Alterations in Central Control of Shoulder Muscles in Office Workers With Non-specific Chronic Neck Pain

Alterations in Corticospinal and Neuromuscular Control of Shoulder Complex in Office Workers With Non-specific Chronic Neck Pain

Non-specific chronic neck pain (NCNP) is commonly seen in office workers. Individuals with NCNP not only demonstrate impaired neck movement control and muscle activation, but also show abnormal scapular kinematics and muscle activation timing. Office workers with NCNP also show higher activity of upper trapezius during computer typing and have difficulty relaxing upper trapezius after typing. These changes related to scapula may increase strain over neck. In addition to the altered neuromuscular control, recent studies found neuroplasticity changes in the central nervous system on patients of chronic musculoskeletal disorders. Therefore, few studies found shifts and alterations of motor cortex representation of neck muscles in individuals with NCNP, which was correlated with delayed muscle activation of deep neck flexors muscle in functional activities. However, no studies have explored that whether this corticospinal adaptation also happens over scapular muscles, especially after a computer typing task. The objectives of this proposal are to investigate the differences in corticospinal and neuromuscular control of shoulder complex between office workers with and without NCNP. Thirty-five individuals with NCNP and 35 healthy controls will be recruited. Twenty young healthy subjects will be also recruited for a pilot study to test the reliability of all the measures. Scapular kinematics and muscle activation will be tested during arm elevation. Corticospinal parameters of trapezius and serratus anterior will be tested with transcranial magnetic stimulation (TMS), including active motor threshold, motor evoked potential, cortical silent period, short interval intracortical facilitation, short interval intracortical inhibition and cortical mapping. Corticospinal parameters, except cortical mapping, will be measured again after a 30-minute computer typing task. Scapular muscle activation will be also recorded during the typing task.

Inclusion Criteria of Patients with Non-specific Chronic Neck Pain

1. Ages ranges from 20-40 years old

2. Work with the computer at least 25 hours per week

3. Neck pain of idiopathic origin ≥ 6 months during the past year

4. Minimum of 3/10 on the numerical rating scale (NRS) in past 7 days

5. No structural abnormalities which are confirmed by neck X-ray or negative results of all the following special tests

   • Exclude nerve root compression: Cervical distraction test and Spurling's test
   • Exclude cervical radiculopathy: Valsalva test
   • Exclude cervical instability: Alar ligament test and Sharp-Purser test

6. Specific head movements or maintaining the fixed posture for a long time reproduced neck pain

Inclusion Criteria of Healthy Subjects in the control group

1. Ages ranges from 20-40 years old
2. Work with the computer at least 25 hours per week
3. No history of neck and/or shoulder pain sustained over one week in the past one year

Inclusion Criteria of Healthy subjects in the Pilot Study

1. Ages ranges from 20-40 years old
2. No history of neck and/or shoulder pain sustained over one week in the past one year

Exclusion Criteria of Patients with Non-specific Chronic Neck Pain and All Healthy Subjects)

1. Any known pathology or impairment in the shoulder joint, which is the origin of neck pain
2. Current episode of neck pain related to a traumatic event (e.g., whiplash injury)
3. Have a history of cervical and/or shoulder pathology (e.g., fracture, dislocation, trauma, surgery of spinal or shoulder joint, inflammatory disease, frequent headache or dizziness)
4. Brain injury and neurological impairment (e.g., radiculopathy, myelopathy or stroke)
5. Systematic diseases (e.g., rheumatoid arthritis, ankylosing spondylitis), fibromyalgia, tumor
6. Contraindications to the use of transcranial magnetic stimulation (TMS), assessed with a safety screening questionnaire, including pregnancy, history of seizure, epilepsy and syncope, having cochlear implant, having medal implant and taking anti-depressant medication
7. Any kind of previous manual and/or movement therapy on upper extremity and neck during in recent 3 months