Investigation of Skin Circulation Hemodynamics Using Skin Laser Speckle Flowgraphy After Trapezius Muscle Self-Stretching

Stretching of the upper trapezius muscle reduces stiffness and choroidal blood flow velocity, but its effect on skin blood flow remains unclear. We evaluated the changes in upper trapezius skin circulation hemodynamics before/after self-stretching using skin laser speckle flowgraphy (LSFG). Twenty-two healthy young adults (median age [Q1–Q3]: 21.0 [20.0–21.0] years) were enrolled. Trapezius stiffness was assessed using ultrasound strain elastography, and skin and choroidal blood were measured with skin and ocular LSFG, respectively, using mean blur rate (MBR) as an index of blood flow velocity. Intraocular pressure (IOP); systolic (SBP), diastolic (DBP), and mean blood pressure (MBP); heart rate (HR); ocular perfusion pressure (OPP); salivary α-amylase (sAA) activity; and subjective eyestrain/shoulder stiffness symptoms (visual analog scale, VAS) were evaluated at baseline and after stretching. SBP, DBP, MBP, OPP, sAA activity, VAS scores for eyestrain and shoulder stiffness, trapezius stiffness, and skin and choroidal MBR decreased significantly after self-stretching, whereas IOP and HR remained unchanged. Trapezius muscle self-stretching reduces muscle stiffness and induces relaxation in healthy adults, accompanied by reduced sympathetic activity and decreased systemic, choroidal, and local skin circulation. These findings suggest that skin LSFG may serve as a useful, non-invasive tool for evaluating shoulder stiffness.