ObjectiveSTo establish normal reference values for deltoid muscle elasticity, represented by mean shear wave velocity (SWV), in healthy individuals and analyze influencing factors.SMethodsSShear wave elastography was performed on 94 healthy volunteers to measure the thickness and mean SWV of the middle deltoid muscle at left/right neutral position (0°) and horizontal abduction position (90°). Differences in mean SWV were compared between positions, and the effects of gender, age, and body mass index (BMI) were assessed using analysis of variance and regression analysis.SResultsSThe mean age and BMI of the volunteers were 42.43 ± 9.22 years and 23.95 ± 2.74 kg/m2, respectively. Significant gender-related differences in mean SWV were found at left 0° (P=0.008) and right 0° (P=0.005), but not at 90° positions. The reference ranges of mean SWV were as follows: left 0°: 2.42-3.05 m/s for males, 2.48-3.19 m/s for females; right 0°: 2.44-3.24 m/s for males, 2.60-3.33 m/s for females; left 90°: 4.96-6.77 m/s; right 90°: 5.12-7.17 m/s.SConclusionSThis study systematically establishes reference ranges for mean SWV of the deltoid muscle at rest and during a functional position in healthy young and middle-aged adults. Gender differences were observed at rest but not in the functional position, where SWV primarily reflects task-dependent muscle tension. These reference values provide an objective baseline for quantitative assessment of deltoid-related shoulder disorders.Keywords:Elasticity; Middle deltoid; Shear wave velocity; Shear wave elastography; Normal reference ranges