Neck muscle fatigue alters the cervical flexion relaxation ratio in sub-clinical neck pain patients

Evaluation of an assistive exosuit for alleviating neck and shoulder muscle fatigue during prolonged flexed neck posture

INTRODUCTION

Neck pain affects 203 million people globally and is prevalent in various settings due to factors like poor posture, lack of exercise, and occupational hazards. Therefore, addressing ergonomic issues with solutions like a wearable robotic device is crucial. This research presents a novel assistive exosuit, characterized by its slim and lightweight structure and intuitive control without the use of hands, designed to mitigate muscle fatigue in the neck and shoulders during prolonged flexed neck posture. The efficacy of the exosuit was confirmed through human experiments and user surveys.

METHODS

The preliminary feasibility experiment was conducted with five subjects for 15 min to verify the effect of supporting the weight of the head with a wire on reducing neck muscle fatigue. The prime experiment was conducted with 26 subjects for 15 min to quantitatively evaluate the reduction in muscle fatigue achieved by wearing the exosuit and to assess its qualitative usability from the user's perspective. For all experiments, surface electromyography (sEMG) data was measured from upper trapezius (UT) and splenius capitis (SC) muscles, the two representative superficial muscles responsible for sustaining flexed neck posture. The analysis of the device's efficiency utilized two parameters: the normalized root mean square value (nRMS), which was employed to assess muscle activity, and the normalized median frequency (nMDF), which was utilized to gauge the extent of muscle fatigue. These parameters were statistically analyzed with the IBM SPSS statistic program.

RESULTS

When wearing the exosuit, the nMDF of UT and SC increased by 7.18% (p < 0.05) and 5.38% (p < 0.05), respectively. For the nRMS, no significant differences were observed in either muscle. The nMDF slope of UT and SC increased by 0.63%/min (p < 0.01) and 0.34%/min (no significance). In the context of the nRMS slope, UT exhibited a reduction of 0.021% MVC/min (p < 0.05), while SC did not demonstrate any statistically significant outcomes. The exosuit received an average system usability scale score of 66.83.

CONCLUSIONS

Based on both qualitative and quantitative evaluations, our proposed assistive exosuit demonstrated that it promises the significant reduction of muscle fatigue in the neck and shoulders.

Electromyographic Activity of Cervical Muscles in Patients with Neck Pain and Changes After Dry Needling: A Narrative Review

Neck pain can be associated with specific conditions, such as neurological disorders, vascular or inflammatory diseases, fractures, herniated discs, etc. However, the majority of neck pain cases cannot be attributed to a specific cause. The objective of this review is to describe the muscle dysfunctions associated with neck pain, as measured by electromyography, and to determine the effectiveness of dry needling in improving these muscular dysfunctions. The research was conducted using the following databases: PubMed, Alcorze, and Google Scholar. The next conclusions have been extracted after the revision of the 65 selected manuscripts. The current scientific evidence supports electromyographic pathological findings in individuals with chronic neck pain, especially during general upper limb movement, repetitive work, violin playing, cervical force, and cervical movement tasks. Dry needling applied to an active myofascial trigger point in the upper trapezius can be suggested as an intervention to enhance the performance in the cranio-cervical flexion. Dry needling applied to latent myofascial trigger points in the upper trapezius after typing tasks in healthy subjects resulted in decreased upper trapezius activity and fatigue in the short term. In women with trapezius myalgia, dry needling applied to the upper trapezius led to a lower increase in electromyography activity compared to no intervention.

Concentric exercise-induced fatigue of the shoulder impairs proprioception but not motor control or performance in healthy young adults

OBJECTIVES

To investigate the effect of concentric fatigue on proprioception, motor control and performance of the shoulder in healthy young adults.

DESIGN

Test-retest experimental design.

SETTING

Human performance laboratory.

PARTICIPANTS

20 healthy adults.

MAIN OUTCOME MEAUSURE(S)

Proprioception was assessed using the joint repositioning sense (JRS) and the threshold to detection of passive movement (TTDPM). Motor control was assessed using the Y-balance Upper Quarter test (YBT-UQ) and performance using the Athletic Shoulder test (ASH test). All tests were conducted before and immediately after fatigue intervention (CON/CON protocol).

RESULTS

Following fatigue, absolute angular error (AAE) was significantly increase by 160.27 %. Moreover, there was a significant increase (48.41 %) in TTDPM after fatigue. Furthermore there was no significant differences in motor control and performance before and after fatigue intervention.

CONCLUSIONS

Since muscular fatigue negatively affects shoulder proprioception, it is essential to assess proprioception before and after fatigue to detect any dysfunctions that may arise as a result of fatigue. To address these dysfunctions, it is recommended to engage in proprioceptive exercises under situations of fatigue in order to enhance the sensitivity of the mechanoreceptors.

Is the disappearance of the cervical flexion-relaxation phenomenon associated with cervical degeneration in healthy people?

PURPOSE

This study aims to explore the differences in cervical degeneration between healthy people with and without cervical flexion-relaxation phenomenon (FRP) and to identify whether the disappearance of cervical FRP is related to cervical degeneration.

METHODS

According to the flexion relaxation ratio (FRR), healthy subjects were divided into the normal FRP group and the abnormal FRP group. Besides, MRI was used to evaluate the degeneration of the passive subsystem (vertebral body, intervertebral disc, cervical sagittal balance, etc.) and the active subsystem (deep flexors [DEs], deep extensors [DFs], and superficial extensors [SEs]). In addition, the correlation of the FRR with the cervical degeneration score, C2-7Cobb, Borden method, relative total cross-sectional area (rTCSA), relative functional cross-sectional area (rFCSA), and fatty infiltration ratio (FIR) was analyzed.

RESULTS

A total of 128 healthy subjects were divided into the normal FRP group (n=52, 40.63%) and the abnormal FRP group (n=76, 59.38%). There were significant differences between the normal FRP group and the abnormal FRP group in the cervical degeneration score (z=-6.819, P<0.001), C2-7Cobb (t=2.994, P=0.004), Borden method (t=2.811, P=0.006), and FIR of DEs (t=-4.322, P<0.001). The FRR was significantly correlated with the cervical degeneration score (r=-0.457, P<0.001), C2-7Cobb (r=0.228, P=0.010), Borden method (r=0.197, P=0.026), and FIR of DEs (r=-0.253, P=0.004).

CONCLUSION

The disappearance of cervical FRP is related to cervical degeneration. A new hypothesis mechanism for FRP is proposed. The cervical FRP test is an effective and noninvasive examination for the differential diagnosis of healthy people, people with potential NSNP, and patients with NSNP.

A systematic review and meta analysis of measurement properties for the flexion relaxation ratio in people with and without non specific spine pain

This review sought to identify, critically appraise, compare, and summarize the literature on the reliability, discriminative validity and responsiveness of the flexion relaxation ratio (FRR) in adults (≥ 18 years old) with or without spine pain (any duration), in either a clinical or research context. The review protocol was registered on Open Science Framework ( https://doi.org/10.17605/OSF.IO/27EDF ) and follows COSMIN, PRISMA, and PRESS guidelines. Six databases were searched from inception to June 1, 2022. The search string was developed by content experts and a health services librarian. Two pairs of reviewers independently completed titles/abstracts and full text screening for inclusion, data extraction, and risk of bias assessment (COSMIN RoB Toolkit). At all stages, discrepancies were resolved through consensus meetings. Data were pooled where possible with a three-level random effects meta-analyses and a modified GRADE assessment was used for the summary of findings. Following duplicate removal, 728 titles/abstracts and 219 full texts were screened with 23 included in this review. We found, with moderate certainty of evidence, that the cervical FRR has high test-retest reliability and lumbar FRR has moderate to high test-retest reliability, and with high certainty of evidence that the cervical and lumbar FRR can discriminate between healthy and clinical groups (standardized mean difference - 1.16 [95% CI - 2.00, - 0.32] and - 1.21 [- 1.84, - 0.58] respectively). There was not enough evidence to summarize findings for thoracic FRR discriminative validity or the standard error of measurement for the FRR. Several studies used FRR assuming responsiveness, but no studies were designed in a way that could confirm responsiveness. The evidence supports adequate reliability of FRR for the cervical and lumbar spine, and discriminative validity for the cervical and lumbar spine only. Improvements in study design and reporting are needed to strengthen the evidence base to determine the remaining measurement properties of this outcome.

Characteristics of Surface Electromyograph Activity of Cervical Extensors and Flexors in Nonspecific Neck Pain Patients: A Cross-Sectional Study

Background and Objectives: We identified typical surface electromyogram (sEMG) activities of the cervical extensors and flexors during motions in the three anatomical planes in healthy adults. The aim of this study was to explore characteristics of sEMG activities of these cervical muscles in nonspecific neck pain (NSNP) patients based on healthy adults. Materials and Methods: Participants were 24 NSNP patients (NSNP group, mean ± SD of age, 47.5 ± 15.5) and 24 healthy adults (control group, 20.5 ± 1.4). For each participant, sEMG of the cervical extensors and flexors was recorded during neck flexion, extension, bilateral lateral flexion, bilateral rotation, and at the neutral position in Phase I (the neck from the neutral position to the maximum range of motion), Phase II (at the maximum range of motion), and Phase III (from the maximum range of motion to the neutral position), yielding a total of 42 phases. A percentage of maximum voluntary contraction to normalize muscle activity in each phase was calculated to obtain the ratio of muscle activities in the extensors and flexors in each of 36 phases of the motions to the neutral position and ratio of the flexors to extensors in activity for 21 phases. Results: In 28 of 36 phases of the motions, the ratios of muscle activities in the extensors and flexors to the neutral position in the NSNP group were significantly larger than the control group (p < 0.05). In 6 of 21 phases, the ratios of the flexors to extensors in activity in the NSNP group were significantly larger than in the control group (p < 0.05). Conclusions: In NSNP patients, the activity of the cervical extensors and flexors associated with neck motion increased with an imbalance in activity between these muscles compared to their activity in healthy adults. The results of this study will be useful in understanding the pathogenesis of NSNP and in constructing an objective evaluation of the treatment efficacy on NSNP patients.

Neck Muscle Vibration Alters Upper Limb Proprioception as Demonstrated by Changes in Accuracy and Precision during an Elbow Repositioning Task

Upper limb control depends on accurate internal models of limb position relative to the head and neck, accurate sensory inputs, and accurate cortical processing. Transient alterations in neck afferent feedback induced by muscle vibration may impact upper limb proprioception. This research aimed to determine the effects of neck muscle vibration on upper limb proprioception using a novel elbow repositioning task (ERT). 26 right-handed participants aged 22.21 ± 2.64 performed the ERT consisting of three target angles between 80−90° (T1), 90−100° (T2) and 100−110° (T3). Controls (CONT) (n = 13, 6F) received 10 min of rest and the vibration group (VIB) (n = 13, 6F) received 10 min of 60 Hz vibration over the right sternocleidomastoid and left cervical extensor muscles. Task performance was reassessed following experimental manipulation. Significant time by group interactions occurred for T1: (F1,24 = 25.330, p < 0.001, ηp2 = 0.513) where CONT improved by 26.08% and VIB worsened by 134.27%, T2: (F1,24 = 16.157, p < 0.001, ηp2 = 0.402) where CONT improved by 20.39% and VIB worsened by 109.54%, and T3: (F1,24 = 21.923, p < 0.001, ηp2 = 0.447) where CONT improved by 37.11% and VIB worsened by 54.39%. Improvements in repositioning accuracy indicates improved proprioceptive ability with practice in controls. Decreased accuracy following vibration suggests that vibration altered proprioceptive inputs used to construct body schema, leading to inaccurate joint position sense and the observed changes in elbow repositioning accuracy.

The Mode of Activity of Cervical Extensors and Flexors in Healthy Adults: A Cross-Sectional Study

Background and Objectives: The purpose of this study was to investigate the activity of bilateral cervical extensors and flexors on the sagittal, frontal, and horizontal planes of healthy adults during motions of the neck in a sitting position, which has not been satisfactorily investigated by surface electromyogram (sEMG). Materialand Methods: We recruited 35 healthy participants (mean ± standard deviation of age, 20.3 ± 2.4). sEMG recordings of the cervical extensors and flexors were performed for a total of nine seconds in three phases: Phase I involved the motion of the neck from the neutral position to the maximum range of motion; Phase II involved maintaining the neck at the maximum range of motion; and Phase III involved the motion of the neck from the maximum range of motion to the neutral position during neck flexion, extension, right and left lateral flexion, right and left rotation, and maintaining the neck in the neutral position. Muscle activities in each motion were normalized as a percentage of maximal voluntary contraction (%MVC) so that the muscles could be compared. Results: The %MVC of the extensors was significantly larger than that of the flexors in the neutral position (p < 0.001). In addition, the %MVCs of the following were significantly larger than the %MVC in the neutral position: the extensors in flexion (p = 0.014) and extension (p = 0.020), the ipsilateral extensors (p = 0.006) and flexors (p < 0.001) in lateral flexion in Phase I; the flexors in flexion (p < 0.001), the extensors in extension (p = 0.010), and the ipsilateral extensors and flexors in lateral flexion (p < 0.001) in Phase II; the extensors and flexors in flexion (p < 0.001), the flexors in extension (p < 0.001), the ipsilateral flexors (p < 0.001), the contralateral flexors (p = 0.004) and the contralateral extensors (p = 0.018) in lateral flexion in Phase III; and the bilateral extensors and contralateral flexors during rotation in all three phases (p < 0.001). Conclusion: The typical sEMG activities of the extensors and flexors during motion of the neck in healthy adults were identified in this study; this information can be used to understand the pathophysiology of non-specific neck pain and to provide an index for evaluating the effect of treatment.

Effect of Neck Muscle Fatigue on Hand Muscle Motor Performance and Early Somatosensory Evoked Potentials

Even on pain free days, recurrent neck pain alters sensorimotor integration (SMI) measured via somatosensory evoked potentials (SEPs). Neck muscle fatigue decreases upper limb proprioception, and thus may interfere with upper limb motor task acquisition and SMI. This study aimed to determine the effect of cervical extensor muscle (CEM) fatigue on upper limb motor acquisition and retention; and SMI, measured via early SEPs. Twenty-four healthy right-handed individuals were randomly assigned to control or CEM fatigue. Baseline SEPs were elicited via median nerve stimulation at the wrist. Participants then lay prone on a padded table. The fatigue group supported a 2 kg weight until they could no longer maintain the position. The control group rested their neck in neutral for 5 min. Participants completed pre- and post-motor skill acquisition while seated, SEPs were again collected. Task retention was measured 24 h later. Accuracy improved post acquisition and at retention for both groups (p < 0.001), with controls outperforming the fatigue group (p < 0.05). The fatigue group had significantly greater increases in the N24 (p = 0.017) and N30 (p = 0.007) SEP peaks. CEM fatigue impaired upper limb motor learning outcomes in conjunction with differential changes in SEP peak amplitudes related to SMI.

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

BACKGROUND

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.

OBJECTIVE

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).

METHODS

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.

RESULTS

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).

CONCLUSIONS

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.

The effect of neck muscle fatigue on shoulder humeral rotation joint position sense

INTRODUCTION

Cervical extensor muscle (CEM) fatigue causes decrements in upper limb proprioceptive accuracy during constrained single-joint tasks. This study used a novel humeral rotation joint position sense (JPS) measurement device to compare JPS accuracy in participants who received acute CEM fatigue vs. non-fatigued controls.

METHODS

Participants had vision occluded and were passively guided into postures of internal humeral rotation from a baseline posture before and after a CEM fatigue or control protocol. Mixed model repeated measures ANOVAs were used to verify fatigue and compared absolute, constant, and variable JPS error between groups.

RESULTS

CEM fatigue was verified via pre-post reduction in CEM strength, and myoelectric indicators of fatigue. However, between-group comparisons of absolute, constant, and variable JPS error were not statistically significant, despite having large effect sizes.

DISCUSSION

Contrary to prevailing literature, unconstrained humeral rotation JPS did not appear to be affected by CEM fatigue in this study. However, between-group differences in JPS error were dwarfed by inter-trial variability, which likely arose due to the unconstrained nature of this task, conflating chances for a Type II error. Future research should perform a kinematic analysis of task constraints to highlight potential compensatory mechanisms obscuring significant findings in this otherwise robust effect.

The impact of forward head posture on the electromyographic activity of the spinal muscles

Objective

This study aims to examine the electromyographic activity of the regional spinal muscle between patients with forward head posture (FHP) and those with a normal cranio-vertebral (CV) angle.

Methods

We recruited 60 adult women aged between 18 and 29 years from a single institution. The CV angle was measured in the sagittal plane, which helped us to assign the participants in the FHP group (n = 30) with a large CV angle (53.1 ± 2.3) and the control group (n = 30) with a normal CV angle (43.0 ± 3.6). The surface electromyography (EMG) was used to measure the magnitude of normalised muscle activity of eight spinal muscles (cervical, lumbar, and thoracic levels) while standing and performing a specific manual handling task.

Results

The CV angle was significantly lower in the FHP group than in the control group (p = .001). The cervical erector spinae (CES) muscle activity was significantly increased in the FHP group compared to that in the control group. The right and left CES of those in the FHP group exhibited 73% and 87%, respectively, higher normalised muscle activity than those in the control group while performing the manual handling task (p = .001). No significant difference was detected for the thoracic or lumbar segment muscles between groups.

Conclusion

Our results indicate that greater neck muscle demands result from anterior head translation in FHP. This effect is a counterbalance to the reduced CV angle and to support the neck. The increased activity of the neck muscles in FHP could demand more support from the neck muscles and might increase the risk of spinal injuries. Management of FHP is essential to avoid overloading the spinal muscles.

A Comparison Study of Posture and Fatigue of Neck According to Monitor Types (Moving and Fixed Monitor) by Using Flexion Relaxation Phenomenon (FRP) and Craniovertebral Angle (CVA)

This study quantified the neck posture and fatigue using the flexion relaxation phenomenon (FRP) and craniovertebral angle (CVA); further, it compared the difference between the level of fatigue and neck posture induced by two types of monitors (regular fixed monitor and moving monitor). Twenty-three male participants were classified into two groups—the low-flexion relaxation ratio (FRR) group and the normal-FRR group, depending on the FRR value. All participants performed a document task for 50 min using both types of monitors. It was found that the FRR values significantly decreased after the documentation task. The CVA analysis showed that the moving monitor’s frequency of forward head posture (FHP) was lower than that for the fixed monitor. Overall, the moving monitor worked better than the fixed monitor; this can be interpreted as proof that such monitors can reduce neck fatigue.

The Influence of Subclinical Neck Pain on Neurophysiological and Behavioral Measures of Multisensory Integration

Multisensory integration (MSI) is necessary for the efficient execution of many everyday tasks. Alterations in sensorimotor integration (SMI) have been observed in individuals with subclinical neck pain (SCNP). Altered audiovisual MSI has previously been demonstrated in this population using performance measures, such as reaction time. However, neurophysiological techniques have not been combined with performance measures in the SCNP population to determine differences in neural processing that may contribute to these behavioral characteristics. Electroencephalography (EEG) event-related potentials (ERPs) have been successfully used in recent MSI studies to show differences in neural processing between different clinical populations. This study combined behavioral and ERP measures to characterize MSI differences between healthy and SCNP groups. EEG was recorded as 24 participants performed 8 blocks of a simple reaction time (RT) MSI task, with each block consisting of 34 auditory (A), visual (V), and audiovisual (AV) trials. Participants responded to the stimuli by pressing a response key. Both groups responded fastest to the AV condition. The healthy group demonstrated significantly faster RTs for the AV and V conditions. There were significant group differences in neural activity from 100-140 ms post-stimulus onset, with the control group demonstrating greater MSI. Differences in brain activity and RT between individuals with SCNP and a control group indicate neurophysiological alterations in how individuals with SCNP process audiovisual stimuli. This suggests that SCNP alters MSI. This study presents novel EEG findings that demonstrate MSI differences in a group of individuals with SCNP.

Reliability of a Method to Measure Neck Surface Electromyography, Kinematics, and Pain Occurrence in Participants With Neck Pain

OBJECTIVE

To investigate the reliability of a novel method to measure neck surface electromyography (SEMG), kinematics, and pain during active movements in participants with neck pain.

METHODS

This test-retest study evaluated 23 participants with chronic neck pain. Each was measured twice within a single session. Three-dimensional kinematics and SEMG were recorded in 10° increments during forward and side flexion, extension, and rotation of the neck. Neck position during pain occurrence was also measured.

RESULTS

Intraclass correlation coefficients were >0.80 for 96% and 100% of SEMG and kinematic data, respectively. The percentage of standard error of the measurement (SEM) values were <25% for 91% of all SEMG measures; most were <15%, and some were <10%. For ranges of motion in the primary plane, percentage of SEM values were all <6% (SEM 1°-3°). Intraclass correlation coefficients for neck position during pain occurrence were all >0.60, except for right rotation (0.48) (SEM values 2°-8°). Pain occurred approximately 59% to 75% into the total range of motion and persisted to its end.

CONCLUSIONS

This methodology showed good reliability. It may be suitable for neck pain subclassification to evaluate the effects of treatment on pain, kinematics, and muscle activity during functional neck movements. The point of pain occurrence suggests increasing mechanical load on tissues may be one of the causative factors for movement-associated neck pain.

Immediate effects of cervical mobilisations on neck muscle activity during active neck movements in patients with non-specific neck pain. A double blind placebo controlled trial

BACKGROUND

Cervical mobilisations are used to treat people with neck pain but their mechanisms of action are unclear. One theorised reason for induced analgesia is effect on neck muscle activity.

OBJECTIVES

To assess the effects of cervical mobilisations on muscle activity during active neck movements and whether changes in muscle activity are associated with changes in symptoms.

DESIGN

Double-blind randomised placebo controlled trial.

SETTING

Primary care.

PARTICIPANTS

40 patients (aged 19 to 80 years, 24 female) with non-specific neck pain.

INTERVENTIONS

One session of cervical mobilisations or motionless manual contact (placebo).

MAIN OUTCOME MEASURES

sternocleidomastoid (SCM), scalene (SCA), upper trapezius (UT) and erector spinae (ES) surface electromyography (SEMG) during active neck flexion, extension, side flexion and rotation was measured immediately before and after the intervention. Patients were classified as responders according to change in symptoms assessed using the Global Rating of Change Scale (GROC).

RESULTS

Compared with placebo, patients receiving mobilisation showed an increase in contralateral UT and ES SEMG during rotation and contralateral and ipsilateral SCM, SCA and UT during side flexion (P<0.05), however changes were mostly associated with an increase in range and speed of movement. The only association with GROC was increased (5%) SEMG in the contralateral SCM during side flexion in the mobilisation group (P=0.013).

CONCLUSION

Cervical mobilisations caused increased neck SEMG, mostly due to increased movement range and speed. Change in muscle activity is unlikely to be a major mechanism of action of cervical mobilisations in symptomatic improvement with physiological neck movements. (ClinicalTrials.gov record number: 2016/066).

CLINICAL TRIALS REGISTRY

ClinicalTrials.gov record number: 2016/066.

Differences in neck surface electromyography, kinematics and pain occurrence during physiological neck movements between neck pain and asymptomatic participants. A cross-sectional study

BACKGROUND

Neck pain has been associated with altered muscle activity and impaired kinematics. Patients frequently report pain during physiological neck movements. Previously, the average muscle activity during these movements has been measured. However, muscle activity is modulated by the position in the range of movement, hence the study of neck muscle activity in discrete sections of the range of movement is warranted. Evidence is conflicting regarding range of movement restriction in neck pain. No study has assessed the point in the range of movement at which pain occurs. This study aimed to investigate neck kinematics, muscle activity and pain during physiological neck movements in participants with and without neck pain.

METHODS

Neck kinematics and surface electromyography were recorded continuously and analysed in 10° increments during forward and side flexion, extension and rotation of the neck in 20 neck pain and 20 asymptomatic participants. Point of pain occurrence in the range of movement was recorded.

FINDINGS

Neck pain participants demonstrated significantly lower activity of scalene during flexion and extension, and a non-significant higher activity in sternocleidomastoids during rotation. No differences in neck kinematics were observed. 65% of neck pain participants reported pain during at least one neck movement. Pain was reported in the last ≈20-40% of the range of movement.

INTERPRETATION

Exercises used in current practice to minimise scalene activity may not be appropriate for all neck pain patients. Restricted range of movement is not a consistent feature of neck pain. Movement associated neck pain is present at the end of range of movement, which has implications for the study of neck pain and rehabilitation.

Subclinical recurrent neck pain and its treatment impacts motor training-induced plasticity of the cerebellum and motor cortex

The cerebellum processes pain inputs and is important for motor learning. Yet, how the cerebellum interacts with the motor cortex in individuals with recurrent pain is not clear. Functional connectivity between the cerebellum and motor cortex can be measured by a twin coil transcranial magnetic stimulation technique in which stimulation is applied to the cerebellum prior to stimulation over the motor cortex, which inhibits motor evoked potentials (MEPs) produced by motor cortex stimulation alone, called cerebellar inhibition (CBI). Healthy individuals without pain have been shown to demonstrate reduced CBI following motor acquisition. We hypothesized that CBI would not reduce to the same extent in those with mild-recurrent neck pain following the same motor acquisition task. We further hypothesized that a common treatment for neck pain (spinal manipulation) would restore reduced CBI following motor acquisition. Motor acquisition involved typing an eight-letter sequence of the letters Z,P,D,F with the right index finger. Twenty-seven neck pain participants received spinal manipulation (14 participants, 18–27 years) or sham control (13 participants, 19–24 years). Twelve healthy controls (20–27 years) also participated. Participants had CBI measured; they completed manipulation or sham control followed by motor acquisition; and then had CBI re-measured. Following motor acquisition, neck pain sham controls remained inhibited (58 ± 33% of test MEP) vs. healthy controls who disinhibited (98 ± 49% of test MEP, P<0.001), while the spinal manipulation group facilitated (146 ± 95% of test MEP, P<0.001). Greater inhibition in neck pain sham vs. healthy control groups suggests that neck pain may change cerebellar-motor cortex interaction. The change to facilitation suggests that spinal manipulation may reverse inhibitory effects of neck pain.

Effects of a 16-week hydrotherapy program on three-dimensional scapular motion and pain of women with fibromyalgia: A single-arm study

BACKGROUND

Although hydrotherapy is widely used to treat women with fibromyalgia, no studies have investigated the effects of this intervention on scapular kinematics in this population. This study verified the effectiveness of a hydrotherapy program on scapular kinematics, pain and quality of life in women with fibromyalgia.

METHODS

Twenty women completed the study and performed three evaluations before treatment (to establish a baseline), and two other evaluations (after 8 and 16weeks of hydrotherapy) at the end of treatment. Three-dimensional kinematics of the scapula was evaluated during arm elevation in two different planes with the Flock of Birds® system. Patients also answered quality of life and Fibromyalgia Impact Questionnaires and had pain assessed with a digital algometer. Treatment consisted of 2 weekly hydrotherapy sessions, lasting 45min each, for 16weeks. Data were analyzed with a two-way ANOVA (for kinematics results) and one-way ANOVA (for the other variables). Effect size was assessed with Cohen's d coefficient for all quantitative variables.

RESULTS

Although an important improvement was achieved in terms of pain and quality of life (P<0.05, effect sizes varied from -1.93 to 1.61 depending on the variable), scapular kinematics did not change after treatment (P>0.05, effect sizes from -0.40 to 0.46 for all kinematic variables).

INTERPRETATION

The proposed program of hydrotherapy was effective to improve quality of life, pain intensity and fibromyalgia impact in women with fibromyalgia. However, scapular kinematics did not change after the period of treatment. Although symptoms improved after the treatment, the lack of changes in scapular kinematics may indicate these women have an adaptive movement pattern due to their chronic painful condition.

The effects of subclinical neck pain on sensorimotor integration following a complex motor pursuit task

Recurrent subclinical neck pain (SCNP) may be associated with neural plastic changes in sensory processing and sensorimotor integration (SMI); however, its impact on motor learning has not been investigated. The aim of this study was to investigate whether SCNP alters neural markers of SMI during a complex motor acquisition task as compared to a healthy control group. Peripheral N9, spinal N13, brainstem N18, and cortical N20, P25, N24 and N30 early somatosensory evoked potentials (SEPs) were recorded following median nerve stimulation for 24 participants (12 control and 12 SCNP) before and after a 10-min tracing motor task intervention. Retention was assessed 24-48 h later. Significant amplitude differences were observed for both N18 and N24 SEP waveforms between groups, indicating there may be a difference in SMI due to altered afferent input as a result of SCNP. Accuracy increased significantly for both groups post-motor training; however, at retention only the control group showed an additional increase in accuracy. Both N18 and N24 SEP peaks are linked with cerebellar pathways, suggesting that SCNP impacts these connections. Significant correlations between these peaks and performance data were also seen. The differential changes in neurophysiological markers of SMI seen in SCNP suggest that SEPs have the potential to be used as an early screening tool for those at risk of having maladaptive neural plastic changes in response to motor training as a result of SCNP.

Novel Electromyographic Protocols Using Axial Rotation and Cervical Flexion-Relaxation for the Assessment of Subjects With Neck Pain: A Feasibility Study

OBJECTIVE

The purpose of this study is to examine the feasibility of novel variations to the way cervical flexion-relaxation phenomenon (FRP) studies are conducted and the feasibility of using cervical axial rotation as an alternative objective measure of cervical pain/dysfunction.

METHODS

Electromyographic data were collected from cervical paraspinal muscles of 5 participants with neck pain and 5 asymptomatic controls. Cervical FRP was conducted as reported in the literature with the participants seated, except that they started with the head fully flexed instead of being erect. Data were also collected with participants laying prone, starting with their head hanging over the edge of the table. Additional data were collected from cervical paraspinal and sternocleidomastoid (SCM) muscles while the seated participants rotated their head fully to the right and left. Ratios were obtained for each type of test by dividing the electromyographic amplitude when muscles were most active by that when they were relaxed or in contralateral rotation.

RESULTS

In each case, the ratio was higher for the controls than for those with neck pain, suggesting that any of the 4 methods could be used to distinguish between 2 groups. The ratios were most pronounced from SCMs during axial rotation. There appeared to be a negative relationship between pain level and the ratios obtained from each method.

CONCLUSION

The findings from this small study are encouraging for all methods used, with axial rotation using SCMs appearing to be the most promising. These results indicate that larger, powered studies are warranted.