China 
Africa 
Explore chapters and articles related to this topic
Designing for Upper Torso and Arm Anatomy
Published in Karen L. LaBat, Karen S. Ryan, Human Body, 2019
The major superficial upper back muscle, the trapezius, arises from the base of the skull and spinous processes in the neck and thorax. It inserts on the spine of the scapula, the clavicle, and the acromion. This large muscle shrugs the shoulders—up and down—and rotates the scapula on the rib cage. The other large superficial back muscle, the latissimus dorsi, originates from spinous processes in the thoracic spine, lumbar spine, and the sacrum plus the iliac crest of the pelvis. It inserts on the humerus, forming the posterior wall of the axilla. It extends, adducts, and rotates the humerus in the glenohumeral joint and raises the body toward the arms, for example during rock climbing activities (Moore et al., 2011, p. 425). Because of their many actions, these muscles change shape frequently.
Impact of rest-break interventions on the neck and shoulder posture of symptomatic VDU operators during prolonged computer work
Published in International Journal of Occupational Safety and Ergonomics, 2018
Montakarn Chaikumarn, Nuttika Nakphet, Prawit Janwantanakul
The first hypothesis of this study was that the two active breaks compare with passive break would cause larger increases in CV and FS angles. The present study did not found significant differences in the CV and FS angles among three types of rest break. However, stretching and dynamic contraction showed a greater trend of a positive effect on the CV and FS angles for the symptomatic VDU operators. This is in line with a previous study reporting that active breaks with stretching and joint mobilization significantly improve muscular discomfort compared with passive breaks [45]. This could positively affect the joint position of the neck–shoulders in the CV and FS angles of the subjects. Furthermore, Blangsted et al. [46] reported that passive breaks are insufficient to attain complete relaxation of the trapezius muscle. As regards the neck–shoulder posture, the trapezius muscle is the main stabilizer. If the trapezius is fatigued during prolonged computer work, the CV and FS angles could be reduced and can cause increased forward head posture. This is in agreement with another study showing that increased forward head posture during VDU work caused an increase in the muscular activity in the neck–shoulder musculature to hold the head and neck in this position, which may then result in muscle fatigue and muscle imbalance [15]. In addition, this present study chose the protocol of adding a 3-min rest break after every 20-min interval because a previous study showed this to have a favourable effect on avoiding neck and shoulder muscle fatigue among symptomatic VDU operators [47].
Impact of a 10-min typing task in the development of trapezius myalgia: a preliminary observational study
Published in International Journal of Occupational Safety and Ergonomics, 2023
Rui José Santiago, João Santos Baptista, André Magalhães, José Torres Costa
The relationship between typing on a computer and the development of musculoskeletal conditions as trapezius myalgia (TM) has long been established in the scientific literature [1–4]. TM is one of several terms that define pain over the trapezius muscle, which is a common way to express neck–shoulder pain [5]. Several other muscles may play a role in the overall sensation of discomfort or pain [6]. TM can be described as a non-specific pain with trigger points (hyper-irritable areas) differentiated from radicular pain arising from the cervical spine. Patients often describe discomfort over the upper trapezius (UT) muscle, worse with activity, and restricted cervical motion [7].
Muscle fatigue during assisted violin performance
Published in Ergonomics, 2023
Clara Ziane, Etienne Goubault, Benjamin Michaud, Mickaël Begon, Fabien Dal Maso
Very few studies have assessed MMF during violin playing and never with DAS. Chan et al. (2000) assessed median frequency of left trapezius and found no significant difference before and after a violin practice session of 2–3 hours. Violinists’ RPE had however only reached 3 ± 2 on the CR10 Borg scale (i.e. light perceived exertion). As perceived exertion is not a direct measure of muscle fatigue, it is possible that increases in RPE at low levels of perceived exertion reflect central or neuromuscular junction fatigue (Merletti and Farina 2006) rather than muscle fatigue itself, which makes Chan et al. (2000)’s results difficult to compare with ours. More recently, Moller et al. (2018) showed an EMG shift towards lower frequencies for the left medial deltoid and upper trapezius after one hour of playing the violin in a group of musicians unaffected by PRMD. Consistent with their results, we found a significant decrease in the left medial deltoid’s median frequency during the unassisted condition, while DAS prevented the MMF at the superior trapezius. Trapezius muscles stabilise and support scapular movements. Fatigue at the trapezius can lead to a muscular imbalance and in turn to an upper crossed syndrome, which is one type of the PRMD reported in violinists (Mizrahi 2020). In addition, we observed a beneficial effect of DAS on left supraspinatus’ median frequency. This Condition*Time interaction was only marginally significant (P=0.057) due to small sample size (n = 6) but effect size was large (dz = 1.0), suggesting a true effect of DAS on this muscle’s MMF. The supraspinatus abducts the arm and stabilises the glenohumeral joint. Reduced muscle fatigue of the supraspinatus may limit occurrence of subacromial impingement syndromes, which also are a type of PRMD reported in violinists (Mizrahi 2020). Lower MMF at shoulder muscles were previously reported by a different research team using the same assistive device (Lavallée-Bourget et al. 2022). These latter findings further support DAS benefits, which were observed for relatively short playing times (∼10 minutes) in our study, making passive assistive devices a promising tool to prevent injuries of the left shoulder.