Trapezius Myalgia

Top Contributors - Nick Van Doorsselaer, Lauren Trehout, Abbey Wright, Elien Clerix, Camille Dewaele, Gayatri Jadav Upadhyay, Kim Jackson, Vanessa Rhule, Admin, Joao Costa, Rachael Lowe, Ajay Upadhyay, Kai A. Sigel, Kirenga Bamurange Liliane, Aminat Abolade and Rishika Babburu  - Simon Vanelewijck - Roel Kelderman

Search Strategy

We searched on different databases such as PubMed and PEDro using the following words in our search terms: myalgia, trapezius myalgia, neck-shoulder disorders, definition, epidemiology, clinical presentation, outcome, physical therapy, surgery, medical intervention, treatment, diagnosis... We only used articles of which the full text was available.

Definition/Description

Myalgia in generally is known as a muscle ache or muscle pain. In case of trapezius myalgia (TM) the pain is localized in the superior fibres, or otherwise the superior part, of the trapezius muscle¹ [LoE: 2B]. Mostly the neck and shoulder area is painful and uncomfortable² [LoE: 2B]. TM is not a medical disorder or disease but rather a symptom of an existing underlying condition. The pain in the muscle can last a few days or longer. It can be continuous and can range from mild to excruciating³ [LoE: 5].

Clinically Relevant Anatomy

The trapezius muscle is a large trapezoid shaped muscle that makes up the majority of the superficial posterior cervical and thoracic musculature and consists of three parts^{4 5}:

‐ Trapezius pars descendens (superior part)
‐ Trapezius pars transversa (middle part)
‐ Trapezius pars ascendens (inferior part)

The visualisation of the course, functions and innervation of all three parts is shown in the following video:
https://www.youtube.com/watch?v=P5sOhwBZon8 
In TM it is the superior part that is painful¹.This part originates from the linea nuchalis superior, the protuberantia externa and through the nuchal ligament from all cervical spinous processes. The insertion is on the lateral third of the clavicula and the acromion⁴.

All parts work together to stabilize the scapula⁵ . The superior fibers are responsible for upward rotation and elevation of the scapula, homolateral lateroflexion and heterolateral rotation of the head. When activated bilaterally, the superior part ensures neck extension⁴. 

Etiology/Epidemiology 

Etiology
There has been a lot of research on the aetiology of work related neck and shoulder disorders and hence of TM. Researchers agree that the disorders arise from both biomechanical and psychosocial factors. Within the biomechanical dimension the m. Trapezius plays an important role. TM may be associated with a lot of peripheral and/or central changes which can interact resulting in muscle pain and fatigue⁶.

The review of Larsson et al.⁶ confirmed that highly repetitive work (industrial jobs like fish processing workers, employees of a car assemblage plant⁴⁷ or from the metal industry ⁴⁸ forceful exertions, high level of static contractions, prolonged static loads, extreme postures or a combination of these factors are possible causes of neck and shoulder disorders (which include TM) in the working population. Several studies reported altered metabolisms and increased intramuscular levels of algesic substances. These local peripheral muscular processes could explain the chronic pain in neck-shoulder disorders. The review of Gerdle et al.⁷  confirms these hypothesises by finding elevated levels of 5-HT, glutamate, lactate and pyruvate in localized chronic myalgias. Other changes that occur at the muscular level are mitochondrial disturbances in the type I fibres^{6 8}  and reduced capillary density and circulation^{6 8}. These changes can possibly cause interferences in the oxidative metabolism of the muscles.

In chronic TM Larsson et al.⁹  found an impaired regulation of local blood flow in the upper trapezius muscle that is not due to intramuscular pressure, to be an important cause of nociceptive pain.

Centrally a reorganization of the neuromotor control strategies takes place. The superficial cervical extensor muscles show a higher muscle activation and deplete faster. So the superficial upper trapezius shows a higher activation then the erector spinae. Szeto et al.¹⁰  demonstrate in their study that the greater recruitment of type II fibres in symptomatic patients could possibly explain the muscle fatigue.

Not only the biomechanical factors play an important role in het onset of TM. Larsson et al.⁶ has described a causal relationship between psychosocial factors and the occurrence of neck and shoulder disorders. There is some evidence that there is a link between disorders and high quantitative and qualitative demands, lack of support of colleagues, low job control and low influence. They also demonstrated a relationship between mental stress at work and disorders. However, the limited amount of literature focusing on causal relationships between psychosocial factors and disorders makes it difficult to estimate the influence of these factors and how they may interact with the biomechanical and individual factors.

Epidemiology
Most epidemiological studies are about neck-shoulder disorders in general. Trapezius myalgia belongs to these kind of disorders and therefore belongs to 20-30% of the estimated prevalence of upper-extremity symptoms in the working population.
Gender seems to play an important role in the development of neck disorders, since the prevalence is much higher among women. Women more often experience neck pain and develop persistent pain than men do. This difference might be explained by the content of their jobs. Women’s work tasks involve more static load on the neck muscles, high repetitiveness, low control and high mental demands, which are all risk factors for develloping neck disorders ( see ‘aetiology’).⁶

The systematic review of Waersted et al.¹¹ states that computer work does not increase the risk of developing musculoskeletal disorders.

Chronic TM concerns 10-20% of the 20% of the adult population with severe chronic pain in the neck and shoulder region.⁷ The chronic form of TM also shows a higher prevalence in women, but also in low income groups⁷. Likewise, in one-third of the office workers with chronic neck pain, TM present¹².

Characteristics/Clinical Presentation

Typical symptoms of “myalgia” are¹³:
- sudden onset of (severe) pain that lingers for a few days to weeks. The pain is associated with stiffness and spasms
- heaviness of the head and occipital headache
- tenderness of the affected area

Other symptoms¹³:
- nausea and vomiting
- onset of fever
- anxiety and depression
- stiffness of the affected muscle
- vertigo
- numbness and tingling sensations

In case of acute myalgia, the patient can be severely incapacitated because of the pain. Chronic myalgia typically causes pain and stiffness after periods of inactivity. The pain usually eases after reasonable exercise.¹³

Valachy¹⁴  describes the clinical presentation of TM to be pain, spasms and tenderness in the upper trapezius. Trigger points in the muscle can cause painful headaches behind the eye, into the temple and in the back of the neck. The review of Larsson et al.⁶ confirms this.

Differential Diagnosis

According to the review of Larsson et al.⁶ TM can only be diagnosed when neck pain, muscle tightness and trigger points are present, but tension neck syndrome or cervical syndrome is not present.

Tension neck syndrome shows the same symptoms, with the pain radiating from the neck to the back of the head and an additional sense of fatigue or stiffness in the neck. In cervical syndrome the pain radiates from the neck to the upper extremity, there is also decreased sensibility in hands and fingers and muscle weakness in the upper limb.

Other pathologies that can cause similar symptoms are:
- Cervicalgia: neck pain and limited mobility in at least four directions⁶
- Thoracic Outlet Syndrome: pain in the neck, trapezius region, supraclavicular region, chest and occipital region and paresthesia in the upper extremity ⁶

Diagnostic Procedures

The review of Larsson et al.⁶ confirms that the basis for diagnostic criteria of neck and shoulder myalgia is not very clear and that the diagnostic terminology and methods for assessment are variable. If the progressing neck and shoulder pain isn’t accompanied by other symptoms or signs (cfr. red flags), specific investigations such as radiography, magnetic resonance imaging, electromyography or nerve conductance testing aren’t required.

When there’s dubiety between several conditions, certain medical tests¹⁵  are helpful to eliminate certain diagnoses. Radiography and MRI eliminate bone or joint disorders, a blood test can detect inflammation and therefore eliminate underlying conditions that may cause muscle disorders. Electromyography can differentiate between a muscle or nerve disorder if one is present. For the diagnosis of inherited metabolic disorders, connective tissue disease, eosinophilia-myalgia, sarcoidosis and trichinosis, muscle biopsy is indicated.

In general, no objective diagnostic methods are available. The diagnosis is mostly based on symptom presentation and history of illness.^{2 15}

Outcome measures

Visual analogue scale¹
This scale measures general pain, worst pain and present pain on a 100 mm line. The endpoints of the line are no pain and worst possible pain.

Pain thresholds
In the study of Waling et al.¹ the pain of the patient is measured in six trigger points (labelled tp 2 right, tp 2 left, tp 4 right, tp 4 left, tp 5 right and tp 5 left). These points were selected by Simons and Travell (1893)¹⁶ . The pain is measured with a pressure algometer, showing the applied pressure in kPa and indicating the rate of pressure increase. The patient has to indicate when the given sensation starts to hurt. This is the pain threshold. If the therapy is successful, the pain threshold should be higher, so it takes longer for the patient to experience a sensation as pain.

Pain drawing¹
The pain distribution and the characteristics of the pain are marked on a drawing of a body. The total body area marked as painful is interpreted as a percentage of the body area.
Ransford et al.¹⁷  developed such a pain drawing. Margolis et al.¹⁸ created a method to calculate the percentage of painful body area.

McGill pain questionnaire¹⁹
The MPQ is a subjective questionnaire used to asses the quality and intensity of pain in patients with a number of diagnoses.

Neck disability index ^{20 21}
The NDI is a questionnaire that inquires the functional status of a patient concern the following 10 items: pain, personal care, lifting, reading, headaches, concentration, work, driving, sleeping and recreation.

Neck Bournemouth Questionnaire ^{22 23}
The NBQ is administered to patients with non specific neck pain. It assesses pain, disability, affective aspects and cognitive aspects of the neck pain. The questionnaire contains seven items: pain intensity, function in activities of daily living, function in social activities, anxiety, depression levels, fear avoidance behavior and locus of control behavior.

Northwick Park Questionnaire
The NPQ is used to measure neck pain and the disabilities associated with it.

Nordic musculoskeletal Questionnaire (NMQ) for neck and shoulder trouble ^{25 26 27}
This questionnaire focuses on the diagnosis of musculoskeletal problems and is specifically used in chronic work-related cases of TM. The questionnaire is composed of two sections. The first one is a general questionnaire of 40 forced-choice items to identify the areas of the body causing musculoskeletal problems. A body map is added to indicate nine symptom sites. The patient is asked if they had any musculoskeletal problems in the last year and the last week that prevented normal activity. In the second section additional questions about the neck and shoulders are asked to get more details about the issue. This section consists of 25 forced-choice questions about accidents affecting the areas and the functional impact at home and at work in the last week.
The study of Kuorinka et al.²⁸ shows the reliability of the questionnaire to be acceptable for a screening tool. Dickinson et al.²⁹  have made some improvements to the questionnaire. Ohlsson et al.³⁰ found that the sensitivity ranges from 66% to 92% and the specificity from 71% to 88%. The NMQ is thus repeatable, sensitive and can be used as a screening and as a surveillance tool.

Examination

A standard clinical examination on the neck and upper extremities can be useful for diagnosing TM. The examination consists of questions about pain, tiredness and stiffness, physical tests including range of motion (ROM) and muscle tightness, pain provocation, sensibility, strength and palpation of trigger points.^{6 31}

Patients suffering from TM usually have neck pain, tightness of the trapezius muscle and palpable trigger points in the trapezius muscle.^{31 32}

A surface electromyography can be done to evaluate muscle function. Parameters that can be studied are amplitude, timing, conduction velocity, fatigability and characteristic frequencies/patterns.³³

In cases where a typical anamnesis with progressing neck and shoulder pain and no other symptoms or signs is mentioned and where a clinical examination can confirm the diagnosis, there is no need for supplementary objective investigations such as a surface electromyography.⁶ But the study of Juul-Kristensen et al. [LoE: 3B] found that for 60% of those with self-reported neck symptoms of a certain duration and intensity, a clinical examination can confirm one or more diagnoses, with trapezius myalgia (38%), tension neck syndrome (17%), and cervicalgia (17%) being the most frequent. But in the other 40% a supplementary objective investigation is needed to make a correct diagnosis.⁴⁹

Medical Management

The most common medical management for TM is medication for pain relief.

According to the review of Jensen et al most of the pharmacological treatments lack effects or haven’t enough evidence. An intra-muscular injection with lidocaine only has short term effect on pain in chronic neck pain. Intravenous methylprednisolone and lidocaine works in short term on pain. There is not enough evidence on the long term effects of surgical interventions. ^34 24

Physical Therapy Management

Prevention
Prolonged stress in the upper trapezius muscle can activate latent trigger points or maintain pain in active trigger points. Electromyographical biofeedback training of the upper trapezius muscle during computer work leeds to significant less activity and more relative rest time of the trapezius. Therefore biofeedback might be useful in the prevention of TM in computer workers. [Holtermann et al³⁵, 2008; LoE: 1B]

Physical applications
According to the review of Vernon & Schneider³⁶ [2009; LoE: 1A] moderate evidence (level B) is available for short-term relief of mysfascial trigger points by Transcutaneous Electro Nerve Stimulation (TENS), acapuncture and magnet therapy. There’s strong evidence (level A) for the same effect of laser therapy. Laser therapy and acapuncture also show long-term relief of myofascial trigger points.
The review of Chow et al.³⁷  [2009; LoE: 1A] shows evidence of pain reduction in patients with acute or chronic neck pain after low-level laser therapy (wavelength: 780, 830 or 904 nm^{37 46}). This table shows used variables for LLT from the reviewed RCT’s by Chow et al. ³⁷

The RCT of Aguilera et al.³⁸  [2009: LoE: 1B] shows an immediate decrease in electrical activity in the trapezius muscle and a reduced sensitivity of myofascial trigger points after ultrasound treatment. The review of Vernon & Schneider show however that there’s conflicting evidence (level C) as to whether ultrasound therapy is no more effective than placebo or somewhat more effective than other therapies in the treatment of myofascial trigger points. Ultrasound can therefore be used as a therapeutic modulation, but is not recommended.

Biofeedback, earlier described as a prevention modality, can also be useful in the treatment of work related neck-and shoulder pain. The RCT of Ma et al.³⁹  [2011; LoE: 1B] shows that six weeks of biofeedback training results in less pain and neck disability than active and passive treatment, which is remained at 6 months pos tintervention. They also found consistent trends of reduced muscle activity in the upper trapezius.
Patients are instructed in how to use a portable biofeedback machine on the bilateral upper trapezius muscle and should use it for 2 hours daily while performing computer work. Surface electrodes are placed on the left and right side of the upper trapezius. By collecting the surface electromyography signals, a threshold amplitude can ben preset by the therapist. Electromyographic signals above the threshold will then trigger an auditory feedback signal which warns the patient to reduce the upper trapezius muscle activity by slightly depressing the shoulders.³⁹

Manual therapies
Ischemic compression, stretch of the upper trapezius muscle, transverse friction massage are manual techniques to help patients with TM. These techniques appear to have instant improvement on pain. Long-term effects have not yet been well investigated. [De Las Penas et al.⁴⁰ , 2005; Level 1A]

The review of Cagnie et al.²⁴ [2015; LoE: 1A] shows that ischemic compression and dry needling can both be recommended in the treatment of neck pain patients with trigger points in the upper trapezius muscle. There is moderate evidence (level B) that ischemic compression has a positive effect on pain intensity and ROM. For dry needling there is strong evidence (level A) that it has a positive effect on pain intensity and moderate evidence for the positive effect on ROM. The review of Liu et al. ⁴¹[2015; LoE: 1A] confirms that dry needling can be recommended for relieving trigger points pain in neck and shoulders in the short en medium term.

The RCT of Aguilera et al.³⁸ [2009; LoE: 1B] shows an immediate decrease in electrical activity in the trapezius muscle and an improvement of active ROM after ischemic compression.

According to Vernon & Schneider³⁶ [2009, LoE: 1A] moderatly strong evidence (level B) is available for immediate pain relief at trigger points due to spinal manipulation and ischemic compression.

Physical exercise
Both general fitness training and specific strength training generate significant effects on decreasing pain. However strength training has proven to be even more effective compared to general fitness training. According to Andersen et al. ⁴² [2008; LoE: 1B] specific strength training leads to reduction in pain intensity with a lasting effect for 10 weeks post intervention. On the other hand general fitness training results in pain reduction immediately after a training session, but shows no long-term benefits. Waling et al.⁴³ [2002; LoE: 1B] noted that the long-term effects of strength training are gone after 3 years.

Supervised high-intensity (8 –12 RM) dynamic strength training of the painful muscle, 3 times a week for 20 minutes should be recommended in the treatment of trapezius myalgia [Andersen et al.⁴², 2008; LoE: 1B].

The review of Rodrigues et al.⁴⁴  [2014; LoE: 1A] shows that strength exercises with intensity of 70-85% of RM performed three times a week for 20 minutes are able to reduce musculoskeletal pain in shoulders and cervical spine.

Waling et al.¹ [2000; LoE: 2B] found that strength training, endurance training and coordination (body awareness) training reduces the pain of work-related Trapezius Myalgia.

Exercises that can be done during a specific strength training [Andersen et al.⁴², 2008; LoE: 1B]:

1. Shoulder shrugs:
The subject is standing erect and holding the dumbbells to the side, then elevates the shoulders while focusing on contracting the upper trapezius muscle.

2. One-arm row:
The subject is bending her torso forward to approximately 30° from horizontal with one knee on the bench and the other foot on the floor. The subject now pulls the dumbbell towards the ipsilateral lower rib, while the contralateral arm is maintained extended and supports the body on the bench.

3. Upright row:
The subject is standing erect and holding the dumbbells while the arms are hanging relaxed in front of the body. The dumbbells are lifted towards the chest in a vertical line close to the body while flexing the elbows and abducting the shoulder. The elbows are pointing out- and upwards.

4. Reverse flyes:
The subject is lying on the chest at a 45° angle from horizontal and the arms pointing towards the floor. The dumbbells are raised until the upper arm is horizontally, while the elbows are in a static slightly flexed position (~5°) during the entire range of motion.

5. Lateral raise:
The subject is standing erect and holding the dumbbells side, and then abducts the shoulder joint until the upper arm is horizontally. The elbows are in a static slightly flexed position (5°) during the entire range of motion.

Other specific strength exercises that can be used in the treatment of TM are latissimus pulldown, triceps press, shoulder anteflexion and scapular retraction. [Waling et al.¹, 2000; LoE: 2B]

Armcycling and cycling with relaxed shoulders are effective exercises that can be done during a general fitness training.^{1 42 45}

Psychosocial involvement
The possible presence of psychosocial causative factors in patients with TM should be considered. If they are present, the patient should certainly be approached biopsychosocially.⁶

Key Research

Systematic reviews of RCT’s

• Macdermid JC, Walton DM, Avery S, Blanchard A, Etruw E, Mcalpine C, Goldsmith CH. Measurement Properties of the Neck Disability Index: A Systematic Review. Journal of Orthopaedic & Sports Physical Therapy. 2009; 39 (5): 400–C12. [LoE: 1A]
• Cagnie B, Castelein B, Pollie F, Steelant L, Verhoeyen H, Cools A. Evidence for the Use of Ischemic Compression and Dry Needling in the Management of Trigger Points of the Upper Trapezius in Patients with Neck Pain: A Systematic Review. Am J Phys Med Rehabil. 2015 Jul;94(7):573-83. [LoE: 1A]
• Jensen I, Harms-Ringdahl K. Neck Pain. Best practice & research clinical rheumatology. Feb 2007; 21 (1): 93-108. [LoE: 1A]
• Vernon H, Schneider M. Management of Myofascial Trigger points and Myofascial Pain Syndrome: A Systematic Review of the Literature. Journal of Manipulative and Physiological Therapeutics. 2009 Jan;32(1):14-24. [LoE: 1A]
• Chow RT, Johnson MI, Lopes-Martins RAB, Bjordal JM. Efficiacy of low-level laser therapy in the management of neck pain: a systematic review and meta-analysis of randomised placebo or active-treatment controlled trials. The Lancet. 2009 Dec;374(9705):1897-1908. [LoE: 1A]
• De Las Penas, CF, Campo MS, Carnero, JF, Page JC. Manual therapies in myofascial trigger point treatment: a systematic review. Journal of Body Work and Movement Therapies. 2005;9:27–34.
  [LoE: 1A]
• Liu L, Huang QM, Liu QG, Ye G, Bo CZ, Chen MJ, Li P. Effectiveness of dry needling for myofascial trigger points associated with neck and shoulder pain: a systematic review and meta-analysis. Arch Phys Med Rehabil. 2015 May. 96(5): 944-55. [LoE: 1A]
• Rodrigues EV, Gomes AR, Tanhoffer AI, Leite N. Effects of exercise on pain of musculoskeletal disorders: a systematic review. Acta Ortop Bras. 2014. 22(6): 334-8. [LoE: 1A]

Individual RCT’s

• Rosendal L, Larsson B, Kristiansen J, Peolsson M, Søgaard K, Kjaer M, Sørensen J, Gerdle B. Increase in muscle nociceptive substances and anaerobic metabolism in patients with trapezius myalgia: microdialysis in rest and during exercise. Pain. December 2004. 112 (3): 324-334 [LoE: 1B]
• Holtermann A, Sogaard K, Christensen H, Dahl B, Blangsted K. The influence of biofeedback training on trapezius activity and rest during occupational computer work: a randomized controlled trial. European Journal of Applied Physiology. 2008 Dec;104(6):983-989. [LoE: 1B]
• Aguilera JM, Martin DP, Masanet RA, Botella AC, Soler LB, Morell FB. Immediate Effect of Ultrasound and Ischemic Compression Techniques for the Treatment of Trapezius Latent Myofascial Trigger Points in Healthy Subjects: A Randomized Controlled Study. Journal of Manipulatice and Physiological Therapeutics. 2009 Sep;32(7):515-520. [LoE: 1B]
• Ma C, Szeto GP, Yan T, Wu S, Lin C, Li L. Comparing Biofeedback With Active Exercise and Passive Treatment for the Management of Work-Related Neck and Shoulder Pain: A Randomized Controlled Trial. Archives of Physical Medicine and Rehabilitation. 2001 Jun;92(6):849-858. [LoE: 1B]
• Andersen LL et al. Effect of two contrasting types of physical exercise on chronic neck muscle pain. Arthritis Rheum. 2008 Jan;59(1):84-91. [LoE: 1B]
• Waling K, Järvholm B, Sundelin G. Effects of training on female TM: An intervention study with a 3-year follow-up period. Spine. 2002 Apr 15;27(8):789-96. [LoE: 1B]

Resources 

• Healthhool. Myalgia [internet]. [Updated 2015]. Available from: http://healthool.com/myalgia/ [LoE: 5]
• MDDK. Myalgia [internet]. [Updated 2015]. Available from: http://mddk.com/myalgia.html#trapezius-myalgia
• Valachy B. TM [internet]. Available from: http://www.rdhmag.com/articles/print/volume-29/issue-7/feature/trapezius-myalgia.html
• Nmihi. Myalgia. [internet]. [Updated July 2011]. Available from: http://www.nmihi.com/m/myalgia.htm [LoE: 5]

Clinical Bottom Line

TM is rather a symptom of an existing underlying condition that is often categorized in the neck and shoulder disorders. The typical symptoms of a patient with TM complaints are pain in the upper trapezius muscle that can linger for a few days to weeks. This pain is often associated with spasms, stiffness and tenderness in the in the neck region. Trigger points can also be present and can cause headaches. Both biomechanical and psychosocial factors or a combination of both can contribute to the development and maintenance of TM. It should be kept in mind that women suffer more frequently of TM than men do. 
TM shouldn’t be confused with the tension neck syndrome, cervical syndrome, cervicalgia or thoracic outlet syndrome. To differentiate between these pathologies, the anamnesis and addition standard clinical examination on neck and upper extremities are very important. The use of a VAS for pain, a pressure algometer, a pain drawing and several questionnaires focused on pain and disabilities could help to evaluate the success of the treatment. Radiography, MRI, electromyography, nerve conductance testing or blood tests could be done to rule out other disorders, but aren’t standard procedures. The medical treatment consists of painkillers, which is the only medication which helps at short-term. The physiotherapist can apply TENS, acapuncture, magnet therapy, laser therapy and ultrasound for short-term relief of the myofascial trigger points. Laser therapy, acapuncture and biofeedback training can also result in a long-term effect. Biofeedback training is also a precautionary measure. Ischemic compression and dry needling are manual techniques which could be used to relieve the pain of the trigger points immediately. Also stretch of the upper trapezius muscle and transverse friction massage are pain mitigation techniques. General fitness training appears to relieve pain immediately while 3 times a week 20 minutes specific strength training of the neck and shoulder musculature at an intensity of 70-85% relieves pain at long term.

Recent Related Research (from Pubmed)

Recent related research is available from: http://www.ncbi.nlm.nih.gov/pubmed/?term=Trapezius+Myalgia

References

1. Waling K, Sundelin G, Ahlgren C, Jarvholm B. Perceived pain before and after three exercise programs -- a controlled clinical trial of women with work-related TM. Pain. 2000 Mar;85(1-2):201-207. [LoE: 2B]
2. Ahlgren C, Waling K, Kadi F, Djupsjobacka M, Thornell LE, Sundelin G. Effects on physical performance and pain from three dynamic training programs for women with work-related TM. J Rehab Med. 2001 Jul;33(4):162-169. [LoE: 2B]
3. Healthhool. Myalgia [internet]. [Updated 2015]. Available from: http://healthool.com/myalgia/   [LoE: 5]
4. Schünke M, Schulte E, Schumacher U. Prometheus – Algemene anatomie en bewegingsapparaat. 2e druk. Houten: Bohn Stafleu van Loghum;2007.
5. Warth RJ, Millett PJ. Physical Examination of the Shoulder: An Evidence-Based Approach. New York: Springer Science + Business Media; 2015.
6. Larsson B, Søgaard K, Rosendal L. Work related neck-shoulder pain: a review on magnitude, risk factors, biochemical characteristics, clinical picture and preventive interventions. Best Pract Res Clin Rheumatol. 2007 Jun;21(3):447-63. [LoE: 2A]
7. Gerdle B, Ghafouri B, Ernberg M, Larsson B. Chronic musculoskeletal pain: review of mechanisms and biochemical biomarkers as assessed by the microdialysis technique. J Pain Res. 2014 Jun 12;7:313-26 [LoE: 2A]
8. Hägg GM. Human muscle fibre abnormalities related to occupational load. Eur J Appl Physiol. 2000 Oct;83(2-3):159-65. [LoE: 3A] 4
9. Larsson R, Öberg PÂ, Larsson S. Changes of trapezius muscle blood flow and electromyography in chronic neck pain due to TM. Pain. 1999 Jan 1;79(1):45-50. [LoE: 3B]
10. Szeto G. Straker LM, O’Sullivan PB. A comparison of symptomatic and asymptomatic office workers performing monotonous keyboard work- 1: neck and shoulder muscle recruitment patterns. Man Ther. 2005 Nov; 10(4):270-80 [LoE: 2C]
11. Waersted M, Hanvold TN, Veiersted KB.Computer work and musculoskeletal disorders of the neck and upper extremity: a systematic review. BMC Musculoskelet Disord. 2010 Apr 29;11:79 [LoE: 3A]
12. Marker RJ, Balter JE, Nofsinger ML, Anton D3, Fethke NB, Maluf KS. Upper trapezius muscle activity in healthy office workers: reliability and sensitivity of occupational exposure measures to differences in sex and hand dominance. Ergonomics. 2016 Feb. 28:1-10. [LoE: 2B]
13. MDDK. Myalgia [internet]. [Updated 2015]. Available from: http://mddk.com/myalgia.html#trapezius-myalgia
14. Valachy B. TM [internet]. Available from: http://www.rdhmag.com/articles/print/volume-29/issue-7/feature/trapezius-myalgia.html
15. Nmihi. Myalgia. [internet]. [Updated July 2011]. Available from: http://www.nmihi.com/m/myalgia.htm [LoE: 5]
16. Simons DG, Travell JG. Myofascial origins of low back pain. 1. Principles of diagnosis and treatment. Postgraduate Medicine. 1983; 73(2): 66, 68-70, 73 [LoE: 3B]
17. Ransford AO, Cairns D, Money V. The pain drawing as an aid to the psychologic evaluation of patients with low-back pain. Spine. June 1976; 1 (2). [LoE: 2B]
18. Margolis RB, Tait RC, Krause SJ. A Rating System for Use with Patient Pain Drawings. Pain. 1986; 24: 57-65. [LoE: 2B]
19. Hawker GA, Mian S, Kendzerska T, French M. Measures of adult pain: Visual Analog Scale for Pain (VAS Pain), Numeric Rating Scale for Pain (NRS Pain), McGill Pain Questionnaire (MPQ), Short-Form McGill Pain Questionnaire (SF-MPQ), Chronic Pain Grade Scale (CPGS), Short Form-36 Bodily Pain Scale (SF-36 BPS), and Measure of Intermittent and Constant Osteoarthritis Pain (ICOAP). Arthritis Care & Research. November 2011; 63 (11): 240-252. [LoE: 3B]
20. Macdermid JC, Walton DM, Avery S, Blanchard A, Etruw E, Mcalpine C, Goldsmith CH. Measurement Properties of the Neck Disability Index: A Systematic Review. Journal of Orthopaedic & Sports Physical Therapy. 2009; 39 (5): 400–C12. [LoE: 1A]
21. Melzack R. "The McGill Pain Questionnaire: major properties and scoring methods." Pain 1975 1(3): 277-299 [LoE: 2B]
22. Bolton J, Humphreys B. The Bournemouth Questionnaire: a short form comprehensive outcome measure. II. Psychometric properties in neck pain patients. J Manipulative Physiol Ther. 2002 Mar-Apr;25(3):141-8 [LoE: 2A]
23. Gay R, Madson T, Cieslak K. Comparison of the neck disability index and the neck Bournemouth questionnaire in a sample of patients with chronic uncomplicated neck pain. Journal of manipulative and physiological therapies. 2007. [LoE: 2B]
24. Cagnie B, Castelein B, Pollie F, Steelant L, Verhoeyen H, Cools A. Evidence for the Use of Ischemic Compression and Dry Needling in the Management of Trigger Points of the Upper Trapezius in Patients with Neck Pain: A Systematic Review. Am J Phys Med Rehabil. 2015 Jul;94(7):573-83. [LoE: 1A]
25. Rosendal L, Larsson B, Kristiansen J, Peolsson M, Søgaard K, Kjaer M, Sørensen J, Gerdle B. Increase in muscle nociceptive substances and anaerobic metabolism in patients with trapezius myalgia: microdialysis in rest and during exercise. Pain. December 2004. 112 (3): 324-334 [LoE: 1B]
26. Kuorinka I, Jonsson B, Kilbom A, Vinterberg H, Bierin-Sørenensen F, Andersson G, Jørgensen K. Standardised Nordic questionnaires for the analysis of musculoskeletal symptoms. Applied Ergonomics. 1987; 18 (3): 233-237. [LoE: 2B]
27. Crawford JA. The Nordic musculoskeletal questionnaire. Occup med. 2007; 57(4): 300-301. [LoE:1A]
28. Kuorinka I, Jonsson B, Kilbom A. Standardized Nordic questionnaires for the analysis of musculoskeletal symptoms. Appl Ergon 1987;18:233-237. [LoE: 3B]
29. Dickinson CE, Campion K, Foster AF, Newman SJ, O’Rourke AM, Thomas PG. Questionnaire development—an examination of the Nordic Musculoskeletal Questionnaire. Appl Ergon. 1992;23:197-201. [LoE: 3B]
30. Ohlsson K, Attewell RG, Johnsson B, Ahlm A, Skerfving S. An assessment of neck and upper extremity disorders by questionnaire and clinical examination. Ergonomics. 1994;37:891-897. [LoE: 3B]
31. Sjøgaard G, Sjøgaard K, Hermens HJ, Sandsjö L, Läubli T, Thorn S, Vollenbroek-Hutten MM, Sell L, Christensen H, Klipstein A, Kadefors R, Merletti R. Neuromuscular assessment in elderly workers with and without work related shoulder/neck trouble: the NEW-study design and physiological findings. Eur J Appl Physiol. 2006 Jan. 96(2): 110-21. [LoE: 3B]
32. Hadrevi J, Ghafouri B, Larsson B, Gerdle B, Hellström F. Multivariate modelling of proteins related to trapezius myalgia, a comparative study of female cleaners with or without pain. PLoS One. 2013 Sep. 8(9):e73285. [LoE: 3B]
33. Castelein B, Cools A, Bostyn E, Delemarre J, Lemahieu T, Cagnie B. Analysis of scapular muscle EMG activity in patients with idiopathic neck pain: a systematic review. J Electromyogr Kinesiol. 2015 Apr. 25(2): 371-386.[LoE: 3A]
34. Jensen I, Harms-Ringdahl K. Neck Pain. Best practice & research clinical rheumatology. Feb 2007; 21 (1): 93-108. [LoE: 1A]
35. Holtermann A, Sogaard K, Christensen H, Dahl B, Blangsted K. The influence of biofeedback training on trapezius activity and rest during occupational computer work: a randomized controlled trial. European Journal of Applied Physiology. 2008 Dec;104(6):983-989. [LoE: 1B]
36. Vernon H, Schneider M. Management of Myofascial Trigger points and Myofascial Pain Syndrome: A Systematic Review of the Literature. Journal of Manipulative and Physiological Therapeutics. 2009 Jan;32(1):14-24. [LoE: 1A]
37. Chow RT, Johnson MI, Lopes-Martins RAB, Bjordal JM. Efficacy of low-level laser therapy in the management of neck pain: a systematic review and meta-analysis of randomised placebo or active-treatment controlled trials. The Lancet. 2009 Dec;374(9705):1897-1908. [LoE: 1A]
38. Aguilera JM, Martin DP, Masanet RA, Botella AC, Soler LB, Morell FB. Immediate Effect of Ultrasound and Ischemic Compression Techniques for the Treatment of Trapezius Latent Myofascial Trigger Points in Healthy Subjects: A Randomized Controlled Study. Journal of Manipulatice and Physiological Therapeutics. 2009 Sep;32(7):515-520. [LoE: 1B]
39. Ma C, Szeto GP, Yan T, Wu S, Lin C, Li L. Comparing Biofeedback With Active Exercise and Passive Treatment for the Management of Work-Related Neck and Shoulder Pain: A Randomized Controlled Trial. Archives of Physical Medicine and Rehabilitation. 2001 Jun;92(6):849-858. [LoE: 1B]
40. De Las Penas, CF, Campo MS, Carnero, JF, Page JC. Manual therapies in myofascial trigger point treatment: a systematic review. Journal of Body Work and Movement Therapies. 2005;9:27–34. [LoE: 1A]
41. Liu L, Huang QM, Liu QG, Ye G, Bo CZ, Chen MJ, Li P. Effectiveness of dry needling for myofascial trigger points associated with neck and shoulder pain: a systematic review and meta-analysis. Arch Phys Med Rehabil. 2015 May. 96(5): 944-55. [LoE: 1A]
42. Andersen LL et al. Effect of two contrasting types of physical exercise on chronic neck muscle pain. Arthritis Rheum. 2008 Jan;59(1):84-91. [LoE: 1B]
43. Waling K, Järvholm B, Sundelin G. Effects of training on female TM: An intervention study with a 3-year follow-up period. Spine. 2002 Apr 15;27(8):789-96. [LoE: 1B]
44. Rodrigues EV, Gomes AR, Tanhoffer AI, Leite N. Effects of exercise on pain of musculoskeletal disorders: a systematic review. Acta Ortop Bras. 2014. 22(6): 334-8. [LoE: 1A]
45. Andersen LL, Blangsted AK, Nielsen PK, Hansen , Vedsted P, Sjøgaard G, Sjøgaard K. Effect of cycling on oxygenation of relaxed neck/shoulder muscles in women with and without chronic pain. Eur J Appl Physiol. 2010 Sep. 110(2): 389-94.[LoE: 3B]
46. Gross RA et al. Low Level Laser Therapy (LLLT) for Neck Pain: A Systematic Review and Meta-Regression. Open Orthoped J. 2013;7:396-419. [LoE: 2A]
47. Garg A, Kapellusch JM. Applications of biomechanics for prevention of work-related musculoskeletal disorders. Ergonomics. 2009 Jan;52(1):36-59. [LoE: 3A]
48. van der Windt DA, Thomas E, Pope DP, de Winter AF, Macfarlane GJ, Bouter LM, Silman AJ. Occupational risk factors for shoulder pain: a systematic review. Occup Environ Med. 2000 Jul;57(7):433-42
    [LoE: 3A]
49. Juul-Kristensen B, Kadefors R, Hansen K, Byström P, Sandsjö L, Sjøgaard G. Clinical signs and physical function in neck and upper extremities among elderly female computer users: the NEW study. Eur J Appl Physiol. 2006 Jan;96(2):136-45. [LoE: 3B]