EMG Activity Before, During and After Dry Needling

An experimental study will be conducted to evaluate the effect of a single dry needling session on surface EMG activity (primary outcome measure), muscle tone, elasticity, stiffness and pain (secondary outcome measures) of the upper trapezius, in female office workers with trapezius myalgia.

Neck-shoulder pain is a frequent problem in office workers . These complaints are often related to myofascial problems of neck and shoulder muscles in which the upper trapezius is frequently involved. Trapezius myalgia (TM) is characterized by pain, palpable stiffness and tenderness of the upper part of the trapezius muscle. Several studies show that myofascial trigger points (MTrP) have an important role in the development and maintenance of myofascial pain.

Trigger points are defined as hyperirritable nodules in a contracture of skeletal muscle fibers.

The pathophysiology of MTrPs is still unclear but several hypothesis exist. The most plausible explanation is that, due to sustained postures or repetitive low-level tasks, a sustained irritation of motor end plates with an excessive release of acetylcholine arises. This may lead to a persistent sarcomere contraction, leading to an impaired blood circulation, a reduced oxygenation and energy depletion, sensitizing nociceptors and causing pain.

Dry needling (DN) is a myofascial treatment technique, in which a thin, solid filiform needle is inserted directly into the MTrP. During dry needling, local twitch responses (LTR) can be elicited. These are involuntary contractions of muscle fibers, leading to muscle relaxation, an increase in blood flow, recovery of the muscle metabolism and thus a reduction of pain and stiffness.

In this experimental study, 25 female office workers with trapezius myalgia are recruited from several work places with predominantly computer based tasks. These subjects have to perform at least 20 hours a week of computer work and this since at least one year. Subjects are included based on online questionnaires, a clinical examination of neck an shoulder and the presence of MTRP 2 in the upper trapezius. All participants will receive information and have to sign an informed consent form.

Participants will be subjected to baseline assessment which involves measuring resting surface EMG activity, muscle tone, stiffness, elasticity and pain. Then, subjects have to perform a computer task during 20 minutes while surface EMG activity will be measured every 5 minutes. After this computer task, all measurements will be repeated. After a resting period of 10 minutes, baseline measurements are repeated, followed by a computer task of 20 minutes and repetition of the same assessment. After this computer task, a single dry needling session of MTrP 2 of the upper trapezius will be performed bilaterally. During this treatment, surface EMG activity will be measured to captivate the EMG activity during local twitch responses.

This is followed by repeating the same measurements 1 and 10 minutes after dry needling.

Eligibility Criteria:
Inclusion Criteria:

* Performing office work since at least one year
* Performing computer based tasks for at least 20 hours a week
* NRS \> or equal to 3/10
* Clinical diagnosis of trapezius myalgia
* Trapezius myalgia is work-related and thus aggravates during working day/week
* Presence of MTrP2 in the upper trapezius muscle (bilaterally)

Exclusion Criteria:

* Being in treatment during the study
* Traumatic injuries/surgery to neck and upper limb region
* Signs of cervical nerve root impingement
* Whiplash injury
* Cardiovascular, neurological, life threatening, systemic and metabolic diseases
* Diagnosis of fibromyalgia/chronic fatigue syndrome
* Shoulder pathology
* Coagulation disorders
* Pregnancy