Neck Extensor Muscle Activity Research Articles

An investigation of an ergonomics intervention to affect neck biomechanics and pain associated with smartphone use

Neck discomfort and pronounced neck flexion have been associated with smartphone use. Eye glasses with a 90 deg prism in each lens were investigated as a potential intervention to reduce awkward head and neck postures during activities involving viewing the device. Sixteen smartphone users with neck pain and 9 asymptomatic users performed a texting task on a smartphone with and without the prism glasses, in sitting and standing postures in a laboratory setting. Cervical erector spinae and upper trapezius muscle activity, head posture and motion, performance, discomfort and other subjective perceptions were assessed. Prism glasses reduced neck extensor muscle activity, neck flexion, and head tilt compared to the direct view. In the symptomatic group, the intervention produced less neck and shoulder discomfort compared to the direct view. This intervention could offer an alternative way of interacting with a smartphone while texting in stationary postures, by reducing exposure to pronounced flexed neck and head posture commonly seen in users, and thereby could reduce neck discomfort associated with smartphone use.

Influence of virtual keyboard design and usage posture on typing performance and muscle activity during tablet interaction

This study aimed to determine the effects of virtual keyboard designs and postures on task performance and muscle activity during tablet use. Eighteen healthy adults were randomly assigned to one of three postures (DESK, LAP, BED) to complete six sessions of 60-minute typing on a tablet with three virtual keyboards (STD, WIDE, SPLIT) twice in an experimental laboratory. Keystroke dynamics and muscle activity of the forearm and neck-shoulder regions were measured by electromyography. The split virtual keyboard was found to be associated with faster typing speed (SPLIT vs STD, p = .015; SPLIT vs WIDE, p < .001) and decreased muscle activity of extensor digitorum communis (SPLIT vs STD, p = .021). Lap posture was associated with faster typing speed (p = .018) and higher forearm muscle activity (p < .05). Typing performance decreased (p < .001) with elevated neck extensor muscle activity (p = .042) when the task duration prolonged. The split virtual keyboard showed potential to improve tablet ergonomics under various postures. Practitioner Summary: Tablets have become widely used for a variety of tasks and have gradually expanded into the realm of mobile productivity and education. Adequate designs of virtual keyboards for tablets show the potential for increased task performance and decreased muscle activity pertinent to typing activity and posture constraints imposed by non-traditional work positions. Abbreviations: WPM: words per minute; IKI: inter-key press interval; EMG: electromyography; EDC: extensor digitorum communis; FDS: flexor digitorum superficialis; CES: cervical erector spinae; UT: upper trapezius; EA: electrical activity; MVC: maximum voluntary contraction; APDF: amplitude probability distribution function

Neck Muscular Load When Using a Smartphone While Sitting, Standing, and Walking

Myoelectric activity of neck extensor muscles and head kinematic variables, when using a smartphone for one-handed browsing and two-handed texting while sitting, standing, and walking, were evaluated to compare the neck muscular load during these tasks and across the posture conditions. There has been limited research on the relation between head-down postures and the muscular load on the neck of smartphone users. Twenty-one asymptomatic young users were asked to perform one-handed browsing and two-handed texting tasks in each of the posture conditions, and the myoelectric activities of the neck extensor muscles, head kinematic variables, and upper back posture were quantified. The muscle activation level when using a phone during walking was 21.2% and 41.7% higher than that of sitting and standing on average (p < .01). Head vertical and angular accelerations were also significantly greater (p < .01) for walking than for sitting and standing conditions. Between the two conducted tasks, participants flexed their heads more significantly (p < .01) with higher activation of the neck extensor muscles (p < .01) when texting as compared to when browsing. Results indicate that two-handed texting while walking would be the most physically demanding scenario for neck musculature, and it might be attributable to the dynamics of the head while walking with the head facing downwards. These findings can be used to better understand the potential relation between smartphone use and the occurrence of neck musculoskeletal problems and to inform the users of the ergonomic risks of using smartphones while walking.

Effects of Trunk and Neck Extensor Muscle Activity on the Bridging Exercise According to Knee Joint Angle

Effects of Trunk and Neck Extensor Muscle Activity on the Bridging Exercise According to Knee Joint Angle

Craniocervical Orientation Affects Muscle Activation When Exercising the Cervical Extensors in Healthy Subjects

Elliott JM, O'Leary SP, Cagnie B, Durbridge G, Danneels L, Jull G. Craniocervical orientation affects muscle activation when exercising the cervical extensors in healthy subjects. Objective To evaluate the activity of neck extensor muscles during different extension exercises with muscle functional magnetic resonance imaging (mfMRI). Design Cross-sectional. Setting University laboratory. Participants Healthy subjects (N=11; 7 men, mean age ± SD, 34±5.6y; 4 women, mean age ± SD, 23.3±5.2y; group mean age ± SD, 30.1±7.5y). Intervention Not applicable. Main Outcome Measures mfMRI measures of T2 relaxation were made for the multifidus (Mul), the semispinalis cervicis (SCe), the semispinalis capitis (SCa), and the splenius capitis (SpC) at C2-3, C5-6, and C7-T1 in response to 2 head/neck orientations: craniocervical neutral (CCN) and craniocervical extension (CCE). Subjects performed three 1-minute repetitions of each condition at 20% maximum voluntary contraction. Results Significant shifts were observed in all muscle groups at the C5-6 and C7-T1 levels after both conditions ( P=.04) except the SpC muscle at C5-6 with CCN ( P=.17). T2 shifts in the SCa were significantly greater in response to CCE than CCN at C2-3 ( P=.03) and C5-6 ( P=.02). Similarly, CCE resulted in larger shifts than CCN in the Mul/SCe at C7-T1 ( P=.003). No segmental differences were observed between exercises for SpC ( P=.25). Conclusions The results of this study provide some preliminary insight into the impact of craniocervical orientation on the differential response of the deep and superficial cervical extensor muscles during the performance of cervical extensor exercises.

Sports Exercise Effect on Shortening of Saccadic Reaction Time Associated with Neck Extensor Muscle Activity

Sports Exercise Effect on Shortening of Saccadic Reaction Time Associated with Neck Extensor Muscle Activity

Sports Exercise Effect on Shortening of Saccadic Reaction Time Associated with Neck Extensor Muscle Activity

We investigated sports exercise effect on shortening of saccadic reaction time associated with neck extensor muscle activity. Saccadic reaction time was measured in neck rest position, 20 degrees neck flexion, and 30 % muscle contraction of the shoulder girdle elevators for two groups. These groups were an untrained group that has never belonged to any sports club (UT group) and a group that has belonged to high-speed ball sports clubs (HS group). In the neck flexion and 30 % muscle contraction conditions, there was a significant shortening of the reaction time for the HS group. For the UT group, no significant shortening was found in those conditions, and the reaction time in the 30 % contraction was rather significantly longer than that in the rest position. Sports experience pursuing a high-speed ball will be effective in the shortening of the saccadic reaction time associated with the activity of neck extensors.

Effects of the liquid crystal display tilt angle of a notebook computer on posture, muscle activities and somatic complaints

More con strained posture and higher neck muscle activities have been reported among users of notebook computers than those of desktop computers. Complaints of eye and musculoskeletal d iscomfort as well as di fficulty of keying were greater during work with notebook computers. These reports ascribed the findings to the differences in the size of desktops and notebooks. Another ergonomic aspect of the notebook computer distinct from the CRT is its angle-dependent luminance contrast. The present study investigated the effects of liquid crystal display (LCD) tilt angle of a notebook computer on posture, muscle activities and somatic complaints in 10 subjects. At the tilt angle of 100°, the subjects were noted to have relatively less neck flexion. The static neck extensor muscle activity was also lowest at this tilt angle. Nonetheless, the complaint survey revealed higher rates of discomfort while viewing and using the LCD set at the tilt angle of 100°. The findings of this study strongly suggested that the ergonomic features and problems attributable to notebook computers are distinct from the desktop computers. The points of interest raised in this paper should be considered when contemplating the use of notebook computers. Relevance to industry The use of notebook computers has increased steadily over the last 5 years , especially in Japan. Few authors have ventured to study the problems associated with these smaller computers . The results and suggestions of this stu dy may contribute to improve the design of notebook computers and the workstations .