Alterations in Central Control of Shoulder Muscles 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.