Scapular Muscle Activation and Shoulder Performance in Migraine

Upper and middle trapezius muscle activations will be assessed on the dominant side using surface electromyography (sEMG). Following skin preparation, EMG sensors will be placed over the upper and middle trapezius muscles according to the recommendations of the Surface Electromyography for the Non-Invasive Assessment of Muscles (SENIAM). Resting muscle activity will be recorded prior to measurements to ensure signal quality. Muscle activations will first be recorded during maximal voluntary isometric contraction (MVIC) and subsequently during arm elevation in the scapular plane. EMG data will be analyzed using EMGworks software; signals will be filtered, processed using the root mean square (RMS) method, and normalized to each participant's MVIC values, expressed as %MVIC. Additionally, upper trapezius/middle trapezius activation ratios will be calculated, and muscle activation levels will be categorized according to predefined threshold values.

Scapular upward rotation will be assessed using a digital inclinometer at shoulder elevation angles of 0°, 45°, 90°, and 135°. Participants will stand comfortably with the elbow extended and elevate the arm with the thumb pointing upward to the target angles. The inclinometer will be positioned over the scapular spine to measure scapular upward rotation at each angle. Three measurements will be obtained at each position with 30-second rest intervals, and the mean value will be used for analysis.

The pressure pain threshold of the upper trapezius muscle will be assessed using a digital algometer. Measurements will be performed at the midpoint between the C7 vertebra and the acromion using a 1-cm diameter rubber probe. Pressure will be gradually increased until the participant first reports pain or discomfort. Three measurements will be obtained with 30-second intervals, and the mean value (N/m²) will be used for analysis.

Upper extremity mobility, stability, and proprioception in a closed kinetic chain will be assessed using the Upper Quarter Y-Balance Test. Participants will perform the test in a push-up position while reaching in the medial, inferolateral, and superolateral directions with the free hand. Reach distances will be recorded in centimeters and normalized to upper extremity length. Composite reach scores will also be calculated, with greater reach distances indicating better upper extremity dynamic balance and function.