Maximum neck extension strength and relative neck muscular load in different cervical spine positions (original) (raw)
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Variation of neck muscle strength along the human cervical spine
Stapp car crash journal, 2004
The aim of this study was to describe and explain the variation of neck muscle strength along the cervical spine. A three-dimensional model of the head-neck complex was developed to test the hypothesis that the moment-generating capacity of the neck musculature is lower in the upper cervical spine than in the lower cervical spine. The model calculations suggest that the neck muscles can protect the lower cervical spine from injury during extension and lateral bending. The maximum flexor moment developed in the lower cervical spine was 2 times higher than that developed in the upper spine. The model also predicted that the neck musculature is 30% stronger in the lower cervical spine during lateral bending. Peak compressive forces (up to 3 times body weight) were higher in the lower cervical spine. These results are consistent with the clinical finding that extension loading of the neck often leads to injuries in the upper cervical spine. Analysis of the model results showed that neck...
The effect of static neck flexion on mechanical and neuromuscular behaviors of the cervical spine
Journal of Biomechanics, 2018
Occupations that involve sustained or repetitive neck flexion are associated with a higher incidence of neck pain. Little in vivo information is available on the impact of static neck flexion on cervical spinal tissue. The aim of this study was to assess changes in mechanical and neuromuscular behaviors to sustained neck flexion in healthy adults. Sixty healthy subjects aged 20-35 years participated in this study. The participants were exposed to static neck flexion at a fixed angle of full flexion for 10 min. Mechanical and neuromuscular responses of the cervical spine to sudden perturbations were measured preand post-exposure. Magnitude of load-relaxation during flexion exposure, stiffness, peak head angular velocity, and reflexive activities of cervical muscles were recorded. Effective neck stiffness decreased significantly, especially in female participants (P = 0.0001). The reflexive response of the cervical erector spinae muscles to head perturbation delayed significantly (P = 0.0001). Peak head angular velocity was significantly increased after exposure to neck flexion for 10 min, especially in female participants (P = 0.001). In the present study, static flexion resulted in changes in mechanical and neuromuscular behavior of the cervical spine, potentially leading to decreased stiffness of the cervical spine. The results confirm the importance of maintaining a correct head and neck position during work and improving the work environment to reduce the cervical spinal load and work-related neck pain
Journal of Biomechanics, 2015
The posture of the head and neck is critical for predicting and assessing the risk of injury during high accelerations, such as those arising during motor accidents or in collision sports. Current knowledge suggests that the head's range-of-motion (ROM) and the torque-generating capability of neck muscles are both dependent and affected by head posture. A deeper understanding of the relationship between head posture, ROM and maximum torque-generating capability of neck muscles may help assess the risk of injury and develop means to reduce such risks. The aim of this study was to use a previously-validated device, known as Neck Flexibility Tester, to quantify the effects of head's posture on the available ROM and torque-generating capability of neck muscles.
Journal of Manipulative and Physiological Therapeutics, 2019
Objective: The objective of the study was to assess the influence of forward head posture on the mechanical parameters and pressure pain threshold of superficial neck muscles in clinically nonsymptomatic individuals with sedentary jobs. Methods: Twenty-five office workers with forward head posture and 25 office workers with normal head posture were matched for sex, age, body mass index, and the nature and duration of their work and were compared at a single point. The study participants were divided into study groups on the basis of photometric craniovertebral angle measurements. The upper trapezius, sternocleidomastoid, and splenius capitis mechanical properties were assessed in the sitting position. Primary outcome measures were muscle stiffness (N/m), muscle tone (Hz), and muscle elasticity. The secondary variable was perceived pain threshold. Results: No significant differences between the groups were found for biomechanical properties and perceived pain threshold in the studied muscles. Conclusion: Forward head posture has no impact on muscle stiffness, tone, and elasticity, nor does it increase the pressure sensitivity of superficial neck muscles in healthy, mildly symptomatic office workers. It is most likely that not incorrect posture of the cervical spine, but probably other factors combined with forward head posture, like comorbid acute and chronic cervical pain and musculoskeletal disorders or prolonged sitting, contribute to changes in active myofascial tone and tensegrity as well as increased pressure sensitivity of neck muscles.
Journal of Back and Musculoskeletal Rehabilitation, 1999
The purposes of this investigation were: 1) to determine whether cervical range of motion and strength differ when measured in resting head posture (RHP) vs. neutral head posture (NHP), 2) to examine gender differences in cervical range of motion, strength, and neck girth, and 3) to examine the relationship between cervical range of motion and strength with: a) neck girth, b) height, and c) weight. Fortysix graduate students (10 males, 36 females) age 20-40 with no history of cervical or shoulder girdle pathology were recruited. Height, weight, and neck girth were measured for each subject. The Cervical Range of Motion (CROM) device was used to determine the amount of forward head posture and active range of motion for flexion (FLEX), extension (EXT), right and left lateral flexion (RLF and LLF), and right and left rotation (RROT and LROT) with subjects seated in a straight-back chair. Isometric cervical strength for FLEX, EXT, RLF, LLF, RROT, and LROT was then determined using the Microfet hand-held dynamometer with subjects seated in a chair which stabilized the trunk. Subjects performed the six active range of motion and the six isometric contractions in the RHP and NHP. Greater range of motion for EXT was achieved in the NHP, while greater RLF, RROT and LROT was achieved in the RHP. LROT in the RHP was the only contraction to demonstrate significantly greater strength. Females had greater cervical extension than males in both postures. Males were consistently stronger than females for all contractions in both postures and had larger neck girths. Strength correlated with neck girth, weight, and then height.
Frontiers in Physiology, 2021
Background: Neck pain is a major cause of disability worldwide. Poor neck posture such as using a smartphone or work-related additional cervical axial load, such headgear of aviators, can cause neck pain. This study aimed at investigating the role of head posture or additional axial load on spinal stiffness, a proxy measure to assess cervical motor control. Methods: The posterior-to-anterior cervical spinal stiffness of 49 young healthy male military employees [mean (SD) age 20 ± 1 years] was measured in two head positions: neutral and 45-degree flexed head position and two loading conditions: with and without additional 3 kg axial load. Each test condition comprised three trials. Measurements were taken at three cervical locations, i.e., spinous processes C2 and C7 and mid-cervical (MC). Results: Cervical spinal stiffness measurements showed good reliability in all test conditions. There was a significant three-way interaction between location × head position × load [F(2, 576) = 9....
Analysis and measurement of neck loads
Journal of Orthopaedic Research, 1988
To examine the loads imposed on the structures of the neck by the performance of physical tasks, a biomechanical model of the neck was constructed. The model incorporated 14 bilateral pairs of muscle equivalents crossing the C4 level. A double linear programming optimization scheme that minimized maximum muscle contraction intensity and then vertebral compression force while equilibrating external loads was used to calculate the muscle contraction forces required and the motion segment reactions produced by task performance. To test model validity, 14 healthy adult subjects performed a series of isometric tasks requiring use of their neck muscles. These tasks included exertions in attempted flexion, extension, and left and right lateral bending and twisting. Subjects exerted maximum and submaximurn voluntary efforts. During the performance, surface myoelectric activities were recorded at eight locations around the periphery of the neck at the C4 level. Calculated forces and measured myoelectric activities were then linearly correlated. Mean measured voluntary neck strengths in 10 male subjects were as large as 29.7 Nm. Four female subjects developed mean strengths that were approximately 60%-90% of those of the males. In both sexes, neck muscle strengths were approximately one order of magnitude lower than previously measured lumbar trunk strengths. Mean calculated neck muscle contraction forces ranged to 180 N. Mean calculated compression forces on the C4-5 motion segment ranged to 1164 N, lateral shear forces ranged to 125 N, and anteroposterior shear forces ranged to 135 N. Correlation coefficients between the calculated muscle forces and the measured myoelectric activities were as large as 0.85 in some muscles, but generally were smaller than this.
Significant change in muscular strength based on the head and neck position
Papers on Anthropology
We present our study of the influence of the head 30 degrees flexion position on the changes in the muscle strength of the upper extremities. This position is typical for a person working in front of a computer.The study involved 100 healthy volunteers and was performed at the Department of Morphology in Riga Stradiņš University, Riga, Latvia. For measurements we have used the MicroFET2 Hand Held Digital Muscle Tester to determine the strength of the muscles of the hand and the arm (M. deltoideus, M. biceps brachii, M. triceps brachii, M. abductor pollicis longus). The results of measurements were then used to analyze the difference in the strength of the muscles innervated by the spinal cord cervical region (C5–C8 nerves) for the same person sitting in the vertical position and sitting with the head flexed at 30°.The results of our study support the hypothesis that the changes in the strength of the measured muscles are related to the mechanical distension of the spinal cord, which...
E.m.g./moment relationships in neck muscles during isometric cervical spine extension
Clinical Biomechanics, 1988
The aim of the study was to describe the e.m.g./muscular moment (torque) relationships for neck and shoulder muscles during cervical spine extension. Ten healthy women participated. Their average age was 25.6 years. The neck extension muscular moments exerted were measured isometrically in neutral and in flexed lower-cervical spine positions with a strain gauge connected to a sling around the back of the head. The moment about the bilateral axis of the C7 -T1 spinal motion segment was calculated as the moment balancing the sum of the moment of the sling resistance force and the moment caused by the gravity forces of the head and neck. Video images were analysed for moment arm length measurements.