Background. Neck and shoulder complaints caused by poor posture may influence upper trapezius stiffness. The relationship between the shear elastic modulus of the upper trapezius and cervical flexion angles is unknown. Therefore, it is essential to assess upper trapezius stiffness during cervical flexion. The objectives of this study were to (1) determine the intra- and interoperator reliabilities of evaluating upper trapezius stiffness and calculate the minimal detectable change (MDC); (2) examine the elastic modulus alterations of the upper trapezius during cervical flexion; and (3) explore the difference of upper trapezius stiffness between the dominant and nondominant sides. Methods. Twenty healthy male participants were recruited in this study. The shear modulus of the upper trapezius was evaluated by two independent investigators using shear wave elastography (SWE) during cervical flexion at 0° and 50°. Findings. The intraoperator (intraclass correlation coefficient –0.86) and interoperator (–0.98) reliabilities for measuring the shear elastic modulus of the upper trapezius during the cervical flexion ranged from good to excellent. An increase of 35.58% in upper trapezius stiffness was found at 0° to 50° of cervical flexion, and the MDC was 7.04 kPa. In addition, a significant difference was obtained in the elastic modulus of the upper trapezius muscle between the dominant and nondominant sides (). Conclusions. Our findings revealed that SWE could quantify the elastic modulus of the upper trapezius and monitor its changes. Therefore, further studies are required to delineate the modulation in upper trapezius muscle stiffness among subjects with neck and shoulder pain.

中文翻译：

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不同颈角上斜方肌弹性特性的调制。

背景。不良姿势引起的颈部和肩部不适可能会影响上斜方肌僵硬。上斜方肌的剪切弹性模量与颈椎屈曲角度之间的关系尚不清楚。因此，有必要在颈椎屈曲时评估上斜方肌的刚度。本研究的目的是 (1) 确定评估上斜方肌刚度的内部和操作者间可靠性并计算最小可检测变化 (MDC)；(2)检查颈椎屈曲时上斜方肌弹性模量的变化；(3) 探索优势侧和非优势侧之间的上斜方肌刚度的差异。方法. 本研究招募了 20 名健康男性参与者。两名独立研究人员在 0° 和 50° 的颈椎屈曲期间使用剪切波弹性成像 (SWE) 评估了上斜方肌的剪切模量。调查结果。操作员内（组内相关系数–0.86）和互操作者（–0.98) 测量颈椎屈曲期间上斜方肌剪切弹性模量的可靠性范围从良好到极好。颈椎屈曲0°～50°时，上斜方肌刚度增加35.58%，MDC为7.04 kPa。此外，优势侧和非优势侧之间的上斜方肌的弹性模量存在显着差异（）。 结论。我们的研究结果表明，SWE 可以量化上斜方肌的弹性模量并监测其变化。因此，需要进一步的研究来描述颈部和肩部疼痛受试者上斜方肌僵硬的调节。