Whether static stretching (SS) frequency has an effect on increasing the range of motion (ROM) and decreasing muscle stiffness remains unclear. Therefore, this study aimed to investigate the effects of two 6-week SS programs performed with different frequencies but generally the same duration of stretching on the passive properties of the medial gastrocnemius muscle-tendon unit. The study participants comprised 24 male volunteers randomly assigned to either the one-time/week group or the three-times/week group, performing 6 min of SS once per week and 2 min of SS thrice per week, respectively. The dorsiflexion ROM (DF ROM) and muscle stiffness of the medial gastrocnemius during passive ankle dorsiflexion were assessed using a dynamometer and ultrasonography before and after 6 weeks of SS programs. The results show that the DF ROM was increased and muscle stiffness was decreased significantly in the three-times/week group (P < 0.01 and P < 0.01, respectively), whereas no significant changes were observed in DF ROM and muscle stiffness in the one-time per week group (P = 0.25 and P = 0.32, respectively). These results suggest that a high-frequency SS program is more effective than a low-frequency SS program in increasing ROM and decreasing muscle stiffness.

中文翻译：

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以不同体积相等的每周频率进行的静态拉伸计划对肌肉肌腱单元被动特性的影响。

静态拉伸 (SS) 频率是否对增加运动范围 (ROM) 和降低肌肉僵硬有影响仍不清楚。因此，本研究旨在调查以不同频率但通常相同的拉伸持续时间执行的两个 6 周 SS 计划对内侧腓肠肌肌腱单元的被动特性的影响。研究参与者包括 24 名男性志愿者，随机分配到 1 次/周组或 3 次/周组，分别每周进行 6 分钟 SS 一次和 2 分钟 SS 每周三次。在 6 周的 SS 计划之前和之后，使用测力计和超声检查在被动踝关节背屈期间的内侧腓肠肌的背屈 ROM (DF ROM) 和肌肉僵硬程度进行了评估。结果显示，3次/周组DF ROM明显增加，肌肉僵硬度显着降低（分别为P < 0.01和P < 0.01），而1组DF ROM和肌肉僵硬度无明显变化。 - 每周组（分别为 P = 0.25 和 P = 0.32）。这些结果表明，在增加 ROM 和降低肌肉僵硬方面，高频 SS 计划比低频 SS 计划更有效。