Relationship between trapezius muscle hardness and transverse cervical artery flow in association with neck and upper-back stiffness.

Neck and upper-back stiffness is a common discomfort encountered occasionally in daily life among otherwise healthy subjects. The pathogenesis of this condition could be attributable to increased tension in muscles such as the trapezius muscle (TM). The transverse cervical artery (TCA) is one of the feeding arteries for the TM, and TCA flow is reportedly related to symptoms of neck and upper-back stiffness. This study quantitatively investigated relationships between TM hardness and TCA hemodynamics as evaluated on Doppler sonography. Questionnaires regarding neck and upper-back stiffness, muscle hardness measurements obtained using a muscle hardness meter and examinations of TCA hemodynamics using Doppler sonography were performed on 55 healthy young adults (25 males, 30 females; mean age, 22 ± 2 years). Subjects displaying neck and upper-back stiffness actually exhibited high muscle hardness (median, 14.0; interquartile range (IQR), 12.9-18.0) compared to those without the symptom (median, 12.0; IQR, 9.9-14.0; p = .002). Peak systolic velocity in the TCA on Doppler sonography was lower in subjects with the symptom (median, 65.1 cm/s; IQR 59.6-72.5 cm/s) than in those without the symptom (median, 72.5 cm/s; IQR 66.5-84.2 cm/s; p = .012). Resistive index in the TCA was high (r2  = .605, p = .014) with increasing TM hardness, particularly among male subjects with the symptom. The present study suggests that high resistance and low blood flow velocity in the TCA could be closely associated with the underlying pathogenesis of neck and upper-back stiffness.