This randomized controlled trial aims to compare the effectiveness of a cervical exercise program, transcutaneous neuromodulation of the spinal accessory nerve, and a placebo intervention on pain intensity, pressure pain threshold, cervical proprioception, functional disability, depression, anxiety, and stress in university students with chronic non-specific neck pain. The study will include a six-week intervention period with pre- and post-treatment assessments. The findings may contribute to the development of accessible physiotherapy interventions within university settings.
Chronic non-specific neck pain is one of the most prevalent musculoskeletal disorders worldwide and represents a significant socioeconomic burden. It affects a large proportion of the adult population and shows increasing prevalence among university students, largely associated with prolonged electronic device use and sustained static postures. Chronic neck pain is defined as pain lasting three months or longer without a specific identifiable pathology. Psychosocial factors such as stress, anxiety, and depression have been strongly associated with the onset and persistence of neck pain. These factors may contribute to functional disability and reduced quality of life. In university students, persistent neck pain may also negatively impact concentration and academic performance. Exercise therapy targeting deep cervical flexor muscles has demonstrated improvements in pain, muscular endurance, posture, and functional outcomes in individuals with chronic non-specific neck pain. Additionally, prolonged upper trapezius muscle spasm and possible involvement of the spinal accessory nerve have been suggested as contributing mechanisms in chronic neck pain. Low-frequency electrical stimulation (below 10 Hz), particularly at 4 Hz, has been associated with analgesic effects mediated by endogenous opioid mechanisms. Placebo interventions have also been shown to activate endogenous analgesic pathways involving cortical and subcortical pain modulation circuits, emphasizing the relevance of patient expectations in rehabilitation outcomes. This study will compare cervical exercise, transcutaneous neuromodulation of the spinal accessory nerve, and a placebo intervention in a randomized, controlled, parallel-group design with blinded outcome assessment. Both physical and psychosocial variables will be evaluated before and after a six-week intervention period.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
SINGLE
Enrollment
51
Participants will perform a supervised cervical and scapular strengthening program focused on deep cervical flexor activation and motor control. The intervention will consist of 12 sessions over six weeks (two sessions per week). Exercises will include cranio-cervical flexion movements, isometric contractions in supine, prone, and side-lying positions, and progressive load adjustments guided by the Borg Rating of Perceived Exertion Scale (target intensity 7/10). Load progression will be implemented after week three to maintain training intensity.
Participants will receive low-frequency electrical stimulation applied bilaterally over the spinal accessory nerve at Erb's point using the Pointer Excel II device. Stimulation parameters will be set at 4 Hz for 5 minutes per side during each session. The intervention will be delivered twice weekly for six weeks.
Participants will undergo a simulated neuromodulation procedure using the same device and positioning as the active neuromodulation group. No electrical current will be delivered. The device will remain in point-detection mode to produce sound without stimulation. The duration and frequency of sessions will match the active intervention group.
Pain Intensity
Pain intensity will be assessed using a 0-10 Visual Analog Scale, where 0 represents no pain and 10 represents the worst imaginable pain.
Time frame: Baseline and week 6
Pressure Pain Threshold
Pressure Pain Threshold (PPT) will be assessed using a validated digital algometer (Digital Force Gauge SF-500). Progressive pressure will be applied at a rate of 1 kg/cm² per second over a 1 cm² surface area at two bilateral anatomical sites: the midpoint between C7 and the acromion (upper trapezius muscle) and the sternocleidomastoid muscle belly. Participants will be positioned supine during assessment. The measurement will stop when the participant verbally indicates the first sensation of pain. Three measurements will be taken at each site with 30-second intervals between trials. The mean value of the three trials will be recorded in kg/cm². Higher values indicate greater pressure pain tolerance.
Time frame: Baseline and week 6
Joint Position Sense Error
Cervical proprioception will be evaluated using the Joint Position Sense Error (JPSE) test. Participants will be seated 90 cm from a visual target with a laser pointer attached to the forehead to establish a neutral head position. After familiarization with eyes open, participants will perform cervical flexion-extension, left rotation, and right rotation movements with eyes closed and attempt to return to the initial neutral position. The angular deviation between the starting reference point and the repositioned point will be measured in degrees. The absolute error value will be recorded. Higher values indicate greater proprioceptive impairment.
Time frame: Baseline and Week 6
Neck Disability
Functional disability related to neck pain will be assessed using the validated Spanish version of the Neck Disability Index (NDI). The NDI consists of 10 items evaluating pain intensity and the impact of neck pain on activities of daily living (personal care, lifting, reading, headaches, concentration, work, driving, sleeping, and recreation). Each item is scored from 0 to 5. The total score (0-50) will be converted to a percentage using the formula: (total score/50) × 100. Higher percentages indicate greater disability.
Time frame: Baseline and week 6
Depression, anxiety and stress
Psychological symptoms will be assessed using the Depression Anxiety Stress Scales-21 (DASS-21). This self-reported questionnaire includes 21 items divided into three subscales (depression, anxiety, and stress), with 7 items per subscale. Each item is rated on a 4-point Likert scale from 0 ("Did not apply to me at all") to 3 ("Applied to me very much or most of the time") based on the past week. Subscale scores will be calculated by summing the corresponding items and multiplying by two, as recommended for the short version. Higher scores indicate greater emotional distress.
Time frame: Baseline and week 6
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