (RJO) exercises, and to compare the effects of these two exercises on the same muscles with the Chin Tuck Against Resistance (CTAR) exercise. The study recruited a total of 37 healthy participants (20 female and 17 male, mean age: 27.45 ± 7.32years). All participants received craniocervical flexion training with the biofeedback pressure unit (Stabilizer™, Chattanooga Group Inc. USA). Shaker, Shaker with CCF, RJO, RJO with CCF and CTAR exercises were performed and surface electromyographic (sEMG) activations of the suprahyoid and SCM muscles were recorded. In addition, the maximum sEMG activations of suprahyoid and SCM muscles were recorded for the normalization procedure. CCF increased the effect of Shaker exercise on the suprahyoid muscle activation (p < 0.001); but this effect was not seen in RJO exercise (p > 0.05). Suprahyoid muscle activation was lower in Shaker exercise compared to RJO and CTAR exercises (p < 0.016). SCM muscle activation was greater in CTAR exercise compared to Shaker and RJO exercises (p < 0.016). The addition of CCF to the Shaker and RJOE exercises did not affect the ranking among the three exercises for both the suprahyoid and SCM muscles. The result of this study suggest that integration of CCF movement to the Shaker exercise would have a greater therapeutic effect. In addition, RJO exercise can be included in the rehabilitation program as an alternate to CTAR exercise.

A comparison of muscle activity, posture and body discomfort during the use of different computer screen sizes

This study aims to compare changes in neck angles, muscle activities, ergonomic risk and body discomfort caused by use of two different computer screen sizes. The 36 female users who participated used displays with 46.99 and 58.42-cm screen sizes and were assessed for craniocervical angle (CCA), craniovertebral angle (CVA), upper trapezius (UT) and sternocleidomastoid (SCM) muscle activity, ergonomic risk and body discomfort for a duration of 1 h. The results showed there were no significant differences when comparing usage between both computer screen sizes (p > 0.05). However, there were significant differences in the CCA, UT muscle activity and body discomfort when comparing before and after usage for both computer screen sizes (p < 0.05). The results indicate that computer users can select different screen sizes for working but should be concerned with neck angle, muscle activity and body discomfort when using for long periods of time.

Electrical activity and fatigue of respiratory and locomotor muscles in obstructive respiratory diseases during field walking test.

IntroductionIn subjects with obstructive respiratory diseases the increased work of breathing during exercise can trigger greater recruitment and fatigue of respiratory muscles. Associated with these changes, lower limb muscle dysfunctions, further contribute to exercise limitations. We aimed to assess electrical activity and fatigue of two respiratory and one locomotor muscle during Incremental Shuttle Walking Test (ISWT) in individuals with obstructive respiratory diseases and compare with healthy.MethodsThis is a case-control study. Seventeen individuals with asthma (asthma group) and fifteen with chronic obstructive pulmonary disease (COPD group) were matched with healthy individuals (asthma and COPD control groups). Surface electromyographic (sEMG) activity of sternocleidomastoid (SCM), scalene (ESC), and rectus femoris (RF) were recorded during ISWT. sEMG activity was analyzed in time and frequency domains at baseline and during the test (33%, 66%, and 100% of ISWT total time) to obtain, respectively, signal amplitude and power spectrum density (EMG median frequency [MF], high- and low-frequency bands, and high/low [H/L] ratio).ResultsAsthma group walked a shorter distance than controls (p = 0.0007). sEMG amplitudes of SCM, ESC, and RF of asthma and COPD groups were higher at 33% and 66% of ISWT compared with controls groups (all p<0.05). SCM and ESC of COPD group remained higher until 100% of the test. MF of ESC and RF decreased in asthma group (p = 0.016 and p < 0.0001, respectively) versus controls, whereas MF of SCM (p < 0.0001) decreased in COPD group compared with controls. H/L ratio of RF decreased (p = 0.002) in COPD group versus controls.ConclusionReduced performance is accompanied by increased electromyographic activity of SCM and ESC and activation of RF in individuals with obstructive respiratory diseases during ISWT. These are susceptible to be more pronounced respiratory and peripheral muscle fatigue than healthy subjects during exercise.