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PubMed1999

[Influence of proprioceptive input from leg, thigh, trunk and neck muscles on the equilibrium of standing].

To investigate and compare the roles of proprioceptive input from the leg, thigh, trunk and neck muscles on equilibrium, we performed static posturography in 50 normal subjects in the standing position on a force platform by applying vibratory stimulations to the muscles. The length of the displacement of the center of gravity, maximum sway length and sway area were measured. The amplitude of the body sway was maximum when the stimulation was applied to the dorsal neck. The forward shift of the center of gravity was also marked by stimulation applied to the dorsal neck. The amplitude of the body sway on stimulation of the leg muscles was also marked, although less than that of dorsal neck stimulation. The backward shift during stimulation of the gastrocnemius and the forward shift during stimulation of the anterior tibialis were remarkable. The results indicate that the leg muscles, which directly regulate the movement of the ankle joint, and the dorsal neck muscles, which change the static equilibrium through the central nervous system, are important for maintaining the standing posture.

Adult↗

PubMed1994

The interactive contribution of neck muscle proprioception and vestibular stimulation to subjective "straight ahead" orientation in man.

Seventeen normal subjects were asked to direct a laser point to the position they felt to lie exactly straight ahead of their body. Subjects were seated in complete darkness in an approximately spherical cabin in an upright position with the orientation of the trunk and head aligned. For both the horizontal and vertical plane, "straight ahead" judgements were closely scattered around the objective straight ahead body position. Posterior neck muscle vibration as well as caloric vestibular stimulation with ice water led to (1) an apparent motion and horizontal displacement of a stationary visual target to the side opposite to stimulation and (2) a horizontal deviation of subjective "straight ahead" perception toward the side of stimulation. Only those subjects who experienced an illusion of target motion also showed a deviation of their subjective body orientation. No systematic effect of a displacement of subjective body orientation in the vertical plane was detected. When vestibular stimulation and neck muscle vibration were combined their effects were additive, i.e. the horizontal deviation of subjective body orientation observed when either type of stimulation was applied in isolation, was linearly combined either by summation or by cancellation. The present results clearly support the assumption that afferent visual, vestibular and proprioceptive input converge to the neural generation of an egocentric, body-centred coordinate system that allows us to determine our body position with respect to visual space.

Adult↗

PubMed1996

Postural responses to vibration of neck muscles in patients with unilateral vestibular lesions.

Postural responses to vibration applied unilaterally to dorsal neck muscles were recorded with a sway platform in nine patients with unilateral vestibular lesions and 19 normal subjects. In normals, the vibration induced a forward postural deviation. In patients, vibration of the neck contralateral to the lesion induced normal forward sway, whereas ipsilateral vibration resulted in sway of lower amplitude than normal and predominantly in the direction of the lesion or backwards. It is suggested that the proprioceptive error signal introduced by the neck vibration combined with an asymmetrical vestibular input due to a unilateral vestibular lesion provoked an erroneous representation of head position in patients resulting in a redirection of their body sway.

Humans↗

PubMed2004

Intra-rater reliability of electromyographic recordings and subjective evaluation of neck muscle fatigue among helicopter pilots.

UNLABELLED: The aim was to evaluate the reliability of a method of measuring neck muscle fatigue among helicopter pilots. METHOD: Surface EMG from three areas in the neck region, bilaterally, was recorded among 10 male helicopter pilots while they were performing isometric contractions in flexion and extension for 45 s, sustaining a force representing 75% of maximum strength in a seated position. Perceived fatigue was rated using the Borg CR-10 scale. The test was repeated twice the first day and then two additional times with one-week intervals. Variables analyzed were the slope of the median frequency change, the normalized slope, and the ratings after 15, 30 and 45 s; and also the initial median frequency (IMDF). The intra-class correlation (ICC) and the measurement error (S(w)), intra- and inter-day were calculated statistically. RESULTS: The best reliability for the slope was found for the 45 s intra-day analysis taking all measurements into account (ICC 0.65-0.83). The reliability after 30 s was poorer but still acceptable (ICC 0.52-0.71). For the subjective ratings, the highest reliability was found after 30 s inter-day (ICC 0.86-0.88). IMDF showed generally high reliability for the intra-day analyses (ICC 0.63-0.80). CONCLUSION: The method is reliable for use in further research. Since performing a contraction of 75% of maximum was quite strenuous, we recommend that the protocol be shortened to 30 s.

Adult↗

PubMed1998

Morphometry of human neck muscles.

STUDY DESIGN: Cadaveric dissections were used to study muscle morphometry. OBJECTIVE: To describe systematically the musculotendinous lengths, fascicle lengths, pennation angles, and physiologic cross-sectional areas of neck and shoulder muscles implicated in head movement. SUMMARY OF BACKGROUND DATA: In previous studies of neck-muscle anatomy, researchers described only a subset of muscle features, often using crude or indirect methods. None used microdissected muscles to correct measured parameters for the presence of multiple fiber compartments, internal aponeuroses, or variations in fiber or sarcomere length required for qualitative models of force-generating capabilities. METHODS: Muscle mass, pennation angle, fascicle length, and sarcomere length were measured in 14 neck muscles from 10 human cadavers. Architecturally complex muscles with multiple attachments were divided into subvolumes, and each subvolume was examined from both the superficial and deep surfaces, Internal aponeuroses were microdissected within muscles to characterize architectural specializations. Physiologic cross-sectional areas were calculated from the morphometric data. RESULTS: The neck musculature was architecturally complex. Many muscles crossed two or more joints and had multiple attachments to different bones. In some, the presence of tendons and aponeuroses was associated with specializations in fascicle organization. Considerable interindividual variation was found in the number and location of tendinous insertions of the scalenes and longissimus capitis muscles. In addition, rhomboideus showed significant variations in its size and shape. The cross-sectional areas of neck muscles from large and small subjects did not scale proportionately with body height and weight, nor did individual muscles with widely varying cross-sectional areas (0.3-15.3cm2) scale from on subject to another. CONCLUSIONS: The accuracy of morphometry can be improved by incorporating measurements made by microdissecting neck muscles. The presence of aponeurotic attachments can greatly shorten fascicle length; failure to identify such attachments can lead to underestimates of cross-sectional areas. Accuracy of a generalized model of the neck is also improved by normalizing sarcomere lengths in all muscles.

Aged↗

PubMed2007

Postural responses to continuous unilateral neck muscle vibration in standing patients with cervical dystonia.

Several observations support the notion that integration of neck proprioceptive input is impaired in cervical dystonia (CD). An example is the inconsistent or opposite to normal effect of lateral neck muscle vibration on body rotation during stepping. We hypothesized that lateral neck vibration produces abnormal responses also in a static task. Normal subjects and patients with CD stood quietly with eyes closed, without or with vibration applied to the sternocleidomastoid muscle, and center of foot pressure and body sway were recorded by a dynamometric platform. Patients had a larger than normal sway under control condition. They showed little or no postural responses to vibration. When body tilt occurred, it was rarely in the frontal plane as in normal subjects, but in the sagittal plane. No relationship existed between vibration-induced tilt during stance and body rotation during stepping. Therefore, in CD, proprioceptive neck input is less used for the construction of the postural vertical during quiet stance than it is used for the definition of the subjective straight ahead during a dynamic task.

Adult↗

PubMed2005

Wireless on-line electromyography in recording neck muscle function: a pilot study.

AIM: The surface electromyography (SEMG) records muscle activity without causing pain and therefore it can be used in the on-line kinetic evaluation of rehabilitation methods. The cables are a problem in the clinical work. The aim of this pilot study was to introduce a wireless on-line SEMG method in the measurements of neck muscle activity and preliminarily evaluate its usability in dynamic exercises in a healthy and a neck pain subject. METHOD: The bilateral wireless on-line SEMG measurements were performed at the level C4-C5 of the cervical spine. The subjects (one healthy 32-year-old female and one neck pain patient, 35-year-old female) were performing slow cervical flexions with eyes open. The angle of the flexion was measured with inclinometer. RESULTS: In healthy subjects, the SEMG curve demonstrated clear flexion-relaxation rhythm whereas in the patient the rhythm was blurred. The SEMG signal quality was, however, good in both cases. CONCLUSION: Wireless on-line SEMG method seems promising in daily clinical work for the measurements of neck muscle activity.

Journal Article↗

PubMed2003

Expiratory-synchronized sleep in a quadriplegic patient using inspiratory neck muscles to breathe.

In a patient with C3 quadriplegia causing complete diaphragm paralysis who developed inspiratory neck muscles (INM) hypertrophy to sustain ventilation, spontaneous breathing deeply altered sleep architecture, relegating sleep to the expiratory phase of the ventilatory cycle. A polysomnographic recording performed during mechanical ventilation (without INM activity), showed that sleep was abnormal but unaffected by the respiratory cycle. During spontaneous breathing, the polygraphic recordings showed expiratory microsleep episodes, with inspiratory arousals synchronous to bursts of INM activity. This case report illustrates the powerful adaptability of the respiratory and sleep control systems to maintain each vital function.

Adult↗

PubMed2006

The postural disorientation induced by neck muscle vibration subsides on lightly touching a stationary surface or aiming at it.

The aim of this study was to investigate whether the standing body spatial disorientation, induced by neck muscle vibration, and the related post-effects can be suppressed by light finger touch (LFT) of a stationary surface. Continuous (60 s) vibration of dorsal neck or sternocleidomastoid muscle was administered with eyes closed. The center of foot pressure (CFP) displacement, measured by a stabilometric platform, indicated the degree of vibration-induced body tilt. We also investigated whether sensory information from LFT itself was necessary or anticipation of a more secure posture was enough for reducing vibration effects. To this aim, we administered a vibration pulse (5 s) to dorsal neck or sternocleidomastoid muscle and during reaching to the stationary surface. CFP was recorded during both vibration and post-vibration condition and during the aiming task. Neck vibration induced significant CFP displacement in the direction opposite to vibration site. Post-vibration, CFP slowly returned to control values with ample oscillations. LFT during vibration reduced body tilt. LFT was more effective when fingertip contact was in the plane of the greatest tilt. LFT applied during either vibration or post-vibration period reduced post-vibration effects. Reaching toward the stationary surface was enough for reducing vibration-induced body tilt to values close to those observed during actual LFT. The novel conclusions of this study are: 1) LFT is able to relieve the effects of vibration-induced abnormal proprioceptive input from the neck, a segment central to postural control and orientation; 2) LFT during vibration also attenuates vibration post-effects, further suggesting that its action is not merely mechanical; 3) the intention to stabilize the body generates a new postural 'set' sufficient for diminishing body tilt.

Adult↗

PubMed1983

[Postsynaptic potentials of motor neurons of neck muscles in the cat evoked by stimulation of the horizontal semicircular canals].

PSPs, evoked by stimulation of the ipsi- and contralateral horizontal semicircular canals (HSC) in motoneurons of neck muscles, were studied in acute experiments on cats under chloralose-nembutal anesthesia. Ipsilateral stimulation evoked EPSP with latencies ranging from 1.8 to 10.0 ms in 25 motoneurons and IPSP with latencies 1.9-3.9 ms in 10 motoneurons. Calculation of conduction time from ipsilateral canal via Deiters nucleus to neck motoneurons gives reason to consider EPSP with latencies less than 3.8 ms as disynaptic, and those with greater latencies as polysynaptic. Contralateral stimulation evoked EPSP with latencies 1.8-6.0 ms in 19 motoneurons and IPSP with latencies 3.2 and 3.9 ms in 2 motoneurons. Possible pathways conducting these influences and their functional role are discussed.

Animals↗

PubMed2004

Gradation of Neck Muscle Responses and Head/Neck Kinematics to Acceleration and Speed Change in Rear-end Collisions.

Recent epidemiological evidence shows that the potential for whiplash injury varies with both the average acceleration and speed change of a rear-end collision. The goal of this study was to examine the gradation of neck muscle responses and the head and neck kinematics to rear-end collision pulses in which the acceleration and speed change were independently varied. Thirty subjects (15F, 15M) underwent 36 consecutive rear-end collisions consisting of three different average accelerations (ā = 0.5, 0.9 and 1.3 g) and three different speed changes (Deltav = 0.25, 0.50 and 0.75 m/s). Onset and amplitude of the sternocleidomastoid (SCM) and cervical paraspinal (PARA) muscle responses were measured using surface electromyography. Kinematic measures included linear and angular accelerations and displacements of the head and torso. The results showed that the amplitude of the muscle and kinematics responses was graded to both collision acceleration and speed change. The magnitude of early peaks in the head/neck kinematics correlated more strongly with collision acceleration (r(2) = 0.63 to 0.69), whereas the magnitude of later kinematic peaks correlated more strongly with collision speed change (r(2) = 0.59 to 0.95). Onset of the SCM muscle response correlated only weakly with collision acceleration and speed change (r(2) </= 0.07). A collision pulse descriptor obtained by multiplying average acceleration and speed change (āDeltav) yielded the strongest and most consistent correlations with neck muscle (r(2) = 0.48 to 0.58) and head/neck kinematic responses (r(2) = 0.78 to 0.94). This measure of collision severity is also consistent with the recent epidemiological evidence that whiplash symptom intensity and duration increases with both average acceleration and speed change.

Journal Article↗

PubMed1992

Evaluation of pressure pain threshold in head and neck muscles by electronic algometer: intrarater and interrater reliability.

Using a new electronic algometer, the mean values and standard deviations of pressure pain threshold and the intrarater and interrater reliability were evaluated on 13 muscles of the human head and neck region. The subjects were 40 healthy individuals, 21 females and 19 males. A comparison with data obtained from contralateral muscles failed to demonstrate significant differences. Statistically significant correlation coefficients were obtained from the values of intra-examiners and inter-examiners in all muscles except the medial pterygoid and middle sternocleidomastoid muscle in male subjects (p < 0.05). This study showed that the electronic algometer could be recommended for evaluation of the pressure pain threshold of human head and neck muscles in clinical and experimental studies.

Adult↗

PubMed1993

[A case of multiple system atrophy presenting a regular involuntary movement of the neck muscles synchronous with respiration].

A patient with multiple system atrophy developed a regular, rhythmic involuntary movement of the neck muscles which appeared synchronous with respiration and could be described as "rocking-of-the-head". He had been treated with antiparkinsonian drugs such as L-dopa, L-dopa/carbidopa, amantadine hydrochloride and trihexiphenidyl hydrochloride for approximately one year. A fluoroscopic study assured that the involuntary "rocking-of-the-head" movement synchronized with the diaphragmatic up-and-down movement. A polygraphic study showed that the accelerometer curve which reflected the rocking movement of the head oscillated at approximately 0.7 Hz and synchronized with the surface EMG discharges of the right sternocleidomastoid muscle and the nasal flow curve. This involuntary movement was seen almost all day long as well as asleep but severest usually in the afternoon. Discontinuation of trihexiphenidyl hydrochloride alone made the involuntary movement less severe but never suppressed it completely. Resumption of the drug made the involuntary movement as severe as it had been. Discontinuation of L-dopa, L-dopa/carbidopa and amantadine hydrochloride was followed by disappearance of the involuntary movement in a day or so, in spite of continued intake of trihexiphenidyl hydrochloride. Rigidity and bradykinesia induced by discontinuation of these drugs, however, made it necessary to resume them. As a result the involuntary movement again exacerbated.

Amantadine↗

PubMed1986

A computer model of neck muscle endurance and fatigue as a function of helmet loading.

A series of experiments were conducted in which the neck muscles of volunteer subjects were dynamically and statistically loaded by systematic variations of twenty-four headgear configurations consisting of eight different centers-of-gravity (CGs) times three different weights. Six subjects would rotate their heads laterally (from side-to-side) for 30 min with each of the headgear loading combinations. Immediately thereafter, the subject would position his head in an isometric head dynamometer and exert a sustained right lateral neck contraction or forward neck contraction at 70% of his maximum strength, during which endurance time (to fatigue) was recorded. The results indicate that the computer model makes reasonable predictions within the boundary conditions. Input data outside the boundary conditions is rejected. The assumption of insensitivity to vertical loading is demonstrated. The assumption of bilateral symmetric response was confirmed for the 1.45 kg and 2.27 kg helmet loads. However, this assumption was not confirmed for the 4.09 kg helmet load. It is concluded from the computer model that aftward, midline loading is the optimal CG location (i.e. maximal endurance) for heavier helmets in the 3-4 km range.

Adult↗

PubMed2002

Head and neck muscle spasm after radiotherapy: management with botulinum toxin A injection.

OBJECTIVE: To introduce the concept of neck muscle pain and spasm after radiotherapy and its treatment with botulinum toxin A. DESIGN: Case series. SETTING: Ambulatory patients at a tertiary care medical center. PATIENTS: Individuals who had undergone primary or adjuvant radiotherapy for treatment of carcinoma of the head and neck were asked about painful spasms of the neck musculature. A volunteer sample was used. If they desired treatment with botulinum toxin A, they were included in the study. INTERVENTION: Patients received botulinum toxin A injections to the affected sternocleidomastoid muscle(s) in 1 or 2 locations. OUTCOME MEASURE: Subjective pain relief. RESULTS: Four of 6 patients with painful tightness of the neck who received botulinum toxin A injections to the sternocleidomastoid muscle achieved pain relief. CONCLUSIONS: A subset of patients with irradiation-induced cervical muscle spasm benefit from treatment with botulinum toxin A injections. Further study is needed to more clearly define the entity and treatment.

Aged↗

PubMed2001

Impact forces and neck muscle activity in heading by collegiate female soccer players.

Three soccer header types (shooting, clearing and passing) and two heading approaches (standing and jumping) were manipulated to quantify impact forces and neck muscle activity in elite female soccer players. The 15 participants were Division I intercollegiate soccer players. Impact forces were measured by a 15-sensor pressure array secured on the forehead. The electromyographic (EMG) activity of the left and right sternocleidomastoid and trapezius muscles was recorded using surface electrodes. Maximum impact forces and impulses as well as the EMG data were analysed with separate repeated-measures analyses of variance. Impact forces and impulses did not differ among the header types or approaches. Higher values were found for jumping versus standing headers in the mean normalized EMG for the right sternocleidomastoid. In addition, the integrated EMG was greater for the right sternocleidomastoid and right and left trapezius (P < 0.05). The sternocleidomastoid became active earlier than the trapezius and showed greater activity before ball contact. The trapezius became active just before ball contact and showed greater activity after ball contact. The increased muscle activity observed in the neck during the jumping approach appears to stabilize the connection between the head and body, thereby increasing the stability of the head-neck complex.

Adult↗

PubMed2006

Eye position modulates the electromyographic responses of neck muscles to electrical stimulation of the superior colliculus in the alert cat.

Rapid gaze shifts are often accomplished with coordinated movements of the eyes and head, the relative amplitude of which depends on the starting position of the eyes. The size of gaze shifts is determined by the superior colliculus (SC) but additional processing in the lower brain stem is needed to determine the relative contributions of eye and head components. Models of eye-head coordination often assume that the strength of the command sent to the head controllers is modified by a signal indicative of the eye position. Evidence in favor of this hypothesis has been recently obtained in a study of phasic electromyographic (EMG) responses to stimulation of the SC in head-restrained monkeys (Corneil et al. in J Neurophysiol 88:2000-2018, 2002b). Bearing in mind that the patterns of eye-head coordination are not the same in all species and because the eye position sensitivity of phasic EMG responses has not been systematically investigated in cats, in the present study we used cats to address this issue. We stimulated electrically the intermediate and deep layers of the caudal SC in alert cats and recorded the EMG responses of neck muscles with horizontal and vertical pulling directions. Our data demonstrate that phasic, short latency EMG responses can be modulated by the eye position such that they increase as the eye occupies more and more eccentric positions in the pulling direction of the muscle tested. However, the influence of the eye position is rather modest, typically accounting for only 10-50% of the variance of EMG response amplitude. Responses evoked from several SC sites were not modulated by the eye position.

Action Potentials↗

PubMed2006

The influence of occlusion on jaw and neck muscle activity: a surface EMG study in healthy young adults.

The electromyographic (EMG) characteristics of masseter, temporalis and sternocleidomastoid (SCM) muscles during maximum voluntary teeth clench were assessed in 27 male and 35 female healthy young adults. Subjects were divided into two groups: (i) 'complete' Angle Class I (bilateral, symmetric canine and molar Class I relationships), and (ii) 'partial' Angle Class I (one to three canine/molar Class I relationships, the remaining relationships were Class II or Class III). On average, standardized muscular symmetry ranged 80.7-87.9%. During maximum voluntary teeth clench, average co-contraction of SCM muscle was 13.7-23.5% of its maximum contraction. On average, all torque coefficients (potential lateral displacing component) were >90%, while all antero-posterior coefficients (relative activities of masseter and temporalis muscles) were >85%. The average integrated areas of the masseter and temporalis EMG potentials over time ranged 87.4-106.8 muV/muV s%. Standardized contractile muscular activities did not differ between 'complete' and 'partial' Angle Class I, and between sexes (two-way analysis of variance). A trend toward a larger intragroup variability in EMG indices was observed in the subjects with 'partial' Angle Class I than in those with 'complete' Angle Class I (significant difference for the temporalis muscle symmetry, P = 0.013, analysis of variance). In conclusion, the presence of a complete or partial Angle occlusal Class I did not seem to influence the standardized contractile activities of masseter, temporalis and SCM muscles during a maximum voluntary clench. Subjects with a 'complete' Angle Class I were somewhat a more homogenous group than subjects with 'partial' Angle Class I.

Adolescent↗